前言
一直以来上位软件比如C++等和西门子等其他品牌PLC之间的数据交换都是大家比较头疼的问题，尤其是C++上位软件程序员。传统的方法一般有OPC、Socket 等，直到LibModbus 开源库出现后这种途径对程序袁来说又有了新的选择。
Modbus简介
Modbus特点
**1 ）使用简单，**利用MUDBUS库文件简单的几条指令就能实现与智能仪表，变频器，打印机等设备进行通讯，且无需加其他硬件上的成本MODBUS总线广泛应用于仪器仪表、智能高低压电器、变送器、可编程控制器、人机界面、变频器、现场智能设备等诸多领域。MODBUS与其他的现场总线和工业网络相比有以下几个显著特点。
2）标准、开放:用户可以免费放心的使用
MODBUS协议，不用缴纳许可费用，不会涉及侵犯知识产权。目前支持MODBUS的厂一家超过400家，支持MODBUS的产品超过600种。在中国，MODBUS已经成为国家标准GB/T19582-2008。据不完全统 计：截止到2007年MODBUS的节点安装数量已经超过了1000万个。
**3）应用广泛：**凡MODBUS协议设备具有RS232/485接口的都可以使用本产品实现与现场总线PROFIBUS的互连。如：具有MODBUS协议接口的变频器、智能高低压电器、电机启动保护装置、电量测量装置、智能现场测量设备、各种变送器及仪表等。
4）MODBUS可以支持较多类型的电气接口：MODBUS 总线协议采用主站查询从站的方式，物理接口可以是RS232、RS485、RS422、RJ45，还可以在各种介质上传送，如双绞线、光纤、无线射频等。
5）MODBUS的帧格式较为简单、紧凑，格式规范，易于传输，通俗易懂。用户使用容易，厂商开发简单。用户不必了解PROFIBUS和MODBUS技术细节，只需参考说明手册及提供的应用实例，按要求完成配置，不需要复杂的编程，即可在短时间内实现设备间的连接通信。
6）透明通信：用户可以依照PROFIBUS通信数据区和MODBUS通信数据区的映射关系，实现PROFIBUS到MODBUS之间的数据透明通信。
LibModbus库下载
https://libmodbus.org/
https://libmodbus.org/
https://gitcode.com/stephane/libmodbus/overview?utm_source=csdn_github_accelerator&isLogin=1https://gitcode.com/stephane/libmodbus/overview?utm_source=csdn_github_accelerator&isLogin=1https://github.com/stephane/libmodbushttps://github.com/stephane/libmodbushttps://download.csdn.net/download/lzc881012/88695801https://download.csdn.net/download/lzc881012/88695801
LibModbus库Windows版本的编译
1、进入到libmodbus\src\win32文件夹下。
2、双击configure.js文件进行编译,成功后会弹出编译完成窗口,点击关闭。
3、然后在双击modbus-9.sln通过VS打开项目,打开项目完成后编译即可。
4、编译完成后libmodbus\src\win32文件夹下就会出现modbus.dll和modbus.lib两个文件。
将上述步骤中生成的modbus.lib文件和libmodbus\src中所有的.h文件通过VS包含到自己的项目中即可。
在程序中包含libModbus/modbus.h一个头文件即可。
将上述步骤在生成的modbus.dll放到你的项目生成目录下,例如Debug/Release目录下。
LibModbus库modbus.h头文件
cpp
/*
* Copyright © 2001-2013 Stéphane Raimbault <stephane.raimbault@gmail.com>
*
* SPDX-License-Identifier: LGPL-2.1+
*/
#ifndef MODBUS_H
#define MODBUS_H
/* Add this for macros that defined unix flavor */
#if (defined(__unix__) || defined(unix)) && !defined(USG)
#include <sys/param.h>
#endif
#ifndef _MSC_VER
#include <stdint.h>
#else
#include "stdint.h"
#endif
#include "modbus-version.h"
#if defined(_MSC_VER)
# if defined(DLLBUILD)
/* define DLLBUILD when building the DLL */
# define MODBUS_API __declspec(dllexport)
# else
# define MODBUS_API __declspec(dllimport)
# endif
#else
# define MODBUS_API
#endif
#ifdef __cplusplus
# define MODBUS_BEGIN_DECLS extern "C" {
# define MODBUS_END_DECLS }
#else
# define MODBUS_BEGIN_DECLS
# define MODBUS_END_DECLS
#endif
MODBUS_BEGIN_DECLS
#ifndef FALSE
#define FALSE 0
#endif
#ifndef TRUE
#define TRUE 1
#endif
#ifndef OFF
#define OFF 0
#endif
#ifndef ON
#define ON 1
#endif
/* Modbus function codes */
#define MODBUS_FC_READ_COILS 0x01
#define MODBUS_FC_READ_DISCRETE_INPUTS 0x02
#define MODBUS_FC_READ_HOLDING_REGISTERS 0x03
#define MODBUS_FC_READ_INPUT_REGISTERS 0x04
#define MODBUS_FC_WRITE_SINGLE_COIL 0x05
#define MODBUS_FC_WRITE_SINGLE_REGISTER 0x06
#define MODBUS_FC_READ_EXCEPTION_STATUS 0x07
#define MODBUS_FC_WRITE_MULTIPLE_COILS 0x0F
#define MODBUS_FC_WRITE_MULTIPLE_REGISTERS 0x10
#define MODBUS_FC_REPORT_SLAVE_ID 0x11
