BACnet plugin: Add web interface for online parameter configuration
authorMario de Sousa <msousa@fe.up.pt>
Thu, 28 May 2020 11:15:22 +0100
changeset 2649 db68cb0e6bdc
parent 2648 e4ab768170f9
child 2650 449c9539887a
child 2654 7575050a80c5
BACnet plugin: Add web interface for online parameter configuration
Beremiz_service.py
bacnet/bacnet.py
bacnet/runtime/device.h
bacnet/runtime/server.c
bacnet/runtime/server.h
runtime/BACnet_config.py
runtime/NevowServer.py
runtime/PLCObject.py
--- a/Beremiz_service.py	Thu May 28 11:01:42 2020 +0100
+++ b/Beremiz_service.py	Thu May 28 11:15:22 2020 +0100
@@ -475,6 +475,8 @@
 
 installThreadExcepthook()
 havewamp = False
+haveBNconf = False
+
 
 if havetwisted:
     if webport is not None:
@@ -483,8 +485,17 @@
         except Exception:
             LogMessageAndException(_("Nevow/Athena import failed :"))
             webport = None
-        NS.WorkingDir = WorkingDir
-
+        NS.WorkingDir = WorkingDir  # bug? what happens if import fails?
+
+    # Try to add support for BACnet configuration via web server interface
+    # NOTE:BACnet web config only makes sense if web server is available
+    if webport is not None:
+        try:
+            import runtime.BACnet_config as BNconf
+            haveBNconf = True
+        except Exception:
+            LogMessageAndException(_("BACnet configuration web interface - import failed :"))
+        
     try:
         import runtime.WampClient as WC  # pylint: disable=ungrouped-imports
         WC.WorkingDir = WorkingDir
@@ -506,6 +517,8 @@
 runtime.CreatePLCObjectSingleton(
     WorkingDir, argv, statuschange, evaluator, pyruntimevars)
 
+plcobj = runtime.GetPLCObjectSingleton()
+
 pyroserver = PyroServer(servicename, interface, port)
 
 if havewx:
@@ -521,6 +534,12 @@
         except Exception:
             LogMessageAndException(_("Nevow Web service failed. "))
 
+    if haveBNconf:
+        try:
+            BNconf.init(plcobj, NS, WorkingDir)
+        except Exception:
+            LogMessageAndException(_("BACnet web configuration failed startup. "))
+
     if havewamp:
         try:
             WC.SetServer(pyroserver)
@@ -584,7 +603,6 @@
 pyroserver.Quit()
 pyro_thread.join()
 
-plcobj = runtime.GetPLCObjectSingleton()
 plcobj.StopPLC()
 plcobj.UnLoadPLC()
 
--- a/bacnet/bacnet.py	Thu May 28 11:01:42 2020 +0100
+++ b/bacnet/bacnet.py	Thu May 28 11:15:22 2020 +0100
@@ -35,11 +35,11 @@
 from bacnet.BacnetSlaveEditor import *
 from bacnet.BacnetSlaveEditor import ObjectProperties
 from PLCControler import LOCATION_CONFNODE, LOCATION_VAR_MEMORY
-
-base_folder = os.path.split(
-    os.path.dirname(os.path.realpath(__file__)))[0]
+from ConfigTreeNode import ConfigTreeNode
+
+base_folder = os.path.split(os.path.dirname(os.path.realpath(__file__)))[0]
 base_folder = os.path.join(base_folder, "..")
-BacnetPath = os.path.join(base_folder, "BACnet")
+BacnetPath  = os.path.join(base_folder, "BACnet")
 BacnetLibraryPath = os.path.join(BacnetPath, "lib")
 BacnetIncludePath = os.path.join(BacnetPath, "include")
 BacnetIncludePortPath = os.path.join(BacnetPath, "ports")
@@ -50,6 +50,10 @@
 BACNET_VENDOR_NAME = "Beremiz.org"
 BACNET_DEVICE_MODEL_NAME = "Beremiz PLC"
 
+
+# Max String Size of BACnet Paramaters
+BACNET_PARAM_STRING_SIZE = 64
+
 #
 #
 #
@@ -97,6 +101,14 @@
       </xsd:element>
     </xsd:schema>
     """
+    # NOTE; Add the following code/declaration to the aboce XSD in order to activate the
+    #          Override_Parameters_Saved_on_PLC   flag (currenty not in use as it requires further
+    #          analysis how the user would interpret this user interface option.
+    #        <--- snip --->
+    #          <xsd:attribute name="Override_Parameters_Saved_on_PLC" 
+    #                                                   type="xsd:boolean" use="optional" default="true"/>
+    #        <--- snip --->
+    #
     # NOTE: BACnet device (object) IDs are 22 bits long (not counting the 10 bits for the type ID)
     #       so the Device instance ID is limited from 0 to 22^2-1 = 4194303
     #       However, 4194303 is reserved for special use (similar to NULL pointer), so last
@@ -552,8 +564,10 @@
             generate_file_handle  .write(generate_file_content)
             generate_file_handle  .close()
 
