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) 2001-2003,2016 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.
*/
/* mb_master.h */
#ifndef MODBUS_MASTER_H
#define MODBUS_MASTER_H
#include <time.h> /* struct timespec data structure */
#include "mb_types.h" /* get the data types */
#include "mb_addr.h" /* get definition of common variable types and error codes */
/***********************************************************************
Note: All functions used for sending or receiving data via
modbus return these return values.
Returns: string_length if OK
-1 on internal error or port failure
-2 on timeout
-3 if a valid yet un-expected frame is received!
-4 for modbus exception errors
(in this case exception code is returned in *error_code)
***********************************************************************/
/* FUNCTION 0x01 - Read Coils
* Bits are stored on an int array, one bit per int.
*/
int read_output_bits(u8 slave,
u16 start_addr,
u16 count,
u16 *dest,
int dest_size,
int fd,
int send_retries,
u8 *error_code,
const struct timespec *response_timeout,
pthread_mutex_t *data_access_mutex);
#define read_coils(p1,p2,p3,p4,p5,p6,p7,p8,p9,p10) \
read_output_bits(p1,p2,p3,p4,p5,p6,p7,p8,p9,p10)
/* FUNCTION 0x01 - Read Coils
* Bits are stored on an u32 array, 32 bits per u32.
* Unused bits in last u32 are set to 0.
*/
int read_output_bits_u32(u8 slave,
u16 start_addr,
u16 count,
u32 *dest,
int fd,
int send_retries,
u8 *error_code,
const struct timespec *response_timeout);
#define read_coils_u32(p1,p2,p3,p4,p5,p6,p7,p8) \
read_output_bits_u32(p1,p2,p3,p4,p5,p6,p7,p8)
/* FUNCTION 0x02 - Read Discrete Inputs
* Bits are stored on an int array, one bit per int.
*/
int read_input_bits(u8 slave,
u16 start_addr,
u16 count,
u16 *dest,
int dest_size,
int fd,
int send_retries,
u8 *error_code,
const struct timespec *response_timeout,
pthread_mutex_t *data_access_mutex);
#define read_discrete_inputs(p1,p2,p3,p4,p5,p6,p7,p8,p9,p10) \
read_input_bits (p1,p2,p3,p4,p5,p6,p7,p8,p9,p10)
/* FUNCTION 0x02 - Read Discrete Inputs
* Bits are stored on an u32 array, 32 bits per u32.
* Unused bits in last u32 are set to 0.
*/
int read_input_bits_u32(u8 slave,
u16 start_addr,
u16 count,
u32 *dest,
int fd,
int send_retries,
u8 *error_code,
const struct timespec *response_timeout);
#define read_discrete_inputs_u32(p1,p2,p3,p4,p5,p6,p7,p8) \
read_input_bits_u32 (p1,p2,p3,p4,p5,p6,p7,p8)
/* FUNCTION 0x03 - Read Holding Registers */
int read_output_words(u8 slave,
u16 start_addr,
u16 count,
u16 *dest,
int dest_size,
int fd,
int send_retries,
u8 *error_code,
const struct timespec *response_timeout,
pthread_mutex_t *data_access_mutex);
#define read_holding_registers(p1,p2,p3,p4,p5,p6,p7,p8,p9,p10) \
read_output_words (p1,p2,p3,p4,p5,p6,p7,p8,p9,p10)
/* FUNCTION 0x03 - Read Holding Registers
* u16 registers are stored in array of u32, two registers per u32.
* Unused bits of last u32 element are set to 0.
*/
int read_output_words_u32(u8 slave,
u16 start_addr,
u16 count,
u32 *dest,
int fd,
int send_retries,
u8 *error_code,
const struct timespec *response_timeout);
#define read_holding_registers_u32(p1,p2,p3,p4,p5,p6,p7,p8) \
read_output_words_u32 (p1,p2,p3,p4,p5,p6,p7,p8)
/* FUNCTION 0x03 - Read Holding Registers
* return the array with the data to the calling function
*/
int read_output_words_u16_ref(u8 slave,
u16 start_addr,
u16 count,
u16 **dest,
int ttyfd,
int send_retries,
u8 *error_code,
const struct timespec *response_timeout);
#define read_holding_registers_u16_ref(p1,p2,p3,p4,p5,p6,p7,p8) \
read_output_words_u16_ref (p1,p2,p3,p4,p5,p6,p7,p8)
/* FUNCTION 0x04 - Read Input Registers */
int read_input_words(u8 slave,
u16 start_addr,
u16 count,
u16 *dest,
int dest_size,
int fd,
int send_retries,
u8 *error_code,
const struct timespec *response_timeout,
pthread_mutex_t *data_access_mutex);
#define read_input_registers(p1,p2,p3,p4,p5,p6,p7,p8,p9,p10) \
read_input_words (p1,p2,p3,p4,p5,p6,p7,p8,p9,p10)
/* FUNCTION 0x04 - Read Input Registers
* u16 registers are stored in array of u32, two registers per u32.
