| author | Florian Pose <fp@igh-essen.com> |
| Thu, 03 Jul 2008 15:17:51 +0000 | |
| changeset 1085 | c75cdcc5ce87 |
| parent 917 | 07b0ad9722a1 |
| child 1086 | 722ead4ecc22 |
| permissions | -rw-r--r-- |
| 369 | 1 |
%------------------------------------------------------------------------------ |
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% IgH EtherCAT Master Documentation |
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% $Id$ |
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% |
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%------------------------------------------------------------------------------ |
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% |
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% Conventions |
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% The IgH EtherCAT Master |
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% Feature Summary |
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% License |
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% Architecture |
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% Phases |
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% Behavior (Scanning) TODO |
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% Application Interface |
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% Interface version |
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% Master Requesting and Releasing |
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% Master Locking |
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% Slave configuration |
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% Configuring Pdo assignment and mapping |
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% Domains (memory) |
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% Pdo entry registration |
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% Sdo configuration |
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% Sdo access |
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% Cyclic operation |
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% Ethernet Devices |
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% Device Interface |
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% Device Modules |
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% Network Driver Basics |
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% EtherCAT Network Drivers |
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% Device Selection |
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% The Device Interface |
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% Patching Network Drivers |
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% The Master's State Machines |
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% Master |
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% Slave scanning |
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% SII |
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% Pdo assign/mapping |
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% Slave configuration |
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% State change |
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% Pdo assign/mapping |
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% CoE upload/download/information |
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% Mailbox Protocol Implementations |
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% Ethernet-over-EtherCAT (EoE) |
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% CANopen-over-EtherCAT (CoE) |
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% User Space |
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% The ethercat command |
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% System Integration |
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% The EtherCAT Init Script |
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% The EtherCAT Sysconfig File |
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% Monitoring and Debugging |
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% Installation |
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% Example applications |
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% Bibliography |
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% Glossary |
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% |
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\documentclass[a4paper,12pt,BCOR6mm,bibtotoc,idxtotoc]{scrbook}
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\usepackage[latin1]{inputenc}
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\usepackage[automark,headsepline]{scrpage2}
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\usepackage{graphicx}
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\usepackage{makeidx}
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\usepackage[refpage]{nomencl}
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\usepackage{listings}
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\usepackage{svn}
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\usepackage{textcomp}
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\usepackage{url}
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\usepackage{SIunits}
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\usepackage[pdfpagelabels,plainpages=false]{hyperref}
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\setlength{\parskip}{0.8ex plus 0.8ex minus 0.5ex}
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\setlength{\parindent}{0mm}
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\setcounter{secnumdepth}{\subsubsectionlevel}
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\DeclareFontShape{OT1}{cmtt}{bx}{n}
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{
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<5><6><7><8><9><10><10.95><12><14.4><17.28><20.74><24.88>cmttb10 |
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}{}
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\lstset{basicstyle=\ttfamily\small,numberstyle=\tiny,aboveskip=4mm,
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belowskip=2mm,escapechar=`} |
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\renewcommand\lstlistlistingname{List of Listings}
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% Workaround for lstlistoflistings bug |
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\makeatletter% --> De-TeX-FAQ |
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\renewcommand*{\lstlistoflistings}{%
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\begingroup |
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\if@twocolumn |
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\@restonecoltrue\onecolumn |
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\else |
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\@restonecolfalse |
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\fi |
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\lol@heading |
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\setlength{\parskip}{\z@}%
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\setlength{\parindent}{\z@}%
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\setlength{\parfillskip}{\z@ \@plus 1fil}%
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\@starttoc{lol}%
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\if@restonecol\twocolumn\fi |
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\endgroup |
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} |
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\makeatother% --> \makeatletter |
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\renewcommand\nomname{Glossary}
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\newcommand{\IgH}{\raisebox{-0.7667ex}
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{\includegraphics[height=2.2ex]{images/ighsign}}}
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\SVN $Date$ |
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\SVN $Revision$ |
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\newcommand{\masterversion}{1.4.0}
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\newcommand{\linenum}[1]{\normalfont\textcircled{\tiny #1}}
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\makeindex |
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\makenomenclature |
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%------------------------------------------------------------------------------ |
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\begin{document}
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\pagenumbering{roman}
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\pagestyle{empty}
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\begin{titlepage}
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\begin{center}
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\rule{\textwidth}{1.5mm}
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{\Huge\bf IgH \includegraphics[height=2.4ex]{images/ethercat}
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Master \masterversion\\[1ex] |
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Documentation} |
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\vspace{1ex}
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\rule{\textwidth}{1.5mm}
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\vspace{\fill}
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{\Large Florian Pose, \url{fp@igh-essen.com}\\[1ex]
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Ingenieurgemeinschaft \IgH} |
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\vspace{\fill}
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{\Large Essen, \SVNDate\\[1ex]
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Revision \SVNRevision} |
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\end{center}
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\end{titlepage}
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%------------------------------------------------------------------------------ |
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\tableofcontents |
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\listoftables |
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\listoffigures |
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\lstlistoflistings |
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%------------------------------------------------------------------------------ |
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\newpage |
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\pagestyle{scrheadings}
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\section*{Conventions}
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\addcontentsline{toc}{section}{Conventions}
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\markleft{Conventions}
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The following typographic conventions are used: |
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\begin{itemize}
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\item \textit{Italic face} is used for newly introduced terms and file names.
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\item \texttt{Typewriter face} is used for code examples and command line
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output. |
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\item \texttt{\textbf{Bold typewriter face}} is used for user input in command
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lines. |
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\end{itemize}
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Data values and addresses are usually specified as hexadecimal values. These |
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are marked in the \textit{C} programming language style with the prefix
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\lstinline+0x+ (example: \lstinline+0x88A4+). Unless otherwise noted, address |
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values are specified as byte addresses. |
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Function names are always printed with parentheses, but without |
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parameters. So, if a function \lstinline+ecrt_request_master()+ has |
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empty parentheses, this shall not imply that it has no parameters. |
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If shell commands have to be entered, this is marked by a dollar prompt: |
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\begin{lstlisting}
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$ |
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\end{lstlisting}
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Further, if a shell command has to be entered as the superuser, the |
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prompt is a mesh: |
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\begin{lstlisting}
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# |
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%------------------------------------------------------------------------------ |
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\chapter{The IgH EtherCAT Master}
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\label{chapter:master}
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\pagenumbering{arabic}
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This chapter covers some general information about the EtherCAT master. |
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%------------------------------------------------------------------------------ |
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\section{Feature Summary}
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\label{sec:summary}
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\index{Master!Features}
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The list below gives a short summary of the master features. |
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\item Designed as a kernel module for Linux 2.6. |
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\item Comes with EtherCAT-capable drivers for several common Ethernet devices. |
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\item The Ethernet hardware is operated without interrupts. |
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\item Drivers for additional Ethernet hardware can easily be implemented |
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using the common device interface (see section~\ref{sec:ecdev}) provided by
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the master module. |
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\end{itemize}
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\item The master module supports multiple EtherCAT masters running in |
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parallel. |
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\item The master code supports any Linux realtime extension through its |
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independent architecture. |
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\begin{itemize}
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\item RTAI\nomenclature{RTAI}{Realtime Application Interface},
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ADEOS\nomenclature{ADEOS}{Adaptive Domain Environment for Operating
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Systems}, etc. |
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\item It runs well even without realtime extensions. |
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\end{itemize}
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\item Common ``realtime interface'' for applications, that want to use |
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EtherCAT functionality (see section~\ref{sec:ecrt}).
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\item \textit{Domains} are introduced, to allow grouping of process
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data transfers with different slave groups and task periods. |
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\begin{itemize}
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\item Handling of multiple domains with different task periods. |
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\item Automatic calculation of process data mapping, FMMU and sync manager |
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configuration within each domain. |
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\end{itemize}
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\item Communication through several finite state machines. |
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\begin{itemize}
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\item Automatic bus scanning after topology changes. |
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\item Bus monitoring during operation. |
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\item Automatic reconfiguration of slaves (for example after power failure) |
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during operation. |
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\end{itemize}
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\item CANopen-over-EtherCAT (CoE) |
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\begin{itemize}
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\item Sdo upload, download and information service. |
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\item Slave configuration via Sdos. |
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\item Sdo access from user-space and from the application. |
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\end{itemize}
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\item Ethernet-over-EtherCAT (EoE) |
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\begin{itemize}
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\item Transparent use of EoE slaves via virtual network interfaces. |
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\item Natively supports either a switched or a routed EoE network |
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architecture. |
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\end{itemize}
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\item User space command-line-tool ``ethercat``. |
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\begin{itemize}
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\item Showing the current bus with slaves, Pdos and Sdos. |
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\item Showing the bus configuration. |
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\item Showing domains and process data. |
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\item Setting the master's debug level. |
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\item Writing alias addresses. |
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\item Sdo uploading/downloading. |
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\item Reading/writing a slave's SII. |
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\item Setting slave states. |
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\item Generate slave description XML. |
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\end{itemize}
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\item Seamless system integration though LSB\nomenclature{LSB}{Linux
|
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Standard Base} compliance. |
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\begin{itemize}
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\item Master and network device configuration via Sysconfig files. |
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\item Init script for master control. |
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\end{itemize}
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\item Virtual read-only network interface for monitoring and debugging |
328 |
purposes. |
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\end{itemize}
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331 |
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332 |
%------------------------------------------------------------------------------ |
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333 |
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334 |
\section{License}
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\label{sec:license}
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337 |
The master code is released under the terms and conditions of the GNU |
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338 |
General Public License\index{GPL} \cite{gpl} (version 2). Other
|
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339 |
developers, that want to use EtherCAT with Linux systems, are invited |
|
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to use the master code or even participate on development. |
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342 |
%------------------------------------------------------------------------------ |
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\chapter{Architecture}
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\label{sec:arch}
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\index{Master!Architecture}
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348 |
The EtherCAT master is integrated into the Linux 2.6 kernel. This was |
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an early design decision, which has been made for several reasons: |
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\item Kernel code has significantly better realtime characteristics, i.~e. |
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less latency than user space code. It was foreseeable, that a fieldbus master |
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has a lot of cyclic work to do. Cyclic work is usually triggered by timer |
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interrupts inside the kernel. The execution delay of a function that processes |
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timer interrupts is less, when it resides in kernel space, because there is no |
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need of time-consuming context switches to a user space process. |
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359 |
|
| 369 | 360 |
\item It was also foreseeable, that the master code has to directly |
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communicate with the Ethernet hardware. This has to be done in the kernel |
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anyway (through network device drivers), which is one more reason for the |
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master code being in kernel space. |
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|
| 369 | 365 |
\end{itemize}
|
366 |
||
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Figure~\ref{fig:arch} gives a general overview of the master architecture.
|
| 369 | 368 |
|
369 |
\begin{figure}[htbp]
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|
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\centering |
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\includegraphics[width=.9\textwidth]{images/architecture}
|
| 369 | 372 |
\caption{Master architecture}
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\label{fig:arch}
|
| 369 | 374 |
\end{figure}
|
375 |
||
376 |
\paragraph{Master Module}
|
|
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\index{Master module}
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|
378 |
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The EtherCAT master mainly consists of the master module, containing one or |
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more EtherCAT masters (section~\ref{sec:mastermod}), the ``Device Interface''
|
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(section~\ref{sec:ecdev}) and the ``Realtime Interface''
|
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(section~\ref{sec:ecrt}).
|
| 369 | 383 |
|
384 |
\paragraph{Device Modules}
|
|
385 |
\index{Device modules}
|
|
386 |
||
387 |
Furthermore there are EtherCAT-capable network device driver |
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modules\index{Device modules}, that connect to the EtherCAT master via the
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device interface. These modified network drivers can handle both network |
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devices used for EtherCAT operation and ``normal'' Ethernet devices. The |
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common case is, that the master module offers a single EtherCAT master: An |
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EtherCAT-capable network device driver module connects one network device to |
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this master, that is now able to send and receive EtherCAT frames, while all |
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other network devices handled by the network driver get connected to the |
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kernel's network stack as usual. |
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396 |
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\paragraph{Application Modules}
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398 |
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An application module''\index{Application module} is a kernel module, that
|
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uses the EtherCAT master (usually for cyclic exchange of process data with |
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EtherCAT slaves). These modules are not part of the EtherCAT master |
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code\footnote{Although there are some examples provided in the
|
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\textit{examples} directory, see chapter~\ref{chapter:usage}}, but have to be
|
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generated or written by the application engineer. An application module can |
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``request'' a master through the realtime interface (see |
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section~\ref{sec:ecrt}). If this succeeds, the module has the control over the
|
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master: It can provide a bus configuration and exchange process data. |
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|
408 |
|
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%------------------------------------------------------------------------------ |
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|
410 |
|
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\section{Phases}
|
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412 |
\index{Master phases}
|
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413 |
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The EtherCAT master has several phases (see fig.~\ref{fig:phases}):
|
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|
415 |
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\begin{figure}[htbp]
|
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\centering |
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\includegraphics[width=.9\textwidth]{images/phases}
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\caption{Master phases and transitions}
|
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\label{fig:phases}
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\end{figure}
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422 |
\begin{description}
|
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|
423 |
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\item[Orphaned phase]\index{Orphaned phase} This mode takes effect, when the
|
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master has no Ethernet device connected. No bus communication is possible. |
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|
426 |
|
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\item[Idle phase]\index{Idle phase} takes effect when the master has an
|
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Ethernet device connected, but is not requested by any application. The master |
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runs its state machine (see section~\ref{sec:fsm-master}), that automatically
|
|
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scans the bus for slaves and executes pending operations from the user space |
|
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431 |
interface (for example Sdo access). The command-line tool can be used to access |
|
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432 |
the bus, but there is no process data exchange because of the missing bus |
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configuration. |
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|
434 |
|
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\item[Operation phase]\index{Operation phase} The master is requested by an
|
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436 |
application that can provide a bus configuration and exchange process data. |
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|
437 |
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\end{description}
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439 |
|
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440 |
%------------------------------------------------------------------------------ |
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441 |
|
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\section{General behavior} % FIXME
|
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\index{Master behavior}
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444 |
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\ldots |
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446 |
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447 |
%------------------------------------------------------------------------------ |
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448 |
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\section{The Master Module} % FIXME
|
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\label{sec:mastermod}
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451 |
\index{Master module}
|
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452 |
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453 |
The EtherCAT master is designed to run as a kernel module. Moreover |
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454 |
the master kernel module \textit{ec\_master} can handle multiple
|
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masters at the same time: The number of masters has to be passed to |
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the module with the parameter \textit{ec\_master\_count}, that
|
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defaults to $1$. A certain master can later be addressed by its index. |
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458 |
For example, if the master module has been loaded with the command |
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459 |
|
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460 |
\begin{lstlisting}[gobble=2]
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# `\textbf{modprobe ec\_master ec\_master\_count=2}`
|
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462 |
\end{lstlisting}
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463 |
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464 |
the two masters can be addressed by their indices 0 and 1 respectively |
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(see figure~\ref{fig:masters}). This master index mandatory for
|
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466 |
certain functions of the master interfaces. |
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467 |
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468 |
\begin{figure}[htbp]
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469 |
\centering |
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470 |
\includegraphics[width=.5\textwidth]{images/masters}
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\caption{Multiple masters in one module}
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\label{fig:masters}
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473 |
\end{figure}
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474 |
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\paragraph{Master Log Messages}
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476 |
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477 |
The master module gives information about it's state and events via |
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478 |
the Syslog interface. The module loading command above should result |
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|
479 |
in the Syslog messages below (or similar): |
|
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|
480 |
|
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|
481 |
\begin{lstlisting}[gobble=2]
|
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482 |
EtherCAT: Master driver, 1.1 (stable) - rev. 513, |
|
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|
483 |
compiled by fp at Aug 09 2006 09:43:50 |
|
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|
484 |
EtherCAT: Initializing 2 EtherCAT master(s)... |
|
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|
485 |
EtherCAT: Initializing master 0. |
|
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|
486 |
EtherCAT: Initializing master 1. |
|
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|
487 |
EtherCAT: Master driver initialized. |
|
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|
488 |
\end{lstlisting}
|
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|
489 |
|
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|
490 |
The master provides information about it's version number, subversion |
|
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|
491 |
revision number and compile information, like the date of compilation |
|
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|
492 |
and the user, who compiled. All messages are prefixed either with |
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|
493 |
\texttt{EtherCAT:}, \texttt{EtherCAT WARNING:} or \texttt{EtherCAT
|
|
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|
494 |
ERROR:}, which makes searching the logs easier. |
|
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|
495 |
|
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|
496 |
%------------------------------------------------------------------------------ |
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|
497 |
|
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|
498 |
\section{Handling of Process Data} % FIXME
|
| 369 | 499 |
\label{sec:processdata}
|
500 |
||
|
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|
501 |
\ldots |
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502 |
|
| 369 | 503 |
\paragraph{Process Data Image}
|
504 |
\index{Process data}
|
|
505 |
||
|
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|
506 |
The slaves offer their inputs and outputs by presenting the master so-called |
|
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|
507 |
``Process Data Objects'' (Pdos\index{Pdo}). The available Pdos can be
|
|
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|
508 |
determined by reading out the slave's TXPDO and RXPDO E$^2$PROM categories. The |
|
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|
509 |
application can register the Pdos for data exchange during cyclic operation. |
|
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|
510 |
The sum of all registered Pdos defines the ``process data image'', which is |
|
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|
511 |
exchanged via the ``Logical ReadWrite'' datagrams introduced |
| 369 | 512 |
in~\cite[section~5.4.2.4]{dlspec}.
|
513 |
||
514 |
\paragraph{Process Data Domains}
|
|
515 |
\index{Domain}
|
|
516 |
||
|
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|
517 |
The process data image can be easily managed by creating so-called |
| 814 | 518 |
``domains'', which group Pdos and allocate the datagrams needed to |
| 369 | 519 |
exchange them. Domains are mandatory for process data exchange, so |
520 |
there has to be at least one. They were introduced for the following |
|
521 |
reasons: |
|
522 |
||
523 |
\begin{itemize}
|
|
524 |
\item The maximum size of a ``Logical ReadWrite'' datagram is limited |
|
525 |
due to the limited size of an Ethernet frame: The maximum data size |
|
526 |
is the Ethernet data field size minus the EtherCAT frame header, |
|
527 |
EtherCAT datagram header and EtherCAT datagram footer: $1500 - 2 - |
|
528 |
12 - 2 = 1484$ octets. If the size of the process data image exceeds |
|
529 |
this limit, multiple frames have to be sent, and the image has to be |
|
530 |
partitioned for the use of multiple datagrams. A domain manages this |
|
531 |
automatically. |
|
| 814 | 532 |
\item Not every Pdo has to be exchanged with the same frequency: The |
533 |
values of Pdos can vary slowly over time (for example temperature |
|
| 369 | 534 |
values), so exchanging them with a high frequency would just waste |
535 |
bus bandwidth. For this reason, multiple domains can be created, to |
|
| 814 | 536 |
group different Pdos and so allow separate exchange. |
| 369 | 537 |
\end{itemize}
|
538 |
||
539 |
There is no upper limit for the number of domains, but each domain |
|
540 |
occupies one FMMU in each slave involved, so the maximum number of |
|
541 |
domains is also limited by the slaves' capabilities. |
|
542 |
||
543 |
\paragraph{FMMU Configuration}
|
|
544 |
\index{FMMU!Configuration}
|
|
545 |
||
|
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|
546 |
An application can register Pdos for process data exchange. Every |
| 814 | 547 |
Pdo is part of a memory area in the slave's physical memory, that is |
| 369 | 548 |
protected by a sync manager \cite[section~6.7]{dlspec} for
|
549 |
synchronized access. In order to make a sync manager react on a |
|
550 |
datagram accessing its memory, it is necessary to access the last byte |
|
551 |
covered by the sync manager. Otherwise the sync manager will not react |
|
552 |
on the datagram and no data will be exchanged. That is why the whole |
|
553 |
synchronized memory area has to be included into the process data |
|
| 814 | 554 |
image: For example, if a certain Pdo of a slave is registered for |
| 369 | 555 |
exchange with a certain domain, one FMMU will be configured to map the |
| 814 | 556 |
complete sync-manager-protected memory, the Pdo resides in. If a |
557 |
second Pdo of the same slave is registered for process data exchange |
|
558 |
within the same domain, and this Pdo resides in the same |
|
559 |
sync-manager-protected memory as the first Pdo, the FMMU configuration |
|
| 369 | 560 |
is not touched, because the appropriate memory is already part of the |
| 814 | 561 |
domain's process data image. If the second Pdo belongs to another |
| 369 | 562 |
sync-manager-protected area, this complete area is also included into |
563 |
the domains process data image. See figure~\ref{fig:fmmus} for an
|
|
564 |
overview, how FMMU's are configured to map physical memory to logical |
|
565 |
process data images. |
|
566 |
||
567 |
\begin{figure}[htbp]
|
|
568 |
\centering |
|
569 |
\includegraphics[width=\textwidth]{images/fmmus}
|
|
|
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|
570 |
\caption{FMMU configuration for several domains}
|
| 369 | 571 |
\label{fig:fmmus}
|
572 |
\end{figure}
|
|
573 |
||
|
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|
574 |
\paragraph{Process Data Pointers} % FIXME
|
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|
575 |
|
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|
576 |
The figure also demonstrates the way, the application can access the exchanged |
|
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|
577 |
process data: At Pdo registration, the application has to provide the address |
|
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|
578 |
of a process data pointer. Upon calculation of the domain image and allocation |
|
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|
579 |
of process data memory, this pointer is redirected to the appropriate location |
|
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|
580 |
inside the domain's process data memory and can later be easily dereferenced by |
|
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|
581 |
the module code. |
|
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|
582 |
|
|
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|
583 |
%------------------------------------------------------------------------------ |
|
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|
584 |
|
|
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|
585 |
\chapter{Application Interface}
|
|
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|
586 |
\label{sec:ecrt}
|
|
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|
587 |
\index{Application interface}
|
|
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|
588 |
|
|
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|
589 |
%------------------------------------------------------------------------------ |
|
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|
590 |
|
|
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|
591 |
\section{The Realtime Interface} % FIXME move information to ecrt.h, reference
|
|
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|
592 |
\label{sec:ecrt}
|
|
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|
593 |
\index{Realtime interface}
|
|
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|
594 |
|
|
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|
595 |
The realtime interface provides functions and data structures for applications |
|
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|
596 |
to access and use an EtherCAT master. |
|
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|
597 |
|
|
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|
598 |
% \paragraph{Master Phases}
|
|
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|
599 |
% |
|
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|
600 |
% Every application should use the master in three phases: |
|
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|
601 |
% |
|
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|
602 |
% \begin{enumerate}
|
|
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|
603 |
% \item \textit{Startup} - The master is requested and the bus is
|
|
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|
604 |
% validated. Domains are created and Pdos are registered. Slave |
|
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|
605 |
% configurations are applied. |
|
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|
606 |
% \item \textit{Operation} - Cyclic code is run, process data is
|
|
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|
607 |
% exchanged and the master state machine is executed. |
|
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|
608 |
% \item \textit{Shutdown} - Cyclic code is stopped and the master
|
|
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|
609 |
% is released. |
|
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|
610 |
% \end{enumerate}
|
|
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|
611 |
|
|
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|
612 |
\subsubsection{Master Requesting and Releasing}
|
|
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|
613 |
|
|
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|
614 |
Before an application can access an EtherCAT master provided by the |
|
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|
615 |
master module, it has to reserve one for exclusive use. After use, it |
|
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|
616 |
has to release the requested master and make it available for other |
|
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|
617 |
modules. This is done with the following functions: |
|
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|
618 |
|
|
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|
619 |
\begin{lstlisting}[gobble=2,language=C]
|
|
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|
620 |
ec_master_t *ecrt_request_master(unsigned int master_index); |
|
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|
621 |
void ecrt_release_master(ec_master_t *master); |
|
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|
622 |
\end{lstlisting}
|
|
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changeset
|
623 |
|
|
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|
624 |
The \textit{ecrt\_request\_master()} function has to be the first function a
|
|
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|
625 |
module has to call, when using EtherCAT. The function takes the index of the |
|
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|
626 |
master as its argument. The first master has index 0, the $n$th master has |
|
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|
627 |
index $n - 1$. The number of existent masters has to be specified when loading |
|
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|
628 |
the master module (see section~\ref{sec:mastermod}). The function tries to
|
|
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|
629 |
reserve the specified master and scans for slaves. It returns a pointer to the |
|
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|
630 |
reserved master object upon success, or \textit{NULL} if an error occurred.
|
|
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|
631 |
|
|
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|
632 |
The \textit{ecrt\_release\_master()} function releases a reserved
|
|
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|
633 |
master after use. It takes the pointer to the master object returned |
|
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|
634 |
by \textit{ecrt\_request\_master()} as its argument and can never
|
|
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|
635 |
fail. |
|
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changeset
|
636 |
|
|
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|
637 |
\subsubsection{Master Methods}
|
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|
638 |
\label{sec:ecrt-master}
|
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|
639 |
|
|
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|
640 |
\paragraph{Domain Creation}
|
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|
641 |
|
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|
642 |
For process data exchange, at least one process data domain is needed |
|
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|
643 |
(see section~\ref{sec:processdata}).
|
|
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|
644 |
|
|
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|
645 |
\begin{lstlisting}[gobble=2,language=C]
|
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|
646 |
ec_domain_t *ecrt_master_create_domain(ec_master_t *master); |
|
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|
647 |
\end{lstlisting}
|
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|
648 |
|
|
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|
649 |
The \textit{ecrt\_master\_create\_domain()} method creates a new
|
|
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|
650 |
process data domain and returns a pointer to the new domain object. |
|
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|
651 |
This object can be used for registering process data objects and |
|
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|
652 |
exchange process data in cyclic operation. On failure, the function |
|
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|
653 |
returns \textit{NULL}.
|
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|
654 |
|
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|
655 |
\paragraph{Slave Handlers}
|
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|
656 |
|
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|
657 |
To access a certain slave, there is a method to get a slave handler: |
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|
658 |
|
|
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|
659 |
\begin{lstlisting}[gobble=2,language=C]
|
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|
660 |
ec_slave_t *ecrt_master_get_slave(const ec_master_t *, |
|
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|
661 |
const char *); |
|
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|
662 |
\end{lstlisting}
|
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|
663 |
|
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|
664 |
The \textit{ecrt\_master\_get\_slave()} method returns a pointer to a
|
|
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|
665 |
certain slave object, specified by its ASCII address (see |
|
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|
666 |
section~\ref{sec:addr}). If the address is invalid, \textit{NULL} is
|
|
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|
667 |
returned. |
|
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|
668 |
|
|
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|
669 |
\paragraph{Master Activation}
|
|
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|
670 |
|
|
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|
671 |
When all domains are created, and all process data objects are |
|
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|
672 |
registered, the master can be activated: |
|
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|
673 |
|
|
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|
674 |
\begin{lstlisting}[gobble=2,language=C]
|
|
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|
675 |
int ecrt_master_activate(ec_master_t *master); |
|
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|
676 |
void ecrt_master_deactivate(ec_master_t *master); |
|
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|
677 |
\end{lstlisting}
|
|
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changeset
|
678 |
|
|
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|
679 |
By calling the \textit{ecrt\_master\_activate()} method, all slaves
|
|
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|
680 |
are configured according to the prior method calls and are brought |
|
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|
681 |
into OP state. In this case, the method has a return value of 0. |
|
c75cdcc5ce87
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|
682 |
Otherwise (wrong configuration or bus failure) the method returns |
|
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|
683 |
non-zero. |
|
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|
684 |
|
|
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|
685 |
The \textit{ecrt\_master\_deactivate()} method is the counterpart to
|
|
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|
686 |
the activate call: It brings all slaves back into INIT state again. |
|
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|
687 |
This method should be called prior to |
|
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|
688 |
\textit{ecrt\_\-master\_\-release()}.
|
|
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|
689 |
|
|
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|
690 |
\paragraph{Locking Callbacks}
|
|
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|
691 |
|
|
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|
692 |
For concurrent master access, the application has to provide a locking |
|
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|
693 |
mechanism (see section~\ref{sec:concurr}):
|
|
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|
694 |
|
|
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|
695 |
\begin{lstlisting}[gobble=2,language=C]
|
|
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|
696 |
void ecrt_master_callbacks(ec_master_t *master, |
|
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|
697 |
int (*request_cb)(void *), |
|
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|
698 |
void (*release_cb)(void *), |
|
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|
699 |
void *cb_data); |
|
c75cdcc5ce87
Started to re-write the documentation.
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|
700 |
\end{lstlisting}
|
|
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changeset
|
701 |
|
|
c75cdcc5ce87
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parents:
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|
702 |
The ``request lock'' and ``release lock'' callbacks can be set with |
|
c75cdcc5ce87
Started to re-write the documentation.
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|
703 |
the \textit{ecrt\_master\_call\-backs()} method. It takes two function
|
|
c75cdcc5ce87
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changeset
|
704 |
pointers and a data value as additional arguments. The arbitrary data |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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|
705 |
value will be passed as argument on every callback. Asynchronous |
|
c75cdcc5ce87
Started to re-write the documentation.
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|
706 |
master access (like EoE processing) is only possible if these |
|
c75cdcc5ce87
Started to re-write the documentation.
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changeset
|
707 |
callbacks have been set. |
|
c75cdcc5ce87
Started to re-write the documentation.
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changeset
|
708 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
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changeset
|
709 |
\paragraph{Preparation of Cyclic Data Exchange}
|
|
c75cdcc5ce87
Started to re-write the documentation.
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|
710 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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|
711 |
Cyclic operation mostly consists of the three steps input, processing and |
|
c75cdcc5ce87
Started to re-write the documentation.
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|
712 |
output. In EtherCAT terms this would mean: Receive datagrams, evaluate process |
|
c75cdcc5ce87
Started to re-write the documentation.
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changeset
|
713 |
data and send datagrams. The first cycle differs from this principle, because |
|
c75cdcc5ce87
Started to re-write the documentation.
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changeset
|
714 |
no datagrams have been sent yet, so there is nothing to receive. To avoid |
|
c75cdcc5ce87
Started to re-write the documentation.
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changeset
|
715 |
having a case differentiation (in terms of an \textit{if} clause), the
|
|
c75cdcc5ce87
Started to re-write the documentation.
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|
716 |
following method exists: |
|
c75cdcc5ce87
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parents:
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changeset
|
717 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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changeset
|
718 |
\begin{lstlisting}[gobble=2,language=C]
|
|
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|
719 |
void ecrt_master_prepare(ec_master_t *master); |
|
c75cdcc5ce87
Started to re-write the documentation.
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changeset
|
720 |
\end{lstlisting}
|
|
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changeset
|
721 |
|
|
c75cdcc5ce87
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parents:
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changeset
|
722 |
As a last thing before cyclic operation, a call to the |
|
c75cdcc5ce87
Started to re-write the documentation.