-    #
-    # Generate the source files #
+
+
+    #
+    # Generate the C source code files
     #
     def CTNGenerate_C(self, buildpath, locations):
         # Determine the current location in Beremiz's project configuration
@@ -596,6 +610,11 @@
         # The BACnetServerNode attribute is added dynamically by ConfigTreeNode._AddParamsMembers()
         # It will be an XML parser object created by
         # GenerateParserFromXSDstring(self.XSD).CreateRoot()
+        #
+        # Note: Override_Parameters_Saved_on_PLC is converted to an integer by int()
+        #       The above flag is not currently in use. It requires further thinking on how the 
+        #       user will interpret and interact with this user interface...
+        #loc_dict["Override_Parameters_Saved_on_PLC"] = int(self.BACnetServerNode.getOverride_Parameters_Saved_on_PLC())
         loc_dict["network_interface"] = self.BACnetServerNode.getNetwork_Interface()
         loc_dict["port_number"] = self.BACnetServerNode.getUDP_Port_Number()
         loc_dict["BACnet_Device_ID"] = self.BACnetServerNode.getBACnet_Device_ID()
@@ -607,6 +626,8 @@
         loc_dict["BACnet_Vendor_ID"] = BACNET_VENDOR_ID
         loc_dict["BACnet_Vendor_Name"] = BACNET_VENDOR_NAME
         loc_dict["BACnet_Model_Name"] = BACNET_DEVICE_MODEL_NAME
+        loc_dict["BACnet_Param_String_Size"] = BACNET_PARAM_STRING_SIZE
+        
 
         # 2) Add the data specific to each BACnet object type
         # For each BACnet object type, start off by creating some intermediate helpful lists
@@ -726,4 +747,33 @@
         CFLAGS = ' -I"' + BacnetIncludePath + '"'
         CFLAGS += ' -I"' + BacnetIncludePortPath + '"'
 
+        # ----------------------------------------------------------------------
+        # Create a file containing the default configuration paramters.
+        # Beremiz will then transfer this file to the PLC, where the web server 
+        # will read it to obtain the default configuration parameters.
+        # ----------------------------------------------------------------------
+        # NOTE: This is no loner needed! The web interface will read these 
+        # parameters directly from the compiled C code (.so file)
+        #
+        ### extra_file_name   = os.path.join(buildpath, "%s_%s.%s" % ('bacnet_extrafile', postfix, 'txt'))
+        ### extra_file_handle = open(extra_file_name, 'w')
+        ### 
+        ### proplist = ["network_interface", "port_number", "BACnet_Device_ID", "BACnet_Device_Name", 
+        ###             "BACnet_Comm_Control_Password", "BACnet_Device_Location", 
+        ###             "BACnet_Device_Description", "BACnet_Device_AppSoft_Version"]
+        ### for propname in proplist:
+        ###     extra_file_handle.write("%s:%s\n" % (propname, loc_dict[propname]))
+        ### 
+        ### extra_file_handle.close()
+        ### extra_file_handle = open(extra_file_name, 'r')
+
+        # Format of data to return:
+        #   [(Cfiles, CFLAGS), ...], LDFLAGS, DoCalls, extra_files
+        # LDFLAGS     = ['flag1', 'flag2', ...]
+        # DoCalls     = true  or  false
+        # extra_files = (fname,fobject), ...
+        # fobject     = file object, already open'ed for read() !!
+        #
+        # extra_files -> files that will be downloaded to the PLC!
         return [(Generated_BACnet_c_mainfile_name, CFLAGS)], LDFLAGS, True
+        #return [(Generated_BACnet_c_mainfile_name, CFLAGS)], LDFLAGS, True, ('extrafile1.txt', extra_file_handle)
--- a/bacnet/runtime/device.h	Thu May 28 11:01:42 2020 +0100
+++ b/bacnet/runtime/device.h	Thu May 28 11:15:22 2020 +0100
@@ -161,11 +161,12 @@
  * Maximum sizes excluding nul terminator .
  */
 #define STRLEN_X(minlen, str)  (((minlen)>sizeof(str))?(minlen):sizeof(str))
-#define MAX_DEV_NAME_LEN STRLEN_X(32, "%(BACnet_Device_Name)s")     /* Device name         */
-#define MAX_DEV_LOC_LEN  STRLEN_X(64, BACNET_DEVICE_LOCATION)       /* Device location     */
-#define MAX_DEV_MOD_LEN  STRLEN_X(32, BACNET_DEVICE_MODEL_NAME)     /* Device model name   */
-#define MAX_DEV_VER_LEN  STRLEN_X(16, BACNET_DEVICE_APPSOFT_VER)    /* Device application software version */
-#define MAX_DEV_DESC_LEN STRLEN_X(64, BACNET_DEVICE_DESCRIPTION)    /* Device description  */
+#define MAX_DEV_NAME_LEN STRLEN_X(%(BACnet_Param_String_Size)d, "%(BACnet_Device_Name)s")     /* Device name         */
+#define MAX_DEV_LOC_LEN  STRLEN_X(%(BACnet_Param_String_Size)d, BACNET_DEVICE_LOCATION)       /* Device location     */
+#define MAX_DEV_MOD_LEN  STRLEN_X(%(BACnet_Param_String_Size)d, BACNET_DEVICE_MODEL_NAME)     /* Device model name   */
+#define MAX_DEV_VER_LEN  STRLEN_X(%(BACnet_Param_String_Size)d, BACNET_DEVICE_APPSOFT_VER)    /* Device application software version */
+#define MAX_DEV_DESC_LEN STRLEN_X(%(BACnet_Param_String_Size)d, BACNET_DEVICE_DESCRIPTION)    /* Device description  */
+
 