* Unused bits of last u32 element are set to 0.
*/
int read_input_words_u32(u8 slave,
u16 start_addr,
u16 count,
u32 *dest,
int fd,
int send_retries,
u8 *error_code,
const struct timespec *response_timeout);
#define read_input_registers_u32(p1,p2,p3,p4,p5,p6,p7,p8) \
read_input_words_u32 (p1,p2,p3,p4,p5,p6,p7,p8)
/* FUNCTION 0x04 - Read Input Registers
* return the array with the data to the calling function
*/
int read_input_words_u16_ref(u8 slave,
u16 start_addr,
u16 count,
u16 **dest,
int ttyfd,
int send_retries,
u8 *error_code,
const struct timespec *response_timeout);
#define read_input_registers_u16_ref(p1,p2,p3,p4,p5,p6,p7,p8) \
read_input_words_u16_ref (p1,p2,p3,p4,p5,p6,p7,p8)
/* FUNCTION 0x05 - Force Single Coil */
int write_output_bit(u8 slave,
u16 coil_addr,
u16 state,
int fd,
int send_retries,
u8 *error_code,
const struct timespec *response_timeout,
pthread_mutex_t *data_access_mutex);
#define force_single_coil(p1,p2,p3,p4,p5,p6,p7,p8) \
write_output_bit (p1,p2,p3,p4,p5,p6,p7,p8)
/* FUNCTION 0x06 - Write Single Register */
int write_output_word(u8 slave,
u16 reg_addr,
u16 value,
int fd,
int send_retries,
u8 *error_code,
const struct timespec *response_timeout,
pthread_mutex_t *data_access_mutex);
#define write_single_register(p1,p2,p3,p4,p5,p6,p7,p8) \
write_output_word (p1,p2,p3,p4,p5,p6,p7,p8)
/* FUNCTION 0x0F - Force Multiple Coils */
int write_output_bits(u8 slave,
u16 start_addr,
u16 coil_count,
u16 *data,
int fd,
int send_retries,
u8 *error_code,
const struct timespec *response_timeout,
pthread_mutex_t *data_access_mutex);
#define force_multiple_coils(p1,p2,p3,p4,p5,p6,p7,p8,p9) \
write_output_bits (p1,p2,p3,p4,p5,p6,p7,p8,p9)
/* FUNCTION 0x0F - Force Multiple Coils
* Bits should be stored on an u32 array, 32 bits per u32.
* Unused bits in last u32 should be set to 0.
*/
int write_output_bits_u32(u8 slave,
u16 start_addr,
u16 coil_count,
u32 *data,
int fd,
int send_retries,
u8 *error_code,
const struct timespec *response_timeout);
#define force_multiple_coils_u32(p1,p2,p3,p4,p5,p6,p7,p8) \
write_output_bits_u32 (p1,p2,p3,p4,p5,p6,p7,p8)
/* FUNCTION 0x10 - Force Multiple Registers */
int write_output_words(u8 slave,
u16 start_addr,
u16 reg_count,
u16 *data,
int fd,
int send_retries,
u8 *error_code,
const struct timespec *response_timeout,
pthread_mutex_t *data_access_mutex);
#define force_multiple_registers(p1,p2,p3,p4,p5,p6,p7,p8,p9) \
write_output_words (p1,p2,p3,p4,p5,p6,p7,p8,p9)
/* FUNCTION 0x10 - Force Multiple Registers
* u16 registers are stored in array of u32, two registers per u32.
* Unused bits of last u32 element are set to 0.
*/
int write_output_words_u32(u8 slave,
u16 start_addr,
u16 reg_count,
u32 *data,
int fd,
int send_retries,
u8 *error_code,
const struct timespec *response_timeout);
#define force_multiple_registers_u32(p1,p2,p3,p4,p5,p6,p7,p8) \
write_output_words_u32 (p1,p2,p3,p4,p5,p6,p7,p8)
/* Initialise the Modbus Library to work as Master only */
int mb_master_init(int nd_count);
/* Shut down the Modbus Library */
int mb_master_done(void);
/* Establish a connection to a remote server/slave.
* The address type (naf_tcp, naf_rtu, naf_ascii) specifies the lower
* layer to use for the newly opened node.
*/
int mb_master_connect(node_addr_t node_addr);
/* Shut down a connection to a remote server/slave */
int mb_master_close(int nd);
/* Tell the library that communications will be suspended for some time. */
/* RTU and ASCII versions ignore this function
* TCP version closes all the open tcp connections (connections are automatically
* re-established the next time an IO function to the slave is requested).
* To be more precise, the TCP version makes an estimate of how long
* the silence will be based on previous invocations to this exact same
* function, and will only close the connections if this silence is
* expected to be longer than 1 second!
*/
int mb_master_tcp_silence_init(void);
#endif /* MODBUS_MASTER_H */