#define MODBUS_FC_MASK_WRITE_REGISTER 0x16
#define MODBUS_FC_WRITE_AND_READ_REGISTERS 0x17
#define MODBUS_BROADCAST_ADDRESS 0
/* Modbus_Application_Protocol_V1_1b.pdf (chapter 6 section 1 page 12)
* Quantity of Coils to read (2 bytes): 1 to 2000 (0x7D0)
* (chapter 6 section 11 page 29)
* Quantity of Coils to write (2 bytes): 1 to 1968 (0x7B0)
*/
#define MODBUS_MAX_READ_BITS 2000
#define MODBUS_MAX_WRITE_BITS 1968
/* Modbus_Application_Protocol_V1_1b.pdf (chapter 6 section 3 page 15)
* Quantity of Registers to read (2 bytes): 1 to 125 (0x7D)
* (chapter 6 section 12 page 31)
* Quantity of Registers to write (2 bytes) 1 to 123 (0x7B)
* (chapter 6 section 17 page 38)
* Quantity of Registers to write in R/W registers (2 bytes) 1 to 121 (0x79)
*/
#define MODBUS_MAX_READ_REGISTERS 125
#define MODBUS_MAX_WRITE_REGISTERS 123
#define MODBUS_MAX_WR_WRITE_REGISTERS 121
#define MODBUS_MAX_WR_READ_REGISTERS 125
/* The size of the MODBUS PDU is limited by the size constraint inherited from
* the first MODBUS implementation on Serial Line network (max. RS485 ADU = 256
* bytes). Therefore, MODBUS PDU for serial line communication = 256 - Server
* address (1 byte) - CRC (2 bytes) = 253 bytes.
*/
#define MODBUS_MAX_PDU_LENGTH 253
/* Consequently:
* - RTU MODBUS ADU = 253 bytes + Server address (1 byte) + CRC (2 bytes) = 256
* bytes.
* - TCP MODBUS ADU = 253 bytes + MBAP (7 bytes) = 260 bytes.
* so the maximum of both backend in 260 bytes. This size can used to allocate
* an array of bytes to store responses and it will be compatible with the two
* backends.
*/
#define MODBUS_MAX_ADU_LENGTH 260
/* Random number to avoid errno conflicts */
#define MODBUS_ENOBASE 112345678
/* Protocol exceptions */
enum {
MODBUS_EXCEPTION_ILLEGAL_FUNCTION = 0x01,
MODBUS_EXCEPTION_ILLEGAL_DATA_ADDRESS,
MODBUS_EXCEPTION_ILLEGAL_DATA_VALUE,
MODBUS_EXCEPTION_SLAVE_OR_SERVER_FAILURE,
MODBUS_EXCEPTION_ACKNOWLEDGE,
MODBUS_EXCEPTION_SLAVE_OR_SERVER_BUSY,
MODBUS_EXCEPTION_NEGATIVE_ACKNOWLEDGE,
MODBUS_EXCEPTION_MEMORY_PARITY,
MODBUS_EXCEPTION_NOT_DEFINED,
MODBUS_EXCEPTION_GATEWAY_PATH,
MODBUS_EXCEPTION_GATEWAY_TARGET,
MODBUS_EXCEPTION_MAX
};
#define EMBXILFUN (MODBUS_ENOBASE + MODBUS_EXCEPTION_ILLEGAL_FUNCTION)
#define EMBXILADD (MODBUS_ENOBASE + MODBUS_EXCEPTION_ILLEGAL_DATA_ADDRESS)
#define EMBXILVAL (MODBUS_ENOBASE + MODBUS_EXCEPTION_ILLEGAL_DATA_VALUE)
#define EMBXSFAIL (MODBUS_ENOBASE + MODBUS_EXCEPTION_SLAVE_OR_SERVER_FAILURE)
#define EMBXACK (MODBUS_ENOBASE + MODBUS_EXCEPTION_ACKNOWLEDGE)
#define EMBXSBUSY (MODBUS_ENOBASE + MODBUS_EXCEPTION_SLAVE_OR_SERVER_BUSY)
#define EMBXNACK (MODBUS_ENOBASE + MODBUS_EXCEPTION_NEGATIVE_ACKNOWLEDGE)
#define EMBXMEMPAR (MODBUS_ENOBASE + MODBUS_EXCEPTION_MEMORY_PARITY)
#define EMBXGPATH (MODBUS_ENOBASE + MODBUS_EXCEPTION_GATEWAY_PATH)
#define EMBXGTAR (MODBUS_ENOBASE + MODBUS_EXCEPTION_GATEWAY_TARGET)
/* Native libmodbus error codes */
#define EMBBADCRC (EMBXGTAR + 1)
#define EMBBADDATA (EMBXGTAR + 2)
#define EMBBADEXC (EMBXGTAR + 3)
#define EMBUNKEXC (EMBXGTAR + 4)
#define EMBMDATA (EMBXGTAR + 5)
#define EMBBADSLAVE (EMBXGTAR + 6)