 /** Structure to define the Object Properties common to all Objects. */
 typedef struct commonBacObj_s {
--- a/bacnet/runtime/server.c	Thu May 28 11:01:42 2020 +0100
+++ b/bacnet/runtime/server.c	Thu May 28 11:15:22 2020 +0100
@@ -52,6 +52,10 @@
 #include "timesync.h"
 
 
+
+
+
+
 /* A utility function used by most (all?) implementations of BACnet Objects */
 /* Adds to Prop_List all entries in Prop_List_XX that are not
  * PROP_OBJECT_IDENTIFIER, PROP_OBJECT_NAME, PROP_OBJECT_TYPE, PROP_PROPERTY_LIST
@@ -454,17 +458,33 @@
     bvlc_bdt_restore_local();
     /* Initiliaze the bacnet server 'device' */    
     Device_Init(server_node->device_name);
-
-    pthread_mutex_lock(&init_done_lock);
-    init_done = 1;
-    pthread_cond_signal(&init_done_cond);
-    pthread_mutex_unlock(&init_done_lock);
-
+    
+    /* Although the default values for the following properties are hardcoded into
+     * the respective variable definition+initialization in the C code,
+     * these values may be potentially changed after compilation but before 
+     * code startup. This is done by the web interface(1), directly loading the .so file, 
+     * and changing the values in the server_node_t variable.
+     * We must therefore honor those values when we start running the BACnet device server
+     * 
+     * (1) Web interface is implemented in runtime/BACnet_config.py
+     *     which works as an extension of the web server in runtime/NevowServer.py
+     *     which in turn is initialised/run by the Beremiz_service.py deamon
+     */
+    Device_Set_Location                    (server_node->device_location,        strlen(server_node->device_location));
+    Device_Set_Description                 (server_node->device_description,     strlen(server_node->device_description));
+    Device_Set_Application_Software_Version(server_node->device_appsoftware_ver, strlen(server_node->device_appsoftware_ver));
     /* Set the password (max 31 chars) for Device Communication Control request. */
     /* Default in the BACnet stack is hardcoded as "filister" */
     /* (char *) cast is to remove the cast. The function is incorrectly declared/defined in the BACnet stack! */
     /* BACnet stack needs to change demo/handler/h_dcc.c and include/handlers.h                               */
     handler_dcc_password_set((char *)server_node->comm_control_passwd);
+
+    
+    pthread_mutex_lock(&init_done_lock);
+    init_done = 1;
+    pthread_cond_signal(&init_done_cond);
+    pthread_mutex_unlock(&init_done_lock);
+
     /* Set callbacks and configure network interface */
     res = Init_Service_Handlers();
     if (res < 0) exit(1);
@@ -661,3 +681,108 @@
 	return res;
 }
 
