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/*

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 * Copyright (c) 2001,2016 Mario de Sousa (msousa@fe.up.pt)

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 *

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 * This file is part of the Modbus library for Beremiz and matiec.

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 *

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 * This Modbus library is free software: you can redistribute it and/or modify

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 * it under the terms of the GNU Lesser General Public License as published by

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 * the Free Software Foundation, either version 3 of the License, or

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 * (at your option) any later version.

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 *

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 * This program is distributed in the hope that it will be useful, but

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 * WITHOUT ANY WARRANTY; without even the implied warranty of

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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser 

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 * General Public License for more details.

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 *

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 * You should have received a copy of the GNU Lesser General Public License

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 * along with this Modbus library.  If not, see <http://www.gnu.org/licenses/>.

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 *

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 * This code is made available on the understanding that it will not be

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 * used in safety-critical situations without a full and competent review.

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 */

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/* mb_slave.c */

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#include <fcntl.h>	/* File control definitions */

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#include <stdio.h>	/* Standard input/output */

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#include <string.h>

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#include <stdlib.h>

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#include <termio.h>	/* POSIX terminal control definitions */

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#include <sys/time.h>	/* Time structures for select() */

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#include <unistd.h>	/* POSIX Symbolic Constants */

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#include <errno.h>	/* Error definitions */

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#include <netinet/in.h> /* required for htons() and ntohs() */

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#include "mb_layer1.h"

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#include "mb_slave.h"

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#include "mb_slave_private.h"

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/* #define DEBUG */		/* uncomment to see the data sent and received */

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#define modbus_write             fptr_[layer1_fin].modbus_write           

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#define modbus_read              fptr_[layer1_fin].modbus_read            

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#define modbus_init              fptr_[layer1_fin].modbus_init            

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#define modbus_done              fptr_[layer1_fin].modbus_done            

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#define modbus_connect           fptr_[layer1_fin].modbus_connect         

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#define modbus_listen            fptr_[layer1_fin].modbus_listen          

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#define modbus_close             fptr_[layer1_fin].modbus_close           

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#define modbus_silence_init      fptr_[layer1_fin].modbus_silence_init    

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#define modbus_get_min_timeout   fptr_[layer1_fin].modbus_get_min_timeout 

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/* the lower two bits of ttyfd are used to store the index to layer1 function pointers */

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/* layer1_fin index to fptr_[] is in lowest 2 bits of fd */

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#define get_ttyfd()     int layer1_fin = fd & 3; int ttyfd = fd / 4;\

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                        if (fd < 0) {ttyfd = fd; layer1_fin = 0; /* use modbusTCP */}

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/******************************************/

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/******************************************/

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/**                                      **/

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/**         Global Variables...          **/

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/**                                      **/

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/******************************************/

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/******************************************/

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/* The layer 1 (RTU, ASCII, TCP) implementations will be adding some 

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 *  header and tail bytes (e.g. CRC) to the packet we build here. Since

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 *  layer1 will re-use the same buffer allocated in this slave layer 

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 *  (so as not to continuosly copy the same info from buffer to buffer),

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 *  we need to allocate more bytes than those strictly required for this

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 *  slave layer. Therefore, the extra_bytes parameter.

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 *

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 *  Note that we add one more extra byte to the response buffer.

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 *  This is because some response packets will not be starting off

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 *  at byte 0, but rather at byte 1 of the buffer. This is in order

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 *  to guarantee that the data that is sent on the buffer is aligned

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 *  on even bytes (the 16 bit words!). This will allow the application

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 *  (layer above the one implemented in this file - i.e. the callback 

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 *  functions) to reference this memory as an u16 *, without producing

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 *  'bus error' messages in some embedded devices that do not allow

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 *   acessing u16 on odd numbered addresses.

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 */

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static int buff_extra_bytes_;

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#define RESP_BUFFER_SIZE       (MAX_L2_FRAME_LENGTH + buff_extra_bytes_ + 1)

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/******************************************/

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/******************************************/

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/**                                      **/

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/**       Local Utility functions...     **/

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/**                                      **/

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/******************************************/

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/******************************************/

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/*

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 * Function to determine next transaction id.

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 *

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 * We use a library wide transaction id, which means that we

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 * use a new transaction id no matter what slave to which we will

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 * be sending the request...

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 */

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static inline u16 next_transaction_id(void) {

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  static u16 next_id = 0;

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  return next_id++;

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}

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/*

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 * Functions to convert u16 variables

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 * between network and host byte order

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 *

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 * NOTE: Modbus uses MSByte first, just like

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 *       tcp/ip, so we could be tempted to use the htons() and

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 *       ntohs() functions to guarantee code portability.