extern const unsigned int libmodbus_version_major;
extern const unsigned int libmodbus_version_minor;
extern const unsigned int libmodbus_version_micro;
typedef struct _modbus modbus_t;
typedef struct _modbus_mapping_t {
int nb_bits;
int start_bits;
int nb_input_bits;
int start_input_bits;
int nb_input_registers;
int start_input_registers;
int nb_registers;
int start_registers;
uint8_t *tab_bits;
uint8_t *tab_input_bits;
uint16_t *tab_input_registers;
uint16_t *tab_registers;
} modbus_mapping_t;
typedef enum
{
MODBUS_ERROR_RECOVERY_NONE = 0,
MODBUS_ERROR_RECOVERY_LINK = (1<<1),
MODBUS_ERROR_RECOVERY_PROTOCOL = (1<<2)
} modbus_error_recovery_mode;
MODBUS_API int modbus_set_slave(modbus_t* ctx, int slave);
MODBUS_API int modbus_get_slave(modbus_t* ctx);
MODBUS_API int modbus_set_error_recovery(modbus_t *ctx, modbus_error_recovery_mode error_recovery);
MODBUS_API int modbus_set_socket(modbus_t *ctx, int s);
MODBUS_API int modbus_get_socket(modbus_t *ctx);
MODBUS_API int modbus_get_response_timeout(modbus_t *ctx, uint32_t *to_sec, uint32_t *to_usec);
MODBUS_API int modbus_set_response_timeout(modbus_t *ctx, uint32_t to_sec, uint32_t to_usec);
MODBUS_API int modbus_get_byte_timeout(modbus_t *ctx, uint32_t *to_sec, uint32_t *to_usec);
MODBUS_API int modbus_set_byte_timeout(modbus_t *ctx, uint32_t to_sec, uint32_t to_usec);
MODBUS_API int modbus_get_indication_timeout(modbus_t *ctx, uint32_t *to_sec, uint32_t *to_usec);
MODBUS_API int modbus_set_indication_timeout(modbus_t *ctx, uint32_t to_sec, uint32_t to_usec);
MODBUS_API int modbus_get_header_length(modbus_t *ctx);
MODBUS_API int modbus_connect(modbus_t *ctx);
MODBUS_API void modbus_close(modbus_t *ctx);
MODBUS_API void modbus_free(modbus_t *ctx);
MODBUS_API int modbus_flush(modbus_t *ctx);
MODBUS_API int modbus_set_debug(modbus_t *ctx, int flag);
MODBUS_API const char *modbus_strerror(int errnum);
MODBUS_API int modbus_read_bits(modbus_t *ctx, int addr, int nb, uint8_t *dest);
MODBUS_API int modbus_read_input_bits(modbus_t *ctx, int addr, int nb, uint8_t *dest);
MODBUS_API int modbus_read_registers(modbus_t *ctx, int addr, int nb, uint16_t *dest);
MODBUS_API int modbus_read_input_registers(modbus_t *ctx, int addr, int nb, uint16_t *dest);
MODBUS_API int modbus_write_bit(modbus_t *ctx, int coil_addr, int status);
MODBUS_API int modbus_write_register(modbus_t *ctx, int reg_addr, const uint16_t value);
MODBUS_API int modbus_write_bits(modbus_t *ctx, int addr, int nb, const uint8_t *data);
MODBUS_API int modbus_write_registers(modbus_t *ctx, int addr, int nb, const uint16_t *data);
MODBUS_API int modbus_mask_write_register(modbus_t *ctx, int addr, uint16_t and_mask, uint16_t or_mask);
MODBUS_API int modbus_write_and_read_registers(modbus_t *ctx, int write_addr, int write_nb,
const uint16_t *src, int read_addr, int read_nb,
uint16_t *dest);
MODBUS_API int modbus_report_slave_id(modbus_t *ctx, int max_dest, uint8_t *dest);
MODBUS_API modbus_mapping_t* modbus_mapping_new_start_address(
unsigned int start_bits, unsigned int nb_bits,
unsigned int start_input_bits, unsigned int nb_input_bits,