+
+
+
+
+/**********************************************/
+/** Functions for Beremiz web interface.     **/
+/**********************************************/
+
+/*
+ * Beremiz has a program to run on the PLC (Beremiz_service.py)
+ * to handle downloading of compiled programs, start/stop of PLC, etc.
+ * (see runtime/PLCObject.py for start/stop, loading, ...)
+ * 
+ * This service also includes a web server to access PLC state (start/stop)
+ * and to change some basic confiuration parameters.
+ * (see runtime/NevowServer.py for the web server)
+ * 
+ * The web server allows for extensions, where additional configuration
+ * parameters may be changed on the running/downloaded PLC.
+ * BACnet plugin also comes with an extension to the web server, through
+ * which the basic BACnet plugin configuration parameters may be changed
+ * (basically, only the parameters in server_node_t may be changed)
+ * 
+ * The following functions are never called from other C code. They are 
+ * called instead from the python code in runtime/BACnet_config.py, that
+ * implements the web server extension for configuring BACnet parameters.
+ */
+
+
+/* The location (in the Config. Node Tree of Beremiz IDE)
+ * of the BACnet plugin.
+ * 
+ * This variable is also used by the BACnet web config code to determine 
+ * whether the current loaded PLC includes the BACnet plugin
+ * (so it should make the BACnet parameter web interface visible to the user).
+ */
+const char * __bacnet_plugin_location = "%(locstr)s";
+
+
+/* NOTE: We could have the python code in runtime/BACnet_config.py
+ *       directly access the server_node_t structure, however
+ *       this would create a tight coupling between these two
+ *       disjoint pieces of code.
+ *       Any change to the server_node_t structure would require the 
+ *       python code to be changed accordingly. I have therefore opted
+ *       to cretae get/set functions, one for each parameter.
+ *       
+ * NOTE: since the BACnet plugin can only support/allow at most one instance 
+ *       of the BACnet plugin in Beremiz (2 or more are not allowed due to 
+ *       limitations of the underlying BACnet protocol stack being used),
+ *       a single generic version of each of the following functions would work.
+ *       However, simply for the sake of keeping things general, we create
+ *       a diferent function for each plugin instance (which, as I said,
+ *       will never occur for now).
+ * 
+ *      The functions being declared are therefoe named:
+ *          __bacnet_0_get_ConfigParam_location
+ *          __bacnet_0_get_ConfigParam_device_name
+ *        etc...
+ *      where the 0 will be replaced by the location of the BACnet plugin
+ *      in the Beremiz configuration tree (will change depending on where
+ *      the user inserted the BACnet plugin into their project) 
+ */
+
+/* macro works for all data types */
+#define __bacnet_get_ConfigParam(param_type,param_name)                 \
+param_type __bacnet_%(locstr)s_get_ConfigParam_##param_name(void) {     \
+    return server_node.param_name;                                      \
+}
+
+/* macro only works for char * data types */
+/* Note that the storage space (max string size) reserved for each parameter
+ * (this storage space is reserved in device.h)
+ * is set to a minimum of 
+ *     %(BACnet_Param_String_Size)d 
+ * which is set to the value of
+ *     BACNET_PARAM_STRING_SIZE
+ * in bacnet.py
+ */
+#define __bacnet_set_ConfigParam(param_type,param_name)                 \
+void __bacnet_%(locstr)s_set_ConfigParam_##param_name(param_type val) { \
+    strncpy(server_node.param_name, val, %(BACnet_Param_String_Size)d); \
+    server_node.param_name[%(BACnet_Param_String_Size)d - 1] = '\0';    \
+}
+
+
+#define __bacnet_ConfigParam_str(param_name)        \
+__bacnet_get_ConfigParam(const char*,param_name)    \
+__bacnet_set_ConfigParam(const char*,param_name)     
+
+
+__bacnet_ConfigParam_str(location)
+__bacnet_ConfigParam_str(network_interface)
+__bacnet_ConfigParam_str(port_number)
+__bacnet_ConfigParam_str(device_name)
+__bacnet_ConfigParam_str(device_location)
+__bacnet_ConfigParam_str(device_description)
+__bacnet_ConfigParam_str(device_appsoftware_ver)
+__bacnet_ConfigParam_str(comm_control_passwd)
+
+__bacnet_get_ConfigParam(uint32_t,device_id)
+void __bacnet_%(locstr)s_set_ConfigParam_device_id(uint32_t val) {
+    server_node.device_id = val;
+}
+
--- a/bacnet/runtime/server.h	Thu May 28 11:01:42 2020 +0100
+++ b/bacnet/runtime/server.h	Thu May 28 11:15:22 2020 +0100
@@ -33,12 +33,19 @@
 
 
 
+
 typedef struct{
-	    const char *location;
-	    const char *network_interface;
-	    const char *port_number;
-	    const char *device_name;
-	    const char *comm_control_passwd;
+	    char location              [%(BACnet_Param_String_Size)d];
+	    char network_interface     [%(BACnet_Param_String_Size)d];
+	    char port_number           [%(BACnet_Param_String_Size)d];
+	    char device_name           [%(BACnet_Param_String_Size)d];
+	    char device_location       [%(BACnet_Param_String_Size)d];        
+	    char device_description    [%(BACnet_Param_String_Size)d];
+	    char device_appsoftware_ver[%(BACnet_Param_String_Size)d];        
+	    char comm_control_passwd   [%(BACnet_Param_String_Size)d];
+// 	    int         override_local_config;  // bool flag => 
+// 	                                        //   true : use these parameter values
+// 	                                        //   false: use values stored on local file in PLC
 	    uint32_t	device_id; // device ID is 22 bits long! uint16_t is not enough!
 	    int		init_state; // store how far along the server's initialization has progressed
 	    pthread_t	thread_id;  // thread handling this server
@@ -49,13 +56,16 @@
 /*initialization following all parameters given by user in application*/
 static server_node_t server_node = {
   "%(locstr)s",
-  "%(network_interface)s",           // interface    (NULL => use default (eth0))
-  "%(port_number)s",                 // Port number  (NULL => use default)
-  "%(BACnet_Device_Name)s",          // BACnet server's device (object) name
-  "%(BACnet_Comm_Control_Password)s",// BACnet server's device (object) name
-   %(BACnet_Device_ID)s              // BACnet server's device (object) ID
+  "%(network_interface)s",              // interface    (NULL => use default (eth0))
+  "%(port_number)s",                    // Port number  (NULL => use default)
+  "%(BACnet_Device_Name)s",             // BACnet server's device (object) Name
+  "%(BACnet_Device_Location)s",         // BACnet server's device (object) Location
+  "%(BACnet_Device_Description)s",      // BACnet server's device (object) Description
+  "%(BACnet_Device_AppSoft_Version)s",  // BACnet server's device (object) App. Software Ver.
+  "%(BACnet_Comm_Control_Password)s",   // BACnet server's device (object) Password
+//  (Override_Parameters_Saved_on_PLC)d, // override locally saved parameters (bool flag)
+  %(BACnet_Device_ID)s                  // BACnet server's device (object) ID
 };
 
