Variables start_addr and count were read from query_packet using function mb_ntoh_safe. It looks like some compilers change the pointer alignment if the first byte starts at an odd address. Because mb_ntoh_safe uses pointers slave address and count (number of registers) were not read correctly from the buffer when several modbus slaves were present in network. In this temporary solution pointer aritmetics is replaced by simple 256 multiplication.
/*
* Copyright (c) 2002,2016 Mario de Sousa (msousa@fe.up.pt)
*
* This file is part of the Modbus library for Beremiz and matiec.
*
* This Modbus 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 3 of the License, or
* (at your option) any later version.
*
* This program 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 Modbus library. If not, see <http://www.gnu.org/licenses/>.
*
* This code is made available on the understanding that it will not be
* used in safety-critical situations without a full and competent review.
*/
#ifndef MODBUS_ASCII_PRIVATE_H
#define MODBUS_ASCII_PRIVATE_H
#include "mb_util.h"
/* serial port default configuration... */
#define DEF_DATA_BITS 7
#define DEF_STOP_BITS_PAR 1 /* default stop bits if parity is used */
#define DEF_STOP_BITS_NOP 2 /* default stop bits if parity is not used */
#define DEF_BAUD_RATE 9600
/* Send retries of ascii frames... */
#define ASC_FRAME_SEND_RETRY 0
/* NOTES:
* - the above are the retries at the layer1 level,
* higher layers may decide to retry for themselves!
* - For ascii frames, it doesn't make much sense to retry
* if the first try failed...
*/
/* Buffer sizes... */
#define SEND_BUFFER_SIZE_SMALL (MAX_ASC_FRAME_LENGTH / 2)
#define SEND_BUFFER_SIZE_LARGE (MAX_ASC_FRAME_LENGTH)
#define RECV_BUFFER_SIZE_SMALL (MAX_ASC_FRAME_LENGTH / 2)
#define RECV_BUFFER_SIZE_LARGE (MAX_ASC_FRAME_LENGTH)
/* Frame lengths... */
/* The smallest element in an ascii frame.
* This is used later to define the smallest value of certain buffers...
*/
#define ASC_FRAME_MIN_ELE_LENGTH ASC_FRAME_HEADER_LENGTH
#if ASC_FRAME_MIN_ELE_LENGTH < ASC_FRAME_TAIL_LENGTH
#undef ASC_FRAME_MIN_ELE_LENGTH
#define ASC_FRAME_MIN_ELE_LENGTH ASC_FRAME_TAIL_LENGTH
#endif
#if ASC_FRAME_MIN_ELE_LENGTH < ASC_FRAME_LRC_LENGTH
#undef ASC_FRAME_MIN_ELE_LENGTH
#define ASC_FRAME_MIN_ELE_LENGTH ASC_FRAME_LRC_LENGTH
#endif
#if ASC_FRAME_MIN_ELE_LENGTH < L2_TO_ASC_CODING
#undef ASC_FRAME_MIN_ELE_LENGTH
#define ASC_FRAME_MIN_ELE_LENGTH L2_TO_ASC_CODING
#endif
#endif /* MODBUS_ASCII_PRIVATE_H */