unsigned int start_registers, unsigned int nb_registers,
unsigned int start_input_registers, unsigned int nb_input_registers);
MODBUS_API modbus_mapping_t* modbus_mapping_new(int nb_bits, int nb_input_bits,
int nb_registers, int nb_input_registers);
MODBUS_API void modbus_mapping_free(modbus_mapping_t *mb_mapping);
MODBUS_API int modbus_send_raw_request(modbus_t *ctx, const uint8_t *raw_req, int raw_req_length);
MODBUS_API int modbus_receive(modbus_t *ctx, uint8_t *req);
MODBUS_API int modbus_receive_confirmation(modbus_t *ctx, uint8_t *rsp);
MODBUS_API int modbus_reply(modbus_t *ctx, const uint8_t *req,
int req_length, modbus_mapping_t *mb_mapping);
MODBUS_API int modbus_reply_exception(modbus_t *ctx, const uint8_t *req,
unsigned int exception_code);
/**
* UTILS FUNCTIONS
**/
#define MODBUS_GET_HIGH_BYTE(data) (((data) >> 8) & 0xFF)
#define MODBUS_GET_LOW_BYTE(data) ((data) & 0xFF)
#define MODBUS_GET_INT64_FROM_INT16(tab_int16, index) \
(((int64_t)tab_int16[(index) ] << 48) + \
((int64_t)tab_int16[(index) + 1] << 32) + \
((int64_t)tab_int16[(index) + 2] << 16) + \
(int64_t)tab_int16[(index) + 3])
#define MODBUS_GET_INT32_FROM_INT16(tab_int16, index) ((tab_int16[(index)] << 16) + tab_int16[(index) + 1])
#define MODBUS_GET_INT16_FROM_INT8(tab_int8, index) ((tab_int8[(index)] << 8) + tab_int8[(index) + 1])
#define MODBUS_SET_INT16_TO_INT8(tab_int8, index, value) \
do { \
tab_int8[(index)] = (value) >> 8; \
tab_int8[(index) + 1] = (value) & 0xFF; \
} while (0)
#define MODBUS_SET_INT32_TO_INT16(tab_int16, index, value) \
do { \
tab_int16[(index) ] = (value) >> 16; \
tab_int16[(index) + 1] = (value); \
} while (0)
#define MODBUS_SET_INT64_TO_INT16(tab_int16, index, value) \
do { \
tab_int16[(index) ] = (value) >> 48; \
tab_int16[(index) + 1] = (value) >> 32; \
tab_int16[(index) + 2] = (value) >> 16; \
tab_int16[(index) + 3] = (value); \
} while (0)
MODBUS_API void modbus_set_bits_from_byte(uint8_t *dest, int idx, const uint8_t value);
MODBUS_API void modbus_set_bits_from_bytes(uint8_t *dest, int idx, unsigned int nb_bits,
const uint8_t *tab_byte);
MODBUS_API uint8_t modbus_get_byte_from_bits(const uint8_t *src, int idx, unsigned int nb_bits);
MODBUS_API float modbus_get_float(const uint16_t *src);
MODBUS_API float modbus_get_float_abcd(const uint16_t *src);
MODBUS_API float modbus_get_float_dcba(const uint16_t *src);
MODBUS_API float modbus_get_float_badc(const uint16_t *src);
MODBUS_API float modbus_get_float_cdab(const uint16_t *src);
MODBUS_API void modbus_set_float(float f, uint16_t *dest);
MODBUS_API void modbus_set_float_abcd(float f, uint16_t *dest);
MODBUS_API void modbus_set_float_dcba(float f, uint16_t *dest);
MODBUS_API void modbus_set_float_badc(float f, uint16_t *dest);
MODBUS_API void modbus_set_float_cdab(float f, uint16_t *dest);
#include "modbus-tcp.h"
#include "modbus-rtu.h"
MODBUS_END_DECLS
#endif /* MODBUS_H */LibModbus库Modbus.h头文件
cpp
/*
* Copyright © 2001-2011 Stéphane Raimbault <stephane.raimbault@gmail.com>
*
* SPDX-License-Identifier: LGPL-2.1+
*
* This library implements the Modbus protocol.