 
-
 #endif /* SERVER_H_ */
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/runtime/BACnet_config.py	Thu May 28 11:15:22 2020 +0100
@@ -0,0 +1,486 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+
+# This file is part of Beremiz runtime.
+#
+# Copyright (C) 2020: Mario de Sousa
+#
+# See COPYING.Runtime file for copyrights details.
+#
+# This library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2.1 of the License, or (at your option) any later version.
+
+# This library is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Lesser General Public License for more details.
+
+# You should have received a copy of the GNU Lesser General Public
+# License along with this library; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+
+
+import json
+import os
+import ctypes
+
+from formless import annotate, webform
+
+
+
+# reference to the PLCObject in runtime/PLCObject.py
+# PLCObject is a singleton, created in runtime/__init__.py
+_plcobj = None
+
+# reference to the Nevow web server (a.k.a as NS in Beremiz_service.py)
+# (Note that NS will reference the NevowServer.py _module_, and not an object/class)
+_NS = None
+
+
+# WorkingDir: the directory on which Beremiz_service.py is running, and where 
+#             all the files downloaded to the PLC get stored
+_WorkingDir = None
+
+
+# Will contain references to the C functions 
+# (implemented in beremiz/bacnet/runtime/server.c)
+# used to get/set the BACnet specific configuration paramters
+GetParamFuncs = {}
+SetParamFuncs = {}
+
+
+# Upon PLC load, this Dictionary is initialised with the BACnet configuration
+# hardcoded in the C file
+# (i.e. the configuration inserted in Beremiz IDE when project was compiled)
+_DefaultConfiguration = None
+
+
+# Dictionary that contains the BACnet configuration currently being shown
+# on the web interface
+# This configuration will almost always be identical to the current
+# configuration in the PLC (i.e., the current state stored in the 
+# C variables in the .so file).
+# The configuration viewed on the web will only be different to the current 
+# configuration when the user edits the configuration, and when
+# the user asks to save the edited configuration but it contains an error.
+_WebviewConfiguration = None
+
+
+# Dictionary that stores the BACnet configuration currently stored in a file
+# Currently only used to decide whether or not to show the "Delete" button on the
+# web interface (only shown if _SavedConfiguration is not None)
+_SavedConfiguration = None
+
+
+# File to which the new BACnet configuration gets stored on the PLC
+# Note that the stored configuration is likely different to the
+# configuration hardcoded in C generated code (.so file), so
+# this file should be persistent across PLC reboots so we can
+# re-configure the PLC (change values of variables in .so file)
+# before it gets a chance to start running
+#
+#_BACnetConfFilename = None
+_BACnetConfFilename = "/tmp/BeremizBACnetConfig.json"
+
+
+
+
+
+
+BACnet_parameters = [
+    #    param. name             label                                            ctype type      annotate type
+    # (C code var name)         (used on web interface)                          (C data type)    (web data type)
+    #                                                                                             (annotate.String,
+    #                                                                                              annotate.Integer, ...)
+    ("network_interface"      , _("Network Interface")                         , ctypes.c_char_p, annotate.String),
+    ("port_number"            , _("UDP Port Number")                           , ctypes.c_char_p, annotate.String),
+    ("comm_control_passwd"    , _("BACnet Communication Control Password")     , ctypes.c_char_p, annotate.String),
+    ("device_id"              , _("BACnet Device ID")                          , ctypes.c_int,    annotate.Integer),
+    ("device_name"            , _("BACnet Device Name")                        , ctypes.c_char_p, annotate.String),
+    ("device_location"        , _("BACnet Device Location")                    , ctypes.c_char_p, annotate.String),
+    ("device_description"     , _("BACnet Device Description")                 , ctypes.c_char_p, annotate.String),
+    ("device_appsoftware_ver" , _("BACnet Device Application Software Version"), ctypes.c_char_p, annotate.String)
+    ]
+
+
+
+
+
+
+def _CheckPortnumber(port_number):
+    """ check validity of the port number """
+    try:
+        portnum = int(port_number)
+        if (portnum < 0) or (portnum > 65535):
+           raise Exception
+    except Exception:    
+        return False
+        
+    return True    
+    
+
+
+def _CheckDeviceID(device_id):
+    """ 
+    # check validity of the Device ID 
+    # NOTE: BACnet device (object) IDs are 22 bits long (not counting the 10 bits for the type ID)
+    #       so the Device instance ID is limited from 0 to 22^2-1 = 4194303
+    #       However, 4194303 is reserved for special use (similar to NULL pointer), so last
+    #       valid ID becomes 4194302
+    """
+    try:
+        devid = int(device_id)
+        if (devid < 0) or (devid > 4194302):
+            raise Exception
+    except Exception:    
+        return False
+        
+    return True    
+
+
+
+
+
+def _CheckConfiguration(BACnetConfig):
+    res = True    
+    res = res and _CheckPortnumber(BACnetConfig["port_number"])
+    res = res and _CheckDeviceID  (BACnetConfig["device_id"])
+    return res
+
+
+
+def _CheckWebConfiguration(BACnetConfig):
+    res = True
+    
+    # check the port number
+    if not _CheckPortnumber(BACnetConfig["port_number"]):
+        raise annotate.ValidateError(
+            {"port_number": "Invalid port number: " + str(BACnetConfig["port_number"])},
+            _("BACnet configuration error:"))
+        res = False
+    
+    if not _CheckDeviceID(BACnetConfig["device_id"]):
+        raise annotate.ValidateError(
+            {"device_id": "Invalid device ID: " + str(BACnetConfig["device_id"])},
+            _("BACnet configuration error:"))
+        res = False
+        
+    return res
+
+
+
+
+
+