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 *

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 *       However, on some embedded systems running Linux

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 *       these functions only work if the 16 bit words are 

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 *       stored on even addresses. This is not always the 

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 *       case in our code, so we have to define our own

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 *       conversion functions...

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 */

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/* if using gcc, use it to determine byte order... */

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#ifndef __BYTE_ORDER

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#if defined(__GNUC__) 

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  /* We have GCC, which should define __LITTLE_ENDIAN__ */ 

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#  if defined(__LITTLE_ENDIAN__)

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#    define __BYTE_ORDER __LITTLE_ENDIAN

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#  else

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#    define __BYTE_ORDER __BIG_ENDIAN

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#  endif

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#endif /* __GNUC__ */ 

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#endif /* __BYTE_ORDER */

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/* If we still don't know byte order, try to get it from <sys/param.h> */

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#ifndef __BYTE_ORDER

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#include <sys/param.h>

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#endif

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#ifndef __BYTE_ORDER

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#  ifdef BYTE_ORDER

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#   if BYTE_ORDER == LITTLE_ENDIAN

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#    define __BYTE_ORDER __LITTLE_ENDIAN

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#   else

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#    if BYTE_ORDER == BIG_ENDIAN

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#      define __BYTE_ORDER __BIG_ENDIAN

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#    endif

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#   endif

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#  endif /* BYTE_ORDER */

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#endif /* __BYTE_ORDER */

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#ifdef __BYTE_ORDER

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# if __BYTE_ORDER == __LITTLE_ENDIAN

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/**************************************************************/

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/* u16 conversion functions to use on little endian platforms */

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/**************************************************************/

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    /* swap the bytes around... 

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     *  a = a ^ b;

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     *  b = a ^ b;

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     *  a = a ^ b;

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     */

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  }

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}

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#define mb_ntoh_count(w, count) mb_hton_count(w, count)

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# else

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#  if __BYTE_ORDER == __BIG_ENDIAN

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/***********************************************************/

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/* u16 conversion functions to use on big endian platforms */

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/***********************************************************/

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#define mb_hton_count(w, count) /* empty ! */

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#define mb_ntoh_count(w, count) /* empty ! */

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#  else

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/********************************************************/

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/* u16 conversion functions to use on generic platforms */

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/********************************************************/

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#  endif

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# endif

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#endif /* __BYTE_ORDER */

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/***********************************************/

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/***********************************************/

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/**                                           **/

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/**    Handle requests from master/client     **/

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/**                                           **/

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/***********************************************/

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/***********************************************/

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/* Handle functions 0x01 and 0x02 */

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typedef int (*read_bits_callback_t)(void *arg, u16 start_addr, u16 bit_count,  u8  *data_bytes);

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static int handle_read_bits (u8 *query_packet,

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                             u8 **resp_packet_ptr,

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                             u8 *error_code,

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                             read_bits_callback_t read_bits_callback,

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                             void *callback_arg

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                            ) {

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  u16 start_addr, count;

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  int res;

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  u8 *resp_packet;

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  /* If no callback, handle as if function is not supported... */

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  if (read_bits_callback == NULL) 

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    {*error_code = ERR_ILLEGAL_FUNCTION; return -1;}

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  /* in oprder for the data in this packet to be aligned on even numbered addresses, this 

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   *  response packet will start off at an odd numbered byte...

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   *  We therefore add 1 to the address where the packet starts.

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   */ 

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  (*resp_packet_ptr)++;

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  resp_packet = *resp_packet_ptr;

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    /* NOTE:

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     *  Modbus uses high level addressing starting off from 1, but

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     *  this is sent as 0 on the wire!

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     *  We could expect the user to specify high level addressing 

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     *   starting at 1, and do the conversion to start off at 0 here.

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     *   However, to do this we would then need to use an u32 data type

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     *   to correctly hold the address supplied by the user (which could

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     *   correctly be 65536, which does not fit in an u16), which would

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     *   in turn require us to check whether the address supplied by the user

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     *   is correct (i.e. <= 65536). 

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     *  I decided to go with the other option of using an u16, and 

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     *   requiring the user to use addressing starting off at 0! 