* http://libmodbus.org/
*/
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <stdarg.h>
#include <errno.h>
#include <limits.h>
#include <time.h>
#ifndef _MSC_VER
#include <unistd.h>
#endif
#include <config.h>
#include "modbus.h"
#include "modbus-private.h"
/* Internal use */
#define MSG_LENGTH_UNDEFINED -1
/* Exported version */
const unsigned int libmodbus_version_major = LIBMODBUS_VERSION_MAJOR;
const unsigned int libmodbus_version_minor = LIBMODBUS_VERSION_MINOR;
const unsigned int libmodbus_version_micro = LIBMODBUS_VERSION_MICRO;
/* Max between RTU and TCP max adu length (so TCP) */
#define MAX_MESSAGE_LENGTH 260
/* 3 steps are used to parse the query */
typedef enum {
_STEP_FUNCTION,
_STEP_META,
_STEP_DATA
} _step_t;
const char *modbus_strerror(int errnum) {
switch (errnum) {
case EMBXILFUN:
return "Illegal function";
case EMBXILADD:
return "Illegal data address";
case EMBXILVAL:
return "Illegal data value";
case EMBXSFAIL:
return "Slave device or server failure";
case EMBXACK:
return "Acknowledge";
case EMBXSBUSY:
return "Slave device or server is busy";
case EMBXNACK:
return "Negative acknowledge";
case EMBXMEMPAR:
return "Memory parity error";
case EMBXGPATH:
return "Gateway path unavailable";
case EMBXGTAR:
return "Target device failed to respond";
case EMBBADCRC:
return "Invalid CRC";
case EMBBADDATA:
return "Invalid data";
case EMBBADEXC:
return "Invalid exception code";
case EMBMDATA:
return "Too many data";
case EMBBADSLAVE:
return "Response not from requested slave";
default:
return strerror(errnum);
}
}
void _error_print(modbus_t *ctx, const char *context)
{
if (ctx->debug) {
fprintf(stderr, "ERROR %s", modbus_strerror(errno));
if (context != NULL) {
fprintf(stderr, ": %s\n", context);
} else {
fprintf(stderr, "\n");
}
}
}
static void _sleep_response_timeout(modbus_t *ctx)
{
/* Response timeout is always positive */
#ifdef _WIN32
/* usleep doesn't exist on Windows */
Sleep((ctx->response_timeout.tv_sec * 1000) +
(ctx->response_timeout.tv_usec / 1000));
#else
/* usleep source code */
struct timespec request, remaining;
request.tv_sec = ctx->response_timeout.tv_sec;
request.tv_nsec = ((long int)ctx->response_timeout.tv_usec) * 1000;
while (nanosleep(&request, &remaining) == -1 && errno == EINTR) {
request = remaining;
}
#endif
}
int modbus_flush(modbus_t *ctx)
{
int rc;
if (ctx == NULL) {
errno = EINVAL;
return -1;
}
rc = ctx->backend->flush(ctx);
if (rc != -1 && ctx->debug) {
/* Not all backends are able to return the number of bytes flushed */
printf("Bytes flushed (%d)\n", rc);
}
return rc;
}
/* Computes the length of the expected response */
static unsigned int compute_response_length_from_request(modbus_t *ctx, uint8_t *req)
{
int length;
const int offset = ctx->backend->header_length;
switch (req[offset]) {
case MODBUS_FC_READ_COILS:
case MODBUS_FC_READ_DISCRETE_INPUTS: {
/* Header + nb values (code from write_bits) */
int nb = (req[offset + 3] << 8) | req[offset + 4];
length = 2 + (nb / 8) + ((nb % 8) ? 1 : 0);
}
break;
case MODBUS_FC_WRITE_AND_READ_REGISTERS:
case MODBUS_FC_READ_HOLDING_REGISTERS:
case MODBUS_FC_READ_INPUT_REGISTERS:
/* Header + 2 * nb values */
length = 2 + 2 * (req[offset + 3] << 8 | req[offset + 4]);
break;
case MODBUS_FC_READ_EXCEPTION_STATUS:
length = 3;
break;
case MODBUS_FC_REPORT_SLAVE_ID:
/* The response is device specific (the header provides the
length) */
return MSG_LENGTH_UNDEFINED;
case MODBUS_FC_MASK_WRITE_REGISTER:
length = 7;
break;
default:
length = 5;
}
return offset + length + ctx->backend->checksum_length;
}
/* Sends a request/response */
static int send_msg(modbus_t *ctx, uint8_t *msg, int msg_length)
{
int rc;
int i;
msg_length = ctx->backend->send_msg_pre(msg, msg_length);