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changeset
|
723 |
\textit{ecrt\_master\_prepare()} method should be issued. It makes all
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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changeset
|
724 |
process data domains queue their datagrams and issues a send command, |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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changeset
|
725 |
so that the first receive call in cyclic operation will not fail. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
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changeset
|
726 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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changeset
|
727 |
\paragraph{Frame Sending and Receiving}
|
|
c75cdcc5ce87
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changeset
|
728 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
729 |
To send all queued datagrams and to later receive the sent datagrams |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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changeset
|
730 |
there are two methods: |
|
c75cdcc5ce87
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parents:
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changeset
|
731 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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changeset
|
732 |
\begin{lstlisting}[gobble=2,language=C]
|
|
c75cdcc5ce87
Started to re-write the documentation.
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changeset
|
733 |
void ecrt_master_send(ec_master_t *master); |
|
c75cdcc5ce87
Started to re-write the documentation.
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changeset
|
734 |
void ecrt_master_receive(ec_master_t *master); |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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changeset
|
735 |
\end{lstlisting}
|
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
736 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
737 |
The \textit{ecrt\_master\_send()} method takes all datagrams, that
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
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changeset
|
738 |
have been queued for transmission, packs them into frames, and passes |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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changeset
|
739 |
them to the network device for sending. |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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changeset
|
740 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
741 |
The \textit{ecrt\_master\_receive()} queries the network device for
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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changeset
|
742 |
received frames (by calling the ISR\index{ISR}), extracts received
|
|
c75cdcc5ce87
Started to re-write the documentation.
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changeset
|
743 |
datagrams and dispatches the results to the datagram objects in the |
|
c75cdcc5ce87
Started to re-write the documentation.
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changeset
|
744 |
queue. Received datagrams, and the ones that timed out, will be |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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changeset
|
745 |
marked, and then dequeued. |
|
c75cdcc5ce87
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changeset
|
746 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
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changeset
|
747 |
\paragraph{Running the Operation State Machine}
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
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|
748 |
|
|
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|
749 |
The master's operation state machine (see section~\ref{sec:fsm-op})
|
|
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|
750 |
monitors the bus in cyclic operation and reconfigures slaves, if |
|
c75cdcc5ce87
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|
751 |
necessary. Therefore, the following method should be called |
|
c75cdcc5ce87
Started to re-write the documentation.
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|
752 |
cyclically: |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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|
753 |
|
|
c75cdcc5ce87
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parents:
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changeset
|
754 |
\begin{lstlisting}[gobble=2,language=C]
|
|
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|
755 |
void ecrt_master_run(ec_master_t *master); |
|
c75cdcc5ce87
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|
756 |
\end{lstlisting}
|
|
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changeset
|
757 |
|
|
c75cdcc5ce87
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changeset
|
758 |
The \textit{ecrt\_master\_run()} method executes the master's
|
|
c75cdcc5ce87
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changeset
|
759 |
operation state machine step by step. It returns after processing one |
|
c75cdcc5ce87
Started to re-write the documentation.
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changeset
|
760 |
state and queuing a datagram. Calling this function is not mandatory, |
|
c75cdcc5ce87
Started to re-write the documentation.
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|
761 |
but highly recommended. |
|
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|
762 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
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|
763 |
\paragraph{Master Monitoring}
|
|
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|
764 |
|
|
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|
765 |
It is also highly recommended to evaluate the master's error state. In |
|
c75cdcc5ce87
Started to re-write the documentation.
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|
766 |
this way it is possible to notice lost network links, failed bus |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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|
767 |
segments, and other issues: |
|
c75cdcc5ce87
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parents:
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changeset
|
768 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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changeset
|
769 |
\begin{lstlisting}[gobble=2,language=C]
|
|
c75cdcc5ce87
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|
770 |
int ecrt_master_state(const ec_master_t *master); |
|
c75cdcc5ce87
Started to re-write the documentation.
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changeset
|
771 |
\end{lstlisting}
|
|
c75cdcc5ce87
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changeset
|
772 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
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|
773 |
The \textit{ecrt\_master\_state()} method returns the master's error
|
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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changeset
|
774 |
state. The following states are defined as part of the realtime |
|
c75cdcc5ce87
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|
775 |
interface: |
| 369 | 776 |
|
777 |
\begin{description}
|
|
|
1085
c75cdcc5ce87
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|
778 |
\item[EC\_MASTER\_OK] means, that no error has occurred. |
|
c75cdcc5ce87
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parents:
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|
779 |
\item[EC\_MASTER\_LINK\_ERROR] means, that the network link is |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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changeset
|
780 |
currently down. |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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|
781 |
\item[EC\_MASTER\_BUS\_ERROR] means, that one or more slaves do not |
|
c75cdcc5ce87
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parents:
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changeset
|
782 |
respond. |
| 369 | 783 |
\end{description}
|
784 |
||
|
1085
c75cdcc5ce87
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|
785 |
\subsubsection{Domain Methods}
|
|
c75cdcc5ce87
Started to re-write the documentation.
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|
786 |
\label{sec:ecrt-domain}
|
|
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|
787 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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changeset
|
788 |
\paragraph{Pdo Registration}
|
|
c75cdcc5ce87
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changeset
|
789 |
|
|
c75cdcc5ce87
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Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
790 |
To access data of a slave's Pdo in cyclic operation, it is necessary |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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changeset
|
791 |
to make it part of a process data domain: |
|
c75cdcc5ce87
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Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
792 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
793 |
\begin{lstlisting}[gobble=2,language=C]
|
|
c75cdcc5ce87
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Florian Pose <fp@igh-essen.com>
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|
794 |
ec_slave_t *ecrt_domain_register_pdo(ec_domain_t *domain, |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
795 |
const char *address, |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
796 |
uint32_t vendor_id, |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
797 |
uint32_t product_code, |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
798 |
const char *pdo_name |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
799 |
void **data_ptr); |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
800 |
int ecrt_domain_register_pdo_list(ec_domain_t *domain, |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
801 |
const ec_pdo_reg_t *pdos); |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
802 |
\end{lstlisting}
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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changeset
|
803 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
804 |
The \textit{ecrt\_domain\_register\_pdo()} method registers a certain
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
805 |
Pdo as part of the domain and takes the address of the process data |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
806 |
pointer. This pointer will be set on master activation and then can be |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
807 |
parameter to the \textit{EC\_READ\_*} and \textit{EC\_WRITE\_*} macros
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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changeset
|
808 |
described below. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
809 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
810 |
A perhaps easier way to register multiple Pdos at the same time is to |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
811 |
fill an array of \textit{ec\_pdo\_reg\_t} and hand it to the
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
812 |
\textit{ecrt\_domain\_register\_pdo\_list()} method. Attention: This
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
813 |
array has to be terminated by an empty structure (\textit{\{\}})!
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
814 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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changeset
|
815 |
\paragraph{Evaluating Domain Data}
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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changeset
|
816 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
817 |
To evaluate domain data, the following method has to be used: |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
818 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
819 |
\begin{lstlisting}[gobble=2,language=C]
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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changeset
|
820 |
void ecrt_domain_process(ec_domain_t *domain); |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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changeset
|
821 |
\end{lstlisting}
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
822 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
823 |
The \textit{ecrt\_domain\_process()} method sets the domains state and
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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changeset
|
824 |
re-queues its datagram for sending. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
825 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
826 |
\paragraph{Domain State}
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
827 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
828 |
Similar to the master state, a domain has an own error state: |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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changeset
|
829 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
830 |
\begin{lstlisting}[gobble=2,language=C]
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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changeset
|
831 |
int ecrt_domain_state(const ec_domain_t *domain); |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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changeset
|
832 |
\end{lstlisting}
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
833 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
834 |
The \textit{ecrt\_domain\_state()} method returns the domain's error state. It
|
|
c75cdcc5ce87
Started to re-write the documentation.
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changeset
|
835 |
is non-zero if \textbf{not} all process data values could be exchanged, and
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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changeset
|
836 |
zero otherwise. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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changeset
|
837 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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changeset
|
838 |
\subsubsection{Slave Methods}
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
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changeset
|
839 |
\label{sec:ecrt-slave}
|
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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changeset
|
840 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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changeset
|
841 |
\paragraph{Sdo Configuration}
|
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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changeset
|
842 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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changeset
|
843 |
To configure slave Sdos, the function interface below can be used: |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
844 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
845 |
\begin{lstlisting}[gobble=2,language=C]
|
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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changeset
|
846 |
int ecrt_slave_conf_sdo8(ec_slave_t *slave, |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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changeset
|
847 |
uint16_t sdo_index, |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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changeset
|
848 |
uint8_t sdo_subindex, |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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changeset
|
849 |
uint8_t value); |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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changeset
|
850 |
int ecrt_slave_conf_sdo16(ec_slave_t *slave, |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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changeset
|
851 |
uint16_t sdo_index, |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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changeset
|
852 |
uint8_t sdo_subindex, |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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changeset
|
853 |
uint16_t value); |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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changeset
|
854 |
int ecrt_slave_conf_sdo32(ec_slave_t *slave, |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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changeset
|
855 |
uint16_t sdo_index, |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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changeset
|
856 |
uint8_t sdo_subindex, |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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changeset
|
857 |
uint32_t value); |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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changeset
|
858 |
\end{lstlisting}
|
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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changeset
|
859 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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changeset
|
860 |
The \textit{ecrt\_slave\_conf\_sdo*()} methods prepare the configuration of a
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
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changeset
|
861 |
certain Sdo. The index and subindex of the Sdo, and the value have to be |
|
c75cdcc5ce87
Started to re-write the documentation.
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changeset
|
862 |
specified. The configuration is done each time, the slave is reconfigured. The |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
863 |
methods only differ in the Sdo's data type. If the configuration could be |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
864 |
prepared, zero is returned. If an error occurred, non-zero is returned. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
865 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
866 |
\paragraph{Variable-sized Pdos}
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
867 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
868 |
For specifying the size of variable-sized Pdos, the following method |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
869 |
can be used: |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
870 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
871 |
\begin{lstlisting}[gobble=2,language=C]
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
872 |
int ecrt_slave_pdo_size(ec_slave_t *slave, |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
873 |
const char *pdo_name, |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
874 |
size_t size); |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
875 |
\end{lstlisting}
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
876 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
877 |
The \textit{ecrt\_slave\_pdo\_size()} method takes the name of the Pdo
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
878 |
and the size. It returns zero on success, otherwise non-zero. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
879 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
880 |
\subsubsection{Process Data Access}
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
881 |
\label{sec:macros}
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
882 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
883 |
The endianess of the process data could differ from that of the CPU. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
884 |
Therefore, process data access has to be done by the macros below, |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
885 |
that are also provided by the realtime interface: |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
886 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
887 |
\begin{lstlisting}[gobble=2,language=C]
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
888 |
#define EC_READ_BIT(DATA, POS) |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
889 |
#define EC_WRITE_BIT(DATA, POS, VAL) |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
890 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
891 |
#define EC_READ_U8(DATA) |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
892 |
#define EC_READ_S8(DATA) |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
893 |
#define EC_READ_U16(DATA) |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
894 |
#define EC_READ_S16(DATA) |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
895 |
#define EC_READ_U32(DATA) |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
896 |
#define EC_READ_S32(DATA) |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
897 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
898 |
#define EC_WRITE_U8(DATA, VAL) |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
899 |
#define EC_WRITE_S8(DATA, VAL) |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
900 |
#define EC_WRITE_U16(DATA, VAL) |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
901 |
#define EC_WRITE_S16(DATA, VAL) |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
902 |
#define EC_WRITE_U32(DATA, VAL) |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
903 |
#define EC_WRITE_S32(DATA, VAL) |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
904 |
\end{lstlisting}
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
905 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
906 |
There are macros for bitwise access (\textit{EC\_READ\_BIT()},
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
907 |
\textit{EC\_WRITE\_BIT()}), and byte-wise access (\textit{EC\_READ\_*()},
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
908 |
\textit{EC\_WRITE\_*()}). The byte-wise macros carry the data type in their
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
909 |
name. Example: \textit{EC\_WRITE\_S16()} writes a 16 bit signed value to
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
910 |
EtherCAT data. The \textit{DATA} parameter is supposed to be a process data
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
911 |
pointer, as provided at Pdo registration. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
912 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
913 |
The macros use the kernel's endianess conversion macros, that are |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
914 |
preprocessed to empty macros in case of equal endianess. This is the |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
915 |
definition for the \textit{EC\_\-READ\_\-U16()} macro:
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
916 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
917 |
\begin{lstlisting}[gobble=2,language=C]
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
918 |
#define EC_READ_U16(DATA) \ |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
919 |
((uint16_t) le16_to_cpup((void *) (DATA))) |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
920 |
\end{lstlisting}
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
921 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
922 |
The \textit{le16\_to\_cpup()} macro converts a little-endian, 16 bit
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
923 |
value to the CPU's architecture and takes a pointer to the input value |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
924 |
as its argument. If the CPU's architecture is little-endian, too (for |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
925 |
example on X86 and compatible), nothing has to be converted. In this |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
926 |
case, the macro is replaced with an empty macro by the preprocessor |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
927 |
and so there is no unneeded function call or case differentiation in |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
928 |
the code. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
929 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
930 |
For keeping it portable, it is highly recommended to make use of these |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
931 |
macros. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
932 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
933 |
%------------------------------------------------------------------------------ |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
934 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
935 |
\subsection{Slave Addressing}
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
936 |
\label{sec:addr}
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
937 |
\index{Slave!Addressing}
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
938 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
939 |
The master offers the several slave addressing schemes (for Pdo |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
940 |
registration or configuration) via the realtime interface. For this |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
941 |
reason, slave addresses are ASCII\nomenclature{ASCII}{American
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
942 |
Standard Code for Information Interchange}-coded and passed as a |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
943 |
string. The addressing schemes are independent of the EtherCAT |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
944 |
protocol and represent an additional feature of the master. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
945 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
946 |
Below, the allowed addressing schemes are described. The descriptions |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
947 |
are followed by a regular expression formally defining the addressing |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
948 |
scheme, and one or more examples. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
949 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
950 |
\begin{description}
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
951 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
952 |
\item[Position Addressing] This is the normal addressing scheme, where each |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
953 |
slave is addressed by its ring position. The first slave has address 0, and the |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
954 |
$n$th slave has address $n - 1$. This addressing scheme is useful for small |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
955 |
buses that have a fixed number of slaves. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
956 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
957 |
RegEx: \texttt{[0-9]+} --- Example: \texttt{"42"}
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
958 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
959 |
\item[Advanced Position Addressing] Bus couplers segment the bus into |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
960 |
(physical) blocks. Though the logical ring positions keep being the same, it is |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
961 |
easier to address a slave with its block number and the relative position |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
962 |
inside the block. This addressing is done by passing the (zero-based) index of |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
963 |
the bus coupler (not the coupler's ring position), followed by a colon and the |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
964 |
relative position of the actual slave starting at the bus coupler. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
965 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
966 |
RegEx: \texttt{[0-9]+:[0-9]+} --- Examples: \texttt{"0:42"}, \texttt{"2:7"}
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
967 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
968 |
\item[Alias Addressing] Each slave can have a ``secondary slave address'' or |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
969 |
``alias address''\footnote{Information about how to set the alias can be found
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
970 |
in section~\ref{sec:eepromaccess}} stored in its E$^2$PROM. The alias is
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
971 |
evaluated by the master and can be used to address the slave, which is useful |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
972 |
when a clearly defined slave has to be addressed and the ring position is not |
|
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|
973 |
known or can change over time. This scheme is used by starting the address |
|
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changeset
|
974 |
string with a mesh (\#) followed by the alias address. The latter can also be |
|
c75cdcc5ce87
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|
975 |
provided as hexadecimal value, prefixed with \textit{0x}.
|
|
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changeset
|
976 |
|
|
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Started to re-write the documentation.
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diff
changeset
|
977 |
RegEx: \texttt{\#(0x[0-9A-F]+|[0-9]+)} --- Examples: \texttt{"\#6622"},
|
|
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changeset
|
978 |
\texttt{"\#0xBEEF"}
|
|
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changeset
|
979 |
|
|
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|
980 |
\item[Advanced Alias Addressing] This is a mixture of the ``Alias Addressing'' |
|
c75cdcc5ce87
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|
981 |
and ``Advanced Position Addressing'' schemes. A certain slave is addressed by |
|
c75cdcc5ce87
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|
982 |
specifying its relative position after an aliased slave. This is very useful, |
|
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|
983 |
if a complete block of slaves can vary its position in the bus. The bus coupler |
|
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|
984 |
preceding the block should get an alias. The block slaves can then be addressed |
|
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|
985 |
by specifying this alias and their position inside the block. This scheme is |
|
c75cdcc5ce87
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|
986 |
used by starting the address string with a mesh (\#) followed by the alias |
|
c75cdcc5ce87
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changeset
|
987 |
address (which can be hexadecimal), then a colon and the relative position of |
|
c75cdcc5ce87
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changeset
|
988 |
the slave to address. |
|
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|
989 |
|
|
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Started to re-write the documentation.
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parents:
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changeset
|
990 |
RegEx: \texttt{\#(0x[0-9A-F]+|[0-9]+):[0-9]+} --- Examples:
|
|
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parents:
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|
991 |
\texttt{"\#0xBEEF:7"}, \texttt{"\#6:2"}
|
|
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|
992 |
|
|
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|
993 |
\end{description}
|
|
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changeset
|
994 |
|
|
c75cdcc5ce87
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changeset
|
995 |
In anticipation of section~\ref{sec:ecrt}, the functions accepting
|
|
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changeset
|
996 |
these address strings are \textit{ecrt\_\-master\_\-get\_slave()},
|
|
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changeset
|
997 |
\textit{ecrt\_domain\_register\_pdo()} and
|
|
c75cdcc5ce87
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changeset
|
998 |
\textit{ecrt\_domain\_register\_pdo\_list()} (the latter through the
|
|
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|
999 |
\textit{ec\_pdo\_reg\_t} structure).
|
|
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changeset
|
1000 |
|
|
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|
1001 |
%------------------------------------------------------------------------------ |
|
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|
1002 |
|
|
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|
1003 |
\subsection{Concurrent Master Access}
|
|
c75cdcc5ce87
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changeset
|
1004 |
\label{sec:concurr}
|
|
c75cdcc5ce87
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changeset
|
1005 |
\index{Concurrency}
|
|
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changeset
|
1006 |
|
|
c75cdcc5ce87
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|
1007 |
In some cases, one master is used by several instances, for example when an |
|
c75cdcc5ce87
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parents:
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|
1008 |
application does cyclic process data exchange, and there are EoE-capable slaves |
|
c75cdcc5ce87
Started to re-write the documentation.
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|
1009 |
that require to exchange Ethernet data with the kernel (see |
|
c75cdcc5ce87
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|
1010 |
section~\ref{sec:eoeimp}). For this reason, the master is a shared resource,
|
|
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|
1011 |
and access to it has to be sequentialized. This is usually done by locking with |
|
c75cdcc5ce87
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|
1012 |
semaphores, or other methods to protect critical sections. |
|
c75cdcc5ce87
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changeset
|
1013 |
|
|
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|
1014 |
The master itself can not provide locking mechanisms, because it has no chance |
|
c75cdcc5ce87
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changeset
|
1015 |
to know the appropriate kind of lock. Imagine, the application uses RTAI |
|
c75cdcc5ce87
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|
1016 |
functionality, then ordinary kernel semaphores would not be sufficient. For |
|
c75cdcc5ce87
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|
1017 |
that, an important design decision was made: The application that reserved a |
|
c75cdcc5ce87
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|
1018 |
master must have the total control, therefore it has to take responsibility for |
|
c75cdcc5ce87
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|
1019 |
providing the appropriate locking mechanisms. If another instance wants to |
|
c75cdcc5ce87
Started to re-write the documentation.
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changeset
|
1020 |
access the master, it has to request the master lock by callbacks, that have to |
|
c75cdcc5ce87
Started to re-write the documentation.
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|
1021 |
be set by the application. Moreover the application can deny access to the |
|
c75cdcc5ce87
Started to re-write the documentation.
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|
1022 |
master if it considers it to be awkward at the moment. |
| 369 | 1023 |
|
1024 |
\begin{figure}[htbp]
|
|
1025 |
\centering |
|
|
1085
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|
1026 |
\includegraphics[width=.6\textwidth]{images/master-locks}
|
|
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Started to re-write the documentation.
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|
1027 |
\caption{Concurrent master access}
|
|
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|
1028 |
\label{fig:locks}
|
| 369 | 1029 |
\end{figure}
|
1030 |
||
|
1085
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|
1031 |
Figure~\ref{fig:locks} exemplary shows, how two processes share one master: The
|
|
c75cdcc5ce87
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|
1032 |
application's cyclic task uses the master for process data exchange, while the |
|
c75cdcc5ce87
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|
1033 |
master-internal EoE process uses it to communicate with EoE-capable slaves. |
|
c75cdcc5ce87
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|
1034 |
Both have to acquire the master lock before access: The application task can |
|
c75cdcc5ce87
Started to re-write the documentation.
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changeset
|
1035 |
access the lock natively, while the EoE process has to use the callbacks. |
|
c75cdcc5ce87
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|
1036 |
Section~\ref{sec:concurrency} gives an example, of how to implement this.
|
|
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|
1037 |
|
|
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|
1038 |
%------------------------------------------------------------------------------ |
|
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|
1039 |
|
|
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|
1040 |
\chapter{Ethernet devices}
|
|
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|
1041 |
\label{sec:devices}
|
|
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|
1042 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
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changeset
|
1043 |
The EtherCAT protocol is based on the Ethernet standard. That's why the master |
|
c75cdcc5ce87
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|
1044 |
relies on standard Ethernet hardware to communicate with the bus. |
|
c75cdcc5ce87
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changeset
|
1045 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
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diff
changeset
|
1046 |
The term \textit{device} is used as a synonym for Ethernet network interface
|
|
c75cdcc5ce87
Started to re-write the documentation.
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|
1047 |
hardware. There are device driver modules that handle Ethernet hardware, which |
|
c75cdcc5ce87
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changeset
|
1048 |
the master can use to connect to an EtherCAT bus. |
| 369 | 1049 |
|
1050 |
Section~\ref{sec:networkdrivers} offers an overview of general Linux
|
|
1051 |
network driver modules, while section~\ref{sec:requirements} will show
|
|
1052 |
the requirements to an EtherCAT-enabled network driver. Finally, |
|
1053 |
sections~\ref{sec:seldev} to~\ref{sec:patching} show how to fulfill
|
|
1054 |
these requirements and implement such a driver module. |
|
1055 |
||
1056 |
%------------------------------------------------------------------------------ |
|
1057 |
||
|
1085
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|
1058 |
\section{Network Driver Basics}
|
| 369 | 1059 |
\label{sec:networkdrivers}
|
1060 |
\index{Network drivers}
|
|
1061 |
||
1062 |
EtherCAT relies on Ethernet hardware and the master needs a physical |
|
1063 |
Ethernet device to communicate with the bus. Therefore it is necessary |
|
1064 |
to understand how Linux handles network devices and their drivers, |
|
1065 |
respectively. |
|
1066 |
||
1067 |
\paragraph{Tasks of a Network Driver}
|
|
1068 |
||
1069 |
Network device drivers handle the lower two layers of the OSI model, |
|
1070 |
that is the physical layer and the data-link layer. A network device |
|
1071 |
itself natively handles the physical layer issues: It represents the |
|
1072 |
hardware to connect to the medium and to send and receive data in the |
|
1073 |
way, the physical layer protocol describes. The network device driver |
|
1074 |
is responsible for getting data from the kernel's networking stack and |
|
1075 |
forwarding it to the hardware, that does the physical transmission. |
|
1076 |
If data is received by the hardware respectively, the driver is |
|
1077 |
notified (usually by means of an interrupt) and has to read the data |
|
1078 |
from the hardware memory and forward it to the network stack. There |
|
1079 |
are a few more tasks, a network device driver has to handle, including |
|
1080 |
queue control, statistics and device dependent features. |
|
1081 |
||
1082 |
\paragraph{Driver Startup}
|
|
1083 |
||
1084 |
Usually, a driver searches for compatible devices on module loading. |
|
1085 |
For PCI drivers, this is done by scanning the PCI bus and checking for |
|
1086 |
known device IDs. If a device is found, data structures are allocated |
|
1087 |
and the device is taken into operation. |
|
1088 |
||
1089 |
\paragraph{Interrupt Operation}
|
|
1090 |
\index{Interrupt}
|
|
1091 |
||
1092 |
A network device usually provides a hardware interrupt that is used to |
|
|
1085
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|
1093 |
notify the driver of received frames and success of transmission, or |
| 369 | 1094 |
errors, respectively. The driver has to register an interrupt service |
1095 |
routine (ISR\index{ISR}\nomenclature{ISR}{Interrupt Service Routine}),
|
|
1096 |
that is executed each time, the hardware signals such an event. If the |
|
1097 |
interrupt was thrown by the own device (multiple devices can share one |
|
1098 |
hardware interrupt), the reason for the interrupt has to be determined |
|
1099 |
by reading the device's interrupt register. For example, if the flag |
|
1100 |
for received frames is set, frame data has to be copied from hardware |
|
1101 |
to kernel memory and passed to the network stack. |
|
1102 |
||
1103 |
\paragraph{The net\_device structure}
|
|
1104 |
\index{net\_device}
|
|
1105 |
||
1106 |
The driver registers a \textit{net\_device} structure for each device
|
|
1107 |
to communicate with the network stack and to create a ``network |
|
1108 |
interface''. In case of an Ethernet driver, this interface appears as |
|
1109 |
\textit{ethX}, where X is a number assigned by the kernel on
|
|
1110 |
registration. The \textit{net\_device} structure receives events
|
|
|
1085
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|
1111 |
(either from user space or from the network stack) via several |
| 369 | 1112 |
callbacks, which have to be set before registration. Not every |
1113 |
callback is mandatory, but for reasonable operation the ones below are |
|
1114 |
needed in any case: |
|
1115 |
||
1116 |
\begin{description}
|
|
1117 |
\item[int (*open)(struct net\_device *)] This function is called when |
|
1118 |
network communication has to be started, for example after a command |
|
1119 |
\textit{ifconfig ethX up} from user space. Frame reception has to be
|
|
1120 |
enabled by the driver. |
|
1121 |
\item[int (*stop)(struct net\_device *)] The purpose of this callback |
|
1122 |
is to ``close'' the device, i.~e. make the hardware stop receiving |
|
1123 |
frames. |
|
1124 |
\item[int (*hard\_start\_xmit)(struct sk\_buff *, struct net\_device |
|
1125 |
*)] This function is cal\-led for each frame that has to be |
|
1126 |
transmitted. The network stack passes the frame as a pointer to an |
|
1127 |
\textit{sk\_buff} structure (``socket buffer''\index{Socket buffer},
|
|
1128 |
see below), which has to be freed after sending. |
|
1129 |
\item[struct net\_device\_stats *(*get\_stats)(struct net\_device *)] |
|
1130 |
This call has to return a pointer to the device's |
|
1131 |
\textit{net\_device\_stats} structure, which permanently has to be
|
|
|
1085
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|
1132 |
filled with frame statistics. This means, that every time a frame is |
| 369 | 1133 |
received, sent, or an error happened, the appropriate counter in |
1134 |
this structure has to be increased. |
|
1135 |
\end{description}
|
|
1136 |
||
1137 |
The actual registration is done with the \textit{register\_netdev()}
|
|
1138 |
call, unregistering is done with \textit{unregister\_netdev()}.
|
|
1139 |
||
1140 |
\paragraph{The netif Interface}
|
|
1141 |
\index{netif}
|
|
1142 |
||
|
1085
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|
1143 |
All other communication in the direction interface $\to$ network stack is done |
|
c75cdcc5ce87
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|
1144 |
via the \textit{netif\_*} calls. For example, on successful device opening, the
|
|
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Started to re-write the documentation.