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     */

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  #ifdef DEBUG

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  printf("handle_read_input_bits() called. slave=%d, function=%d, start_addr=%d, count=%d\n", 

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          query_packet[0], query_packet[1], start_addr, count);

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  #endif

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  if ((count > MAX_READ_BITS) || (count < 1)) 

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    {*error_code = ERR_ILLEGAL_DATA_VALUE; return -1;}

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  /* Remember, we are using addressing starting off at 0, in the start_addr variable! */

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  /*  This means that he highest acceptable address is 65535, when count=1 .... */

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  /* Note the use of 65536 in the comparison will force automatic upgrade of u16 variables! */

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  /*    => start_addr + count will nver overflow the u16 type!                              */

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  if (start_addr + count > 65536) 

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    {*error_code = ERR_ILLEGAL_DATA_ADDRESS; return -1;}

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  /* start building response frame... */

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  resp_packet[0] = query_packet[0]; /* slave */ 

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  resp_packet[1] = query_packet[1]; /* function (either 0x01 or 0x02 ! */

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  resp_packet[2] = (count + 7) / 8; /* number of data bytes = ceil(count/8) */

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  res = read_bits_callback(callback_arg, start_addr, count, &(resp_packet[3]));

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  if (res == -2) {*error_code = ERR_ILLEGAL_DATA_ADDRESS; return -1;}

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  if (res  <  0) {*error_code = ERR_SLAVE_DEVICE_FAILURE; return -1;}

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  return resp_packet[2] + 3; /* packet size is data length + 3 bytes -> slave, function, count */

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}

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/* Handle function 0x01 */

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int handle_read_output_bits  (u8 *query_packet, u8 **resp_packet_ptr, u8 *error_code, mb_slave_callback_t *callbacks)

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  {return handle_read_bits(query_packet, resp_packet_ptr, error_code, callbacks->read_outbits, callbacks->arg);}

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/* Handle function 0x02 */

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int handle_read_input_bits   (u8 *query_packet, u8 **resp_packet_ptr, u8 *error_code, mb_slave_callback_t *callbacks)

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  {return handle_read_bits(query_packet, resp_packet_ptr, error_code, callbacks->read_inbits, callbacks->arg);}

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/* Handle functions 0x03 and 0x04 */

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typedef int (*read_words_callback_t)(void *arg, u16 start_addr, u16 word_count, u16 *data_words);

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static int handle_read_words (u8 *query_packet, 

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                              u8 **resp_packet_ptr, 

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                              u8 *error_code, 

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                              read_words_callback_t read_words_callback,

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                              void *callback_arg

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                             ) {

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  u16 start_addr, count;

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  int res;

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  u8 *resp_packet;

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  /* If no callback, handle as if function is not supported... */

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  if (read_words_callback == NULL) 

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    {*error_code = ERR_ILLEGAL_FUNCTION; return -1;}

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  /* See equivalent comment in handle_read_bits() */ 

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  (*resp_packet_ptr)++;

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  resp_packet = *resp_packet_ptr;

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  /* See equivalent comment in handle_read_bits() */ 

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  #ifdef DEBUG

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  printf("handle_read_output_words() called. slave=%d, function=%d, start_addr=%d, count=%d\n", 

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         query_packet[0], query_packet[1], start_addr, count);

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  #endif

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  if ((count > MAX_READ_REGS) || (count < 1))

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    {*error_code = ERR_ILLEGAL_DATA_VALUE; return -1;}

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  /* See equivalent comment in handle_read_bits() */ 

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  if (start_addr + count > 65536)

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    {*error_code = ERR_ILLEGAL_DATA_ADDRESS; return -1;}

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  /* start building response frame... */

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  resp_packet[0] = query_packet[0]; /* slave     */

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  resp_packet[1] = query_packet[1]; /* function code, either 0x03 or 0x04 !!!*/

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  resp_packet[2] = count * 2;       /* number of bytes of data... */

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   411

  res = read_words_callback(callback_arg, start_addr, count, (u16 *)&(resp_packet[3]));

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  if (res == -2) {*error_code = ERR_ILLEGAL_DATA_ADDRESS; return -1;}

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  if (res  <  0) {*error_code = ERR_SLAVE_DEVICE_FAILURE; return -1;}

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  /* convert all data from host to network byte order. */

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  return resp_packet[2] + 3; /* packet size is data length + 3 bytes -> slave, function, count */

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}

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/* Handle function 0x03 */

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int handle_read_output_words (u8 *query_packet, u8 **resp_packet_ptr, u8 *error_code, mb_slave_callback_t *callbacks) 

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  {return handle_read_words(query_packet, resp_packet_ptr, error_code, callbacks->read_outwords, callbacks->arg);}

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/* Handle function 0x04 */

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int handle_read_input_words  (u8 *query_packet, u8 **resp_packet_ptr, u8 *error_code, mb_slave_callback_t *callbacks) 