if (ctx->debug) {
for (i = 0; i < msg_length; i++)
printf("[%.2X]", msg[i]);
printf("\n");
}
/* In recovery mode, the write command will be issued until to be
successful! Disabled by default. */
do {
rc = ctx->backend->send(ctx, msg, msg_length);
if (rc == -1) {
_error_print(ctx, NULL);
if (ctx->error_recovery & MODBUS_ERROR_RECOVERY_LINK) {
int saved_errno = errno;
if ((errno == EBADF || errno == ECONNRESET || errno == EPIPE)) {
modbus_close(ctx);
_sleep_response_timeout(ctx);
modbus_connect(ctx);
} else {
_sleep_response_timeout(ctx);
modbus_flush(ctx);
}
errno = saved_errno;
}
}
} while ((ctx->error_recovery & MODBUS_ERROR_RECOVERY_LINK) &&
rc == -1);
if (rc > 0 && rc != msg_length) {
errno = EMBBADDATA;
return -1;
}
return rc;
}
int modbus_send_raw_request(modbus_t *ctx, const uint8_t *raw_req, int raw_req_length)
{
sft_t sft;
uint8_t req[MAX_MESSAGE_LENGTH];
int req_length;
if (ctx == NULL) {
errno = EINVAL;
return -1;
}
if (raw_req_length < 2 || raw_req_length > (MODBUS_MAX_PDU_LENGTH + 1)) {
/* The raw request must contain function and slave at least and
must not be longer than the maximum pdu length plus the slave
address. */
errno = EINVAL;
return -1;
}
sft.slave = raw_req[0];
sft.function = raw_req[1];
/* The t_id is left to zero */
sft.t_id = 0;
/* This response function only set the header so it's convenient here */
req_length = ctx->backend->build_response_basis(&sft, req);
if (raw_req_length > 2) {
/* Copy data after function code */
memcpy(req + req_length, raw_req + 2, raw_req_length - 2);
req_length += raw_req_length - 2;
}
return send_msg(ctx, req, req_length);
}
/*
* ---------- Request Indication ----------
* | Client | ---------------------->| Server |
* ---------- Confirmation Response ----------
*/
/* Computes the length to read after the function received */
static uint8_t compute_meta_length_after_function(int function,
msg_type_t msg_type)
{
int length;
if (msg_type == MSG_INDICATION) {
if (function <= MODBUS_FC_WRITE_SINGLE_REGISTER) {
length = 4;
} else if (function == MODBUS_FC_WRITE_MULTIPLE_COILS ||
function == MODBUS_FC_WRITE_MULTIPLE_REGISTERS) {
length = 5;
} else if (function == MODBUS_FC_MASK_WRITE_REGISTER) {
length = 6;
} else if (function == MODBUS_FC_WRITE_AND_READ_REGISTERS) {
length = 9;
} else {
/* MODBUS_FC_READ_EXCEPTION_STATUS, MODBUS_FC_REPORT_SLAVE_ID */
length = 0;
}
} else {
/* MSG_CONFIRMATION */
switch (function) {
case MODBUS_FC_WRITE_SINGLE_COIL:
case MODBUS_FC_WRITE_SINGLE_REGISTER:
case MODBUS_FC_WRITE_MULTIPLE_COILS:
case MODBUS_FC_WRITE_MULTIPLE_REGISTERS:
length = 4;
break;
case MODBUS_FC_MASK_WRITE_REGISTER:
length = 6;
break;
default:
length = 1;
}
}
return length;
}
/* Computes the length to read after the meta information (address, count, etc) */
static int compute_data_length_after_meta(modbus_t *ctx, uint8_t *msg,
msg_type_t msg_type)
{
int function = msg[ctx->backend->header_length];
int length;
if (msg_type == MSG_INDICATION) {
switch (function) {
case MODBUS_FC_WRITE_MULTIPLE_COILS:
case MODBUS_FC_WRITE_MULTIPLE_REGISTERS:
length = msg[ctx->backend->header_length + 5];
break;
case MODBUS_FC_WRITE_AND_READ_REGISTERS:
length = msg[ctx->backend->header_length + 9];
break;
default:
length = 0;
}
} else {
/* MSG_CONFIRMATION */
if (function <= MODBUS_FC_READ_INPUT_REGISTERS ||
function == MODBUS_FC_REPORT_SLAVE_ID ||
function == MODBUS_FC_WRITE_AND_READ_REGISTERS) {
length = msg[ctx->backend->header_length + 1];
} else {
length = 0;
}
}
length += ctx->backend->checksum_length;
return length;
}
/* Waits a response from a modbus server or a request from a modbus client.
This function blocks if there is no replies (3 timeouts).