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|
1145 |
network stack has to be notified, that it can now pass frames to the interface. |
|
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|
1146 |
This is done by calling \textit{netif\_start\_queue()}. After this call, the
|
|
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changeset
|
1147 |
\textit{hard\_start\_xmit()} callback can be called by the network stack.
|
|
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|
1148 |
Furthermore a network driver usually manages a frame transmission queue. If |
|
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changeset
|
1149 |
this gets filled up, the network stack has to be told to stop passing further |
|
c75cdcc5ce87
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changeset
|
1150 |
frames for a while. This happens with a call to \textit{netif\_stop\_queue()}.
|
|
c75cdcc5ce87
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changeset
|
1151 |
If some frames have been sent, and there is enough space again to queue new |
|
c75cdcc5ce87
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diff
changeset
|
1152 |
frames, this can be notified with \textit{netif\_wake\_queue()}. Another
|
|
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diff
changeset
|
1153 |
important call is \textit{netif\_receive\_skb()}\footnote{This function is part
|
|
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changeset
|
1154 |
of the NAPI (``New API''), that replaces the ``old'' kernel 2.4 technique for |
|
c75cdcc5ce87
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changeset
|
1155 |
interfacing to the network stack (with \textit{netif\_rx()}). NAPI is a
|
|
c75cdcc5ce87
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|
1156 |
technique to improve network performance on Linux. Read more in |
|
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|
1157 |
\url{http://www.cyberus.ca/~hadi/usenix-paper.tgz}}: It passes a frame to the
|
|
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changeset
|
1158 |
network stack, that was just received by the device. Frame data has to be |
|
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|
1159 |
packed into a so-called ``socket buffer'' for that (see below). |
| 369 | 1160 |
|
1161 |
\paragraph{Socket Buffers}
|
|
1162 |
\index{Socket buffer}
|
|
1163 |
||
1164 |
Socket buffers are the basic data type for the whole network stack. |
|
1165 |
They serve as containers for network data and are able to quickly add |
|
1166 |
data headers and footers, or strip them off again. Therefore a socket |
|
|
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|
1167 |
buffer consists of an allocated buffer and several pointers that mark |
| 369 | 1168 |
beginning of the buffer (\textit{head}), beginning of data
|
1169 |
(\textit{data}), end of data (\textit{tail}) and end of buffer
|
|
1170 |
(\textit{end}). In addition, a socket buffer holds network header
|
|
1171 |
information and (in case of received data) a pointer to the |
|
1172 |
\textit{net\_device}, it was received on. There exist functions that
|
|
1173 |
create a socket buffer (\textit{dev\_alloc\_skb()}), add data either
|
|
1174 |
from front (\textit{skb\_push()}) or back (\textit{skb\_put()}),
|
|
1175 |
remove data from front (\textit{skb\_pull()}) or back
|
|
1176 |
(\textit{skb\_trim()}), or delete the buffer (\textit{kfree\_skb()}).
|
|
1177 |
A socket buffer is passed from layer to layer, and is freed by the |
|
1178 |
layer that uses it the last time. In case of sending, freeing has to |
|
1179 |
be done by the network driver. |
|
1180 |
||
1181 |
%------------------------------------------------------------------------------ |
|
1182 |
||
|
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|
1183 |
\section{EtherCAT Device Drivers}
|
| 369 | 1184 |
\label{sec:requirements}
|
1185 |
||
1186 |
There are a few requirements for Ethernet network devices to function |
|
1187 |
as EtherCAT devices, when connected to an EtherCAT bus. |
|
1188 |
||
1189 |
\paragraph{Dedicated Interfaces}
|
|
1190 |
||
1191 |
For performance and realtime purposes, the EtherCAT master needs |
|
1192 |
direct and exclusive access to the Ethernet hardware. This implies |
|
1193 |
that the network device must not be connected to the kernel's network |
|
1194 |
stack as usual, because the kernel would try to use it as an ordinary |
|
1195 |
Ethernet device. |
|
1196 |
||
1197 |
\paragraph{Interrupt-less Operation}
|
|
1198 |
\index{Interrupt}
|
|
1199 |
||
1200 |
EtherCAT frames travel through the logical EtherCAT ring and are then |
|
1201 |
sent back to the master. Communication is highly deterministic: A |
|
1202 |
frame is sent and will be received again after a constant time. |
|
1203 |
Therefore, there is no need to notify the driver about frame |
|
1204 |
reception: The master can instead query the hardware for received |
|
1205 |
frames. |
|
1206 |
||
1207 |
Figure~\ref{fig:interrupt} shows two workflows for cyclic frame
|
|
|
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|
1208 |
transmission and reception with and without interrupts. |
| 369 | 1209 |
|
1210 |
\begin{figure}[htbp]
|
|
1211 |
\centering |
|
1212 |
\includegraphics[width=.8\textwidth]{images/interrupt}
|
|
1213 |
\caption{Interrupt Operation versus Interrupt-less Operation}
|
|
1214 |
\label{fig:interrupt}
|
|
1215 |
\end{figure}
|
|
1216 |
||
1217 |
In the left workflow ``Interrupt Operation'', the data from the last |
|
1218 |
cycle is first processed and a new frame is assembled with new |
|
1219 |
datagrams, which is then sent. The cyclic work is done for now. |
|
1220 |
Later, when the frame is received again by the hardware, an interrupt |
|
1221 |
is triggered and the ISR is executed. The ISR will fetch the frame |
|
1222 |
data from the hardware and initiate the frame dissection: The |
|
1223 |
datagrams will be processed, so that the data is ready for processing |
|
1224 |
in the next cycle. |
|
1225 |
||
1226 |
In the right workflow ``Interrupt-less Operation'', there is no |
|
1227 |
hardware interrupt enabled. Instead, the hardware will be polled by |
|
1228 |
the master by executing the ISR. If the frame has been received in the |
|
1229 |
meantime, it will be dissected. The situation is now the same as at |
|
1230 |
the beginning of the left workflow: The received data is processed and |
|
1231 |
a new frame is assembled and sent. There is nothing to do for the rest |
|
1232 |
of the cycle. |
|
1233 |
||
1234 |
The interrupt-less operation is desirable, because there is simply no |
|
1235 |
need for an interrupt. Moreover hardware interrupts are not conducive |
|
|
1085
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|
1236 |
in improving the driver's realtime behaviour: Their indeterministic |
| 369 | 1237 |
incidences contribute to increasing the jitter. Besides, if a realtime |
1238 |
extension (like RTAI) is used, some additional effort would have to be |
|
|
1085
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|
1239 |
made to prioritize interrupts. |
| 369 | 1240 |
|
1241 |
\paragraph{Ethernet and EtherCAT Devices}
|
|
1242 |
||
1243 |
Another issue lies in the way Linux handles devices of the same type. |
|
1244 |
For example, a PCI\nomenclature{PCI}{Peripheral Component
|
|
1245 |
Interconnect, Computer Bus} driver scans the PCI bus for devices it |
|
1246 |
can handle. Then it registers itself as the responsible driver for all |
|
1247 |
of the devices found. The problem is, that an unmodified driver can |
|
1248 |
not be told to ignore a device because it will be used for EtherCAT |
|
1249 |
later. There must be a way to handle multiple devices of the same |
|
1250 |
type, where one is reserved for EtherCAT, while the other is treated |
|
1251 |
as an ordinary Ethernet device. |
|
1252 |
||
1253 |
For all this reasons, the author has decided that the only acceptable |
|
1254 |
solution is to modify standard Ethernet drivers in a way that they |
|
1255 |
keep their normal functionality, but gain the ability to treat one or |
|
1256 |
more of the devices as EtherCAT-capable. |
|
1257 |
||
1258 |
Below are the advantages of this solution: |
|
1259 |
||
1260 |
\begin{itemize}
|
|
1261 |
\item No need to tell the standard drivers to ignore certain devices. |
|
1262 |
\item One networking driver for EtherCAT and non-EtherCAT devices. |
|
1263 |
\item No need to implement a network driver from scratch and running |
|
1264 |
into issues, the former developers already solved. |
|
1265 |
\end{itemize}
|
|
1266 |
||
1267 |
The chosen approach has the following disadvantages: |
|
1268 |
||
1269 |
\begin{itemize}
|
|
1270 |
\item The modified driver gets more complicated, as it must handle |
|
1271 |
EtherCAT and non-EtherCAT devices. |
|
1272 |
\item Many additional case differentiations in the driver code. |
|
|
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|
1273 |
\item Changes and bug fixes on the standard drivers have to be ported |
| 369 | 1274 |
to the Ether\-CAT-capable versions from time to time. |
1275 |
\end{itemize}
|
|
1276 |
||
1277 |
%------------------------------------------------------------------------------ |
|
1278 |
||
|
1085
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changeset
|
1279 |
\section{Device Selection}
|
|
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|
1280 |
\label{sec:deviceselection}
|
| 369 | 1281 |
|
1282 |
After loading the master module, at least one EtherCAT-capable network |
|
1283 |
driver module has to be loaded, that connects one of its devices to |
|
1284 |
the master. To specify an EtherCAT device and the master to connect |
|
1285 |
to, all EtherCAT-capable network driver modules should provide two |
|
1286 |
module parameters: |
|
1287 |
||
1288 |
\begin{description}
|
|
1289 |
\item[ec\_device\_index] PCI device index of the device that is |
|
1290 |
connected to the EtherCAT bus. If this parameter is left away, all |
|
1291 |
devices found are treated as ordinary Ethernet devices. Default: |
|
1292 |
$-1$ |
|
1293 |
\item[ec\_master\_index] Index of the master to connect to. Default: |
|
1294 |
$0$ |
|
1295 |
\end{description}
|
|
1296 |
||
1297 |
The following command loads the EtherCAT-capable RTL8139 device |
|
1298 |
driver, telling it to handle the second device as an EtherCAT device |
|
1299 |
and connecting it to the first master: |
|
1300 |
||
|
1085
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|
1301 |
\begin{lstlisting}[gobble=2]
|
| 379 | 1302 |
# `\textbf{modprobe ec\_8139too ec\_device\_index=1}`
|
| 369 | 1303 |
\end{lstlisting}
|
1304 |
||
1305 |
Usually, this command does not have to be entered manually, but is |
|
1306 |
called by the EtherCAT init script. See section~\ref{sec:init} for
|
|
1307 |
more information. |
|
1308 |
||
1309 |
%------------------------------------------------------------------------------ |
|
1310 |
||
|
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changeset
|
1311 |
\section{The Device Interface}
|
| 369 | 1312 |
\label{sec:ecdev}
|
1313 |
\index{Device interface}
|
|
1314 |
||
1315 |
An anticipation to the section about the master module |
|
1316 |
(section~\ref{sec:mastermod}) has to be made in order to understand
|
|
1317 |
the way, a network device driver module can connect a device to a |
|
1318 |
specific EtherCAT master. |
|
1319 |
||
1320 |
The master module provides a ``device interface'' for network device |
|
1321 |
drivers. To use this interface, a network device driver module must |
|
1322 |
include the header |
|
1323 |
\textit{devices/ecdev.h}\nomenclature{ecdev}{EtherCAT Device}, coming
|
|
1324 |
with the EtherCAT master code. This header offers a function interface |
|
1325 |
for EtherCAT devices which is explained below. All functions of the |
|
1326 |
device interface are named with the prefix \textit{ecdev}.
|
|
1327 |
||
1328 |
\paragraph{Device Registration}
|
|
1329 |
||
1330 |
A network device driver can connect a physical device to an EtherCAT |
|
1331 |
master with the \textit{ecdev\_register()} function.
|
|
1332 |
||
|
1085
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diff
changeset
|
1333 |
\begin{lstlisting}[gobble=2,language=C]
|
| 369 | 1334 |
ec_device_t *ecdev_register(unsigned int master_index, |
1335 |
struct net_device *net_dev, |
|
1336 |
ec_isr_t isr, |
|
1337 |
struct module *module); |
|
1338 |
\end{lstlisting}
|
|
1339 |
||
1340 |
The first parameter \textit{master\_index} must be the index of the
|
|
1341 |
EtherCAT master to connect to (see section~\ref{sec:mastermod}),
|
|
1342 |
followed by \textit{net\_dev}, the pointer to the corresponding
|
|
1343 |
net\_device structure, which represents the network device to connect. |
|
1344 |
The third parameter \textit{isr} must be a pointer to the interrupt
|
|
1345 |
service routine (ISR\index{ISR}) handling the device. The master will
|
|
1346 |
later execute the ISR in order to receive frames and to update the |
|
1347 |
device status. The last parameter \textit{module} must be the pointer
|
|
1348 |
to the device driver module, which is usually accessible via the macro |
|
1349 |
\textit{THIS\_MODULE} (see next paragraph). On success, the function
|
|
1350 |
returns a pointer to an \textit{ec\_device\_t} object, which has to be
|
|
1351 |
specified when calling further functions of the device interface. |
|
1352 |
Therefore the device module has to store this pointer for future use. |
|
1353 |
In error case, the \textit{ecdev\_register()} returns \textit{NULL},
|
|
1354 |
which means that the device could not be registered. The reason for |
|
|
1085
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parents:
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diff
changeset
|
1355 |
this is printed to \textit{Syslog}\index{Syslog}. In this case, the
|
| 369 | 1356 |
device module is supposed to abort the module initialisation and let |
1357 |
the \textit{insmod} command fail.
|
|
1358 |
||
1359 |
\paragraph{Implicit Dependencies}
|
|
1360 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
1361 |
The reason for the module pointer has to be specified at device registration is |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
1362 |
a non-trivial one: The master has to know about the module, because there will |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
1363 |
be an implicit dependency between the device module and a later connected |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
1364 |
application module: When an application module connects to the master, the use |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
1365 |
count of the master module will be increased, so that the master module can not |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
1366 |
be unloaded for the time of the connection. This is reasonable, and so |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
1367 |
automatically done by the kernel. The kernel knows about this dependency, |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
1368 |
because the application module uses kernel symbols provided by the master |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
1369 |
module. Moreover it is mandatory, that the device module can be unloaded |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
1370 |
neither, because it is implicitly used by the application module, too. |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
1371 |
Unloading it would lead to a fatal situation, because the master would have no |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
1372 |
device to send and receive frames for the application. This dependency can not |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
1373 |
be detected automatically, because the application module does not use any |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
1374 |
symbols of the device module. Therefore the master explicitly increments the |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
1375 |
use counter of the connected device module upon connection of an application |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
1376 |
and decrements it, if it disconnects again. In this manner, it is impossible to |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
1377 |
unload a device module while the master is in use. This is done with the kernel |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
1378 |
function pair \textit{try\_module\_get()}
|
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
1379 |
\index{try\_module\_get@\textit{try\_module\_get()}} and \textit{module\_put()}
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
1380 |
\index{module\_put@\textit{module\_put()}}. The first one increases the use
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
1381 |
count of a module and only fails, if the module is currently being unloaded. |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
1382 |
The last one decreases the use count again and never fails. Both functions take |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
1383 |
a pointer to the module as their argument, which the device module therefore |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
1384 |
has to specify upon device registration. |
| 369 | 1385 |
|
1386 |
\paragraph{Device Unregistering}
|
|
1387 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
1388 |
The deregistration of a device is usually done in the device module's cleanup |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
1389 |
function, by calling the \textit{ecdev\_unregister()} function and specifying
|
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
1390 |
the master index and a pointer to the device object again. |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
1391 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
1392 |
\begin{lstlisting}[gobble=2,language=C]
|
| 369 | 1393 |
void ecdev_unregister(unsigned int master_index, |
1394 |
ec_device_t *device); |
|
1395 |
\end{lstlisting}
|
|
1396 |
||
1397 |
This function can fail too (if the master index is invalid, or the |
|
1398 |
given device was not registered), but due to the fact, that this |
|
1399 |
failure can not be dealt with appropriately, because the device module |
|
1400 |
is unloading anyway, the failure code would not be of any interest. So |
|
1401 |
the function has a void return value. |
|
1402 |
||
1403 |
\paragraph{Starting the Master}
|
|
1404 |
||
1405 |
When a device has been initialized completely and is ready to send and |
|
1406 |
receive frames, the master has to be notified about this by calling |
|
1407 |
the \textit{ecdev\_start()} function.
|
|
1408 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
1409 |
\begin{lstlisting}[gobble=2,language=C]
|
| 369 | 1410 |
int ecdev_start(unsigned int master_index); |
1411 |
\end{lstlisting}
|
|
1412 |
||
1413 |
The master will then enter ``Idle Mode'' and start scanning the bus |
|
1414 |
(and possibly handling EoE slaves). Moreover it will make the bus |
|
1415 |
accessible via Sysfs interface and react to user interactions. The |
|
1416 |
function takes one parameter \textit{master\_index}, which has to be
|
|
1417 |
the same as at the call to \textit{ecdev\_register()}. The return
|
|
1418 |
value will be non-zero if the starting process failed. In this case |
|
1419 |
the device module is supposed to abort the init sequence and make the |
|
1420 |
init function return an error code. |
|
1421 |
||
1422 |
\paragraph{Stopping the Master}
|
|
1423 |
||
1424 |
Before a device can be unregistered, the master has to be stopped by |
|
1425 |
calling the \textit{ecdev\_stop()} function. It will stop processing
|
|
1426 |
messages of EoE slaves and leave ``Idle Mode''. The only parameter is |
|
1427 |
\textit{master\_index}. This function can not fail.
|
|
1428 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
1429 |
\begin{lstlisting}[gobble=2,language=C]
|
| 369 | 1430 |
void ecdev_stop(unsigned int master_index); |
1431 |
\end{lstlisting}
|
|
1432 |
||
1433 |
A subsequent call to \textit{ecdev\_unregister()} will now unregister
|
|
1434 |
the device savely. |
|
1435 |
||
1436 |
\paragraph{Receiving Frames}
|
|
1437 |
||
1438 |
The interrupt service routine handling device events usually has a |
|
1439 |
section where new frames are fetched from the hardware and forwarded |
|
1440 |
to the kernel network stack via \textit{netif\_receive\_skb()}. For an
|
|
1441 |
EtherCAT-capable device, this has to be replaced by calling the |
|
1442 |
\textit{ecdev\_receive()} function to forward the received data to the
|
|
1443 |
connected EtherCAT master instead. |
|
1444 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
1445 |
\begin{lstlisting}[gobble=2,language=C]
|
| 369 | 1446 |
void ecdev_receive(ec_device_t *device, |
1447 |
const void *data, |
|
1448 |
size_t size); |
|
1449 |
\end{lstlisting}
|
|
1450 |
||
1451 |
This function takes 3 arguments, a pointer to the device object |
|
1452 |
(\textit{device}), a pointer to the received data, and the size of the
|
|
1453 |
received data. The data range has to include the Ethernet headers |
|
1454 |
starting with the destination address and reach up to the last octet |
|
1455 |
of EtherCAT data, excluding the FCS. Most network devices handle the |
|
1456 |
FCS in hardware, so it is not seen by the driver code and therefore |
|
1457 |
doesn't have to be cut off manually. |
|
1458 |
||
1459 |
\paragraph{Handling the Link Status}
|
|
1460 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
1461 |
Information about the link status (i.~e. if there is a carrier signal detected |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
1462 |
on the physical port) is also important to the master. This information is |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
1463 |
usually gathered by the ISR and should be forwarded to the master by calling |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
1464 |
the \textit{ecdev\_link\_state()} function. The master then can react on this
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
1465 |
and warn the application of a lost link. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
1466 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
1467 |
\begin{lstlisting}[gobble=2,language=C]
|
| 369 | 1468 |
void ecdev_link_state(ec_device_t *device, |
1469 |
uint8_t new_state); |
|
1470 |
\end{lstlisting}
|
|
1471 |
||
1472 |
The parameter \textit{device} has to be a pointer to the device object
|
|
1473 |
returned by \textit{ecdev\_\-register()}. With the second parameter
|
|
1474 |
\textit{new\_state}, the new link state is passed: 1, if the link went
|
|
1475 |
up, and 0, if it went down. |
|
1476 |
||
1477 |
%------------------------------------------------------------------------------ |
|
1478 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
1479 |
\section{Patching Network Drivers}
|
| 369 | 1480 |
\label{sec:patching}
|
1481 |
\index{Network drivers}
|
|
1482 |
||
1483 |
This section will demonstrate, how to make a standard Ethernet driver |
|
1484 |
EtherCAT-capable. The below code examples are taken out of the |
|
1485 |
modified RealTek RTL8139 driver coming with the EtherCAT master |
|
1486 |
(\textit{devices/8139too.c}). The driver was originally developed by
|
|
1487 |
Donald Becker, and is currently maintained by Jeff Garzik. |
|
1488 |
||
1489 |
Unfortunately, there is no standard procedure to enable an Ethernet |
|
1490 |
driver for use with the EtherCAT master, but there are a few common |
|
1491 |
techniques, that are described in this section. |
|
1492 |
||
1493 |
\begin{enumerate}
|
|
1494 |
\item A first simple rule is, that \textit{netif\_*()}-calls must be
|
|
1495 |
strictly avoided for all EtherCAT devices. As mentioned before, |
|
1496 |
EtherCAT devices have no connection to the network stack, and |
|
1497 |
therefore must not call its interface functions. |
|
1498 |
\item Another important thing is, that EtherCAT devices should be |
|
1499 |
operated without interrupts. So any calls of registering interrupt |
|
1500 |
handlers and enabling interrupts at hardware level must be avoided, |
|
1501 |
too. |
|
1502 |
\item The master does not use a new socket buffer for each send |
|
1503 |
operation: Instead there is a fix one allocated on master |
|
1504 |
initialization. This socket buffer is filled with an EtherCAT frame |
|
1505 |
with every send operation and passed to the |
|
1506 |
\textit{hard\_start\_xmit()} callback. For that it is necessary,
|
|
1507 |
that the socket buffer is not be freed by the network driver as |
|
1508 |
usual. |
|
1509 |
\end{enumerate}
|
|
1510 |
||
1511 |
As mentioned before, the driver will handle both EtherCAT and ordinary |
|
1512 |
Ethernet devices. This implies, that for each device-dependent |
|
1513 |
operation, it has to be checked if an EtherCAT device is involved, or |
|
1514 |
just an Ethernet device. For means of simplicity, this example driver |
|
1515 |
will only handle one EtherCAT device. This makes the case |
|
1516 |
differentiations easier. |
|
1517 |
||
1518 |
\paragraph{Global Variables}
|
|
1519 |
||
1520 |
First of all, there have to be additional global variables declared, |
|
1521 |
as shown in the listing: |
|
1522 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
1523 |
\begin{lstlisting}[gobble=2,language=C,numbers=left]
|
| 369 | 1524 |
static int ec_device_index = -1; |
1525 |
static int ec_device_master_index = 0; |
|
1526 |
static ec_device_t *rtl_ec_dev; |
|
1527 |
struct net_device *rtl_ec_net_dev = NULL; |
|
1528 |
\end{lstlisting}
|
|
1529 |
||
1530 |
\begin{description}
|
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
1531 |
\item[\linenum{1} -- \linenum{2}] To
|
| 369 | 1532 |
comply to the requirements for parameters of EtherCAT device modules |
1533 |
described in section~\ref{sec:seldev}, there have to be additional
|
|
1534 |
parameter variables: \textit{ec\_\-device\_\-index} holds the index
|
|
1535 |
of the EtherCAT device and defaults to $-1$ (no EtherCAT device), |
|
1536 |
while \textit{ec\_device\_master\_index} stores index of the master,
|
|
1537 |
the single device will be connected to. Default: $0$ |
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
1538 |
\item[\linenum{3}] \textit{rtl\_ec\_dev} will be
|
| 369 | 1539 |
the pointer to the later registered RealTek EtherCAT device, which |
1540 |
can be used as a parameter for device methods. |
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
1541 |
\item[\linenum{4}] \textit{rtl\_ec\_net\_dev} is
|
| 369 | 1542 |
a pointer to the \textit{net\_device} structure of the dedicated
|
1543 |
device and is set while scanning the PCI bus and finding the device |
|
1544 |
with the specified index. This is done inside the |
|
1545 |
\textit{pci\_module\_init()} function executed as the first thing on
|
|
1546 |
module loading. |
|
1547 |
\end{description}
|
|
1548 |
||
1549 |
\paragraph{Module Initialization}
|
|
1550 |
||
1551 |
Below is the (shortened) coding of the device driver's module init |
|
1552 |
function: |
|
1553 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
1554 |
\begin{lstlisting}[gobble=2,language=C,numbers=left]
|
| 369 | 1555 |
static int __init rtl8139_init_module(void) |
1556 |
{
|
|
1557 |
if (pci_module_init(&rtl8139_pci_driver) < 0) {
|
|
1558 |
printk(KERN_ERR "Failed to init PCI mod.\n"); |
|
1559 |
goto out_return; |
|
1560 |
} |
|
1561 |
||
1562 |
if (rtl_ec_net_dev) {
|
|
1563 |
printk(KERN_INFO "Registering" |
|
1564 |
" EtherCAT device...\n"); |
|
1565 |
if (!(rtl_ec_dev = |
|
1566 |
ecdev_register(ec_device_master_index, |
|
1567 |
rtl_ec_net_dev, |
|
1568 |
rtl8139_interrupt, |
|
1569 |
THIS_MODULE))) {
|
|
1570 |
printk(KERN_ERR "Failed to reg." |
|
1571 |
" EtherCAT device!\n"); |
|
1572 |
goto out_unreg_pci; |
|
1573 |
} |
|
1574 |
||
1575 |
printk(KERN_INFO "Starting EtherCAT" |
|
1576 |
" device...\n"); |
|
1577 |
if (ecdev_start(ec_device_master_index)) {
|
|
1578 |
printk(KERN_ERR "Failed to start" |
|
1579 |
" EtherCAT device!\n"); |
|
1580 |
goto out_unreg_ec; |
|
1581 |
} |
|
1582 |
} else {
|
|
1583 |
printk(KERN_WARNING "No EtherCAT device" |
|
1584 |
" registered!\n"); |
|
1585 |
} |
|
1586 |
||
1587 |
return 0; |
|
1588 |
||
1589 |
out_unreg_ec: |
|
1590 |
ecdev_unregister(ec_device_master_index, rtl_ec_dev); |
|
1591 |
out_unreg_pci: |
|
1592 |
pci_unregister_driver(&rtl8139_pci_driver); |
|
1593 |
out_return: |
|
1594 |
return -1; |
|
1595 |
} |
|
1596 |
\end{lstlisting}
|
|
1597 |
||
1598 |
\begin{description}
|
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
1599 |
\item[\linenum{3}] This call initializes all
|
| 369 | 1600 |
RTL8139-compatible devices found on the pci bus. If a device with |
1601 |
index \textit{ec\_device\_index} is found, a pointer to its
|
|
1602 |
\textit{net\_device} structure is stored in
|
|
1603 |
\textit{rtl\_ec\_net\_dev} for later use (see next listings).
|
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
1604 |
\item[\linenum{8}] If the specified device was
|
| 369 | 1605 |
found, \textit{rtl\_ec\_net\_dev} is non-zero.
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
1606 |
\item[\linenum{11}] The device is connected to
|
| 369 | 1607 |
the specified master with a call to \textit{ecdev\_register()}. If
|
1608 |
this fails, module loading is aborted. |
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
1609 |
\item[\linenum{23}] The device registration was
|
| 369 | 1610 |
successful and the master is started. This can fail, which aborts |
1611 |
module loading. |
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
1612 |
\item[\linenum{29}] If no EtherCAT device was
|
| 369 | 1613 |
found, a warning is output. |
1614 |
\end{description}
|
|
1615 |
||
1616 |
\paragraph{Device Searching}
|
|
1617 |
||
1618 |
During the PCI initialization phase, a variable \textit{board\_idx} is
|
|
1619 |
increased for each RTL8139-compatible device found. The code below is |
|
1620 |
executed for each device: |
|
1621 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
1622 |
\begin{lstlisting}[gobble=2,language=C,numbers=left]
|
| 369 | 1623 |
if (board_idx == ec_device_index) {
|
1624 |
rtl_ec_net_dev = dev; |
|
1625 |
strcpy(dev->name, "ec0"); |
|
1626 |
} |
|
1627 |
\end{lstlisting}
|
|
1628 |
||
1629 |
\begin{description}
|
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
1630 |
\item[\linenum{1}] The device with the specified
|
| 369 | 1631 |
index will be the EtherCAT device. |
1632 |
\end{description}
|
|
1633 |
||
1634 |
\paragraph{Avoiding Device Registration}
|
|
1635 |
||
1636 |
Later in the PCI initialization phase, the net\_devices get |
|
1637 |
registered. This has to be avoided for EtherCAT devices and so this is |
|
1638 |
a typical example for an EtherCAT case differentiation: |
|
1639 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
1640 |
\begin{lstlisting}[gobble=2,language=C,numbers=left]
|
| 369 | 1641 |
if (dev != rtl_ec_net_dev) {
|
1642 |
i = register_netdev(dev); |
|
1643 |
if (i) goto err_out; |
|
1644 |
} |
|
1645 |
\end{lstlisting}
|
|
1646 |
||
1647 |
\begin{description}
|
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
1648 |
\item[\linenum{1}] If the current net\_device is
|
| 369 | 1649 |
not the EtherCAT device, it is registered at the network stack. |
1650 |
\end{description}
|
|
1651 |
||
1652 |
\paragraph{Avoiding Interrupt Registration}
|
|
1653 |
||
1654 |
In the next two listings, there is an interrupt requested and the |
|
1655 |
device's interrupts are enabled. This also has to be encapsulated by |
|
1656 |
if-clauses, because interrupt operation is not wanted for EtherCAT |
|
1657 |
devices. |
|
1658 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
1659 |
\begin{lstlisting}[gobble=2,language=C,numbers=left]
|
| 369 | 1660 |
if (dev != rtl_ec_net_dev) {
|
1661 |
retval = request_irq(dev->irq, rtl8139_interrupt, |
|
1662 |
SA_SHIRQ, dev->name, dev); |
|
1663 |
if (retval) return retval; |
|
1664 |
} |
|
1665 |
\end{lstlisting}
|
|
1666 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
1667 |
\begin{lstlisting}[gobble=2,language=C,numbers=left]
|
| 369 | 1668 |
if (dev != rtl_ec_net_dev) {
|
1669 |
/* Enable all known interrupts by setting |
|
1670 |
the interrupt mask. */ |
|
1671 |
RTL_W16(IntrMask, rtl8139_intr_mask); |
|
1672 |
} |
|
1673 |
\end{lstlisting}
|
|
1674 |
||
1675 |
\paragraph{Frame Sending}
|
|
1676 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
1677 |
The listing below shows an excerpt of the function representing the |
| 369 | 1678 |
\textit{hard\_start\_xmit()} callback of the net\_device.
|
1679 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
1680 |
\begin{lstlisting}[gobble=2,language=C,numbers=left]
|
| 369 | 1681 |
/* Note: the chip doesn't have auto-pad! */ |
1682 |
if (likely(len < TX_BUF_SIZE)) {
|
|
1683 |
if (len < ETH_ZLEN) |
|
1684 |
memset(tp->tx_buf[entry], 0, ETH_ZLEN); |
|
1685 |
skb_copy_and_csum_dev(skb, tp->tx_buf[entry]); |
|
1686 |
if (dev != rtl_ec_net_dev) {
|
|
1687 |
dev_kfree_skb(skb); |
|
1688 |
} |
|
1689 |
} else {
|
|
1690 |
if (dev != rtl_ec_net_dev) {
|
|
1691 |
dev_kfree_skb(skb); |
|
1692 |
} |
|
1693 |
tp->stats.tx_dropped++; |
|
1694 |
return 0; |
|
1695 |
} |
|
1696 |
\end{lstlisting}
|
|
1697 |
||
1698 |
\begin{description}
|
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
1699 |
\item[\linenum{6} + \linenum{10}] The
|
| 369 | 1700 |
master uses a fixed socket buffer for transmission, which is reused |
1701 |
and may not be freed. |
|
1702 |
\end{description}
|
|
1703 |
||
1704 |
\paragraph{Frame Receiving}
|
|
1705 |
||
1706 |
During ordinary frame reception, a socket buffer is created and filled |
|
1707 |
with the received data. This is not necessary for an EtherCAT device: |
|
1708 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
1709 |
\begin{lstlisting}[gobble=2,language=C,numbers=left]
|
| 369 | 1710 |
if (dev != rtl_ec_net_dev) {
|
1711 |
/* Malloc up new buffer, compatible with net-2e. */ |
|
1712 |
/* Omit the four octet CRC from the length. */ |
|
1713 |
||
1714 |
skb = dev_alloc_skb (pkt_size + 2); |
|
1715 |
if (likely(skb)) {
|
|
1716 |
skb->dev = dev; |
|
1717 |
skb_reserve(skb, 2); /* 16 byte align |
|
1718 |
the IP fields. */ |
|
1719 |
eth_copy_and_sum(skb, &rx_ring[ring_off + 4], |
|
1720 |
pkt_size, 0); |
|
1721 |
skb_put(skb, pkt_size); |
|
1722 |
skb->protocol = eth_type_trans(skb, dev); |
|
1723 |
||
1724 |
dev->last_rx = jiffies; |
|
1725 |
tp->stats.rx_bytes += pkt_size; |
|
1726 |
tp->stats.rx_packets++; |
|
1727 |
||
1728 |
netif_receive_skb (skb); |
|
1729 |
} else {
|
|
1730 |
if (net_ratelimit()) |
|
1731 |
printk(KERN_WARNING |
|
1732 |
"%s: Memory squeeze, dropping" |
|
1733 |
" packet.\n", dev->name); |
|
1734 |
tp->stats.rx_dropped++; |
|
1735 |
} |
|
1736 |
} else {
|
|
1737 |
ecdev_receive(rtl_ec_dev, |
|
1738 |
&rx_ring[ring_offset + 4], pkt_size); |
|
1739 |
dev->last_rx = jiffies; |
|
1740 |
tp->stats.rx_bytes += pkt_size; |
|
1741 |
tp->stats.rx_packets++; |
|
1742 |
} |
|
1743 |
\end{lstlisting}
|
|
1744 |
||
1745 |
\begin{description}
|
|
|
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diff
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|
1746 |
\item[\linenum{28}] If the device is an EtherCAT
|
| 369 | 1747 |
device, no socket buffer is allocated. Instead a pointer to the data |
1748 |
(which is still in the device's receive ring) is passed to the |
|
1749 |
EtherCAT master. Unnecessary copy operations are avoided. |
|
|
1085
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diff
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|
1750 |
\item[\linenum{30} -- \linenum{32}] The
|
| 369 | 1751 |
device's statistics are updated as usual. |
1752 |
\end{description}
|
|
1753 |
||
1754 |
\paragraph{Link State}
|
|
1755 |
||
1756 |
The link state (i.~e. if there is a carrier signal detected on the |
|
1757 |
receive port) is determined during execution of the ISR. The listing |
|
1758 |
below shows the different processing for Ethernet and EtherCAT |
|
1759 |
devices: |
|
1760 |
||
|
1085
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|
1761 |
\begin{lstlisting}[gobble=2,language=C,numbers=left]
|
| 369 | 1762 |
if (dev != rtl_ec_net_dev) {
|
1763 |
if (tp->phys[0] >= 0) {
|
|
1764 |
mii_check_media(&tp->mii, netif_msg_link(tp), |
|
1765 |
init_media); |
|
1766 |
} |
|
1767 |
} else {
|
|
1768 |
void __iomem *ioaddr = tp->mmio_addr; |
|
1769 |
uint16_t link = RTL_R16(BasicModeStatus) |
|
1770 |
& BMSR_LSTATUS; |
|
1771 |
ecdev_link_state(rtl_ec_dev, link ? 1 : 0); |
|
1772 |
} |
|
1773 |
\end{lstlisting}
|
|
1774 |
||
1775 |
\begin{description}
|
|
|
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diff
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|
1776 |
\item[\linenum{3}] The ``media check'' is done
|
| 369 | 1777 |
via the media independent interface (MII\nomenclature{MII}{Media
|
1778 |
Independent Interface}), a standard interface for Fast Ethernet |
|
1779 |
devices. |
|
|
1085
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parents:
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diff
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|
1780 |
\item[\linenum{7} -- \linenum{10}] For
|
| 369 | 1781 |
EtherCAT devices, the link state is fetched manually from the |
1782 |
appropriate device register, and passed to the EtherCAT master by |
|
1783 |
calling \textit{ecdev\_\-link\_\-state()}.