+def _SetSavedConfiguration(BACnetConfig):
+    """ Stores in a file a dictionary containing the BACnet parameter configuration """
+    with open(os.path.realpath(_BACnetConfFilename), 'w') as f:
+        json.dump(BACnetConfig, f, sort_keys=True, indent=4)
+    global _SavedConfiguration
+    _SavedConfiguration = BACnetConfig
+
+
+def _DelSavedConfiguration():
+    """ Deletes the file cotaining the persistent BACnet configuration """
+    if os.path.exists(_BACnetConfFilename):
+        os.remove(_BACnetConfFilename)
+
+
+def _GetSavedConfiguration():
+    """
+    # Returns a dictionary containing the BACnet parameter configuration
+    # that was last saved to file. If no file exists, then return None
+    """
+    try:
+        #if os.path.isfile(_BACnetConfFilename):
+        saved_config = json.load(open(_BACnetConfFilename))
+    except Exception:    
+        return None
+
+    if _CheckConfiguration(saved_config):
+        return saved_config
+    else:
+        return None
+
+
+def _GetPLCConfiguration():
+    """
+    # Returns a dictionary containing the current BACnet parameter configuration
+    # stored in the C variables in the loaded PLC (.so file)
+    """
+    current_config = {}
+    for par_name, x1, x2, x3 in BACnet_parameters:
+        value = GetParamFuncs[par_name]()
+        if value is not None:
+            current_config[par_name] = value
+    
+    return current_config
+
+
+def _SetPLCConfiguration(BACnetConfig):
+    """
+    # Stores the BACnet parameter configuration into the
+    # the C variables in the loaded PLC (.so file)
+    """
+    for par_name in BACnetConfig:
+        value = BACnetConfig[par_name]
+        #_plcobj.LogMessage("BACnet web server extension::_SetPLCConfiguration()  Setting "
+        #                       + par_name + " to " + str(value) )
+        if value is not None:
+            SetParamFuncs[par_name](value)
+    # update the configuration shown on the web interface
+    global _WebviewConfiguration 
+    _WebviewConfiguration = _GetPLCConfiguration()
+
+
+
+def _GetWebviewConfigurationValue(ctx, argument):
+    """
+    # Callback function, called by the web interface (NevowServer.py)
+    # to fill in the default value of each parameter
+    """
+    try:
+        return _WebviewConfiguration[argument.name]
+    except Exception:
+        return ""
+
+
+# The configuration of the web form used to see/edit the BACnet parameters
+webFormInterface = [(name, web_dtype (label=web_label, default=_GetWebviewConfigurationValue)) 
+                    for name, web_label, c_dtype, web_dtype in BACnet_parameters]
+
+
+
+def _updateWebInterface():
+    """
+    # Add/Remove buttons to/from the web interface depending on the current state
+    #
+    #  - If there is a saved state => add a delete saved state button
+    """
+
+    # Add a "Delete Saved Configuration" button if there is a saved configuration!
+    if _SavedConfiguration is None:
+        _NS.ConfigurableSettings.delSettings("BACnetConfigDelSaved")
+    else:
+        _NS.ConfigurableSettings.addSettings(
+            "BACnetConfigDelSaved",                   # name
+            _("BACnet Configuration"),                # description
+            [],                                       # fields  (empty, no parameters required!)
+            _("Delete Configuration Stored in Persistent Storage"), # button label
+            OnButtonDel)                              # callback    
+
+
+
+def OnButtonSave(**kwargs):
+    """
+    # Function called when user clicks 'Save' button in web interface
+    # The function will configure the BACnet plugin in the PLC with the values
+    # specified in the web interface. However, values must be validated first!
+    """
+
+    #_plcobj.LogMessage("BACnet web server extension::OnButtonSave()  Called")
+    
+    newConfig = {}
+    for par_name, x1, x2, x3 in BACnet_parameters:
+        value = kwargs.get(par_name, None)
+        if value is not None:
+            newConfig[par_name] = value
+
+    global _WebviewConfiguration
+    _WebviewConfiguration = newConfig
+    
+    # First check if configuration is OK.
+    if not _CheckWebConfiguration(newConfig):
+        return
+
+    # store to file the new configuration so that 
+    # we can recoup the configuration the next time the PLC
+    # has a cold start (i.e. when Beremiz_service.py is retarted)
+    _SetSavedConfiguration(newConfig)
+
+    # Configure PLC with the current BACnet parameters
+    _SetPLCConfiguration(newConfig)
+
+    # File has just been created => Delete button must be shown on web interface!
+    _updateWebInterface()
+
+
+
+
+def OnButtonDel(**kwargs):
+    """
+    # Function called when user clicks 'Delete' button in web interface
+    # The function will delete the file containing the persistent
+    # BACnet configution
+    """
+
+    # Delete the file
+    _DelSavedConfiguration()
+    # Set the current configuration to the default (hardcoded in C)
+    _SetPLCConfiguration(_DefaultConfiguration)
+    # Reset global variable
+    global _SavedConfiguration
+    _SavedConfiguration = None
+    # File has just been deleted => Delete button on web interface no longer needed!
+    _updateWebInterface()
+
+
+
+def OnButtonShowCur(**kwargs):
+    """
+    # Function called when user clicks 'Show Current PLC Configuration' button in web interface
+    # The function will load the current PLC configuration into the web form
+    """
+    
+    global _WebviewConfiguration
+    _WebviewConfiguration = _GetPLCConfiguration()
+    # File has just been deleted => Delete button on web interface no longer needed!
+    _updateWebInterface()
+
+
+
+
+def OnLoadPLC():
+    """
+    # Callback function, called (by PLCObject.py) when a new PLC program
+    # (i.e. XXX.so file) is transfered to the PLC runtime
+    # and oaded into memory
+    """
+
+    #_plcobj.LogMessage("BACnet web server extension::OnLoadPLC() Called...")
+
+    if _plcobj.PLClibraryHandle is None:
+        # PLC was loaded but we don't have access to the library of compiled code (.so lib)?
+        # Hmm... This shold never occur!! 
+        return  
+    
+    # Get the location (in the Config. Node Tree of Beremiz IDE) the BACnet plugin