The function shall return the number of received characters and the received
message in an array of uint8_t if successful. Otherwise it shall return -1
and errno is set to one of the values defined below:
- ECONNRESET
- EMBBADDATA
- EMBUNKEXC
- ETIMEDOUT
- read() or recv() error codes
*/
int _modbus_receive_msg(modbus_t *ctx, uint8_t *msg, msg_type_t msg_type)
{
int rc;
fd_set rset;
struct timeval tv;
struct timeval *p_tv;
int length_to_read;
int msg_length = 0;
_step_t step;
if (ctx->debug) {
if (msg_type == MSG_INDICATION) {
printf("Waiting for an indication...\n");
} else {
printf("Waiting for a confirmation...\n");
}
}
/* Add a file descriptor to the set */
FD_ZERO(&rset);
FD_SET(ctx->s, &rset);
/* We need to analyse the message step by step. At the first step, we want
* to reach the function code because all packets contain this
* information. */
step = _STEP_FUNCTION;
length_to_read = ctx->backend->header_length + 1;
if (msg_type == MSG_INDICATION) {
/* Wait for a message, we don't know when the message will be
* received */
if (ctx->indication_timeout.tv_sec == 0 && ctx->indication_timeout.tv_usec == 0) {
/* By default, the indication timeout isn't set */
p_tv = NULL;
} else {
/* Wait for an indication (name of a received request by a server, see schema) */
tv.tv_sec = ctx->indication_timeout.tv_sec;
tv.tv_usec = ctx->indication_timeout.tv_usec;
p_tv = &tv;
}
} else {
tv.tv_sec = ctx->response_timeout.tv_sec;
tv.tv_usec = ctx->response_timeout.tv_usec;
p_tv = &tv;
}
while (length_to_read != 0) {
rc = ctx->backend->select(ctx, &rset, p_tv, length_to_read);
if (rc == -1) {
_error_print(ctx, "select");
if (ctx->error_recovery & MODBUS_ERROR_RECOVERY_LINK) {
int saved_errno = errno;
if (errno == ETIMEDOUT) {
_sleep_response_timeout(ctx);
modbus_flush(ctx);
} else if (errno == EBADF) {
modbus_close(ctx);
modbus_connect(ctx);
}
errno = saved_errno;
}
return -1;
}
rc = ctx->backend->recv(ctx, msg + msg_length, length_to_read);
if (rc == 0) {
errno = ECONNRESET;
rc = -1;
}
if (rc == -1) {
_error_print(ctx, "read");
if ((ctx->error_recovery & MODBUS_ERROR_RECOVERY_LINK) &&
(errno == ECONNRESET || errno == ECONNREFUSED ||
errno == EBADF)) {
int saved_errno = errno;
modbus_close(ctx);
modbus_connect(ctx);
/* Could be removed by previous calls */
errno = saved_errno;
}
return -1;
}
/* Display the hex code of each character received */
if (ctx->debug) {
int i;
for (i=0; i < rc; i++)
printf("<%.2X>", msg[msg_length + i]);
}
/* Sums bytes received */
msg_length += rc;
/* Computes remaining bytes */
length_to_read -= rc;
if (length_to_read == 0) {
switch (step) {
case _STEP_FUNCTION:
/* Function code position */
length_to_read = compute_meta_length_after_function(
msg[ctx->backend->header_length],
msg_type);
if (length_to_read != 0) {
step = _STEP_META;
break;
} /* else switches straight to the next step */
case _STEP_META:
length_to_read = compute_data_length_after_meta(
ctx, msg, msg_type);
if ((msg_length + length_to_read) > (int)ctx->backend->max_adu_length) {
errno = EMBBADDATA;
_error_print(ctx, "too many data");
return -1;
}
step = _STEP_DATA;
break;
default:
break;
}
}
if (length_to_read > 0 &&
(ctx->byte_timeout.tv_sec > 0 || ctx->byte_timeout.tv_usec > 0)) {
/* If there is no character in the buffer, the allowed timeout
interval between two consecutive bytes is defined by
byte_timeout */
tv.tv_sec = ctx->byte_timeout.tv_sec;
tv.tv_usec = ctx->byte_timeout.tv_usec;
p_tv = &tv;
}
/* else timeout isn't set again, the full response must be read before
expiration of response timeout (for CONFIRMATION only) */
}
if (ctx->debug)
printf("\n");
return ctx->backend->check_integrity(ctx, msg, msg_length);
}
/* Receive the request from a modbus master */
int modbus_receive(modbus_t *ctx, uint8_t *req)
{
if (ctx == NULL) {
errno = EINVAL;
return -1;
}
return ctx->backend->receive(ctx, req);
}
/* Receives the confirmation.
The function shall store the read response in rsp and return the number of
values (bits or words). Otherwise, its shall return -1 and errno is set.
The function doesn't check the confirmation is the expected response to the
initial request.