|
|
1784 |
\end{description}
|
|
1785 |
||
1786 |
\paragraph{Module Cleanup}
|
|
1787 |
||
1788 |
Below is the module's cleanup function: |
|
1789 |
||
|
1085
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parents:
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diff
changeset
|
1790 |
\begin{lstlisting}[gobble=2,language=C,numbers=left]
|
| 369 | 1791 |
static void __exit rtl8139_cleanup_module (void) |
1792 |
{
|
|
1793 |
printk(KERN_INFO "Cleaning up RTL8139-EtherCAT" |
|
1794 |
" module...\n"); |
|
1795 |
||
1796 |
if (rtl_ec_net_dev) {
|
|
1797 |
printk(KERN_INFO "Stopping device...\n"); |
|
1798 |
ecdev_stop(ec_device_master_index); |
|
1799 |
printk(KERN_INFO "Unregistering device...\n"); |
|
1800 |
ecdev_unregister(ec_device_master_index, |
|
1801 |
rtl_ec_dev); |
|
1802 |
rtl_ec_dev = NULL; |
|
1803 |
} |
|
1804 |
||
1805 |
pci_unregister_driver(&rtl8139_pci_driver); |
|
1806 |
||
1807 |
printk(KERN_INFO "RTL8139-EtherCAT module" |
|
1808 |
" cleaned up.\n"); |
|
1809 |
} |
|
1810 |
\end{lstlisting}
|
|
1811 |
||
1812 |
\begin{description}
|
|
|
1085
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parents:
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diff
changeset
|
1813 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
1814 |
\item[\linenum{6}] Stopping and deregistration is only done, if a device was
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
1815 |
registered before. |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
1816 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
1817 |
\item[\linenum{8}] The master is first stopped, so it does not access the
|
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
1818 |
device any more. |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
917
diff
changeset
|
1819 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
1820 |
\item[\linenum{10}] After this, the device is unregistered. The master is now
|
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
1821 |
``orphaned''. |
|
c75cdcc5ce87
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parents:
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diff
changeset
|
1822 |
|
| 369 | 1823 |
\end{description}
|
1824 |
||
1825 |
%------------------------------------------------------------------------------ |
|
1826 |
||
|
1085
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parents:
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diff
changeset
|
1827 |
\chapter{State Machines}
|
| 369 | 1828 |
\label{sec:fsm}
|
1829 |
\index{FSM}
|
|
1830 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
1831 |
Many parts of the EtherCAT master are implemented as \textit{finite state
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
1832 |
machines} (FSMs\nomenclature{FSM}{Finite State Machine}). Though this leads
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
1833 |
to a higher grade of complexity in some aspects, is opens many new |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
1834 |
possibilities. |
| 369 | 1835 |
|
1836 |
The below short code example exemplary shows how to read all slave |
|
1837 |
states and moreover illustrates the restrictions of ``sequential'' |
|
1838 |
coding: |
|
1839 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
1840 |
\begin{lstlisting}[gobble=2,language=C,numbers=left]
|
| 369 | 1841 |
ec_datagram_brd(datagram, 0x0130, 2); // prepare datagram |
1842 |
if (ec_master_simple_io(master, datagram)) return -1; |
|
1843 |
slave_states = EC_READ_U8(datagram->data); // process datagram |
|
1844 |
\end{lstlisting}
|
|
1845 |
||
|
1085
c75cdcc5ce87
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parents:
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diff
changeset
|
1846 |
The \textit{ec\_master\_simple\_io()} function provides a simple interface for
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
1847 |
synchronously sending a single datagram and receiving the result\footnote{For
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
1848 |
all communication issues have been meanwhile sourced out into state machines, |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
1849 |
the function is deprecated and stopped existing. Nevertheless it is adequate |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
1850 |
for showing it's own restrictions.}. Internally, it queues the specified |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
1851 |
datagram, invokes the \textit{ec\_master\_send\_datagrams()} function to send
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
1852 |
a frame with the queued datagram and then waits actively for its reception. |
| 369 | 1853 |
|
1854 |
This sequential approach is very simple, reflecting in only three |
|
1855 |
lines of code. The disadvantage is, that the master is blocked for the |
|
1856 |
time it waits for datagram reception. There is no difficulty when only |
|
1857 |
one instance is using the master, but if more instances want to |
|
1858 |
(synchronously\footnote{At this time, synchronous master access will
|
|
1859 |
be adequate to show the advantages of an FSM. The asynchronous |
|
1860 |
approach will be discussed in section~\ref{sec:eoeimp}}) use the
|
|
1861 |
master, it is inevitable to think about an alternative to the |
|
1862 |
sequential model. |
|
1863 |
||
1864 |
Master access has to be sequentialized for more than one instance |
|
1865 |
wanting to send and receive datagrams synchronously. With the present |
|
1866 |
approach, this would result in having one phase of active waiting for |
|
1867 |
each instance, which would be non-acceptable especially in realtime |
|
1868 |
circumstances, because of the huge time overhead. |
|
1869 |
||
1870 |
A possible solution is, that all instances would be executed |
|
1871 |
sequentially to queue their datagrams, then give the control to the |
|
1872 |
next instance instead of waiting for the datagram reception. Finally, |
|
1873 |
bus IO is done by a higher instance, which means that all queued |
|
1874 |
datagrams are sent and received. The next step is to execute all |
|
1875 |
instances again, which then process their received datagrams and issue |
|
1876 |
new ones. |
|
1877 |
||
1878 |
This approach results in all instances having to retain their state, |
|
1879 |
when giving the control back to the higher instance. It is quite |
|
1880 |
obvious to use a \textit{finite state machine} model in this case.
|
|
1881 |
Section~\ref{sec:fsmtheory} will introduce some of the theory used,
|
|
1882 |
while the listings below show the basic approach by coding the example |
|
1883 |
from above as a state machine: |
|
1884 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
1885 |
\begin{lstlisting}[gobble=2,language=C,numbers=left]
|
| 369 | 1886 |
// state 1 |
1887 |
ec_datagram_brd(datagram, 0x0130, 2); // prepare datagram |
|
1888 |
ec_master_queue(master, datagram); // queue datagram |
|
1889 |
next_state = state_2; |
|
1890 |
// state processing finished |
|
1891 |
\end{lstlisting}
|
|
1892 |
||
1893 |
After all instances executed their current state and queued their |
|
1894 |
datagrams, these are sent and received. Then the respective next |
|
1895 |
states are executed: |
|
1896 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
1897 |
\begin{lstlisting}[gobble=2,language=C,numbers=left]
|
| 369 | 1898 |
// state 2 |
1899 |
if (datagram->state != EC_DGRAM_STATE_RECEIVED) {
|
|
1900 |
next_state = state_error; |
|
1901 |
return; // state processing finished |
|
1902 |
} |
|
1903 |
slave_states = EC_READ_U8(datagram->data); // process datagram |
|
1904 |
// state processing finished. |
|
1905 |
\end{lstlisting}
|
|
1906 |
||
1907 |
See section~\ref{sec:statemodel} for an introduction to the
|
|
1908 |
state machine programming concept used in the master code. |
|
1909 |
||
1910 |
%------------------------------------------------------------------------------ |
|
1911 |
||
|
1085
c75cdcc5ce87
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diff
changeset
|
1912 |
\section{State Machine Theory}
|
| 369 | 1913 |
\label{sec:fsmtheory}
|
1914 |
\index{FSM!Theory}
|
|
1915 |
||
1916 |
A finite state machine \cite{automata} is a model of behavior with
|
|
1917 |
inputs and outputs, where the outputs not only depend on the inputs, |
|
1918 |
but the history of inputs. The mathematical definition of a finite |
|
1919 |
state machine (or finite automaton) is a six-tuple $(\Sigma, \Gamma, |
|
1920 |
S, s_0, \delta, \omega)$, with |
|
1921 |
||
1922 |
\begin{itemize}
|
|
1923 |
\item the input alphabet $\Sigma$, with $\Sigma \neq |
|
1924 |
\emptyset$, containing all input symbols, |
|
1925 |
\item the output alphabet $\Gamma$, with $\Gamma \neq |
|
1926 |
\emptyset$, containing all output symbols, |
|
1927 |
\item the set of states $S$, with $S \neq \emptyset$, |
|
1928 |
\item the set of initial states $s_0$ with $s_0 \subseteq S, s_0 \neq |
|
1929 |
\emptyset$ |
|
1930 |
\item the transition function $\delta: S \times \Sigma \rightarrow S |
|
1931 |
\times \Gamma$ |
|
1932 |
\item the output function $\omega$. |
|
1933 |
\end{itemize}
|
|
1934 |
||
1935 |
The state transition function $\delta$ is often specified by a |
|
1936 |
\textit{state transition table}, or by a \textit{state transition
|
|
1937 |
diagram}. The transition table offers a matrix view of the state |
|
1938 |
machine behavior (see table~\ref{tab:statetrans}). The matrix rows
|
|
1939 |
correspond to the states ($S = \{s_0, s_1, s_2\}$) and the columns
|
|
1940 |
correspond to the input symbols ($\Gamma = \{a, b, \varepsilon\}$).
|
|
1941 |
The table contents in a certain row $i$ and column $j$ then represent |
|
1942 |
the next state (and possibly the output) for the case, that a certain |
|
1943 |
input symbol $\sigma_j$ is read in the state $s_i$. |
|
1944 |
||
1945 |
\begin{table}[htbp]
|
|
1946 |
\caption{A typical state transition table}
|
|
1947 |
\label{tab:statetrans}
|
|
1948 |
\vspace{2mm}
|
|
1949 |
\centering |
|
1950 |
\begin{tabular}{l|ccc}
|
|
1951 |
& $a$ & $b$ & $\varepsilon$\\ \hline |
|
1952 |
$s_0$ & $s_1$ & $s_1$ & $s_2$\\ |
|
1953 |
$s_1$ & $s_2$ & $s_1$ & $s_0$\\ |
|
1954 |
$s_2$ & $s_0$ & $s_0$ & $s_0$\\ \hline |
|
1955 |
\end{tabular}
|
|
1956 |
\end{table}
|
|
1957 |
||
1958 |
The state diagram for the same example looks like the one in |
|
1959 |
figure~\ref{fig:statetrans}. The states are represented as circles or
|
|
1960 |
ellipses and the transitions are drawn as arrows between them. Close |
|
1961 |
to a transition arrow can be the condition that must be fulfilled to |
|
1962 |
allow the transition. The initial state is marked by a filled black |
|
1963 |
circle with an arrow pointing to the respective state. |
|
1964 |
||
1965 |
\begin{figure}[htbp]
|
|
1966 |
\centering |
|
1967 |
\includegraphics[width=.5\textwidth]{images/statetrans}
|
|
1968 |
\caption{A typical state transition diagram}
|
|
1969 |
\label{fig:statetrans}
|
|
1970 |
\end{figure}
|
|
1971 |
||
1972 |
\paragraph{Deterministic and non-deterministic state machines}
|
|
1973 |
||
1974 |
A state machine can be deterministic, meaning that for one state and |
|
1975 |
input, there is one (and only one) following state. In this case, the |
|
1976 |
state machine has exactly one starting state. Non-deterministic state |
|
1977 |
machines can have more than one transitions for a single state-input |
|
1978 |
combination. There is a set of starting states in the latter case. |
|
1979 |
||
1980 |
\paragraph{Moore and Mealy machines}
|
|
1981 |
||
1982 |
There is a distinction between so-called \textit{Moore machines}, and
|
|
1983 |
\textit{Mealy machines}. Mathematically spoken, the distinction lies
|
|
1984 |
in the output function $\omega$: If it only depends on the current |
|
1985 |
state ($\omega: S \rightarrow \Gamma$), the machine corresponds to the |
|
1986 |
``Moore Model''. Otherwise, if $\omega$ is a function of a state and |
|
1987 |
the input alphabet ($\omega: S \times \Sigma \rightarrow \Gamma$) the |
|
1988 |
state machine corresponds to the ``Mealy model''. Mealy machines are |
|
1989 |
the more practical solution in most cases, because their design allows |
|
1990 |
machines with a minimum number of states. In practice, a mixture of |
|
1991 |
both models is often used. |
|
1992 |
||
1993 |
\paragraph{Misunderstandings about state machines}
|
|
1994 |
||
|
1085
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diff
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|
1995 |
There is a phenomenon called ``state explosion'', that is often taken as a |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
1996 |
counter-argument against general use of state machines in complex environments. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
1997 |
It has to be mentioned, that this point is misleading~\cite{fsmmis}. State
|
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
1998 |
explosions happen usually as a result of a bad state machine design: Common |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
1999 |
mistakes are storing the present values of all inputs in a state, or not |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
2000 |
dividing a complex state machine into simpler sub state machines. The EtherCAT |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2001 |
master uses several state machines, that are executed hierarchically and so |
|
c75cdcc5ce87
Started to re-write the documentation.
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changeset
|
2002 |
serve as sub state machines. These are also described below. |
|
c75cdcc5ce87
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changeset
|
2003 |
|
|
c75cdcc5ce87
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parents:
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diff
changeset
|
2004 |
%------------------------------------------------------------------------------ |
|
c75cdcc5ce87
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changeset
|
2005 |
|
|
c75cdcc5ce87
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|
2006 |
\section{The Master's State Model}
|
| 369 | 2007 |
\label{sec:statemodel}
|
2008 |
||
2009 |
This section will introduce the techniques used in the master to |
|
2010 |
implement state machines. |
|
2011 |
||
2012 |
\paragraph{State Machine Programming}
|
|
2013 |
||
2014 |
There are certain ways to implement a state machine in \textit{C}
|
|
2015 |
code. An obvious way is to implement the different states and actions |
|
2016 |
by one big case differentiation: |
|
2017 |
||
|
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|
2018 |
\begin{lstlisting}[gobble=2,language=C,numbers=left]
|
| 369 | 2019 |
enum {STATE_1, STATE_2, STATE_3};
|
2020 |
int state = STATE_1; |
|
2021 |
||
2022 |
void state_machine_run(void *priv_data) {
|
|
2023 |
switch (state) {
|
|
2024 |
case STATE_1: |
|
2025 |
action_1(); |
|
2026 |
state = STATE_2; |
|
2027 |
break; |
|
2028 |
case STATE_2: |
|
2029 |
action_2() |
|
2030 |
if (some_condition) state = STATE_1; |
|
2031 |
else state = STATE_3; |
|
2032 |
break; |
|
2033 |
case STATE_3: |
|
2034 |
action_3(); |
|
2035 |
state = STATE_1; |
|
2036 |
break; |
|
2037 |
} |
|
2038 |
} |
|
2039 |
\end{lstlisting}
|
|
2040 |
||
2041 |
For small state machines, this is an option. The disadvantage is, that |
|
2042 |
with an increasing number of states the code soon gets complex and an |
|
2043 |
additional case differentiation is executed each run. Besides, lots of |
|
2044 |
indentation is wasted. |
|
2045 |
||
2046 |
The method used in the master is to implement every state in an own |
|
2047 |
function and to store the current state function with a function |
|
2048 |
pointer: |
|
2049 |
||
|
1085
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|
2050 |
\begin{lstlisting}[gobble=2,language=C,numbers=left]
|
| 369 | 2051 |
void (*state)(void *) = state1; |
2052 |
||
2053 |
void state_machine_run(void *priv_data) {
|
|
2054 |
state(priv_data); |
|
2055 |
} |
|
2056 |
||
2057 |
void state1(void *priv_data) {
|
|
2058 |
action_1(); |
|
2059 |
state = state2; |
|
2060 |
} |
|
2061 |
||
2062 |
void state2(void *priv_data) {
|
|
2063 |
action_2(); |
|
2064 |
if (some_condition) state = state1; |
|
2065 |
else state = state2; |
|
2066 |
} |
|
2067 |
||
2068 |
void state3(void *priv_data) {
|
|
2069 |
action_3(); |
|
2070 |
state = state1; |
|
2071 |
} |
|
2072 |
\end{lstlisting}
|
|
2073 |
||
|
1085
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changeset
|
2074 |
In the master code, state pointers of all state machines\footnote{All except
|
|
c75cdcc5ce87
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|
2075 |
for the EoE state machine, because multiple EoE slaves have to be handled in |
|
c75cdcc5ce87
Started to re-write the documentation.
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changeset
|
2076 |
parallel. For this reason each EoE handler object has its own state pointer.} |
|
c75cdcc5ce87
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diff
changeset
|
2077 |
are gathered in a single object of the \textit{ec\_fsm\_t} class. This is
|
|
c75cdcc5ce87
Started to re-write the documentation.
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|
2078 |
advantageous, because there is always one instance of every state machine |
|
c75cdcc5ce87
Started to re-write the documentation.
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|
2079 |
available and can be started on demand. |
| 369 | 2080 |
|
2081 |
\paragraph{Mealy and Moore}
|
|
2082 |
||
2083 |
If a closer look is taken to the above listing, it can be seen that |
|
2084 |
the actions executed (the ``outputs'' of the state machine) only |
|
2085 |
depend on the current state. This accords to the ``Moore'' model |
|
2086 |
introduced in section~\ref{sec:fsmtheory}. As mentioned, the ``Mealy''
|
|
2087 |
model offers a higher flexibility, which can be seen in the listing |
|
2088 |
below: |
|
2089 |
||
|
1085
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diff
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|
2090 |
\begin{lstlisting}[gobble=2,language=C,numbers=left]
|
| 369 | 2091 |
void state7(void *priv_data) {
|
2092 |
if (some_condition) {
|
|
2093 |
action_7a(); |
|
2094 |
state = state1; |
|
2095 |
} |
|
2096 |
else {
|
|
2097 |
action_7b(); |
|
2098 |
state = state8; |
|
2099 |
} |
|
2100 |
} |
|
2101 |
\end{lstlisting}
|
|
2102 |
||
2103 |
\begin{description}
|
|
|
1085
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|
2104 |
\item[\linenum{3} + \linenum{7}] The
|
| 369 | 2105 |
state function executes the actions depending on the state |
2106 |
transition, that is about to be done. |
|
2107 |
\end{description}
|
|
2108 |
||
2109 |
The most flexible alternative is to execute certain actions depending |
|
2110 |
on the state, followed by some actions dependent on the state |
|
2111 |
transition: |
|
2112 |
||
|
1085
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Started to re-write the documentation.
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|
2113 |
\begin{lstlisting}[gobble=2,language=C,numbers=left]
|
| 369 | 2114 |
void state9(void *priv_data) {
|
2115 |
action_9(); |
|
2116 |
if (some_condition) {
|
|
2117 |
action_9a(); |
|
2118 |
state = state7; |
|
2119 |
} |
|
2120 |
else {
|
|
2121 |
action_9b(); |
|
2122 |
state = state10; |
|
2123 |
} |
|
2124 |
} |
|
2125 |
\end{lstlisting}
|
|
2126 |
||
2127 |
This model is oftenly used in the master. It combines the best aspects |
|
2128 |
of both approaches. |
|
2129 |
||
2130 |
\paragraph{Using Sub State Machines}
|
|
2131 |
||
|
1085
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Started to re-write the documentation.
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parents:
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diff
changeset
|
2132 |
To avoid having too much states, certain functions of the EtherCAT master state |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
917
diff
changeset
|
2133 |
machine have been sourced out into sub state machines. This helps to |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2134 |
encapsulate the related workflows and moreover avoids the ``state explosion'' |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2135 |
phenomenon described in section~\ref{sec:fsmtheory}. If the master would
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2136 |
instead use one big state machine, the number of states would be a multiple of |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
917
diff
changeset
|
2137 |
the actual number. This would increase the level of complexity to a |
| 369 | 2138 |
non-manageable grade. |
2139 |
||
2140 |
\paragraph{Executing Sub State Machines}
|
|
2141 |
||
2142 |
If a state machine starts to execute a sub state machine, it usually |
|
2143 |
remains in one state until the sub state machine terminates. This is |
|
2144 |
usually done like in the listing below, which is taken out of the |
|
2145 |
slave configuration state machine code: |
|
2146 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
2147 |
\begin{lstlisting}[gobble=2,language=C,numbers=left]
|
|
813
bfc3f1ab52de
Fixed typo SAVEOP -> SAFEOP.
Florian Pose <fp@igh-essen.com>
parents:
487
diff
changeset
|
2148 |
void ec_fsm_slaveconf_safeop(ec_fsm_t *fsm) |
| 369 | 2149 |
{
|
2150 |
fsm->change_state(fsm); // execute state change |
|
2151 |
// sub state machine |
|
2152 |
||
2153 |
if (fsm->change_state == ec_fsm_error) {
|
|
2154 |
fsm->slave_state = ec_fsm_end; |
|
2155 |
return; |
|
2156 |
} |
|
2157 |
||
2158 |
if (fsm->change_state != ec_fsm_end) return; |
|
2159 |
||
2160 |
// continue state processing |
|
2161 |
... |
|
2162 |
\end{lstlisting}
|
|
2163 |
||
2164 |
\begin{description}
|
|
|
1085
c75cdcc5ce87
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parents:
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diff
changeset
|
2165 |
\item[\linenum{3}] \textit{change\_state} is the
|
| 369 | 2166 |
state pointer of the state change state machine. The state function, |
2167 |
the pointer points on, is executed\ldots |
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
2168 |
\item[\linenum{6}] \ldots either until the state
|
| 369 | 2169 |
machine terminates with the error state \ldots |
|
1085
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
2170 |
\item[\linenum{11}] \ldots or until the state
|
| 369 | 2171 |
machine terminates in the end state. Until then, the ``higher'' |
2172 |
state machine remains in the current state and executes the sub |
|
2173 |
state machine again in the next cycle. |
|
2174 |
\end{description}
|
|
2175 |
||
2176 |
\paragraph{State Machine Descriptions}
|
|
2177 |
||
2178 |
The below sections describe every state machine used in the EtherCAT |
|
2179 |
master. The textual descriptions of the state machines contain |
|
2180 |
references to the transitions in the corresponding state transition |
|
2181 |
diagrams, that are marked with an arrow followed by the name of the |
|
2182 |
successive state. Transitions caused by trivial error cases (i.~e. no |
|
2183 |
response from slave) are not described explicitly. These transitions |
|
2184 |
are drawn as dashed arrows in the diagrams. |
|
2185 |
||
2186 |
%------------------------------------------------------------------------------ |
|
2187 |
||
|
1085
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diff
changeset
|
2188 |
\section{The Operation State Machine}
|
| 369 | 2189 |
\label{sec:fsm-op}
|
2190 |
\index{FSM!Operation}
|
|
2191 |
||
2192 |
The Operation state machine is executed by calling the |
|
2193 |
\textit{ecrt\_master\_run()} method in cyclic realtime code. Its
|
|
2194 |
purpose is to monitor the bus and to reconfigure slaves after a bus |
|
2195 |
failure or power failure. Figure~\ref{fig:fsm-op} shows its transition
|
|
2196 |
diagram. |
|
2197 |
||
2198 |
\begin{figure}[htbp]
|
|
2199 |
\centering |
|
2200 |
\includegraphics[width=.8\textwidth]{images/fsm-op}
|
|
2201 |
\caption{Transition diagram of the operation state machine}
|
|
2202 |
\label{fig:fsm-op}
|
|
2203 |
\end{figure}
|
|
2204 |
||
2205 |
\begin{description}
|
|
2206 |
\item[START] This is the beginning state of the operation state |
|
2207 |
machine. There is a datagram issued, that queries the ``AL Control |
|
2208 |
Response'' attribute \cite[section~5.3.2]{alspec} of all slaves via
|
|
2209 |
broadcast. In this way, all slave states and the number of slaves |
|
| 379 | 2210 |
responding can be determined. $\rightarrow$~BROADCAST |
| 369 | 2211 |
|
|
1085
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diff
changeset
|
2212 |
\item[BROADCAST] The broadcast datagram is evaluated. A change in the number of |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
917
diff
changeset
|
2213 |
responding slaves is treated as a topology change. If the number of slaves is |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
917
diff
changeset
|
2214 |
not as expected, the bus is marked as ``tainted''. In this state, no slave |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2215 |
reconfiguration is possible, because the assignment of known slaves and those |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2216 |
present on the bus is ambiguous. If the number of slaves is considered as |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2217 |
right, the bus is marked for validation, because it turned from tainted to |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2218 |
normal state and it has to be checked, if all slaves are valid. Now, the state |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2219 |
of every single slave has to be determined. For that, a (unicast) datagram is |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2220 |
issued, that queries the first slave's ``AL Control Response'' attribute. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2221 |
$\rightarrow$~READ STATES |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
2222 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
2223 |
\item[READ STATES] If the current slave did not respond to its configured |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
2224 |
station address, it is marked as offline, and the next slave is queried. |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
2225 |
$\rightarrow$~READ STATES |
| 369 | 2226 |
|
2227 |
If the slave responded, it is marked as online and its current state |
|
| 379 | 2228 |
is stored. The next slave is queried. $\rightarrow$~READ STATES |
| 369 | 2229 |
|
2230 |
If all slaves have been queried, and the bus is marked for |
|
2231 |
validation, the validation is started by checking the first slaves |
|
| 379 | 2232 |
vendor ID. $\rightarrow$~VALIDATE VENDOR |
| 369 | 2233 |
|
2234 |
If no validation has to be done, it is checked, if all slaves are in |
|
2235 |
the state they are supposed to be. If not, the first of slave with |
|
2236 |
the wrong state is reconfigured and brought in the required state. |
|
| 379 | 2237 |
$\rightarrow$~CONFIGURE SLAVES |
| 369 | 2238 |
|
2239 |
If all slaves are in the correct state, the state machine is |
|
| 379 | 2240 |
restarted. $\rightarrow$~START |
| 369 | 2241 |
|
2242 |
\item[CONFIGURE SLAVES] The slave configuration state machine is |
|
| 379 | 2243 |
executed until termination. $\rightarrow$~CONFIGURE SLAVES |
| 369 | 2244 |
|
2245 |
If there are still slaves in the wrong state after another check, |
|
2246 |
the first of these slaves is configured and brought into the correct |
|
| 379 | 2247 |
state again. $\rightarrow$~CONFIGURE SLAVES |
| 369 | 2248 |
|
2249 |
If all slaves are in the correct state, the state machine is |
|
| 379 | 2250 |
restarted. $\rightarrow$~START |
| 369 | 2251 |
|
2252 |
\item[VALIDATE VENDOR] The SII state machine is executed until |
|
2253 |
termination. If the slave has the wrong vendor ID, the state machine |
|
| 379 | 2254 |
is restarted. $\rightarrow$~START |
| 369 | 2255 |
|
2256 |
If the slave has the correct vendor ID, its product ID is queried. |
|
| 379 | 2257 |
$\rightarrow$~VALIDATE PRODUCT |
| 369 | 2258 |
|
2259 |
\item[VALIDATE PRODUCT] The SII state machine is executed until |
|
2260 |
termination. If the slave has the wrong product ID, the state |
|
| 379 | 2261 |
machine is restarted. $\rightarrow$~START |
| 369 | 2262 |
|
2263 |
If the slave has the correct product ID, the next slave's vendor ID |
|
| 379 | 2264 |
is queried. $\rightarrow$~VALIDATE VENDOR |
| 369 | 2265 |
|
2266 |
If all slaves have the correct vendor IDs and product codes, the |
|
2267 |
configured station addresses can be safely rewritten. This is done |
|
2268 |
for the first slave marked as offline. |
|
| 379 | 2269 |
$\rightarrow$~REWRITE ADDRESSES |
| 369 | 2270 |
|
2271 |
\item[REWRITE ADDRESSES] If the station address was successfully |
|
2272 |
written, it is sear\-ched for the next slave marked as offline. If |
|
2273 |
there is one, its address is reconfigured, too. |
|
| 379 | 2274 |
$\rightarrow$~REWRITE ADDRESSES |
| 369 | 2275 |
|
2276 |
If there are no more slaves marked as offline, the state machine is |
|
| 379 | 2277 |
restarted. $\rightarrow$~START |
| 369 | 2278 |
\end{description}
|
2279 |
||
2280 |
%------------------------------------------------------------------------------ |
|
2281 |
||
|
1085
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diff
changeset
|
2282 |
\section{The Idle State Machine}
|
| 369 | 2283 |
\label{sec:fsm-idle}
|
2284 |
\index{FSM!Idle}
|
|
2285 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
2286 |
The Idle state machine is executed by a kernel thread, if no application is |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
2287 |
connected. Its purpose is to make slave information available to user space, |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2288 |
operate EoE-capable slaves, read and write SII contents and test slave |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2289 |
functionality. Figure~\ref{fig:fsm-idle} shows its transition diagram.