+    # occupies in the currently loaded PLC project (i.e., the .so file)
+    # If the "__bacnet_plugin_location" C variable is not present in the .so file,
+    # we conclude that the currently loaded PLC does not have the BACnet plugin
+    # included (situation (2b) described above init())
+    try:
+        location = ctypes.c_char_p.in_dll(_plcobj.PLClibraryHandle, "__bacnet_plugin_location")
+    except Exception:
+        # Loaded PLC does not have the BACnet plugin => nothing to do
+        #   (i.e. do _not_ configure and make available the BACnet web interface)
+        return
+
+    # Map the get/set functions (written in C code) we will be using to get/set the configuration parameters
+    for name, web_label, c_dtype, web_dtype in BACnet_parameters:
+        GetParamFuncName = "__bacnet_" + location.value + "_get_ConfigParam_" + name
+        SetParamFuncName = "__bacnet_" + location.value + "_set_ConfigParam_" + name
+        
+        GetParamFuncs[name]          = getattr(_plcobj.PLClibraryHandle, GetParamFuncName)
+        GetParamFuncs[name].restype  = c_dtype
+        GetParamFuncs[name].argtypes = None
+        
+        SetParamFuncs[name]          = getattr(_plcobj.PLClibraryHandle, SetParamFuncName)
+        SetParamFuncs[name].restype  = None
+        SetParamFuncs[name].argtypes = [c_dtype]
+
+    # Default configuration is the configuration done in Beremiz IDE
+    # whose parameters get hardcoded into C, and compiled into the .so file
+    # We read the default configuration from the .so file before the values
+    # get changed by the user using the web server, or by the call (further on)
+    # to _SetPLCConfiguration(SavedConfiguration)
+    global _DefaultConfiguration 
+    _DefaultConfiguration = _GetPLCConfiguration()
+    
+    # Show the current PLC configuration on the web interface        
+    global _WebviewConfiguration
+    _WebviewConfiguration = _GetPLCConfiguration()
+ 
+    # Read from file the last used configuration, which is likely
+    # different to the hardcoded configuration.
+    # We Reset the current configuration (i.e., the config stored in the 
+    # variables of .so file) to this saved configuration
+    # so the PLC will start off with this saved configuration instead
+    # of the hardcoded (in Beremiz C generated code) configuration values.
+    #
+    # Note that _SetPLCConfiguration() will also update 
+    # _WebviewConfiguration , if necessary.
+    global _SavedConfiguration
+    _SavedConfiguration  = _GetSavedConfiguration()
+    if _SavedConfiguration is not None:
+        if _CheckConfiguration(_SavedConfiguration):
+            _SetPLCConfiguration(_SavedConfiguration)
+            
+    # Configure the web interface to include the BACnet config parameters
+    _NS.ConfigurableSettings.addSettings(
+        "BACnetConfigParm",                # name
+        _("BACnet Configuration"),         # description
+        webFormInterface,                  # fields
+        _("Save Configuration to Persistent Storage"),  # button label
+        OnButtonSave)                      # callback    
+    
+    # Add a "View Current Configuration" button 
+    _NS.ConfigurableSettings.addSettings(
+        "BACnetConfigViewCur",                    # name
+        _("BACnet Configuration"),                # description
+        [],                                       # fields  (empty, no parameters required!)
+        _("Show Current PLC Configuration"),      # button label
+        OnButtonShowCur)                          # callback    
+
+    # Add the Delete button to the web interface, if required
+    _updateWebInterface()
+
+
+
+
+
+def OnUnLoadPLC():
+    """
+    # Callback function, called (by PLCObject.py) when a PLC program is unloaded from memory
+    """
+
+    #_plcobj.LogMessage("BACnet web server extension::OnUnLoadPLC() Called...")
+    
+    # Delete the BACnet specific web interface extensions
+    # (Safe to ask to delete, even if it has not been added!)
+    _NS.ConfigurableSettings.delSettings("BACnetConfigParm")
+    _NS.ConfigurableSettings.delSettings("BACnetConfigViewCur")  
+    _NS.ConfigurableSettings.delSettings("BACnetConfigDelSaved")  
+    GetParamFuncs = {}
+    SetParamFuncs = {}
+    _WebviewConfiguration = None
+    _SavedConfiguration   = None
+
+
+
+
+# The Beremiz_service.py service, along with the integrated web server it launches
+# (i.e. Nevow web server, in runtime/NevowServer.py), will go through several states
+# once started:
+#  (1) Web server is started, but no PLC is loaded
+#  (2) PLC is loaded (i.e. the PLC compiled code is loaded)
+#         (a) The loaded PLC includes the BACnet plugin
+#         (b) The loaded PLC does not have the BACnet plugin
+#
+# During (1) and (2a):
+#     we configure the web server interface to not have the BACnet web configuration extension
+# During (2b) 
+#     we configure the web server interface to include the BACnet web configuration extension
+#
+# plcobj    : reference to the PLCObject defined in PLCObject.py
+# NS        : reference to the web server (i.e. the NevowServer.py module)
+# WorkingDir: the directory on which Beremiz_service.py is running, and where 
+#             all the files downloaded to the PLC get stored, including
+#             the .so file with the compiled C generated code
+def init(plcobj, NS, WorkingDir):
+    #plcobj.LogMessage("BACnet web server extension::init(plcobj, NS, " + WorkingDir + ") Called")
+    global _WorkingDir
+    _WorkingDir = WorkingDir
+    global _plcobj
+    _plcobj = plcobj
+    global _NS
+    _NS = NS
+    global _BACnetConfFilename
+    if _BACnetConfFilename is None:
+        _BACnetConfFilename = os.path.join(WorkingDir, "BACnetConfig.json")
+    
+    _plcobj.RegisterCallbackLoad  ("BACnet_Settins_Extension", OnLoadPLC)
+    _plcobj.RegisterCallbackUnLoad("BACnet_Settins_Extension", OnUnLoadPLC)
+    OnUnLoadPLC() # init is called before the PLC gets loaded...  so we make sure we have the correct state
--- a/runtime/NevowServer.py	Thu May 28 11:01:42 2020 +0100
+++ b/runtime/NevowServer.py	Thu May 28 11:15:22 2020 +0100
@@ -179,7 +179,13 @@
 