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  {return handle_read_words(query_packet, resp_packet_ptr, error_code, callbacks->read_inwords, callbacks->arg);}

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/* Handle function 0x05 */

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int handle_write_output_bit  (u8 *query_packet, u8 **resp_packet_ptr, u8 *error_code, mb_slave_callback_t *callbacks) {

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  u16 start_addr;

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  int res;

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  u8 *resp_packet;

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   440

  /* If no callback, handle as if function is not supported... */

   441

  if (callbacks->write_outbits == NULL)

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    {*error_code = ERR_ILLEGAL_FUNCTION; return -1;}

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   444

  resp_packet = *resp_packet_ptr;

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   446

  /* See equivalent comment in handle_read_bits() */ 

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   449

  #ifdef DEBUG

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  printf("handle_write_output_bit() called. slave=%d, function=%d, start_addr=%d\n", 

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         query_packet[0], query_packet[1], start_addr);

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  #endif

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  // byte 5 Must be 0x00, byte 4 must be 0x00 or 0xFF !!

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  if ( (query_packet[5] != 0) || 

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      ((query_packet[4] != 0) && (query_packet[4] != 0xFF)))

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    {*error_code = ERR_ILLEGAL_DATA_VALUE; return -1;}

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   459

  /* Address will always be valid, no need to check! */

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  // if (start_addr > 65535) {*error_code = ERR_ILLEGAL_DATA_ADDRESS; return -1;}

   461

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  /* start building response frame... */

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  resp_packet[0] = query_packet[0]; /* slave */ 

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  resp_packet[1] = query_packet[1]; /* function */ 

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  resp_packet[2] = query_packet[2]; /* start address - hi byte */

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  resp_packet[3] = query_packet[3]; /* start address - lo byte */

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  resp_packet[4] = query_packet[4]; /* value: 0x00 or 0xFF */

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  resp_packet[5] = query_packet[5]; /* value: must be 0x00 */

   469

   470

  res = (callbacks->write_outbits)(callbacks->arg, start_addr, 1, &(query_packet[4]));

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  if (res == -2) {*error_code = ERR_ILLEGAL_DATA_ADDRESS; return -1;}

   472

  if (res  <  0) {*error_code = ERR_SLAVE_DEVICE_FAILURE; return -1;}

   473

   474

  return 6; /* response packet size, including slave id in byte 0 */

   475

}

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   477

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   479

/* Handle function 0x06 */

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int handle_write_output_word (u8 *query_packet, u8 **resp_packet_ptr, u8 *error_code, mb_slave_callback_t *callbacks) {

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  u16 start_addr;

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  int res;

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  u8 *resp_packet;

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   485

  /* If no callback, handle as if function is not supported... */

   486

  if (callbacks->write_outwords == NULL)

   487

    {*error_code = ERR_ILLEGAL_FUNCTION; return -1;}

   488

   489

  resp_packet = *resp_packet_ptr;

   490

   491

  /* See equivalent comment in handle_read_bits() */ 

   493

   494

  #ifdef DEBUG

   495

  printf("handle_write_output_word() called. slave=%d, function=%d, start_addr=%d\n", 

   496

         query_packet[0], query_packet[1], start_addr);

   497

  #endif

   498

   499

  /* Address will always be valid, no need to check! */

   500

  // if (start_addr > 65535) {*error_code = ERR_ILLEGAL_DATA_ADDRESS; return -1;}

   501

   502

  /* start building response frame... */

   503

  resp_packet[0] = query_packet[0]; /* slave           */

   504

  resp_packet[1] = query_packet[1]; /* function        */ 

   505

  resp_packet[2] = query_packet[2]; /* start address - hi byte */

   506

  resp_packet[3] = query_packet[3]; /* start address - lo byte */

   507

  resp_packet[4] = query_packet[4]; /* value - hi byte */

   508

  resp_packet[5] = query_packet[5]; /* value - lo byte */

   509

   510

  /* convert data from network to host byte order */

   512

   513

  res = (callbacks->write_outwords)(callbacks->arg, start_addr, 1, (u16 *)&(query_packet[4]));

   514

  if (res == -2) {*error_code = ERR_ILLEGAL_DATA_ADDRESS; return -1;}

   515

  if (res  <  0) {*error_code = ERR_SLAVE_DEVICE_FAILURE; return -1;}

   516

   517

  return 6; /* packet size is 6 -> slave, function, addr(2), value(2) */

   518

}

   519

   520

   521

   522

/* Handle function 0x0F */

   523