|
| 369 | 2290 |
|
2291 |
\begin{figure}[htbp]
|
|
2292 |
\centering |
|
2293 |
\includegraphics[width=.8\textwidth]{images/fsm-idle}
|
|
2294 |
\caption{Transition diagram of the idle state machine}
|
|
2295 |
\label{fig:fsm-idle}
|
|
2296 |
\end{figure}
|
|
2297 |
||
2298 |
\begin{description}
|
|
2299 |
\item[START] The beginning state of the idle state machine. Similar to |
|
2300 |
the operation state machine, a broadcast datagram is issued, to |
|
2301 |
query all slave states and the number of slaves. |
|
| 379 | 2302 |
$\rightarrow$~BROADCAST |
| 369 | 2303 |
|
2304 |
\item[BROADCAST] The number of responding slaves is evaluated. If it |
|
2305 |
has changed since the last time, this is treated as a topology |
|
2306 |
change and the internal list of slaves is cleared and rebuild |
|
2307 |
completely. The slave scan state machine is started for the first |
|
| 379 | 2308 |
slave. $\rightarrow$~SCAN FOR SLAVES |
| 369 | 2309 |
|
2310 |
If no topology change happened, every single slave state is fetched. |
|
| 379 | 2311 |
$\rightarrow$~READ STATES |
| 369 | 2312 |
|
2313 |
\item[SCAN FOR SLAVES] The slave scan state machine is executed until |
|
| 379 | 2314 |
termination. $\rightarrow$~SCAN FOR SLAVES |
| 369 | 2315 |
|
2316 |
If there is another slave to scan, the slave scan state machine is |
|
| 379 | 2317 |
started again. $\rightarrow$~SCAN FOR SLAVES |
| 369 | 2318 |
|
2319 |
If all slave information has been fetched, slave addresses are |
|
2320 |
calculated and EoE processing is started. Then, the state machine is |
|
| 379 | 2321 |
restarted. $\rightarrow$~START |
| 369 | 2322 |
|
2323 |
\item[READ STATES] If the slave did not respond to the query, it is |
|
2324 |
marked as offline. The next slave is queried. |
|
| 379 | 2325 |
$\rightarrow$~READ STATES |
| 369 | 2326 |
|
2327 |
If the slave responded, it is marked as online. And the next slave |
|
| 379 | 2328 |
is queried. $\rightarrow$~READ STATES |
| 369 | 2329 |
|
2330 |
If all slave states have been determined, it is checked, if any |
|
2331 |
slaves are not in the state they supposed to be. If this is true, |
|
2332 |
the slave configuration state machine is started for the first of |
|
| 379 | 2333 |
them. $\rightarrow$~CONFIGURE SLAVES |
| 369 | 2334 |
|
2335 |
If all slaves are in the correct state, it is checked, if any |
|
2336 |
E$^2$PROM write operations are pending. If this is true, the first |
|
2337 |
pending operation is executed by starting the SII state machine for |
|
| 379 | 2338 |
writing access. $\rightarrow$~WRITE EEPROM |
| 369 | 2339 |
|
2340 |
If all these conditions are false, there is nothing to do and the |
|
| 379 | 2341 |
state machine is restarted. $\rightarrow$~START |
| 369 | 2342 |
|
2343 |
\item[CONFIGURE SLAVES] The slave configuration state machine is |
|
| 379 | 2344 |
executed until termination. $\rightarrow$~CONFIGURE SLAVES |
| 369 | 2345 |
|
2346 |
After this, it is checked, if another slave needs a state change. If |
|
2347 |
this is true, the slave state change state machine is started for |
|
| 379 | 2348 |
this slave. $\rightarrow$~CONFIGURE SLAVES |
| 369 | 2349 |
|
2350 |
If all slaves are in the correct state, it is determined, if any |
|
2351 |
E$^2$PROM write operations are pending. If this is true, the first |
|
2352 |
pending operation is executed by starting the SII state machine for |
|
| 379 | 2353 |
writing access. $\rightarrow$~WRITE EEPROM |
| 369 | 2354 |
|
2355 |
If all prior conditions are false, the state machine is restarted. |
|
| 379 | 2356 |
$\rightarrow$~START |
| 369 | 2357 |
|
2358 |
\item[WRITE EEPROM] The SII state machine is executed until |
|
| 379 | 2359 |
termination. $\rightarrow$~WRITE EEPROM |
| 369 | 2360 |
|
2361 |
If the current word has been written successfully, and there are |
|
2362 |
still word to write, the SII state machine is started for the next |
|
| 379 | 2363 |
word. $\rightarrow$~WRITE EEPROM |
| 369 | 2364 |
|
2365 |
If all words have been written successfully, the new E$^2$PROM |
|
2366 |
contents are evaluated and the state machine is restarted. |
|
| 379 | 2367 |
$\rightarrow$~START |
| 369 | 2368 |
|
2369 |
\end{description}
|
|
2370 |
||
2371 |
%------------------------------------------------------------------------------ |
|
2372 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2373 |
\section{The Slave Scan State Machine}
|
| 369 | 2374 |
\label{sec:fsm-scan}
|
2375 |
\index{FSM!Slave Scan}
|
|
2376 |
||
2377 |
The slave scan state machine, which can be seen in |
|
2378 |
figure~\ref{fig:fsm-slavescan}, leads through the process of fetching
|
|
2379 |
all slave information. |
|
2380 |
||
2381 |
\begin{figure}[htbp]
|
|
2382 |
\centering |
|
2383 |
\includegraphics[width=.6\textwidth]{images/fsm-slavescan}
|
|
2384 |
\caption{Transition diagram of the slave scan state machine}
|
|
2385 |
\label{fig:fsm-slavescan}
|
|
2386 |
\end{figure}
|
|
2387 |
||
2388 |
\begin{description}
|
|
2389 |
\item[START] In the beginning state of the slave scan state machine, |
|
2390 |
the station address is written to the slave, which is always the |
|
2391 |
ring position~+~$1$. In this way, the address 0x0000 (default |
|
2392 |
address) is not used, which makes it easy to detect unconfigured |
|
| 379 | 2393 |
slaves. $\rightarrow$~ADDRESS |
| 369 | 2394 |
|
2395 |
\item[ADDRESS] The writing of the station address is verified. After |
|
2396 |
that, the slave's ``AL Control Response'' attribute is queried. |
|
| 379 | 2397 |
$\rightarrow$~STATE |
| 369 | 2398 |
|
2399 |
\item[STATE] The AL state is evaluated. A warning is output, if the |
|
2400 |
slave has still the \textit{Change} bit set. After that, the slave's
|
|
2401 |
``DL Information'' attribute is queried. |
|
| 379 | 2402 |
$\rightarrow$~BASE |
| 369 | 2403 |
|
2404 |
\item[BASE] The queried base data are evaluated: Slave type, revision |
|
2405 |
and build number, and even more important, the number of supported |
|
2406 |
sync managers and FMMUs are stored. After that, the slave's data |
|
2407 |
link layer information is read from the ``DL Status'' attribute at |
|
| 379 | 2408 |
address 0x0110. $\rightarrow$~DATALINK |
| 369 | 2409 |
|
2410 |
\item[DATALINK] In this state, the DL information is evaluated: This |
|
2411 |
information about the communication ports contains, if the link is |
|
2412 |
up, if the loop has been closed and if there is a carrier detected |
|
2413 |
on the RX side of each port. |
|
2414 |
||
2415 |
Then, the state machine starts measuring the size of the slave's |
|
2416 |
E$^2$PROM contents. This is done by subsequently reading out each |
|
2417 |
category header, until the last category is reached (type 0xFFFF). |
|
2418 |
This procedure is started by querying the first category header at |
|
2419 |
word address 0x0040 via the SII state machine. |
|
| 379 | 2420 |
$\rightarrow$~EEPROM SIZE |
| 369 | 2421 |
|
2422 |
\item[EEPROM SIZE] The SII state machine is executed until |
|
| 379 | 2423 |
termination. $\rightarrow$~EEPROM SIZE |
| 369 | 2424 |
|
2425 |
If the category type does not mark the end of the categories, the |
|
2426 |
position of the next category header is determined via the length of |
|
2427 |
the current category, and the SII state machine is started again. |
|
| 379 | 2428 |
$\rightarrow$~EEPROM SIZE |
| 369 | 2429 |
|
2430 |
If the size of the E$^2$PROM contents has been determined, memory is |
|
2431 |
allocated, to read all the contents. The SII state machine is |
|
| 379 | 2432 |
started to read the first word. $\rightarrow$~EEPROM DATA |
| 369 | 2433 |
|
2434 |
\item[EEPROM DATA] The SII state machine is executed until |
|
| 379 | 2435 |
termination. $\rightarrow$~EEPROM DATA |
| 369 | 2436 |
|
2437 |
Two words have been read. If more than one word is needed, the two |
|
2438 |
words are written in the allocated memory. Otherwise only one word |
|
2439 |
(the last word) is copied. If more words are to read, the SII state |
|
2440 |
machine is started again to read the next two words. |
|
| 379 | 2441 |
$\rightarrow$~EEPROM DATA |
| 369 | 2442 |
|
2443 |
The complete E$^2$PROM contents have been read. The slave's identity |
|
2444 |
object and mailbox information are evaluated. Moreover the category |
|
2445 |
types STRINGS, GENERAL, SYNC and PDO are evaluated. The slave |
|
| 379 | 2446 |
scanning has been completed. $\rightarrow$~END |
| 369 | 2447 |
|
2448 |
\item[END] Slave scanning has been finished. |
|
2449 |
||
2450 |
\end{description}
|
|
2451 |
||
2452 |
%------------------------------------------------------------------------------ |
|
2453 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2454 |
\section{The Slave Configuration State Machine}
|
| 369 | 2455 |
\label{sec:fsm-conf}
|
2456 |
\index{FSM!Slave Configuration}
|
|
2457 |
||
2458 |
The slave configuration state machine, which can be seen in |
|
2459 |
figure~\ref{fig:fsm-slaveconf}, leads through the process of
|
|
2460 |
configuring a slave and bringing it to a certain state. |
|
2461 |
||
2462 |
\begin{figure}[htbp]
|
|
2463 |
\centering |
|
2464 |
\includegraphics[width=.6\textwidth]{images/fsm-slaveconf}
|
|
2465 |
\caption{Transition diagram of the slave configuration state
|
|
2466 |
machine} |
|
2467 |
\label{fig:fsm-slaveconf}
|
|
2468 |
\end{figure}
|
|
2469 |
||
2470 |
\begin{description}
|
|
2471 |
\item[INIT] The state change state machine has been initialized to |
|
| 379 | 2472 |
bring the slave into the INIT state. Now, the slave state change |
2473 |
state machine is executed until termination. $\rightarrow$~INIT |
|
| 369 | 2474 |
|
2475 |
If the slave state change failed, the configuration has to be |
|
| 379 | 2476 |
aborted. $\rightarrow$~END |
2477 |
||
2478 |
The slave state change succeeded and the slave is now in INIT state. |
|
2479 |
If this is the target state, the configuration is finished. |
|
2480 |
$\rightarrow$~END |
|
| 369 | 2481 |
|
2482 |
If the slave does not support any sync managers, the sync manager |
|
2483 |
configuration can be skipped. The state change state machine is |
|
| 379 | 2484 |
started to bring the slave into PREOP state. |
2485 |
$\rightarrow$~PREOP |
|
| 369 | 2486 |
|
2487 |
Sync managers are configured conforming to the sync manager category |
|
2488 |
information provided in the slave's E$^2$PROM. The corresponding |
|
| 379 | 2489 |
datagram is issued. $\rightarrow$~SYNC |
| 369 | 2490 |
|
2491 |
\item[SYNC] If the sync manager configuration datagram is accepted, |
|
2492 |
the sync manager configuration was successful. The slave may now |
|
| 379 | 2493 |
enter the PREOP state, and the state change state machine is |
2494 |
started. $\rightarrow$~PREOP |
|
| 369 | 2495 |
|
2496 |
\item[PREOP] The state change state machine is executed until |
|
| 379 | 2497 |
termination. $\rightarrow$~PREOP |
| 369 | 2498 |
|
2499 |
If the state change failed, the configuration has to be aborted. |
|
| 379 | 2500 |
$\rightarrow$~END |
2501 |
||
2502 |
If the PREOP state was the target state, the configuration is |
|
2503 |
finished. $\rightarrow$~END |
|
| 369 | 2504 |
|
2505 |
If the slave supports no FMMUs, the FMMU configuration can be |
|
| 814 | 2506 |
skipped. If the slave has Sdos to configure, it is begun with |
2507 |
sending the first Sdo. $\rightarrow$~SDO\_CONF |
|
2508 |
||
2509 |
If no Sdo configurations are provided, the slave can now directly be |
|
|
813
bfc3f1ab52de
Fixed typo SAVEOP -> SAFEOP.
Florian Pose <fp@igh-essen.com>
parents:
487
diff
changeset
|
2510 |
brought into the SAFEOP state and the state change state machine is |
|
bfc3f1ab52de
Fixed typo SAVEOP -> SAFEOP.
Florian Pose <fp@igh-essen.com>
parents:
487
diff
changeset
|
2511 |
started again. $\rightarrow$~SAFEOP |
| 369 | 2512 |
|
| 814 | 2513 |
Otherwise, all supported FMMUs are configured according to the Pdos |
| 369 | 2514 |
requested via the master's realtime interface. The appropriate |
| 379 | 2515 |
datagram is issued. $\rightarrow$~FMMU |
| 369 | 2516 |
|
2517 |
\item[FMMU] The FMMU configuration datagram was accepted. If the slave |
|
| 814 | 2518 |
has Sdos to configure, it is begun with sending the first Sdo. |
| 379 | 2519 |
$\rightarrow$~SDO\_CONF |
2520 |
||
|
813
bfc3f1ab52de
Fixed typo SAVEOP -> SAFEOP.
Florian Pose <fp@igh-essen.com>
parents:
487
diff
changeset
|
2521 |
Otherwise, the slave can now be brought into the SAFEOP state. The |
| 379 | 2522 |
state change state machine is started. |
|
813
bfc3f1ab52de
Fixed typo SAVEOP -> SAFEOP.
Florian Pose <fp@igh-essen.com>
parents:
487
diff
changeset
|
2523 |
$\rightarrow$~SAFEOP |
| 369 | 2524 |
|
2525 |
\item[SDO\_CONF] The CoE state machine is executed until termination. |
|
| 379 | 2526 |
$\rightarrow$~SDO\_CONF |
| 369 | 2527 |
|
| 814 | 2528 |
If another Sdo has to be configured, a new Sdo download sequence is |
| 379 | 2529 |
begun. $\rightarrow$~SDO\_CONF |
2530 |
||
|
813
bfc3f1ab52de
Fixed typo SAVEOP -> SAFEOP.
Florian Pose <fp@igh-essen.com>
parents:
487
diff
changeset
|
2531 |
Otherwise, the slave can now be brought into the SAFEOP state. The |
| 379 | 2532 |
state change state machine is started. |
|
813
bfc3f1ab52de
Fixed typo SAVEOP -> SAFEOP.
Florian Pose <fp@igh-essen.com>
parents:
487
diff
changeset
|
2533 |
$\rightarrow$~SAFEOP |
|
bfc3f1ab52de
Fixed typo SAVEOP -> SAFEOP.
Florian Pose <fp@igh-essen.com>
parents:
487
diff
changeset
|
2534 |
|
|
bfc3f1ab52de
Fixed typo SAVEOP -> SAFEOP.
Florian Pose <fp@igh-essen.com>
parents:
487
diff
changeset
|
2535 |
\item[SAFEOP] The state change state machine is executed until |
|
bfc3f1ab52de
Fixed typo SAVEOP -> SAFEOP.
Florian Pose <fp@igh-essen.com>
parents:
487
diff
changeset
|
2536 |
termination. $\rightarrow$~SAFEOP |
| 369 | 2537 |
|
2538 |
If the state change failed, the configuration has to be aborted. |
|
| 379 | 2539 |
$\rightarrow$~END |
2540 |
||
|
813
bfc3f1ab52de
Fixed typo SAVEOP -> SAFEOP.
Florian Pose <fp@igh-essen.com>
parents:
487
diff
changeset
|
2541 |
If the SAFEOP state was the target state, the configuration is |
| 379 | 2542 |
finished. $\rightarrow$~END |
2543 |
||
2544 |
The slave can now directly be brought into the OP state and the |
|
2545 |
state change state machine is started a last time. |
|
2546 |
$\rightarrow$~OP |
|
| 369 | 2547 |
|
2548 |
\item[OP] The state change state machine is executed until |
|
| 379 | 2549 |
termination. $\rightarrow$~OP |
| 369 | 2550 |
|
2551 |
If the state change state machine terminates, the slave |
|
2552 |
configuration is finished, regardless of its success. |
|
| 379 | 2553 |
$\rightarrow$~END |
| 369 | 2554 |
|
2555 |
\item[END] The termination state. |
|
2556 |
||
2557 |
\end{description}
|
|
2558 |
||
2559 |
%------------------------------------------------------------------------------ |
|
2560 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2561 |
\section{The State Change State Machine}
|
| 369 | 2562 |
\label{sec:fsm-change}
|
2563 |
\index{FSM!State Change}
|
|
2564 |
||
2565 |
The state change state machine, which can be seen in |
|
2566 |
figure~\ref{fig:fsm-change}, leads through the process of changing a
|
|
2567 |
slave's state. This implements the states and transitions described in |
|
2568 |
\cite[section~6.4.1]{alspec}.
|
|
2569 |
||
2570 |
\begin{figure}[htbp]
|
|
2571 |
\centering |
|
2572 |
\includegraphics[width=.9\textwidth]{images/fsm-change}
|
|
2573 |
\caption{Transition diagram of the state change state machine}
|
|
2574 |
\label{fig:fsm-change}
|
|
2575 |
\end{figure}
|
|
2576 |
||
2577 |
\begin{description}
|
|
2578 |
\item[START] The beginning state, where a datagram with the state |
|
2579 |
change command is written to the slave's ``AL Control Request'' |
|
| 379 | 2580 |
attribute. Nothing can fail. $\rightarrow$~CHECK |
| 369 | 2581 |
|
2582 |
\item[CHECK] After the state change datagram has been sent, the ``AL |
|
2583 |
Control Response'' attribute is queried with a second datagram. |
|
| 379 | 2584 |
$\rightarrow$~STATUS |
| 369 | 2585 |
|
2586 |
\item[STATUS] The read memory contents are evaluated: While the |
|
2587 |
parameter \textit{State} still contains the old slave state, the
|
|
2588 |
slave is busy with reacting on the state change command. In this |
|
2589 |
case, the attribute has to be queried again. |
|
| 379 | 2590 |
$\rightarrow$~STATUS |
| 369 | 2591 |
|
2592 |
In case of success, the \textit{State} parameter contains the new
|
|
2593 |
state and the \textit{Change} bit is cleared. The slave is in the
|
|
| 379 | 2594 |
requested state. $\rightarrow$~END |
| 369 | 2595 |
|
2596 |
If the slave can not process the state change, the \textit{Change}
|
|
2597 |
bit is set: Now the master tries to get the reason for this by |
|
2598 |
querying the \textit{AL Status Code} parameter.
|
|
| 379 | 2599 |
$\rightarrow$~CODE |
| 369 | 2600 |
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2601 |
\item[END] If the state machine ends in this state, the slave's state |
| 369 | 2602 |
change has been successful. |
2603 |
||
2604 |
\item[CODE] The status code query has been sent. Reading the |
|
2605 |
\textit{AL Status Code} might fail, because not all slaves support
|
|
2606 |
this parameter. Anyway, the master has to acknowledge the state |
|
2607 |
change error by writing the current slave state to the ``AL Control |
|
2608 |
Request'' attribute with the \textit{Acknowledge} bit set.
|
|
| 379 | 2609 |
$\rightarrow$~ACK |
| 369 | 2610 |
|
2611 |
\item[ACK] After that, the ``AL Control Response'' attribute is |
|
2612 |
queried for the state of the acknowledgement. |
|
| 379 | 2613 |
$\rightarrow$~CHECK ACK |
| 369 | 2614 |
|
2615 |
\item[CHECK ACK] If the acknowledgement has been accepted by the |
|
2616 |
slave, the old state is kept. Still, the state change was |
|
| 379 | 2617 |
unsuccessful. $\rightarrow$~ERROR |
| 369 | 2618 |
|
2619 |
If the acknowledgement is ignored by the slave, a timeout happens. |
|
2620 |
In any case, the overall state change was unsuccessful. |
|
| 379 | 2621 |
$\rightarrow$~ERROR |
| 369 | 2622 |
|
2623 |
If there is still now response from the slave, but the timer did not |
|
2624 |
run out yet, the slave's ``AL Control Response'' attribute is |
|
| 379 | 2625 |
queried again. $\rightarrow$~CHECK ACK |
| 369 | 2626 |
|
2627 |
\item[ERROR] If the state machine ends in this state, the slave's |
|
2628 |
state change was unsuccessful. |
|
2629 |
||
2630 |
\end{description}
|
|
2631 |
||
2632 |
%------------------------------------------------------------------------------ |
|
2633 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2634 |
\section{The SII State Machine}
|
| 369 | 2635 |
\label{sec:fsm-sii}
|
2636 |
\index{FSM!SII}
|
|
2637 |
||
2638 |
The SII\index{SII} state machine (shown in figure~\ref{fig:fsm-sii})
|
|
2639 |
implements the process of reading or writing E$^2$PROM data via the |
|
2640 |
Slave Information Interface described in \cite[section~5.4]{alspec}.
|
|
2641 |
||
2642 |
\begin{figure}[htbp]
|
|
2643 |
\centering |
|
2644 |
\includegraphics[width=.9\textwidth]{images/fsm-sii}
|
|
2645 |
\caption{Transition diagram of the SII state machine}
|
|
2646 |
\label{fig:fsm-sii}
|
|
2647 |
\end{figure}
|
|
2648 |
||
2649 |
\begin{description}
|
|
2650 |
\item[READ\_START] The beginning state for reading access, where the |
|
2651 |
read request and the requested address are written to the SII |
|
2652 |
attribute. Nothing can fail up to now. |
|
| 379 | 2653 |
$\rightarrow$~READ\_CHECK |
| 369 | 2654 |
|
2655 |
\item[READ\_CHECK] When the SII read request has been sent |
|
2656 |
successfully, a timer is started. A check/fetch datagram is issued, |
|
2657 |
that reads out the SII attribute for state and data. |
|
| 379 | 2658 |
$\rightarrow$~READ\_FETCH |
| 369 | 2659 |
|
2660 |
\item[READ\_FETCH] Upon reception of the check/fetch datagram, the |
|
2661 |
\textit{Read Operation} and \textit{Busy} parameters are checked:
|
|
2662 |
\begin{itemize}
|
|
2663 |
\item If the slave is still busy with fetching E$^2$PROM data into |
|
2664 |
the interface, the timer is checked. If it timed out, the reading |
|
| 379 | 2665 |
is aborted ($\rightarrow$~ERROR), if not, the check/fetch datagram |
2666 |
is issued again. $\rightarrow$~READ\_FETCH |
|
| 369 | 2667 |
|
2668 |
\item If the slave is ready with reading data, these are copied from |
|
2669 |
the datagram and the read cycle is completed. |
|
| 379 | 2670 |
$\rightarrow$~END |
| 369 | 2671 |
\end{itemize}
|
2672 |
\end{description}
|
|
2673 |
||
2674 |
The write access states behave nearly the same: |
|
2675 |
||
2676 |
\begin{description}
|
|
2677 |
\item[WRITE\_START] The beginning state for writing access, |
|
2678 |
respectively. A write request, the target address and the data word |
|
2679 |
are written to the SII attribute. Nothing can fail. |
|
| 379 | 2680 |
$\rightarrow$~WRITE\_CHECK |
| 369 | 2681 |
|
2682 |
\item[WRITE\_CHECK] When the SII write request has been sent |
|
2683 |
successfully, the timer is started. A check datagram is issued, that |
|
2684 |
reads out the SII attribute for the state of the write operation. |
|
| 379 | 2685 |
$\rightarrow$~WRITE\_CHECK2 |
| 369 | 2686 |
|
2687 |
\item[WRITE\_CHECK2] Upon reception of the check datagram, the |
|
2688 |
\textit{Write Operation} and \textit{Busy} parameters are checked:
|
|
2689 |
\begin{itemize}
|
|
2690 |
\item If the slave is still busy with writing E$^2$PROM data, the |
|
2691 |
timer is checked. If it timed out, the operation is aborted |
|
| 379 | 2692 |
($\rightarrow$~ERROR), if not, the check datagram is issued again. |
2693 |
$\rightarrow$~WRITE\_CHECK2 |
|
| 369 | 2694 |
\item If the slave is ready with writing data, the write cycle is |
| 379 | 2695 |
completed. $\rightarrow$~END |
| 369 | 2696 |
\end{itemize}
|
2697 |
\end{description}
|
|
2698 |
||
2699 |
%------------------------------------------------------------------------------ |
|
2700 |
||
|
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diff
changeset
|
2701 |
\chapter{Mailbox Protocol Implementations}
|
| 369 | 2702 |
\index{Mailbox}
|
2703 |
||
2704 |
The EtherCAT master implements the EoE and the CoE mailbox |
|
2705 |
protocols. See the below section for details. |
|
2706 |
||
2707 |
%------------------------------------------------------------------------------ |
|
2708 |
||
|
1085
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diff
changeset
|
2709 |
\section{Ethernet-over-EtherCAT (EoE)}
|
| 369 | 2710 |
\label{sec:eoeimp}
|
2711 |
\index{EoE}
|
|
2712 |
||
2713 |
The EtherCAT master implements the Ethernet-over-EtherCAT mailbox |
|
2714 |
protocol to enable the tunneling of Ethernet frames to special slaves, |
|
2715 |
that can either have physical Ethernet ports to forward the frames to, |
|
2716 |
or have an own IP stack to receive the frames. |
|
2717 |
||
2718 |
\paragraph{Virtual Network Interfaces}
|
|
2719 |
||
2720 |
The master creates a virtual EoE network interface for every |
|
2721 |
EoE-capable slave. These interfaces are called \textit{eoeX}, where X
|
|
2722 |
is a number provided by the kernel on interface registration. Frames |
|
2723 |
sent to these interfaces are forwarded to the associated slaves by the |
|
2724 |
master. Frames, that are received by the slaves, are fetched by the |
|
2725 |
master and forwarded to the virtual interfaces. |
|
2726 |
||
2727 |
This bears the following advantages: |
|
2728 |
||
2729 |
\begin{itemize}
|
|
2730 |
\item Flexibility: The user can decide, how the EoE-capable slaves are |
|
2731 |
interconnected with the rest of the world. |
|
2732 |
\item Standard tools can be used to monitor the EoE activity and to |
|
2733 |
configure the EoE interfaces. |
|
2734 |
\item The Linux kernel's layer-2-bridging implementation (according to |
|
2735 |
the IEEE 802.1D MAC Bridging standard) can be used natively to |
|
2736 |
bridge Ethernet traffic between EoE-capable slaves. |
|
2737 |
\item The Linux kernel's network stack can be used to route packets |
|
2738 |
between EoE-capable slaves and to track security issues, just like |
|
2739 |
having physical network interfaces. |
|
2740 |
\end{itemize}
|
|
2741 |
||
2742 |
\paragraph{EoE Handlers}
|
|
2743 |
||
|
1085
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diff
changeset
|
2744 |
The virtual EoE interfaces and the related functionality is encapsulated in the |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
917
diff
changeset
|
2745 |
\textit{ec\_eoe\_t} class (see section~\ref{sec:class-eoe}). So the master
|
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
2746 |
does not create the network interfaces directly: This is done inside the |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2747 |
constructor of the \textit{ec\_eoe\_t} class. An object of this class is called
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2748 |
``EoE handler'' below. An EoE handler additionally contains a frame queue. Each |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2749 |
time, the kernel passes a new socket buffer for sending via the interface's |
| 369 | 2750 |
\textit{hard\_start\_xmit()} callback, the socket buffer is queued for
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2751 |
transmission by the EoE state machine (see below). If the queue gets filled up, |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2752 |
the passing of new socket buffers is suspended with a call to |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2753 |
\textit{netif\_stop\_queue()}.
|
| 369 | 2754 |
|
2755 |
\paragraph{Static Handler Creation}
|
|
2756 |
||
2757 |
The master creates a pool of EoE handlers at startup, that are coupled |
|
2758 |
to EoE-capable slaves on demand. The lifetime of the corresponding |
|
2759 |
network interfaces is equal to the lifetime of the master module. |
|
2760 |
This approach is opposed to creating the virtual network interfaces on |
|
2761 |
demand (i.~e. on running across a new EoE-capable slave). The latter |
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
2762 |
approach was considered as difficult, because of several reasons: |
| 369 | 2763 |
|
2764 |
\begin{itemize}
|
|
2765 |
\item The \textit{alloc\_netdev()} function can sleep and must be
|
|
2766 |
called from a non-interrupt context. This reduces the flexibility of |
|
2767 |
choosing an appropriate method for cyclic EoE processing. |
|
2768 |
\item Unregistering network interfaces requires them to be ``down'', |
|
2769 |
which can not be guaranteed upon sudden disappearing of an |
|
2770 |
EoE-capable slave. |
|
2771 |
\item The connection to the EoE-capable slaves must be as continuous |
|
2772 |
as possible. Especially the transition from idle to operation mode |
|
2773 |
(and vice versa) causes the rebuilding of the internal data |
|
2774 |
structures. These transitions must be as transparent as possible for |
|
2775 |
the instances using the network interfaces. |
|
2776 |
\end{itemize}
|
|
2777 |
||
2778 |
\paragraph{Number of Handlers}
|
|
2779 |
||
2780 |
The master module has a parameter \textit{ec\_eoeif\_count} to specify
|
|
2781 |
the number of EoE interfaces (and handlers) per master to create. This |
|
2782 |
parameter can either be specified when manually loading the master |
|
2783 |
module, or (when using the init script) by setting the |
|
| 379 | 2784 |
\$EOE\_INTERFACES variable in the sysconfig file (see |
| 369 | 2785 |
section~\ref{sec:sysconfig}). Upon loading of the master module, the
|
2786 |
virtual interfaces become available: |
|
2787 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
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parents:
917
diff
changeset
|
2788 |
\begin{lstlisting}[gobble=2]
|
| 379 | 2789 |
# `\textbf{ifconfig -a}`
|
| 369 | 2790 |
eoe0 Link encap:Ethernet HWaddr 00:11:22:33:44:06 |
2791 |
BROADCAST MULTICAST MTU:1500 Metric:1 |
|
2792 |
RX packets:0 errors:0 dropped:0 overruns:0 frame:0 |
|
2793 |
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 |
|
2794 |
collisions:0 txqueuelen:1000 |
|
2795 |
RX bytes:0 (0.0 b) TX bytes:0 (0.0 b) |
|
2796 |
||
2797 |
eoe1 Link encap:Ethernet HWaddr 00:11:22:33:44:07 |
|
2798 |
BROADCAST MULTICAST MTU:1500 Metric:1 |
|
2799 |
RX packets:0 errors:0 dropped:0 overruns:0 frame:0 |
|
2800 |
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 |
|
2801 |
collisions:0 txqueuelen:1000 |
|
2802 |
RX bytes:0 (0.0 b) TX bytes:0 (0.0 b) |
|
2803 |
... |
|
2804 |
\end{lstlisting}
|
|
2805 |
||
2806 |
\paragraph{Coupling of EoE Slaves}
|
|
2807 |
||
2808 |
During execution of the slave scan state machine (see |
|
2809 |
section~\ref{sec:fsm-scan}), the master determines the supported
|
|
2810 |
mailbox protocols. This is done by examining the ``Supported Mailbox |
|
2811 |
Protocols'' mask field at word address 0x001C of the SII\index{SII}.
|
|
2812 |
If bit 1 is set, the slave supports the EoE protocol. After slave |
|
2813 |
scanning, the master runs through all slaves again and couples each |
|
2814 |
EoE-capable slave to a free EoE handler. It can happen, that there are |
|
2815 |
not enough EoE handlers to cover all EoE-capable slaves. In this case, |
|
2816 |
the number of EoE handlers must be increased accordingly. |
|
2817 |
||
2818 |
\paragraph{EoE State Machine}
|
|
2819 |
\index{FSM!EoE}
|
|
2820 |
||
2821 |
Every EoE handler owns an EoE state machine, that is used to send |
|
2822 |
frames to the coupled slave and receive frames from the it via the EoE |
|
2823 |
communication primitives. This state machine is showed in |
|
2824 |
figure~\ref{fig:fsm-eoe}.