         setattr(self, 'action_' + name, callback)
 
-        self.bindingsNames.append(name)
+        if name not in self.bindingsNames:
+            self.bindingsNames.append(name)
+
+
+    def delSettings(self, name):
+        if name in self.bindingsNames:
+            self.bindingsNames.remove(name)
 
 
 ConfigurableSettings = ConfigurableBindings()
--- a/runtime/PLCObject.py	Thu May 28 11:01:42 2020 +0100
+++ b/runtime/PLCObject.py	Thu May 28 11:15:22 2020 +0100
@@ -99,6 +99,9 @@
         self.TraceLock = Lock()
         self.Traces = []
         self.DebugToken = 0
+        # Callbacks used by web settings extensions (e.g.: BACnet_config.py, Modbus_config.py)
+        self.LoadCallbacks   = {} # list of functions to call when PLC is   loaded
+        self.UnLoadCallbacks = {} # list of functions to call when PLC is unloaded
 
         self._init_blobs()
 
@@ -167,6 +170,22 @@
             return self._loading_error, 0, 0, 0
         return None
 
+    def RegisterCallbackLoad(self, ExtensionName, ExtensionCallback):
+        """
+        Register function to be called when PLC is loaded
+        ExtensionName: a string with the name of the extension asking to register the callback 
+        ExtensionCallback: the function to be called...
+        """
+        self.LoadCallbacks[ExtensionName] = ExtensionCallback
+
+    def RegisterCallbackUnLoad(self, ExtensionName, ExtensionCallback):
+        """
+        Register function to be called when PLC is unloaded
+        ExtensionName: a string with the name of the extension asking to register the callback 
+        ExtensionCallback: the function to be called...
+        """
+        self.UnLoadCallbacks[ExtensionName] = ExtensionCallback
+
     def _GetMD5FileName(self):
         return os.path.join(self.workingdir, "lasttransferedPLC.md5")
 
@@ -270,6 +289,8 @@
         res = self._LoadPLC()
         if res:
             self.PythonRuntimeInit()
+            for name, callbackFunc in self.LoadCallbacks.items():
+                callbackFunc()
         else:
             self._FreePLC()
 
@@ -278,6 +299,8 @@
     @RunInMain
     def UnLoadPLC(self):
         self.PythonRuntimeCleanup()
+        for name, callbackFunc in self.UnLoadCallbacks.items():
+            callbackFunc()        
         self._FreePLC()
 
     def _InitPLCStubCalls(self):