|
|
2825 |
||
2826 |
\begin{figure}[htbp]
|
|
2827 |
\centering |
|
2828 |
\includegraphics[width=.7\textwidth]{images/fsm-eoe}
|
|
2829 |
\caption{Transition diagram of the EoE state machine}
|
|
2830 |
\label{fig:fsm-eoe}
|
|
2831 |
\end{figure}
|
|
2832 |
||
2833 |
\begin{description}
|
|
2834 |
\item[RX\_START] The beginning state of the EoE state machine. A |
|
2835 |
mailbox check datagram is sent, to query the slave's mailbox for new |
|
| 379 | 2836 |
frames. $\rightarrow$~RX\_CHECK |
| 369 | 2837 |
|
2838 |
\item[RX\_CHECK] The mailbox check datagram is received. If the |
|
2839 |
slave's mailbox did not contain data, a transmit cycle is started. |
|
| 379 | 2840 |
$\rightarrow$~TX\_START |
| 369 | 2841 |
|
2842 |
If there are new data in the mailbox, a datagram is sent to fetch |
|
| 379 | 2843 |
the new data. $\rightarrow$~RX\_FETCH |
| 369 | 2844 |
|
2845 |
\item[RX\_FETCH] The fetch datagram is received. If the mailbox data |
|
2846 |
do not contain a ``EoE Fragment request'' command, the data are |
|
2847 |
dropped and a transmit sequence is started. |
|
| 379 | 2848 |
$\rightarrow$~TX\_START |
| 369 | 2849 |
|
2850 |
If the received Ethernet frame fragment is the first fragment, a new |
|
2851 |
socket buffer is allocated. In either case, the data are copied into |
|
2852 |
the correct position of the socket buffer. |
|
2853 |
||
2854 |
If the fragment is the last fragment, the socket buffer is forwarded |
|
2855 |
to the network stack and a transmit sequence is started. |
|
| 379 | 2856 |
$\rightarrow$~TX\_START |
| 369 | 2857 |
|
2858 |
Otherwise, a new receive sequence is started to fetch the next |
|
| 379 | 2859 |
fragment. $\rightarrow$~RX\_\-START |
| 369 | 2860 |
|
2861 |
\item[TX\_START] The beginning state of a transmit sequence. It is |
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
2862 |
checked, if the transmission queue contains a frame to send. If not, |
| 379 | 2863 |
a receive sequence is started. $\rightarrow$~RX\_START |
| 369 | 2864 |
|
2865 |
If there is a frame to send, it is dequeued. If the queue was |
|
2866 |
inactive before (because it was full), the queue is woken up with a |
|
2867 |
call to \textit{netif\_wake\_queue()}. The first fragment of the
|
|
| 379 | 2868 |
frame is sent. $\rightarrow$~TX\_SENT |
| 369 | 2869 |
|
2870 |
\item[TX\_SENT] It is checked, if the first fragment was sent |
|
2871 |
successfully. If the current frame consists of further fragments, |
|
| 379 | 2872 |
the next one is sent. $\rightarrow$~TX\_SENT |
| 369 | 2873 |
|
2874 |
If the last fragment was sent, a new receive sequence is started. |
|
| 379 | 2875 |
$\rightarrow$~RX\_START |
| 369 | 2876 |
\end{description}
|
2877 |
||
2878 |
\paragraph{EoE Processing}
|
|
2879 |
||
2880 |
To execute the EoE state machine of every active EoE handler, there |
|
2881 |
must be a cyclic process. The easiest thing would be to execute the |
|
2882 |
EoE state machines synchronously to the operation state machine (see |
|
2883 |
section~\ref{sec:fsm-op}) with every realtime cycle. This approach has
|
|
2884 |
the following disadvantages: |
|
2885 |
||
2886 |
\begin{itemize}
|
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2887 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2888 |
\item Only one EoE fragment can be sent or received every few cycles. This |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2889 |
causes the data rate to be very low, because the EoE state machines are not |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2890 |
executed in the time between the application cycles. Moreover, the data rate |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2891 |
would be dependent on the period of the application task. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2892 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2893 |
\item The receiving and forwarding of frames to the kernel requires the dynamic |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2894 |
allocation of frames. Some realtime extensions do not support calling memory |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2895 |
allocation functions in realtime context, so the EoE state machine may not be |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2896 |
executed with each application cycle. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2897 |
|
| 369 | 2898 |
\end{itemize}
|
2899 |
||
2900 |
To overcome these problems, an own cyclic process is needed to |
|
2901 |
asynchronously execute the EoE state machines. For that, the master |
|
2902 |
owns a kernel timer, that is executed each timer interrupt. This |
|
2903 |
guarantees a constant bandwidth, but poses the new problem of |
|
2904 |
concurrent access to the master. The locking mechanisms needed for |
|
2905 |
this are introduced in section~\ref{sec:concurr}.
|
|
2906 |
Section~\ref{sec:concurrency} gives practical implementation examples.
|
|
2907 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
2908 |
\paragraph{Idle phase}
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2909 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2910 |
EoE data must also be exchanged in idle phase, to guarantee the continuous |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2911 |
availability of the connection to the EoE-capable slaves. Although there is no |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2912 |
application connected in this case, the master is still accessed by the master |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2913 |
state machine (see section~\ref{sec:fsm-master}). With the EoE timer running in
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2914 |
addition, there is still concurrency, that has to be protected by a lock. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2915 |
Therefore the master owns an internal spinlock that is used protect master |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2916 |
access during idle phase. |
| 369 | 2917 |
|
2918 |
\paragraph{Automatic Configuration}
|
|
2919 |
||
| 379 | 2920 |
By default, slaves are left in INIT state during idle mode. If an EoE |
2921 |
interface is set to running state (i.~e. with the \textit{ifconfig up}
|
|
2922 |
command), the requested slave state of the related slave is |
|
2923 |
automatically set to OP, whereupon the idle state machine will attempt |
|
2924 |
to configure the slave and put it into operation. |
|
| 369 | 2925 |
|
2926 |
%------------------------------------------------------------------------------ |
|
2927 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
2928 |
\section{CANopen-over-EtherCAT (CoE)}
|
| 369 | 2929 |
\label{sec:coeimp}
|
2930 |
\index{CoE}
|
|
2931 |
||
2932 |
The CANopen-over-EtherCAT protocol \cite[section~5.6]{alspec} is used
|
|
2933 |
to configure slaves on application level. Each CoE-capable slave |
|
| 814 | 2934 |
provides a list of Sdos for this reason. |
2935 |
||
2936 |
\paragraph{Sdo Configuration}
|
|
2937 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
2938 |
The Sdo configurations have to be provided by the application. This is done |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2939 |
via the \textit{ecrt\_slave\_conf\_sdo*()} methods (see
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
2940 |
section~\ref{sec:ecrt-slave}), that are part of the realtime interface. The
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
2941 |
slave stores the Sdo configurations in a linked list, but does not apply them |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
2942 |
at once. |
| 369 | 2943 |
|
| 814 | 2944 |
\paragraph{Sdo Download State Machine}
|
2945 |
||
2946 |
The best time to apply Sdo configurations is during the slave's PREOP |
|
| 379 | 2947 |
state, because mailbox communication is already possible and slave's |
2948 |
application will start with updating input data in the succeeding |
|
| 814 | 2949 |
SAFEOP state. Therefore the Sdo configuration has to be part of the |
| 379 | 2950 |
slave configuration state machine (see section~\ref{sec:fsm-conf}): It
|
| 814 | 2951 |
is implemented via an Sdo download state machine, that is executed |
|
813
bfc3f1ab52de
Fixed typo SAVEOP -> SAFEOP.
Florian Pose <fp@igh-essen.com>
parents:
487
diff
changeset
|
2952 |
just before entering the slave's SAFEOP state. In this way, it is |
| 814 | 2953 |
guaranteed that the Sdo configurations are applied each time, the |
| 379 | 2954 |
slave is reconfigured. |
| 369 | 2955 |
|
| 814 | 2956 |
The transition diagram of the Sdo Download state machine can be seen |
| 369 | 2957 |
in figure~\ref{fig:fsm-coedown}.
|
2958 |
||
2959 |
\begin{figure}[htbp]
|
|
2960 |
\centering |
|
2961 |
\includegraphics[width=.9\textwidth]{images/fsm-coedown}
|
|
2962 |
\caption{Transition diagram of the CoE download state machine}
|
|
2963 |
\label{fig:fsm-coedown}
|
|
2964 |
\end{figure}
|
|
2965 |
||
2966 |
\begin{description}
|
|
2967 |
\item[START] The beginning state of the CoE download state |
|
| 814 | 2968 |
machine. The ``Sdo Download Normal Request'' mailbox command is |
| 379 | 2969 |
sent. $\rightarrow$~REQUEST |
| 369 | 2970 |
|
2971 |
\item[REQUEST] It is checked, if the CoE download request has been |
|
2972 |
received by the slave. After that, a mailbox check command is issued |
|
| 379 | 2973 |
and a timer is started. $\rightarrow$~CHECK |
| 369 | 2974 |
|
2975 |
\item[CHECK] If no mailbox data is available, the timer is checked. |
|
2976 |
\begin{itemize}
|
|
| 814 | 2977 |
\item If it timed out, the Sdo download is aborted. |
| 379 | 2978 |
$\rightarrow$~ERROR |
| 369 | 2979 |
\item Otherwise, the mailbox is queried again. |
| 379 | 2980 |
$\rightarrow$~CHECK |
| 369 | 2981 |
\end{itemize}
|
2982 |
||
2983 |
If the mailbox contains new data, the response is fetched. |
|
| 379 | 2984 |
$\rightarrow$~RESPONSE |
| 369 | 2985 |
|
2986 |
\item[RESPONSE] If the mailbox response could not be fetched, the data |
|
| 814 | 2987 |
is invalid, the wrong protocol was received, or a ``Abort Sdo |
2988 |
Transfer Request'' was received, the Sdo download is aborted. |
|
| 379 | 2989 |
$\rightarrow$~ERROR |
| 369 | 2990 |
|
| 814 | 2991 |
If a ``Sdo Download Normal Response'' acknowledgement was received, |
2992 |
the Sdo download was successful. $\rightarrow$~END |
|
2993 |
||
2994 |
\item[END] The Sdo download was successful. |
|
2995 |
||
2996 |
\item[ERROR] The Sdo download was aborted due to an error. |
|
| 369 | 2997 |
|
2998 |
\end{description}
|
|
2999 |
||
3000 |
%------------------------------------------------------------------------------ |
|
3001 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3002 |
\chapter{User Space}
|
| 369 | 3003 |
\label{sec:user}
|
3004 |
\index{User space}
|
|
3005 |
||
3006 |
For the master runs as a kernel module, accessing it is natively |
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3007 |
limited to analyzing Syslog messages and controlling using modutils. |
| 369 | 3008 |
|
3009 |
It is necessary to implement further interfaces, that make it easier |
|
3010 |
to access the master from user space and allow a finer influence. It |
|
3011 |
should be possible to view and to change special parameters at runtime. |
|
3012 |
||
3013 |
Bus visualization is a second point: For development and debugging |
|
3014 |
purposes it would be nice, if one could show the connected slaves with |
|
3015 |
a single command. |
|
3016 |
||
3017 |
Another aspect is automatic startup and configuration. If the master |
|
3018 |
is to be integrated into a running system, it must be able to |
|
3019 |
automatically start with a persistent configuration. |
|
3020 |
||
3021 |
A last thing is monitoring EtherCAT communication. For debugging |
|
3022 |
purposes, there had to be a way to analyze EtherCAT datagrams. The |
|
3023 |
best way would be with a popular network analyzer, like Wireshark |
|
3024 |
\cite{wireshark} (the former Ethereal) or others.
|
|
3025 |
||
3026 |
This section covers all those points and introduces the interfaces and |
|
3027 |
tools to make all that possible. |
|
3028 |
||
3029 |
%------------------------------------------------------------------------------ |
|
3030 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3031 |
\section{The Sysfs Interface}
|
| 369 | 3032 |
\label{sec:sysfs}
|
3033 |
||
3034 |
The system filesystem (Sysfs\index{Sysfs}) was introduced with Linux
|
|
3035 |
kernel 2.5 and is a well-defined interface for drivers to export |
|
3036 |
information to user space. It serves also as an relief for the process |
|
3037 |
filesystem (Procfs), where over the years much non-process information |
|
3038 |
was concentrated. |
|
3039 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3040 |
Sysfs exports information about devices, classes and buses via a |
| 369 | 3041 |
virtual filesystem, usually mounted to \textit{/sys}. The EtherCAT
|
3042 |
master slightly differs from this concept, because the only physical |
|
3043 |
device is the network adapter it uses for bus communication, which is |
|
3044 |
already represented in Sysfs. For the EtherCAT bus is no system bus |
|
3045 |
like PCI (with device and driver structures), it would not make any |
|
3046 |
sense to represent it as bus structure in Sysfs. |
|
3047 |
||
3048 |
Therefore, the EtherCAT master is represented as a new directory |
|
3049 |
directly unter the Sysfs root. Every master gets its own Sysfs entry |
|
3050 |
named \textit{ethercatX}, where X is the index of the master. Two
|
|
3051 |
masters would result in the directories \textit{/sys/ethercat0} and
|
|
3052 |
\textit{/sys/ethercat1}, respectively.
|
|
3053 |
||
3054 |
The Sysfs base class in the kernel code is the \textit{kobject}
|
|
3055 |
structure. Each object structure, that is to be represented in Sysfs, |
|
3056 |
has to contain such a structure, because due to the concurrent access |
|
3057 |
(through ``normal'' kernel code and Sysfs code) the object deletion |
|
3058 |
gets a little more complicated: The object may not be freed until no |
|
3059 |
instance uses it any more. Therefore, each kobject maintains a |
|
3060 |
reference counter. If the reference counter gets zero, the object is |
|
3061 |
finally freed. A kobject can be registered to appear as a directory in |
|
3062 |
Sysfs with a call to \textit{kobject\_add()}. Each kobject type can
|
|
3063 |
define attributes, that appear as files in the kobject's |
|
3064 |
directory. Callback functions have to be provided for reading (and |
|
3065 |
perhaps writing) access. |
|
3066 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3067 |
\subsection{Master Attributes}
|
| 369 | 3068 |
\label{sec:sysfs-master}
|
3069 |
||
3070 |
Below is a typical listing of the masters Sysfs directory (that is a |
|
3071 |
file system representation of the master's kobject): |
|
3072 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3073 |
\begin{lstlisting}[gobble=2]
|
| 379 | 3074 |
`\$` `\textbf{ls /sys/ethercat0}`
|
| 369 | 3075 |
debug_level slave000 slave003 slave006 |
3076 |
eeprom_write_enable slave001 slave004 slave007 |
|
3077 |
info slave002 slave005 slave008 |
|
3078 |
\end{lstlisting}
|
|
3079 |
||
3080 |
The following attributes exist in the master directory: |
|
3081 |
||
3082 |
\begin{description}
|
|
3083 |
\item[debug\_level] (read/write) This attribute contains the master's |
|
3084 |
debug level, which controls, how much information is printed into |
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3085 |
Syslog. The values 0 (no additional debug messages), 1 (a few |
| 369 | 3086 |
additional debug messages) and 2 (all additional debug messages) are |
3087 |
defined. Writing is done with command like |
|
3088 |
||
3089 |
\begin{lstlisting}[gobble=4]
|
|
| 379 | 3090 |
# `\textbf{echo 1 > /sys/ethercat0/debug\_level}`
|
| 369 | 3091 |
\end{lstlisting}
|
3092 |
||
3093 |
and is receipted with a syslog message by the master: |
|
3094 |
||
3095 |
\begin{lstlisting}[gobble=4]
|
|
3096 |
EtherCAT: Master debug level set to 1. |
|
3097 |
\end{lstlisting}
|
|
3098 |
||
3099 |
\item[enable\_eeprom\_writing] (read/write) See |
|
3100 |
section~\ref{sec:eepromaccess} for how to use this attribute.
|
|
3101 |
||
3102 |
\item[info] (read only) This attribute contains information about the |
|
3103 |
master. Example contents are below: |
|
3104 |
||
3105 |
\begin{lstlisting}[gobble=4]
|
|
| 379 | 3106 |
`\$` `\textbf{cat /sys/ethercat0/info}`
|
| 369 | 3107 |
|
3108 |
Mode: IDLE |
|
3109 |
Slaves: 9 |
|
3110 |
||
3111 |
Timing (min/avg/max) [us]: |
|
3112 |
Idle cycle: 4 / 4.38 / 34 |
|
3113 |
EoE cycle: 9 / 11.91 / 23 |
|
3114 |
||
3115 |
EoE statistics (RX/TX) [bps]: |
|
3116 |
eoe0: 0 / 3184 |
|
3117 |
\end{lstlisting}
|
|
3118 |
||
3119 |
The mode can be \textit{ORPHANED}, \textit{IDLE} or
|
|
3120 |
\textit{OPERATION}. The other parameters are self-explanatory.
|
|
3121 |
||
3122 |
\end{description}
|
|
3123 |
||
3124 |
\subsubsection{Domain Attributes}
|
|
3125 |
\label{sec:sysfs-domain}
|
|
3126 |
||
3127 |
In operation mode, each created domain is represented as a directory |
|
3128 |
\textit{domainX}, where X is the domain index. Below is a listing of
|
|
3129 |
the domain directory contents: |
|
3130 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3131 |
\begin{lstlisting}[gobble=2]
|
| 379 | 3132 |
`\$` `\textbf{ls /sys/ethercat0/domain0}`
|
| 369 | 3133 |
image_size |
3134 |
\end{lstlisting}
|
|
3135 |
||
3136 |
The domain directories currently only export the domain's image size. |
|
3137 |
It is planned to export the whole process data mapping for debugging |
|
3138 |
purposes. |
|
3139 |
||
3140 |
\subsubsection{Slave Attributes}
|
|
3141 |
\label{sec:sysfs-slave}
|
|
3142 |
||
3143 |
Each slave on the bus is represented in its own directory |
|
3144 |
\textit{slaveXXX}, where XXX is the slave's 3-digit ring position in
|
|
3145 |
the EtherCAT bus. Below is a listing of a slave directory: |
|
3146 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3147 |
\begin{lstlisting}[gobble=2]
|
| 379 | 3148 |
`\$` `\textbf{ls /sys/ethercat0/slave003}`
|
| 369 | 3149 |
eeprom info state |
3150 |
\end{lstlisting}
|
|
3151 |
||
3152 |
\begin{description}
|
|
3153 |
\item[eeprom] (read/write) See section~\ref{sec:eepromaccess} for how
|
|
3154 |
to use this attribute. |
|
3155 |
||
3156 |
\item[info] (read only) This attribute contains a bunch of information |
|
3157 |
about the slave. Below is an example output: |
|
3158 |
||
3159 |
\begin{lstlisting}[gobble=4]
|
|
| 379 | 3160 |
`\$` `\textbf{cat /sys/ethercat0/slave003/info}`
|
| 369 | 3161 |
|
3162 |
Name: EL4132 2K. Ana. Ausgang +/-10V |
|
3163 |
Vendor ID: 0x00000002 |
|
3164 |
Product code: 0x10243052 |
|
3165 |
||
3166 |
State: INIT |
|
3167 |
Ring position: 3 |
|
3168 |
Advanced position: 1:3 |
|
3169 |
||
3170 |
Data link status: |
|
3171 |
Port 0 (EBUS) Link down, Loop open, Signal detected |
|
3172 |
Port 1 (EBUS) Link down, Loop open, Signal detected |
|
3173 |
Port 2 (EBUS) Link down, Loop closed, No signal |
|
3174 |
Port 3 (EBUS) Link down, Loop closed, No signal |
|
3175 |
||
3176 |
Mailboxes: |
|
3177 |
RX mailbox: 0x1800/246, TX mailbox: 0x18F6/246 |
|
3178 |
Supported protocols: CoE, FoE |
|
3179 |
||
3180 |
SII data: |
|
3181 |
Group: AnaOut |
|
3182 |
Image: TERM_AO |
|
3183 |
Order#: EL4132 |
|
3184 |
||
3185 |
Sync-Managers: |
|
3186 |
0: 0x1800, length 246, control 0x26, enable |
|
3187 |
1: 0x18F6, length 246, control 0x22, enable |
|
3188 |
2: 0x1000, length 0, control 0x24, enable |
|
3189 |
3: 0x1100, length 0, control 0x20, enable |
|
3190 |
||
| 814 | 3191 |
Pdos: |
| 369 | 3192 |
RXPDO "Channel 1" (0x1600), Sync-Manager 2 |
3193 |
"Output" 0x6411:1, 16 bit |
|
3194 |
RXPDO "Channel 2" (0x1601), Sync-Manager 2 |
|
3195 |
"Output" 0x6411:2, 16 bit |
|
3196 |
\end{lstlisting}
|
|
3197 |
||
3198 |
This is nearly all of the SII category information needed to |
|
3199 |
configure the slave, supplemented with state and addressing |
|
3200 |
information. |
|
3201 |
||
3202 |
\item[state] (read/write) This attribute contains the slave's state. |
|
3203 |
It can be read or written: |
|
3204 |
||
3205 |
\begin{lstlisting}[gobble=4]
|
|
| 379 | 3206 |
# `\textbf{cat /sys/ethercat0/slave003/state}`
|
| 369 | 3207 |
OP |
|
813
bfc3f1ab52de
Fixed typo SAVEOP -> SAFEOP.
Florian Pose <fp@igh-essen.com>
parents:
487
diff
changeset
|
3208 |
# `\textbf{echo SAFEOP > /sys/ethercat0/slave003/state}`
|
| 369 | 3209 |
\end{lstlisting}
|
3210 |
||
3211 |
This command should also be receipted with a syslog message: |
|
3212 |
||
3213 |
\begin{lstlisting}[gobble=4]
|
|
|
813
bfc3f1ab52de
Fixed typo SAVEOP -> SAFEOP.
Florian Pose <fp@igh-essen.com>
parents:
487
diff
changeset
|
3214 |
EtherCAT: Accepted new state SAFEOP for slave 3. |
|
bfc3f1ab52de
Fixed typo SAVEOP -> SAFEOP.
Florian Pose <fp@igh-essen.com>
parents:
487
diff
changeset
|
3215 |
EtherCAT: Changing state of slave 3 from OP to SAFEOP. |
|
bfc3f1ab52de
Fixed typo SAVEOP -> SAFEOP.
Florian Pose <fp@igh-essen.com>
parents:
487
diff
changeset
|
3216 |
EtherCAT: Slave states: INIT, SAFEOP, OP. |
| 369 | 3217 |
\end{lstlisting}
|
3218 |
||
3219 |
After the new requested state was accepted from user space, the |
|
3220 |
operation state machine (see section~\ref{sec:fsm-op}) or the idle
|
|
3221 |
state machine (section~\ref{sec:fsm-idle}) notices, that the
|
|
3222 |
requested slave state differs from the current one, and therefore |
|
3223 |
executes the slave configuration state machine, until the slave has |
|
3224 |
reached the requested state. |
|
3225 |
\end{description}
|
|
3226 |
||
3227 |
%------------------------------------------------------------------------------ |
|
3228 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3229 |
\subsection{SII Access}
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3230 |
\label{sec:siiaccess}
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3231 |
\index{SII!Access}
|
| 369 | 3232 |
|
3233 |
It is possible to directly read or write the complete E$^2$PROM |
|
3234 |
contents of the slaves. This was introduced for the reasons below: |
|
3235 |
||
3236 |
\begin{itemize}
|
|
3237 |
\item The format of the E$^2$PROM data is still in development and |
|
3238 |
categories can be added in the future. With read and write access, |
|
3239 |
the complete memory contents can be easily backed up and restored. |
|
3240 |
\item Some E$^2$PROM data fields have to be altered (like the alias |
|
3241 |
address). A quick writing must be possible for that. |
|
3242 |
\item Through read access, analyzing category data is possible from |
|
3243 |
user space. |
|
3244 |
\end{itemize}
|
|
3245 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3246 |
Reading out E$^2$PROM data is as easy as reading other attributes. Though the |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3247 |
data are in binary format, analysis is easier with a tool like |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3248 |
\textit{hexdump}:
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3249 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3250 |
\begin{lstlisting}[gobble=2]
|
| 379 | 3251 |
`\$` `\textbf{cat /sys/ethercat0/slave003/eeprom | hexdump}`
|
| 369 | 3252 |
0000000 0103 0000 0000 0000 0000 0000 0000 008c |
3253 |
0000010 0002 0000 3052 07f0 0000 0000 0000 0000 |
|
3254 |
0000020 0000 0000 0000 0000 0000 0000 0000 0000 |
|
3255 |
... |
|
3256 |
\end{lstlisting}
|
|
3257 |
||
3258 |
Backing up E$^2$PROM contents gets as easy as copying a file: |
|
3259 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3260 |
\begin{lstlisting}[gobble=2]
|
| 379 | 3261 |
`\$` `\textbf{cp /sys/ethercat0/slave003/eeprom slave003.eep}`
|
| 369 | 3262 |
\end{lstlisting}
|
3263 |
||
3264 |
Writing access is only possible as \textit{root}. Moreover writing has
|
|
3265 |
to be explicitly enabled and is only allowed in idle mode. This is a |
|
3266 |
safety measure, because without the correct memory contents, a slave |
|
3267 |
is unusable. Writing E$^2$PROM contents in operation mode is not |
|
3268 |
provided yet. |
|
3269 |
||
3270 |
E$^2$PROM writing is enabled with the command below: |
|
3271 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3272 |
\begin{lstlisting}[gobble=2]
|
| 379 | 3273 |
# `\textbf{echo 1 > /sys/ethercat0/eeprom\_write\_enable}`
|
| 369 | 3274 |
\end{lstlisting}
|
3275 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3276 |
The success can be seen in the Syslog messages again: |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3277 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3278 |
\begin{lstlisting}[gobble=2]
|
| 369 | 3279 |
EtherCAT: Slave EEPROM writing enabled. |
3280 |
\end{lstlisting}
|
|
3281 |
||
3282 |
Now, it is possible to write E$^2$PROM contents to a slave. The master |
|
3283 |
will accept data through the \textit{eeprom} file and will perform a
|
|
3284 |
short validation of the contents, before starting the write operation. |
|
3285 |
This validation checks the complete size and the category headers. |
|
3286 |
||
|
1085
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Started to re-write the documentation.
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diff
changeset
|
3287 |
\begin{lstlisting}[gobble=2]
|
| 379 | 3288 |
# `\textbf{cat slave003.eep > /sys/ethercat0/slave003/eeprom}`
|
| 369 | 3289 |
\end{lstlisting}
|
3290 |
||
3291 |
The write operation can take a few seconds. |
|
3292 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
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diff
changeset
|
3293 |
\begin{lstlisting}[gobble=2]
|
| 369 | 3294 |
EtherCAT: EEPROM writing scheduled for slave 3, 88 words. |
3295 |
EtherCAT: Writing EEPROM of slave 3... |
|
3296 |
EtherCAT: Finished writing EEPROM of slave 3. |
|
3297 |
\end{lstlisting}
|
|
3298 |
||
3299 |
%------------------------------------------------------------------------------ |
|
3300 |
||
|
1085
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diff
changeset
|
3301 |
\section{User Space Tools}
|
| 369 | 3302 |
\index{User space!Tools}
|
3303 |
||
3304 |
There is a user space tool called \textit{lsec}\index{lsec} (``List
|
|
3305 |
EtherCAT'') to visualize the EtherCAT bus. Running it usually results |
|
3306 |
in an output like this: |
|
3307 |
||
|
1085
c75cdcc5ce87
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diff
changeset
|
3308 |
\begin{lstlisting}[gobble=2]
|
| 379 | 3309 |
`\$` `\textbf{lsec}`
|
| 369 | 3310 |
EtherCAT bus listing for master 0: |
3311 |
0 1:0 OP EK1100 Ethernet Kopplerklemme (2A E-Bus) |
|
3312 |
1 1:1 INIT EL4132 2K. Ana. Ausgang +/-10V |
|
3313 |
2 1:2 INIT EL4132 2K. Ana. Ausgang +/-10V |
|
|
813
bfc3f1ab52de
Fixed typo SAVEOP -> SAFEOP.
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diff
changeset
|
3314 |
3 1:3 SAFEOP EL4132 2K. Ana. Ausgang +/-10V |
| 369 | 3315 |
4 1:4 INIT EL5101 Incremental Encoder Interface |
3316 |
5 1:5 INIT EL1014 4K. Dig. Eingang 24V, 10s |
|
3317 |
6 1:6 OP EL6601 1 Port Switch (Ethernet, CoE) |
|
3318 |
7 1:7 INIT EL5101 Incremental Encoder Interface |
|
3319 |
8 1:8 INIT EL5001 1K. SSI Encoder |
|
3320 |
\end{lstlisting}
|
|
3321 |
||
3322 |
Every slave is displayed as one text row. The first column shows its |
|
3323 |
ring position, the second displays the ``advanced position address'' |
|
3324 |
(see section~\ref{sec:addr}) and the third column displays the current
|
|
3325 |
slave state. The last column is the slave's name, as it appears in the |
|
3326 |
``general'' E$^2$PROM category. |
|
3327 |
||
3328 |
The lsec program is a Perl script, that evaluates the Sysfs |
|
3329 |
\textit{info} attributes of the slaves (see
|
|
3330 |
section~\ref{sec:sysfs-slave}). This is done for master $0$ by
|
|
3331 |
default, but the master index can be specified via command line: |
|
3332 |
||
|
1085
c75cdcc5ce87
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diff
changeset
|
3333 |
\begin{lstlisting}[gobble=2]
|
| 379 | 3334 |
`\$` `\textbf{lsec -h}`
|
| 369 | 3335 |
Usage: ec_list [OPTIONS] |
3336 |
-m <IDX> Query master <IDX>. |
|
3337 |
-h Show this help. |
|
3338 |
\end{lstlisting}
|
|
3339 |
||
3340 |
This script has proved as useful for troubleshooting: If it displays |
|
3341 |
slaves, the master is up and running, and the bus connection is |
|
3342 |
present, too. It is also useful when building up a bus: It can verify |
|
3343 |
the list of slaves and help to create a process data image (see |
|
3344 |
chapter~\ref{chapter:usage}).
|
|
3345 |
||
3346 |
%------------------------------------------------------------------------------ |
|
3347 |
||
|
1085
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changeset
|
3348 |
\section{System Integration}
|
| 369 | 3349 |
\label{sec:system}
|
3350 |
||
3351 |
To integrate the EtherCAT master into a running system, it has to be |
|
3352 |
guaranteed, that it is started on system startup. In addition, there has |
|
3353 |
to be a persistent configuration, that is also applied on startup. |
|
3354 |
||
3355 |
\subsubsection{The EtherCAT Init Script}
|
|
3356 |
\label{sec:init}
|
|
3357 |
\index{Init script}
|
|
3358 |
||
3359 |
The EtherCAT master provides an ``init script'', that conforms to the |
|
3360 |
requirements of the ``Linux Standard Base'' (LSB\index{LSB},
|
|
|
374
e43a29f9079e
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diff
changeset
|
3361 |
\cite{lsb}). The script is installed to \textit{etc/init.d/ethercat}
|
|
e43a29f9079e
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371
diff
changeset
|
3362 |
below the installation prefix and has to be copied to the appropriate |
|
e43a29f9079e
Updated documentation concerning autotools/installation.
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371
diff
changeset
|
3363 |
location (see section~\ref{sec:make}), before the master can be
|
|
e43a29f9079e
Updated documentation concerning autotools/installation.
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371
diff
changeset
|
3364 |
inserted as a service. The different Linux distributions offer |
|
e43a29f9079e
Updated documentation concerning autotools/installation.
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parents:
371
diff
changeset
|
3365 |
different ways to mark the service for starting and stopping in |
|
e43a29f9079e
Updated documentation concerning autotools/installation.
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parents:
371
diff
changeset
|
3366 |
certain runlevels (for example, SUSE Linux provides the |
|
e43a29f9079e
Updated documentation concerning autotools/installation.
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371
diff
changeset
|
3367 |
\textit{insserv} command).
|
| 369 | 3368 |
|
3369 |
To provide service dependencies (i.~e. which services have to be |
|
3370 |
started before) right inside the init script code, LSB defines a |
|
3371 |
special comment block. System tools can extract this information to |
|
3372 |
insert the EtherCAT init script at the correct place in the startup |
|
3373 |
sequence: |
|
3374 |
||
|
1085
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diff
changeset
|
3375 |
\begin{lstlisting}[gobble=2]
|
| 369 | 3376 |
### BEGIN INIT INFO |
3377 |
# Provides: ethercat |
|
3378 |
# Required-Start: $local_fs $syslog $network |
|
3379 |
# Should-Start: $time |
|
3380 |
# Required-Stop: $local_fs $syslog $network |
|
3381 |
# Should-Stop: $time |
|
3382 |
# Default-Start: 3 5 |
|
3383 |
# Default-Stop: 0 1 2 6 |
|
3384 |
# Short-Description: EtherCAT master modules |
|
3385 |
# Description: |
|
3386 |
### END INIT INFO |
|
3387 |
\end{lstlisting}
|
|
3388 |
||
3389 |
The init script can also be used for manually starting and stopping |
|
3390 |
the EtherCAT master. It has to be executed with one of the parameters |
|
| 379 | 3391 |
\texttt{start}, \texttt{stop}, \texttt{restart} or \texttt{status}.
|
| 369 | 3392 |
|
|
1085
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parents:
917
diff
changeset
|
3393 |
\begin{lstlisting}[gobble=2]
|
| 379 | 3394 |
# `\textbf{/etc/init.d/ethercat restart}`
|
| 369 | 3395 |
Shutting down EtherCAT master done |
3396 |
Starting EtherCAT master done |
|
3397 |
\end{lstlisting}
|
|
3398 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
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parents:
917
diff
changeset
|
3399 |
\subsubsection{Sysconfig} % FIXME
|
| 369 | 3400 |
\label{sec:sysconfig}
|
3401 |
\index{Sysconfig file}
|
|
3402 |
||
3403 |
For persistent configuration, the init script uses a sysconfig file |
|
|
374
e43a29f9079e
Updated documentation concerning autotools/installation.
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diff
changeset
|
3404 |
installed to \textit{etc/sysconfig/ethercat} (below the installation
|
|
e43a29f9079e
Updated documentation concerning autotools/installation.
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371
diff
changeset
|
3405 |
prefix), that is mandatory for the init script. The sysconfig file |
|
e43a29f9079e
Updated documentation concerning autotools/installation.
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371
diff
changeset
|
3406 |
contains all configuration variables needed to operate a master: |
| 369 | 3407 |
|
3408 |
\begin{description}
|
|
3409 |
\item[DEVICE\_INDEX] This variable must contain the PCI index of the |
|
3410 |
EtherCAT device. Setting this is mandatory for the EtherCAT init |
|
3411 |
script. Default: $-1$ |
|
3412 |
\item[EOE\_INTERFACES] The number of virtual Ethernet-over-EtherCAT |
|
3413 |
interfaces, every master creates on startup. See |
|
3414 |
section~\ref{sec:eoeimp}. Default: $0$
|
|
3415 |
\item[EOE\_BRIDGE] If this variable is set, all EoE interfaces will be |
|
3416 |
added to a network bridge according to IEEE 802.1D after master |
|
3417 |
startup. The variable must contain the name of the bridge. To use |
|
3418 |
this functionality, the kernel must be configured with the |
|
| 379 | 3419 |
CONFIG\_BRIDGE option and the \textit{bridge-utils} package must be
|
3420 |
installed (i.~e. the \textit{brctl} command is needed).
|
|
| 369 | 3421 |
\item[EOE\_IP\_ADDRESS] The IP address of the EoE bridge. Setting this |
| 379 | 3422 |
together with \$EOE\_IP\_NETMASK will let the local host communicate |
3423 |
with devices on the EoE bridge. |
|
| 369 | 3424 |
\item[EOE\_IP\_NETMASK] IP netmask of the EoE bridge. |
3425 |
\item[EOE\_EXTRA\_INTERFACES] The list of extra interfaces to include |
|
3426 |
in the EoE brid\-ge. Set this to interconnect the EoE bridge with |
|
| 379 | 3427 |
other local interfaces. If \$EOE\_\-BRIDGE is empty or undefined, |
3428 |
setting this variable has no effect. Important: The IP address of |
|
3429 |
the listed interfaces will be cleared. Setting |
|
3430 |
\$EOE\_\-IP\_\-ADDRESS and \$EOE\_IP\_NETMASK will re-enable them |
|
3431 |
for IP traffic. |
|
| 369 | 3432 |
\item[EOE\_GATEWAY] The IP address of the default gateway. If this |
3433 |
variable is set, the gateway will be renewed after bridge |
|
3434 |
installation. This is necessary, if the default gateway's interface |
|
| 379 | 3435 |
is one of the \$EOE\_EXTRA\_INTERFACES. |
| 369 | 3436 |
\end{description}
|
3437 |
||
3438 |
%------------------------------------------------------------------------------ |
|
3439 |
||
|
1085
c75cdcc5ce87
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parents:
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diff
changeset
|
3440 |
\section{Monitoring and Debugging}
|
| 369 | 3441 |
\label{sec:debug}
|
3442 |
\index{Monitoring}
|
|
3443 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3444 |
For debugging purposes, every EtherCAT master registers a read-only network |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3445 |
interface \textit{ecX}, where X is a number, provided by the kernel on device
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3446 |
registration. While it is ``up'', the master forwards every frame sent and |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3447 |
received to this interface. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3448 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3449 |
This makes it possible to connect an network monitor (like Wireshark or |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3450 |
tcpdump) to the debug interface and monitor the EtherCAT frames. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3451 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3452 |
% FIXME schedule() |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3453 |
It has to be considered, that can be frame rate can be very high. The master |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3454 |
state machine usually runs every kernel timer interrupt (usually up to |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3455 |
\unit{1}{\kilo\hertz}) and with a connected application, the rate can be even
|
| 369 | 3456 |
higher. |
3457 |
||
3458 |
\paragraph{Attention:} The socket buffers needed for the operation of
|
|
3459 |
the debugging interface have to be allocated dynamically. Some Linux |
|
3460 |
realtime extensions do not allow this in realtime context! |
|
3461 |
||
3462 |
%------------------------------------------------------------------------------ |
|
3463 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
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parents:
917
diff
changeset
|
3464 |
\chapter{Timing Aspects}
|
| 369 | 3465 |
\label{sec:timing}
|
3466 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3467 |
Although EtherCAT's timing is highly deterministic and therefore timing issues |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3468 |
are rare, there are a few aspects that can (and should be) dealt with. |
| 369 | 3469 |
|
3470 |
%------------------------------------------------------------------------------ |
|
3471 |
||
3472 |
\subsection{Realtime Interface Profiling}
|
|
3473 |
\label{sec:timing-profile}
|
|
3474 |
\index{Realtime!Profiling}
|
|
3475 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
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parents:
917
diff
changeset
|
3476 |
One of the most important timing aspects are the execution times of the |
| 369 | 3477 |
realtime interface functions, that are called in cyclic context. These |
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3478 |
functions make up an important part of the overall timing of the application. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3479 |
To measure the timing of the functions, the following code was used: |
| 369 | 3480 |
|
3481 |
\begin{lstlisting}[gobble=2,language=C]
|
|
3482 |
c0 = get_cycles(); |
|
3483 |
ecrt_master_receive(master); |
|
3484 |
c1 = get_cycles(); |
|
3485 |
ecrt_domain_process(domain1); |
|
3486 |
c2 = get_cycles(); |
|
3487 |
ecrt_master_run(master); |
|
3488 |
c3 = get_cycles(); |
|
3489 |
ecrt_master_send(master); |
|
3490 |
c4 = get_cycles(); |
|
3491 |
\end{lstlisting}
|
|
3492 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3493 |
Between each call of an interface function, the CPU timestamp counter is read. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3494 |
The counter differences are converted to \micro\second\ with help of the |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3495 |
\lstinline+cpu_khz+ variable, that contains the number of increments per |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3496 |
\milli\second. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3497 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3498 |
For the actual measuring, a system with a \unit{2.0}{\giga\hertz} CPU was used,
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3499 |
that ran the above code in an RTAI thread with a period of |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3500 |
\unit{100}{\micro\second}. The measuring was repeated $n = 100$ times and the
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3501 |
results were averaged. These can be seen in table~\ref{tab:profile}.
|
| 369 | 3502 |
|
3503 |
\begin{table}[htpb]
|
|
3504 |
\centering |
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3505 |
\caption{Profiling of a Realtime Cycle on a \unit{2.0}{\giga\hertz}
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3506 |
Processor} |
| 369 | 3507 |
\label{tab:profile}
|
3508 |
\vspace{2mm}
|
|
3509 |
\begin{tabular}{l|r|r}
|
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
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diff
changeset
|
3510 |
Element & Mean Duration [\second] & Standard Deviancy [\micro\second] \\ |
| 369 | 3511 |
\hline |
3512 |
\textit{ecrt\_master\_receive()} & 8.04 & 0.48\\
|
|
3513 |
\textit{ecrt\_domain\_process()} & 0.14 & 0.03\\
|
|
3514 |
\textit{ecrt\_master\_run()} & 0.29 & 0.12\\
|
|
3515 |
\textit{ecrt\_master\_send()} & 2.18 & 0.17\\ \hline
|
|
3516 |
Complete Cycle & 10.65 & 0.69\\ \hline |
|
3517 |
\end{tabular}
|
|
3518 |
\end{table}
|
|
3519 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
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diff
changeset
|
3520 |
It is obvious, that the functions accessing hardware make up the |
| 369 | 3521 |
lion's share. The \textit{ec\_master\_receive()} executes the ISR of
|
3522 |
the Ethernet device, analyzes datagrams and copies their contents into |
|
3523 |
the memory of the datagram objects. The \textit{ec\_master\_send()}
|
|
3524 |
assembles a frame out of different datagrams and copies it to the |
|
3525 |
hardware buffers. Interestingly, this makes up only a quarter of the |
|
3526 |
receiving time. |
|
3527 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3528 |
The functions that only operate on the masters internal data structures are |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3529 |
very fast ($\Delta t < \unit{1}{\micro\second}$). Interestingly the runtime of
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3530 |
\textit{ec\_domain\_process()} has a small standard deviancy relative to the
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3531 |
mean value, while this ratio is about twice as big for |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3532 |
\textit{ec\_master\_run()}: This probably results from the latter function
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3533 |
having to execute code depending on the current state and the different state |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3534 |
functions are more or less complex. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3535 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3536 |
For a realtime cycle makes up about \unit{10}{\micro\second}, the theoretical
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3537 |
frequency can be up to \unit{100}{\kilo\hertz}. For two reasons, this frequency
|
| 369 | 3538 |
keeps being theoretical: |
3539 |
||
3540 |
\begin{enumerate}
|
|
|
1085
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parents:
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diff
changeset
|
3541 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3542 |
\item The processor must still be able to run the operating system between the |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3543 |
realtime cycles. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3544 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3545 |
\item The EtherCAT frame must be sent and received, before the next realtime |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3546 |
cycle begins. The determination of the bus cycle time is difficult and covered |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3547 |
in section~\ref{sec:timing-bus}.
|
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
3548 |
|
| 369 | 3549 |
\end{enumerate}
|
3550 |
||
3551 |
%------------------------------------------------------------------------------ |
|
3552 |
||
3553 |
\subsection{Bus Cycle Measuring}
|
|
3554 |
\label{sec:timing-bus}
|
|
3555 |
\index{Bus cycle}
|
|
3556 |
||
3557 |
For measuring the time, a frame is ``on the wire'', two timestamps |
|
3558 |
must be be taken: |
|
3559 |
||
3560 |
\begin{enumerate}
|
|
3561 |
\item The time, the Ethernet hardware begins with physically sending |
|
3562 |
the frame. |
|
3563 |
\item The time, the frame is completely received by the Ethernet |
|
3564 |
hardware. |
|
3565 |
\end{enumerate}
|
|
3566 |
||
3567 |
Both times are difficult to determine. The first reason is, that the |
|
3568 |
interrupts are disabled and the master is not notified, when a frame |
|
3569 |
is sent or received (polling would distort the results). The second |
|
3570 |
reason is, that even with interrupts enabled, the time from the event |
|
3571 |
to the notification is unknown. Therefore the only way to confidently |
|
3572 |
determine the bus cycle time is an electrical measuring. |
|
3573 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
3574 |
Anyway, the bus cycle time is an important factor when designing realtime code, |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3575 |
because it limits the maximum frequency for the cyclic task of the application. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3576 |
In practice, these timing parameters are highly dependent on the hardware and |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3577 |
often a trial and error method must be used to determine the limits of the |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3578 |
system. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3579 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3580 |
The central question is: What happens, if the cycle frequency is too high? The |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3581 |
answer is, that the EtherCAT frames that have been sent at the end of the cycle |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3582 |
are not yet received, when the next cycle starts. First this is noticed by |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3583 |
\textit{ecrt\_domain\_process()}, because the working counter of the process
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3584 |
data datagrams were not increased. The function will notify the user via |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3585 |
Syslog\footnote{To limit Syslog output, a mechanism has been implemented, that
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3586 |
outputs a summarized notification at maximum once a second.}. In this case, the |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3587 |
process data keeps being the same as in the last cycle, because it is not |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3588 |
erased by the domain. When the domain datagrams are queued again, the master |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3589 |
notices, that they are already queued (and marked as sent). The master will |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3590 |
mark them as unsent again and output a warning, that datagrams were |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3591 |
``skipped''. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3592 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3593 |
On the mentioned \unit{2.0}{\giga\hertz} system, the possible cycle frequency
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3594 |
can be up to \unit{25}{\kilo\hertz} without skipped frames. This value can
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3595 |
surely be increased by choosing faster hardware. Especially the RealTek network |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3596 |
hardware could be replaced by a faster one. Besides, implementing a dedicated |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3597 |
ISR for EtherCAT devices would also contribute to increasing the latency. These |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3598 |
are two points on the author's to-do list. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3599 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3600 |
%------------------------------------------------------------------------------ |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3601 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3602 |
\chapter{Installation}
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3603 |
\label{sec:installation}
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3604 |
\index{Master!Installation}
|
| 369 | 3605 |
|
|
376
d1441d87f5c1
Documentation: EtherLab-CD; obtaining the DEVICE_INDEX.
Florian Pose <fp@igh-essen.com>
parents:
374
diff
changeset
|
3606 |
The current EtherCAT master code is available at~\cite{etherlab} or
|
|
d1441d87f5c1
Documentation: EtherLab-CD; obtaining the DEVICE_INDEX.
Florian Pose <fp@igh-essen.com>
parents:
374
diff
changeset
|
3607 |
can be obtained from the EtherLab\textsuperscript{\textregistered} CD.
|
| 487 | 3608 |
The \textit{tar.bz2} file has to be unpacked with the commands below
|
|
376
d1441d87f5c1
Documentation: EtherLab-CD; obtaining the DEVICE_INDEX.
Florian Pose <fp@igh-essen.com>
parents:
374
diff
changeset
|
3609 |
(or similar): |
| 369 | 3610 |
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
3611 |
\begin{lstlisting}[gobble=2]
|
| 487 | 3612 |
`\$` `\textbf{tar xjf ethercat-\masterversion.tar.bz2}`
|
3613 |
`\$` `\textbf{cd ethercat-\masterversion/}`
|
|
|
374
e43a29f9079e
Updated documentation concerning autotools/installation.
Florian Pose <fp@igh-essen.com>
parents:
371
diff
changeset
|
3614 |
\end{lstlisting}
|
|
e43a29f9079e
Updated documentation concerning autotools/installation.
Florian Pose <fp@igh-essen.com>
parents:
371
diff
changeset
|
3615 |
|
|
e43a29f9079e
Updated documentation concerning autotools/installation.
Florian Pose <fp@igh-essen.com>
parents:
371
diff
changeset
|
3616 |
The tarball was created with GNU Autotools, so the build process |
| 487 | 3617 |
follows the below commands: |
| 369 | 3618 |
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
3619 |
\begin{lstlisting}[gobble=2]
|
| 379 | 3620 |
`\$` `\textbf{./configure}`
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3621 |
`\$` `\textbf{make}`
|
| 487 | 3622 |
`\$` `\textbf{make modules}`
|
|
374
e43a29f9079e
Updated documentation concerning autotools/installation.
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371
diff
changeset
|
3623 |
\end{lstlisting}
|
|
e43a29f9079e
Updated documentation concerning autotools/installation.
Florian Pose <fp@igh-essen.com>
parents:
371
diff
changeset
|
3624 |
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3625 |
Table~\ref{tab:config} lists important configuration switches and options.
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3626 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3627 |
\begin{table}
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3628 |
\caption{Configuration options}
|
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
917
diff
changeset
|
3629 |
\label{tab:config}
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3630 |
\vspace{2mm}
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3631 |
\begin{tabular}{l|p{.3\textwidth}|l}
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3632 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3633 |
\bf Option/Switch & \bf Description & \bf Default\\\hline |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
3634 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3635 |
\lstinline+--prefix+ & Installation prefix & \textit{/opt/etherlab}\\
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
3636 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3637 |
\lstinline+--with-linux-dir+ & Linux kernel sources & Use running kernel\\ |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3638 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3639 |
\lstinline+--with-rtai-dir+ & RTAI path (only for RTAI example) & \\ |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
3640 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3641 |
\hline |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3642 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3643 |
\lstinline+--enable-eoe+ & Enable EoE support & yes\\ |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3644 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3645 |
\lstinline+--enable-cycles+ & Use CPU timestamp counter. Enable this on Intel |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3646 |
architecture to get finer timing calculation. & no\\ |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3647 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3648 |
\lstinline+--enable-debug-if+ & Create a debug interface for each master & no\\ |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3649 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3650 |
\lstinline+--enable-debug-ring+ & Create a debug ring to record frames & no\\ |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3651 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
3652 |
\hline |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
3653 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3654 |
\lstinline+--enable-8139too+ & Build the 8139too driver & yes\\ |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
3655 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3656 |
\lstinline+--with-8139too-kernel+ & 8139too kernel & $\dagger$\\ |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
3657 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3658 |
\lstinline+--enable-e100+ & Build the e100 driver & no\\ |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
3659 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3660 |
\lstinline+--with-e100-kernel+ & e100 kernel & $\dagger$\\ |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
3661 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3662 |
\lstinline+--enable-forcedeth+ & Enable forcedeth driver & no\\ |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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changeset
|
3663 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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changeset
|
3664 |
\lstinline+--with-forcedeth-kernel+ & forcedeth kernel & $\dagger$\\ |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
917
diff
changeset
|
3665 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3666 |
\lstinline+--enable-e1000+ & Enable e1000 driver & no\\ |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3667 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3668 |
\lstinline+--with-e1000-kernel+ & e1000 kernel & $\dagger$\\ |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
917
diff
changeset
|
3669 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3670 |
\lstinline+--enable-r8169+ & Enable r8169 driver & no\\ |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
917
diff
changeset
|
3671 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3672 |
\lstinline+--with-r8169-kernel+ & r8169 kernel & $\dagger$\\ |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
3673 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
917
diff
changeset
|
3674 |
\end{tabular}
|
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
917
diff
changeset
|
3675 |
\vspace{2mm}
|
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
917
diff
changeset
|
3676 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
917
diff
changeset
|
3677 |
\begin{description}
|
|
c75cdcc5ce87
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parents:
917
diff
changeset
|
3678 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
917
diff
changeset
|
3679 |
\item[$\dagger$] If this option is not specified, the kernel version to use is |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3680 |
extracted from the Linux kernel sources. |
|
c75cdcc5ce87
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parents:
917
diff
changeset
|
3681 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
3682 |
\end{description}
|
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
917
diff
changeset
|
3683 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
917
diff
changeset
|
3684 |
\end{table}
|
| 487 | 3685 |
|
3686 |
The below commands have to be entered as \textit{root}: The first one
|
|
3687 |
will install the kernel modules to the kernel's modules directory. The |
|
3688 |
second one will install EtherCAT headers, the init script, the |
|
3689 |
sysconfig file and the user space tools to the prefix path. |
|
| 369 | 3690 |
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
changeset
|
3691 |
\begin{lstlisting}[gobble=2]
|
| 487 | 3692 |
# `\textbf{make modules\_install}`
|
| 379 | 3693 |
# `\textbf{make install}`
|
| 369 | 3694 |
\end{lstlisting}
|
3695 |
||
| 487 | 3696 |
If the target kernel's modules directory is not under |
3697 |
\textit{/lib/modules}, a different destination directory can be
|
|
3698 |
specified with the \textit{DESTDIR} make variable. For example:
|
|
3699 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3700 |
\begin{lstlisting}[gobble=2]
|
| 487 | 3701 |
# `\textbf{make DESTDIR=/vol/nfs/root modules\_install}`
|
3702 |
\end{lstlisting}
|
|
3703 |
||
3704 |
This command will install the compiled kernel modules to |
|
3705 |
\textit{/vol/nfs/root/lib/modules}, prepended by the kernel release.
|
|
3706 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3707 |
If the EtherCAT master shall be run as a service\footnote{Even if the EtherCAT
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3708 |
master shall not be loaded on system startup, the use of the init script is |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3709 |
recommended for manual (un-)loading.}, the init script and the sysconfig file |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3710 |
have to be copied (or linked) to the appropriate locations. The below example |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3711 |
is suitable for SUSE Linux. It may vary for other distributions. |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
917
diff
changeset
|
3712 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3713 |
\begin{lstlisting}[gobble=2]
|
| 379 | 3714 |
# `\textbf{cd /opt/etherlab}`
|
3715 |
# `\textbf{cp etc/sysconfig/ethercat /etc/sysconfig/}`
|
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
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parents:
917
diff
changeset
|
3716 |
# `\textbf{ln -s etc/init.d/ethercat /etc/init.d/}`
|
| 379 | 3717 |
# `\textbf{insserv ethercat}`
|
|
374
e43a29f9079e
Updated documentation concerning autotools/installation.
Florian Pose <fp@igh-essen.com>
parents:
371
diff
changeset
|
3718 |
\end{lstlisting}
|
|
e43a29f9079e
Updated documentation concerning autotools/installation.
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parents:
371
diff
changeset
|
3719 |
|
|
376
d1441d87f5c1
Documentation: EtherLab-CD; obtaining the DEVICE_INDEX.
Florian Pose <fp@igh-essen.com>
parents:
374
diff
changeset
|
3720 |
Now the sysconfig file \texttt{/etc/sysconfig/ethercat} (see
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3721 |
section~\ref{sec:sysconfig}) has to be customized. The minimal customization
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3722 |
is to set the \lstinline+MASTER0_DEVICE+ variable to the MAC address of the |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3723 |
Ethernet device to use (or \lstinline+ff:ff:ff:ff:ff:ff+ to use the first |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3724 |
device offered) and selecting the driver(s) to load via the |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3725 |
\lstinline+DEVICE_MODULES+ variable. |
| 369 | 3726 |
|
3727 |
After the basic configuration is done, the master can be started with |
|
3728 |
the below command: |
|
3729 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3730 |
\begin{lstlisting}[gobble=2]
|
| 379 | 3731 |
# `\textbf{/etc/init.d/ethercat start}`
|
| 369 | 3732 |
\end{lstlisting}
|
3733 |
||
3734 |
The operation of the master can be observed by looking at the |
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3735 |
Syslog\index{Syslog} messages, which should look like the ones below. If
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3736 |
EtherCAT slaves are connected to the master's EtherCAT device, the activity |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3737 |
indicators should begin to flash. |
| 369 | 3738 |
|
3739 |
\begin{lstlisting}[numbers=left]
|
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3740 |
EtherCAT: Master driver `\masterversion` |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3741 |
EtherCAT: 1 master waiting for devices. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3742 |
EtherCAT Intel(R) PRO/1000 Network Driver - version 6.0.60-k2 |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3743 |
Copyright (c) 1999-2005 Intel Corporation. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3744 |
PCI: Found IRQ 12 for device 0000:01:01.0 |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3745 |
PCI: Sharing IRQ 12 with 0000:00:1d.2 |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3746 |
PCI: Sharing IRQ 12 with 0000:00:1f.1 |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3747 |
EtherCAT: Accepting device 00:0E:0C:DA:A2:20 for master 0. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3748 |
EtherCAT: Starting master thread. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3749 |
ec_e1000: ec0: e1000_probe: Intel(R) PRO/1000 Network |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3750 |
Connection |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3751 |
ec_e1000: ec0: e1000_watchdog_task: NIC Link is Up 100 Mbps |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3752 |
Full Duplex |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3753 |
EtherCAT: Link state changed to UP. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3754 |
EtherCAT: 7 slave(s) responding. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3755 |
EtherCAT: Slave states: PREOP. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3756 |
EtherCAT: Scanning bus. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3757 |
EtherCAT: Bus scanning completed in 431 ms. |
| 369 | 3758 |
\end{lstlisting}
|
3759 |
||
3760 |
\begin{description}
|
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
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parents:
917
diff
changeset
|
3761 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3762 |
\item[\linenum{1} -- \linenum{2}] The master module is loading, and one master
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3763 |
is initialized. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3764 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3765 |
\item[\linenum{3} -- \linenum{8}] The EtherCAT-capable e1000 driver is
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3766 |
loading. The master accepts the device with the address |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3767 |
\lstinline+00:0E:0C:DA:A2:20+. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3768 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3769 |
\item[\linenum{9} -- \linenum{16}] The master goes to idle phase, starts its
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3770 |
state machine and begins scanning the bus. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3771 |
|
| 369 | 3772 |
\end{description}
|
3773 |
||
3774 |
%------------------------------------------------------------------------------ |
|
3775 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
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parents:
917
diff
changeset
|
3776 |
\chapter{Application examples}
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3777 |
\label{chapter:examples}
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
3778 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3779 |
This chapter will give practical examples of how to use the EtherCAT master via |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3780 |
the realtime interface by writing an application module. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3781 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3782 |
%------------------------------------------------------------------------------ |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
917
diff
changeset
|
3783 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3784 |
\section{Minimal Example}
|
| 369 | 3785 |
\label{sec:mini}
|
3786 |
\index{Examples!Minimal}
|
|
3787 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
3788 |
This section will explain the use of the EtherCAT master from a minimal kernel |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3789 |
module. The complete module code is obtainable as a part of the EtherCAT master |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3790 |
code release (see~\cite{etherlab}, file \textit{examples/mini/mini.c}).
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3791 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3792 |
The minimal example uses a kernel timer (software interrupt) to generate a |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3793 |
cyclic task. After the timer function is executed, it re-adds itself with a |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3794 |
delay of one \textit{jiffy}\index{jiffies}, which results in a timer frequency
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3795 |
of \textit{HZ}\nomenclature{HZ}{Kernel macro containing the timer interrupt
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
3796 |
frequency} |
| 369 | 3797 |
|
3798 |
The module-global variables, needed to operate the master can be seen |
|
3799 |
in listing~\ref{lst:minivar}.
|
|
3800 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
3801 |
\begin{lstlisting}[gobble=2,language=C,numbers=left,caption={Minimal
|
| 369 | 3802 |
variables},label=lst:minivar] |
3803 |
struct timer_list timer; |
|
3804 |
||
3805 |
ec_master_t *master = NULL; |
|
3806 |
ec_domain_t *domain1 = NULL; |
|
3807 |
||
3808 |
void *r_dig_in, *r_ana_out; |
|
3809 |
||
3810 |
ec_pdo_reg_t domain1_pdos[] = {
|
|
3811 |
{"1", Beckhoff_EL1014_Inputs, &r_dig_in},
|
|
3812 |
{"2", Beckhoff_EL4132_Ouput1, &r_ana_out},
|
|
3813 |
{}
|
|
3814 |
}; |
|
3815 |
\end{lstlisting}
|
|
3816 |
||
3817 |
\begin{description}
|
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
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diff
changeset
|
3818 |
\item[\linenum{1}] There is a timer object
|
| 369 | 3819 |
declared, that is needed to tell the kernel to install a timer and |
3820 |
execute a certain function, if it runs out. This is done by a |
|
3821 |
variable of the \textit{timer\_list} structure.
|
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3822 |
\item[\linenum{3} -- \linenum{4}] There
|
| 369 | 3823 |
is a pointer declared, that will later point to a requested EtherCAT |
3824 |
master. Additionally there is a pointer to a domain object needed, |
|
3825 |
that will manage process data IO. |
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3826 |
\item[\linenum{6}] The pointers \textit{r\_*}
|
| 369 | 3827 |
will later point to the \underline{r}aw process data values inside
|
3828 |
the domain memory. The addresses they point to will be set during a |
|
3829 |
call to \textit{ec\_\-master\_\-activate()}, that will create the
|
|
3830 |
domain memory and configure the mapped process data image. |
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3831 |
\item[\linenum{8} -- \linenum{12}] The
|
| 814 | 3832 |
configuration of the mapping of certain Pdos in a domain can easily |
| 369 | 3833 |
be done with the help of an initialization array of the |
3834 |
\textit{ec\_pdo\_reg\_t} type, defined as part of the realtime
|
|
3835 |
interface. Each record must contain the ASCII bus-address of the |
|
3836 |
slave (see section~\ref{sec:addr}), the slave's vendor ID and
|
|
| 814 | 3837 |
product code, and the index and subindex of the Pdo to map (these |
| 369 | 3838 |
four fields can be specified in junction, by using one of the |
3839 |
defines out of the \textit{include/ecdb.h} header). The last field
|
|
3840 |
has to be the address of the process data pointer, so it can later |
|
3841 |
be redirected appropriately. Attention: The initialization array |
|
3842 |
must end with an empty record (\textit{\{\}})!
|
|
3843 |
\end{description}
|
|
3844 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3845 |
The initialization of the minimal application is done by the ``Minimal init |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3846 |
function'' in listing~\ref{lst:miniinit}.
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3847 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3848 |
\begin{lstlisting}[gobble=2,language=C,numbers=left,caption={Minimal init
|
| 369 | 3849 |
function},label={lst:miniinit}]
|
3850 |
int __init init_mini_module(void) |
|
3851 |
{
|
|
3852 |
if (!(master = ecrt_request_master(0))) {
|
|
3853 |
goto out_return; |
|
3854 |
} |
|
3855 |
||
3856 |
if (!(domain1 = ecrt_master_create_domain(master))) {
|
|
3857 |
goto out_release_master; |
|
3858 |
} |
|
3859 |
||
3860 |
if (ecrt_domain_register_pdo_list(domain1, |
|
3861 |
domain1_pdos)) {
|
|
3862 |
goto out_release_master; |
|
3863 |
} |
|
3864 |
||
3865 |
if (ecrt_master_activate(master)) {
|
|
3866 |
goto out_release_master; |
|
3867 |
} |
|
3868 |
||
3869 |
ecrt_master_prepare(master); |
|
3870 |
||
3871 |
init_timer(&timer); |
|
3872 |
timer.function = run; |
|
3873 |
timer.expires = jiffies + 10; |
|
3874 |
add_timer(&timer); |
|
3875 |
||
3876 |
return 0; |
|
3877 |
||
3878 |
out_release_master: |
|
3879 |
ecrt_release_master(master); |
|
3880 |
out_return: |
|
3881 |
return -1; |
|
3882 |
} |
|
3883 |
\end{lstlisting}
|
|
3884 |
||
3885 |
\begin{description}
|
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3886 |
\item[\linenum{3}] It is tried to request the
|
| 369 | 3887 |
first EtherCAT master (index 0). On success, the |
3888 |
\textit{ecrt\_\-request\_\-master()} function returns a pointer to
|
|
3889 |
the reserved master, that can be used as an object to following |
|
3890 |
functions calls. On failure, the function returns \textit{NULL}.
|
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3891 |
\item[\linenum{7}] In order to exchange process
|
| 369 | 3892 |
data, a domain object has to be created. The |
3893 |
\textit{ecrt\_\-master\_\-create\_domain()} function also returns a
|
|
3894 |
pointer to the created domain, or \textit{NULL} in error case.
|
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3895 |
\item[\linenum{11}] The registration of domain
|
| 814 | 3896 |
Pdos with an initialization array results in a single function call. |
| 369 | 3897 |
Alternatively the data fields could be registered with individual |
3898 |
calls of \textit{ecrt\_domain\_register\_pdo()}.
|
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3899 |
\item[\linenum{16}] After the configuration of
|
| 369 | 3900 |
process data mapping, the master can be activated for cyclic |
3901 |
operation. This will configure all slaves and bring them into |
|
| 379 | 3902 |
OP state. |
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3903 |
\item[\linenum{20}] This call is needed to avoid
|
| 369 | 3904 |
a case differentiation in cyclic operation: The first operation in |
3905 |
cyclic mode is a receive call. Due to the fact, that there is |
|
3906 |
nothing to receive during the first cycle, there had to be an |
|
3907 |
\textit{if}-statement to avoid a warning. A call to
|
|
3908 |
\textit{ec\_master\_prepare()} sends a first datagram containing a
|
|
3909 |
process data exchange datagram, so that the first receive call will |
|
3910 |
not fail. |
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3911 |
\item[\linenum{22} -- \linenum{25}] The
|
| 369 | 3912 |
master is now ready for cyclic operation. The kernel timer that |
3913 |
cyclically executes the \textit{run()} function is initialized and
|
|
3914 |
started. |
|
3915 |
\end{description}
|
|
3916 |
||
3917 |
The coding of a cleanup function fo the minimal module can be seen in |
|
3918 |
listing~\ref{lst:miniclean}.
|
|
3919 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3920 |
\begin{lstlisting}[gobble=2,language=C,numbers=left,caption={Minimal cleanup
|
| 369 | 3921 |
function},label={lst:miniclean}]
|
3922 |
void __exit cleanup_mini_module(void) |
|
3923 |
{
|
|
3924 |
del_timer_sync(&timer); |
|
3925 |
ecrt_master_deactivate(master); |
|
3926 |
ecrt_release_master(master); |
|
3927 |
} |
|
3928 |
\end{lstlisting}
|
|
3929 |
||
3930 |
\begin{description}
|
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3931 |
\item[\linenum{3}] To cleanup the module, it it
|
| 369 | 3932 |
necessary to stop the cyclic processing. This is done by a call to |
3933 |
\textit{del\_timer\_sync()} which safely removes a queued timer
|
|
3934 |
object. It is assured, that no cyclic work will be done after this |
|
3935 |
call returns. |
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3936 |
\item[\linenum{4}] This call deactivates the
|
| 379 | 3937 |
master, which results in all slaves being brought to their INIT |
3938 |
state again. |
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3939 |
\item[\linenum{5}] This call releases the master,
|
| 369 | 3940 |
removes any existing configuration and silently starts the idle |
3941 |
mode. The value of the master pointer is invalid after this call and |
|
3942 |
the module can be safely unloaded. |
|
3943 |
\end{description}
|
|
3944 |
||
3945 |
The final part of the minimal module is that for the cyclic work. Its |
|
3946 |
coding can be seen in listing~\ref{lst:minirun}.
|
|
3947 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3948 |
\begin{lstlisting}[gobble=2,language=C,numbers=left,caption={Minimal cyclic
|
| 369 | 3949 |
function},label={lst:minirun}]
|
3950 |
void run(unsigned long data) |
|
3951 |
{
|
|
3952 |
static uint8_t dig_in_0; |
|
3953 |
||
3954 |
ecrt_master_receive(master); |
|
3955 |
ecrt_domain_process(domain1); |
|
3956 |
||
3957 |
dig_in_0 = EC_READ_BIT(r_dig_in, 0); |
|
3958 |
EC_WRITE_S16(r_ana_out, dig_in_0 * 0x3FFF); |
|
3959 |
||
3960 |
ecrt_master_run(master); |
|
3961 |
ecrt_master_send(master); |
|
3962 |
||
3963 |
timer.expires += 1; // frequency = HZ |
|
3964 |
add_timer(&timer); |
|
3965 |
} |
|
3966 |
\end{lstlisting}
|
|
3967 |
||
3968 |
\begin{description}
|
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3969 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3970 |
\item[\linenum{5}] The cyclic processing starts with receiving datagrams, that
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3971 |
were sent in the last cycle. The frames containing these datagrams have to be |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3972 |
received by the network interface card prior to this call. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3973 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3974 |
\item[\linenum{6}] The process data of domain 1 has been automatically copied
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3975 |
into domain memory while datagram reception. This call checks the working |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3976 |
counter for changes and re-queues the domain's datagram for sending. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3977 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3978 |
\item[\linenum{8}] This is an example for reading out a bit-oriented process
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3979 |
data value (i.~e. bit 0) via the \textit{EC\_READ\_BIT()} macro. See
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3980 |
section~\ref{sec:macros} for more information about those macros.
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3981 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3982 |
\item[\linenum{9}] This line shows how to write a signed, 16-bit process data
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3983 |
value. In this case, the slave is able to output voltages of |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3984 |
\unit{-10--+10}{\volt} with a resolution of \unit{16}{bit}. This write command
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3985 |
outputs either \unit{0}{\volt} or \unit{+5}{\volt}, depending of the value of
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3986 |
\textit{dig\_in\_0}.
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3987 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3988 |
\item[\linenum{11}] This call runs the master's operation state machine (see
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3989 |
section~\ref{sec:fsm-op}). A single state is processed, and datagrams are
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3990 |
queued. Mainly bus observation is done: The bus state is determined and in case |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3991 |
of slaves that lost their configuration, reconfiguration is tried. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3992 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3993 |
\item[\linenum{12}] This method sends all queued datagrams, in this case the
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3994 |
domain's datagram and one of the master state machine. In best case, all |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3995 |
datagrams fit into one frame. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3996 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3997 |
\item[\linenum{14} -- \linenum{15}] Kernel timers are implemented as
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3998 |
``one-shot'' timers, so they have to be re-added after each execution. The time |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
3999 |
of the next execution is specified in \textit{jiffies} and will happen at the
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4000 |
time of the next system timer interrupt. This results in the \textit{run()}
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4001 |
function being executed with a frequency of \textit{HZ}.
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4002 |
|
| 369 | 4003 |
\end{description}
|
4004 |
||
4005 |
%------------------------------------------------------------------------------ |
|
4006 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4007 |
\section{RTAI Example}
|
| 369 | 4008 |
\label{sec:rtai}
|
4009 |
\index{Examples!RTAI}
|
|
4010 |
||
4011 |
The whole code can be seen in the EtherCAT master code release |
|
4012 |
(see~\cite{etherlab}, file \textit{examples/rtai/rtai\_sample.c}).
|
|
4013 |
||
4014 |
Listing~\ref{lst:rtaivar} shows the defines and global variables
|
|
4015 |
needed for a minimal RTAI module with EtherCAT processing. |
|
4016 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4017 |
\begin{lstlisting}[gobble=2,language=C,numbers=left,caption={RTAI task
|
| 369 | 4018 |
declaration},label={lst:rtaivar}]
|
4019 |
#define FREQUENCY 10000 |
|
4020 |
#define TIMERTICKS (1000000000 / FREQUENCY) |
|
4021 |
||
4022 |
RT_TASK task; |
|
4023 |
\end{lstlisting}
|
|
4024 |
||
4025 |
\begin{description}
|
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4026 |
\item[\linenum{1} -- \linenum{2}] RTAI
|
| 369 | 4027 |
takes the cycle period as nanoseconds, so the easiest way is to |
4028 |
define a frequency and convert it to a cycle time in nanoseconds. |
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4029 |
\item[\linenum{4}] The \textit{task} variable
|
| 369 | 4030 |
later contains information about the running RTAI task. |
4031 |
\end{description}
|
|
4032 |
||
4033 |
Listing~\ref{lst:rtaiinit} shows the module init function for the RTAI
|
|
4034 |
module. Most lines are the same as in listing~\ref{lst:miniinit},
|
|
4035 |
differences come up when starting the cyclic code. |
|
4036 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4037 |
\begin{lstlisting}[gobble=2,language=C,numbers=left,caption={RTAI module init
|
| 369 | 4038 |
function},label={lst:rtaiinit}]
|
4039 |
int __init init_mod(void) |
|
4040 |
{
|
|
4041 |
RTIME requested_ticks, tick_period, now; |
|
4042 |
||
4043 |
if (!(master = ecrt_request_master(0))) {
|
|
4044 |
goto out_return; |
|
4045 |
} |
|
4046 |
||
4047 |
if (!(domain1 = ecrt_master_create_domain(master))) {
|
|
4048 |
goto out_release_master; |
|
4049 |
} |
|
4050 |
||
4051 |
if (ecrt_domain_register_pdo_list(domain1, |
|
4052 |
domain1_pdos)) {
|
|
4053 |
goto out_release_master; |
|
4054 |
} |
|
4055 |
||
4056 |
if (ecrt_master_activate(master)) {
|
|
4057 |
goto out_release_master; |
|
4058 |
} |
|
4059 |
||
4060 |
ecrt_master_prepare(master); |
|
4061 |
||
4062 |
requested_ticks = nano2count(TIMERTICKS); |
|
4063 |
tick_period = start_rt_timer(requested_ticks); |
|
4064 |
||
4065 |
if (rt_task_init(&task, run, 0, 2000, 0, 1, NULL)) {
|
|
4066 |
goto out_stop_timer; |
|
4067 |
} |
|
4068 |
||
4069 |
now = rt_get_time(); |
|
4070 |
if (rt_task_make_periodic(&task, now + tick_period, |
|
4071 |
tick_period)) {
|
|
4072 |
goto out_stop_task; |
|
4073 |
} |
|
4074 |
||
4075 |
return 0; |
|
4076 |
||
4077 |
out_stop_task: |
|
4078 |
rt_task_delete(&task); |
|
4079 |
out_stop_timer: |
|
4080 |
stop_rt_timer(); |
|
4081 |
out_deactivate: |
|
4082 |
ecrt_master_deactivate(master); |
|
4083 |
out_release_master: |
|
4084 |
ecrt_release_master(master); |
|
4085 |
out_return: |
|
4086 |
return -1; |
|
4087 |
} |
|
4088 |
\end{lstlisting}
|
|
4089 |
||
4090 |
\begin{description}
|
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4091 |
\item[\linenum{24} -- \linenum{25}] The
|
| 369 | 4092 |
nanoseconds are converted to RTAI timer ticks and an RTAI timer is |
4093 |
started. \textit{tick\_period} will be the ``real'' number of ticks
|
|
4094 |
used for the timer period (which can be different to the requested |
|
4095 |
one). |
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4096 |
\item[\linenum{27}] The RTAI task is initialized
|
| 369 | 4097 |
by specifying the cyclic function, the parameter to hand over, the |
4098 |
stack size, priority, a flag that tells, if the function will use |
|
4099 |
floating point operations and a signal handler. |
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4100 |
\item[\linenum{32}] The task is made periodic by
|
| 369 | 4101 |
specifying a start time and a period. |
4102 |
\end{description}
|
|
4103 |
||
4104 |
The cleanup function of the RTAI module in listing~\ref{lst:rtaiclean}
|
|
4105 |
is nearly as simple as that of the minimal module. |
|
4106 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4107 |
\begin{lstlisting}[gobble=2,language=C,numbers=left,caption={RTAI module
|
| 369 | 4108 |
cleanup function},label={lst:rtaiclean}]
|
4109 |
void __exit cleanup_mod(void) |
|
4110 |
{
|
|
4111 |
rt_task_delete(&task); |
|
4112 |
stop_rt_timer(); |
|
4113 |
ecrt_master_deactivate(master); |
|
4114 |
ecrt_release_master(master); |
|
4115 |
rt_sem_delete(&master_sem); |
|
4116 |
} |
|
4117 |
\end{lstlisting}
|
|
4118 |
||
4119 |
\begin{description}
|
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4120 |
\item[\linenum{2}] The RTAI task will be stopped
|
| 369 | 4121 |
and deleted. |
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4122 |
\item[\linenum{3}] After that, the RTAI timer can
|
| 369 | 4123 |
be stopped. |
4124 |
\end{description}
|
|
4125 |
||
4126 |
The rest is the same as for the minimal module. |
|
4127 |
||
4128 |
Worth to mention is, that the cyclic function of the RTAI module |
|
4129 |
(listing~\ref{lst:rtairun}) has a slightly different architecture. The
|
|
4130 |
function is not executed until returning for every cycle, but has an |
|
4131 |
infinite loop in it, that is placed in a waiting state for the rest of |
|
4132 |
each cycle. |
|
4133 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4134 |
\begin{lstlisting}[gobble=2,language=C,numbers=left,caption={RTAI module cyclic
|
| 369 | 4135 |
function},label={lst:rtairun}]
|
4136 |
void run(long data) |
|
4137 |
{
|
|
4138 |
while (1) {
|
|
4139 |
ecrt_master_receive(master); |
|
4140 |
ecrt_domain_process(domain1); |
|
4141 |
||
4142 |
k_pos = EC_READ_U32(r_ssi_input); |
|
4143 |
||
4144 |
ecrt_master_run(master); |
|
4145 |
ecrt_master_send(master); |
|
4146 |
||
4147 |
rt_task_wait_period(); |
|
4148 |
} |
|
4149 |
} |
|
4150 |
\end{lstlisting}
|
|
4151 |
||
4152 |
\begin{description}
|
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4153 |
\item[\linenum{3}] The \textit{while (1)} loop
|
| 369 | 4154 |
executes for the lifetime of the RTAI task. |
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4155 |
\item[\linenum{12}] The
|
| 369 | 4156 |
\textit{rt\_task\_wait\_period()} function sets the process into a
|
4157 |
sleeping state until the beginning of the next cycle. It also |
|
4158 |
checks, if the cyclic function has to be terminated. |
|
4159 |
\end{description}
|
|
4160 |
||
4161 |
%------------------------------------------------------------------------------ |
|
4162 |
||
4163 |
\section{Concurrency Example}
|
|
4164 |
\label{sec:concurrency}
|
|
4165 |
\index{Examples!Concurrency}
|
|
4166 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4167 |
As mentioned before, there can be concurrent access to the EtherCAT master. The |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4168 |
application and a EoE\index{EoE} process can compete for master access, for
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4169 |
example. In this case, the module has to provide the locking mechanism, because |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4170 |
it depends on the module's architecture which lock has to be used. The module |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4171 |
makes this locking mechanism available to the master through the master's |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4172 |
locking callbacks. |
| 369 | 4173 |
|
4174 |
In case of RTAI, the lock can be an RTAI semaphore, as shown in |
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4175 |
listing~\ref{lst:convar}. A normal Linux semaphore would not be appropriate,
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4176 |
because it could not block the RTAI task due to RTAI running in a higher domain |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4177 |
than the Linux kernel (see~\cite{rtai}).
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4178 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4179 |
\begin{lstlisting}[gobble=2,language=C,numbers=left,caption={RTAI semaphore for
|
| 369 | 4180 |
concurrent access},label={lst:convar}]
|
4181 |
SEM master_sem; |
|
4182 |
\end{lstlisting}
|
|
4183 |
||
4184 |
The module has to implement the two callbacks for requesting and |
|
4185 |
releasing the master lock. An exemplary coding can be seen in |
|
4186 |
listing~\ref{lst:conlock}.
|
|
4187 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4188 |
\begin{lstlisting}[gobble=2,language=C,numbers=left,caption={RTAI locking
|
| 369 | 4189 |
callbacks for concurrent access},label={lst:conlock}]
|
4190 |
int request_lock(void *data) |
|
4191 |
{
|
|
4192 |
rt_sem_wait(&master_sem); |
|
4193 |
return 0; |
|
4194 |
} |
|
4195 |
||
4196 |
void release_lock(void *data) |
|
4197 |
{
|
|
4198 |
rt_sem_signal(&master_sem); |
|
4199 |
} |
|
4200 |
\end{lstlisting}
|
|
4201 |
||
4202 |
\begin{description}
|
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4203 |
\item[\linenum{1}] The \textit{request\_lock()}
|
| 369 | 4204 |
function has a data parameter. The master always passes the value, |
4205 |
that was specified when registering the callback function. This can |
|
4206 |
be used for handing the master pointer. Notice, that it has an |
|
4207 |
integer return value (see line 4). |
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4208 |
\item[\linenum{3}] The call to
|
| 369 | 4209 |
\textit{rt\_sem\_wait()} either returns at once, when the semaphore
|
4210 |
was free, or blocks until the semaphore is freed again. In any case, |
|
4211 |
the semaphore finally is reserved for the process calling the |
|
4212 |
request function. |
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4213 |
\item[\linenum{4}] When the lock was requested
|
| 369 | 4214 |
successfully, the function should return 0. The module can prohibit |
4215 |
requesting the lock by returning non-zero (see paragraph ``Tuning |
|
4216 |
the jitter'' below). |
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4217 |
\item[\linenum{7}] The \textit{release\_lock()}
|
| 369 | 4218 |
function gets the same argument passed, but has a void return value, |
4219 |
because is always succeeds. |
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4220 |
\item[\linenum{9}] The \textit{rt\_sem\_signal()}
|
| 369 | 4221 |
function frees the semaphore, that was prior reserved with |
4222 |
\textit{rt\_sem\_wait()}.
|
|
4223 |
\end{description}
|
|
4224 |
||
4225 |
In the module's init function, the semaphore must be initialized, and |
|
4226 |
the callbacks must be passed to the EtherCAT master: |
|
4227 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4228 |
\begin{lstlisting}[gobble=2,language=C,numbers=left,caption={Module init
|
| 369 | 4229 |
function for concurrent access},label={lst:coninit}]
|
4230 |
int __init init_mod(void) |
|
4231 |
{
|
|
4232 |
RTIME tick_period, requested_ticks, now; |
|
4233 |
||
4234 |
rt_sem_init(&master_sem, 1); |
|
4235 |
||
4236 |
if (!(master = ecrt_request_master(0))) {
|
|
4237 |
goto out_return; |
|
4238 |
} |
|
4239 |
||
4240 |
ecrt_master_callbacks(master, request_lock, |
|
4241 |
release_lock, NULL); |
|
4242 |
// ... |
|
4243 |
\end{lstlisting}
|
|
4244 |
||
4245 |
\begin{description}
|
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4246 |
\item[\linenum{5}] The call to
|
| 369 | 4247 |
\textit{rt\_sem\_init()} initializes the semaphore and sets its
|
4248 |
value to 1, meaning that only one process can reserve the semaphore |
|
4249 |
without blocking. |
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4250 |
\item[\linenum{11}] The callbacks are passed to
|
| 369 | 4251 |
the master with a call to \textit{ecrt\_master\_callbacks()}. The
|
4252 |
last parameter is the argument, that the master should pass with |
|
4253 |
each call to a callback function. Here it is not used and set to |
|
4254 |
\textit{NULL}.
|
|
4255 |
\end{description}
|
|
4256 |
||
4257 |
For the cyclic function being only one competitor for master access, |
|
4258 |
it has to request the lock like any other process. There is no need to |
|
4259 |
use the callbacks (which are meant for processes of lower priority), |
|
4260 |
so it can access the semaphore directly: |
|
4261 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4262 |
\begin{lstlisting}[gobble=2,language=C,numbers=left,caption={RTAI cyclic
|
| 369 | 4263 |
function for concurrent access},label={lst:conrun}]
|
4264 |
void run(long data) |
|
4265 |
{
|
|
4266 |
while (1) {
|
|
4267 |
rt_sem_wait(&master_sem); |
|
4268 |
||
4269 |
ecrt_master_receive(master); |
|
4270 |
ecrt_domain_process(domain1); |
|
4271 |
||
4272 |
k_pos = EC_READ_U32(r_ssi_input); |
|
4273 |
||
4274 |
ecrt_master_run(master); |
|
4275 |
ecrt_master_send(master); |
|
4276 |
||
4277 |
rt_sem_signal(&master_sem); |
|
4278 |
rt_task_wait_period(); |
|
4279 |
} |
|
4280 |
} |
|
4281 |
\end{lstlisting}
|
|
4282 |
||
4283 |
\begin{description}
|
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4284 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4285 |
\item[\linenum{4}] Every access to the master has to be preceded by a call to
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4286 |
\textit{rt\_sem\_wait()}, because another instance might currently access the
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4287 |
master. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4288 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4289 |
\item[\linenum{14}] When cyclic processing finished, the semaphore has to be
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4290 |
freed again, so that other processes have the possibility to access the master. |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4291 |
|
| 369 | 4292 |
\end{description}
|
4293 |
||
4294 |
A little change has to be made to the cleanup function in case of |
|
4295 |
concurrent master access. |
|
4296 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4297 |
\begin{lstlisting}[gobble=2,language=C,numbers=left,caption={RTAI module
|
| 369 | 4298 |
cleanup function for concurrent access},label={lst:conclean}]
|
4299 |
void __exit cleanup_mod(void) |
|
4300 |
{
|
|
4301 |
rt_task_delete(&task); |
|
4302 |
stop_rt_timer(); |
|
4303 |
ecrt_master_deactivate(master); |
|
4304 |
ecrt_release_master(master); |
|
4305 |
rt_sem_delete(&master_sem); |
|
4306 |
} |
|
4307 |
\end{lstlisting}
|
|
4308 |
||
4309 |
\begin{description}
|
|
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4310 |
\item[\linenum{7}] Upon module cleanup, the
|
| 369 | 4311 |
semaphore has to be deleted, so that memory can be freed. |
4312 |
\end{description}
|
|
4313 |
||
4314 |
\paragraph{Tuning the Jitter}
|
|
4315 |
\index{Jitter}
|
|
4316 |
||
|
1085
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4317 |
Concurrent access leads to higher jitter for the application task, because |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4318 |
there are situations, in which the task has to wait for a process of lower |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4319 |
priority to finish accessing the master. In most cases this is acceptable, |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4320 |
because a master access cycle (receive/process/send) only takes |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4321 |
\unit{10-20}{\micro\second} on recent systems, what would be the maximum
|
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4322 |
additional jitter. However some applications demand a minimum jitter. For this |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4323 |
reason the master access can be prohibited by the application: If the time, |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4324 |
another process wants to access the master, is to close to the beginning of the |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4325 |
next application cycle, the module can disallow, that the lock is taken. In |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4326 |
this case, the request callback has to return $1$, meaning that the lock has |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4327 |
not been taken. The foreign process must abort its master access and try again |
|
c75cdcc5ce87
Started to re-write the documentation.
Florian Pose <fp@igh-essen.com>
parents:
917
diff
changeset
|
4328 |
next time. |
|
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Started to re-write the documentation.
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|
4329 |
|
|
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Started to re-write the documentation.
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|
4330 |
This measure helps to significantly reducing the jitter produced by concurrent |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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|
4331 |
master access. Below are excerpts of an example coding: |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
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|
4332 |
|
|
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|
4333 |
\begin{lstlisting}[gobble=2,language=C,numbers=left,caption={Variables for
|
| 369 | 4334 |
jitter reduction},label={lst:redvar}]
|
4335 |
#define FREQUENCY 10000 // RTAI task frequency in Hz |
|
4336 |
// ... |
|
4337 |
cycles_t t_last_cycle = 0; |
|
4338 |
const cycles_t t_critical = cpu_khz * 1000 / FREQUENCY |
|
4339 |
- cpu_khz * 30 / 1000; |
|
4340 |
\end{lstlisting}
|
|
4341 |
||
4342 |
\begin{description}
|
|
|
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Started to re-write the documentation.
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|
4343 |
|
|
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Started to re-write the documentation.
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|
4344 |
\item[\linenum{3}] The variable \textit{t\_last\_cycle} holds the timer ticks
|
|
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|
4345 |
at the beginning of the last realtime cycle. |
|
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Started to re-write the documentation.
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parents:
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diff
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|
4346 |
|
|
c75cdcc5ce87
Started to re-write the documentation.
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diff
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|
4347 |
\item[\linenum{4}] \textit{t\_critical} contains the number of ticks, that may
|
|
c75cdcc5ce87
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diff
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|
4348 |
have passed since the beginning of the last cycle, until there is no more |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
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|
4349 |
foreign access possible. It is calculated by subtracting the ticks for |
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
917
diff
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|
4350 |
\unit{30}{\micro\second} from the ticks for a complete cycle.
|
|
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|
4351 |
|
| 369 | 4352 |
\end{description}
|
4353 |
||
|
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|
4354 |
\begin{lstlisting}[gobble=2,language=C,numbers=left,caption={Cyclic function
|
| 369 | 4355 |
with reduced jitter},label={lst:redrun}]
|
4356 |
void run(long data) |
|
4357 |
{
|
|
4358 |
while (1) {
|
|
4359 |
t_last_cycle = get_cycles(); |
|
4360 |
rt_sem_wait(&master_sem); |
|
4361 |
// ... |
|
4362 |
\end{lstlisting}
|
|
4363 |
||
4364 |
\begin{description}
|
|
|
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c75cdcc5ce87
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|
4365 |
\item[\linenum{4}] The ticks of the beginning of
|
| 369 | 4366 |
the current realtime cycle are taken before reserving the semaphore. |
4367 |
\end{description}
|
|
4368 |
||
|
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|
4369 |
\begin{lstlisting}[gobble=2,language=C,numbers=left,caption={Request callback
|
| 369 | 4370 |
for reduced jitter},label={lst:redreq}]
|
4371 |
int request_lock(void *data) |
|
4372 |
{
|
|
4373 |
// too close to the next RT cycle: deny access. |
|
4374 |
if (get_cycles() - t_last_cycle > t_critical) |
|
4375 |
return -1; |
|
4376 |
||
4377 |
// allow access |
|
4378 |
rt_sem_wait(&master_sem); |
|
4379 |
return 0; |
|
4380 |
} |
|
4381 |
\end{lstlisting}
|
|
4382 |
||
4383 |
\begin{description}
|
|
|
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Started to re-write the documentation.
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parents:
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diff
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|
4384 |
|
|
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Started to re-write the documentation.
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parents:
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diff
changeset
|
4385 |
\item[\linenum{4}] If the time of request is too close to the next realtime
|
|
c75cdcc5ce87
Started to re-write the documentation.
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parents:
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diff
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|
4386 |
cycle (here: \unit{<30}{\micro\second} before the estimated beginning), the
|
|
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Started to re-write the documentation.
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parents:
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diff
changeset
|
4387 |
locking is denied. The requesting process must abort its cycle. |
|
c75cdcc5ce87
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parents:
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diff
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|
4388 |
|
| 369 | 4389 |
\end{description}
|
4390 |
||
4391 |
%------------------------------------------------------------------------------ |
|
4392 |
||
4393 |
\begin{thebibliography}{99}
|
|
4394 |
\bibitem{etherlab} Ingenieurgemeinschaft IgH: EtherLab -- Open Source
|
|
4395 |
Toolkit for rapid realtime code generation under Linux with |
|
4396 |
Simulink/RTW and EtherCAT technology. URL: http://etherlab.org, |
|
4397 |
July~31, 2006. |
|
4398 |
\bibitem{dlspec} IEC 61158-4-12: Data-link Protocol Specification.
|
|
4399 |
International Electrotechnical Comission (IEC), 2005. |
|
4400 |
\bibitem{alspec} IEC 61158-6-12: Application Layer Protocol
|
|
4401 |
Specification. International Electrotechnical Comission (IEC), 2005. |
|
4402 |
\bibitem{gpl} GNU General Public License, Version 2. URL:
|
|
4403 |
http://www.gnu.org/licenses/gpl.txt. August~9, 2006. |
|
4404 |
\bibitem{lsb} Linux Standard Base. URL:
|
|
4405 |
http://www.freestandards.org/en/LSB. August~9, 2006. |
|
4406 |
\bibitem{wireshark} Wireshark. URL: http://www.wireshark.org.
|
|
4407 |
August~9, 2006. |
|
4408 |
\bibitem{automata} {\it Hopcroft, J.~E. / Ullman, J.~D.}: Introduction
|
|
4409 |
to Automata Theory, Languages and Computation. Adison-Wesley, |
|
4410 |
Reading, Mass.~1979. |
|
4411 |
\bibitem{fsmmis} {\it Wagner, F. / Wolstenholme, P.}: State machine
|
|
4412 |
misunderstandings. In: IEE journal ``Computing and Control |
|
4413 |
Engineering'', 2004. |
|
4414 |
\bibitem{rtai} RTAI. The RealTime Application Interface for Linux from
|
|
4415 |
DIAPM. URL: http://www.rtai.org, 2006. |
|
4416 |
\end{thebibliography}
|
|
4417 |
||
|
917
07b0ad9722a1
Fixed bug concerning listings package.
Florian Pose <fp@igh-essen.com>
parents:
814
diff
changeset
|
4418 |
\printnomenclature |
| 369 | 4419 |
\addcontentsline{toc}{chapter}{\nomname}
|
4420 |
\markleft{\nomname}
|
|
4421 |
||
4422 |
\printindex |
|
4423 |
\markleft{Index}
|
|
4424 |
||
4425 |
%------------------------------------------------------------------------------ |
|
4426 |
||
4427 |
\end{document}
|
|
4428 |
||
4429 |
%------------------------------------------------------------------------------ |