*/
int modbus_receive_confirmation(modbus_t *ctx, uint8_t *rsp)
{
if (ctx == NULL) {
errno = EINVAL;
return -1;
}
return _modbus_receive_msg(ctx, rsp, MSG_CONFIRMATION);
}
static int check_confirmation(modbus_t *ctx, uint8_t *req,
uint8_t *rsp, int rsp_length)
{
int rc;
int rsp_length_computed;
const int offset = ctx->backend->header_length;
const int function = rsp[offset];
if (ctx->backend->pre_check_confirmation) {
rc = ctx->backend->pre_check_confirmation(ctx, req, rsp, rsp_length);
if (rc == -1) {
if (ctx->error_recovery & MODBUS_ERROR_RECOVERY_PROTOCOL) {
_sleep_response_timeout(ctx);
modbus_flush(ctx);
}
return -1;
}
}
rsp_length_computed = compute_response_length_from_request(ctx, req);
/* Exception code */
if (function >= 0x80) {
if (rsp_length == (offset + 2 + (int)ctx->backend->checksum_length) &&
req[offset] == (rsp[offset] - 0x80)) {
/* Valid exception code received */
int exception_code = rsp[offset + 1];
if (exception_code < MODBUS_EXCEPTION_MAX) {
errno = MODBUS_ENOBASE + exception_code;
} else {
errno = EMBBADEXC;
}
_error_print(ctx, NULL);
return -1;
} else {
errno = EMBBADEXC;
_error_print(ctx, NULL);
return -1;
}
}
/* Check length */
if ((rsp_length == rsp_length_computed ||
rsp_length_computed == MSG_LENGTH_UNDEFINED) &&
function < 0x80) {
int req_nb_value;
int rsp_nb_value;
/* Check function code */
if (function != req[offset]) {
if (ctx->debug) {
fprintf(stderr,
"Received function not corresponding to the request (0x%X != 0x%X)\n",
function, req[offset]);
}
if (ctx->error_recovery & MODBUS_ERROR_RECOVERY_PROTOCOL) {
_sleep_response_timeout(ctx);
modbus_flush(ctx);
}
errno = EMBBADDATA;
return -1;
}
/* Check the number of values is corresponding to the request */
switch (function) {
case MODBUS_FC_READ_COILS:
case MODBUS_FC_READ_DISCRETE_INPUTS:
/* Read functions, 8 values in a byte (nb
* of values in the request and byte count in
* the response. */
req_nb_value = (req[offset + 3] << 8) + req[offset + 4];
req_nb_value = (req_nb_value / 8) + ((req_nb_value % 8) ? 1 : 0);
rsp_nb_value = rsp[offset + 1];
break;
case MODBUS_FC_WRITE_AND_READ_REGISTERS:
case MODBUS_FC_READ_HOLDING_REGISTERS:
case MODBUS_FC_READ_INPUT_REGISTERS:
/* Read functions 1 value = 2 bytes */
req_nb_value = (req[offset + 3] << 8) + req[offset + 4];
rsp_nb_value = (rsp[offset + 1] / 2);
break;
case MODBUS_FC_WRITE_MULTIPLE_COILS:
case MODBUS_FC_WRITE_MULTIPLE_REGISTERS:
/* N Write functions */
req_nb_value = (req[offset + 3] << 8) + req[offset + 4];
rsp_nb_value = (rsp[offset + 3] << 8) | rsp[offset + 4];
break;
case MODBUS_FC_REPORT_SLAVE_ID:
/* Report slave ID (bytes received) */
req_nb_value = rsp_nb_value = rsp[offset + 1];
break;
default:
/* 1 Write functions & others */
req_nb_value = rsp_nb_value = 1;
}
if (req_nb_value == rsp_nb_value) {
rc = rsp_nb_value;
} else {
if (ctx->debug) {
fprintf(stderr,
"Quantity not corresponding to the request (%d != %d)\n",
rsp_nb_value, req_nb_value);
}
if (ctx->error_recovery & MODBUS_ERROR_RECOVERY_PROTOCOL) {
_sleep_response_timeout(ctx);
modbus_flush(ctx);
}
errno = EMBBADDATA;
rc = -1;
}
} else {
if (ctx->debug) {
fprintf(stderr,
"Message length not corresponding to the computed length (%d != %d)\n",
rsp_length, rsp_length_computed);
}
if (ctx->error_recovery & MODBUS_ERROR_RECOVERY_PROTOCOL) {
_sleep_response_timeout(ctx);
modbus_flush(ctx);
}
errno = EMBBADDATA;
rc = -1;
}
return rc;
}
static int response_io_status(uint8_t *tab_io_status,
int address, int nb,
uint8_t *rsp, int offset)
{
int shift = 0;
/* Instead of byte (not allowed in Win32) */
int one_byte = 0;
int i;
for (i = address; i < address + nb; i++) {
one_byte |= tab_io_status[i] << shift;
if (shift == 7) {
/* Byte is full */
rsp[offset++] = one_byte;
one_byte = shift = 0;
} else {
shift++;
}
}
if (shift != 0)
rsp[offset++] = one_byte;
return offset;
}
/* Build the exception response */
static int response_exception(modbus_t *ctx, sft_t *sft,
int exception_code, uint8_t *rsp,
unsigned int to_flush,
const char* template, ...)
{
int rsp_length;
/* Print debug message */
if (ctx->debug) {
va_list ap;
va_start(ap, template);
vfprintf(stderr, template, ap);
va_end(ap);
}
/* Flush if required */
if (to_flush) {
_sleep_response_timeout(ctx);
modbus_flush(ctx);
}
/* Build exception response */
sft->function = sft->function + 0x80;
rsp_length = ctx->backend->build_response_basis(sft, rsp);
rsp[rsp_length++] = exception_code;
return rsp_length;
}
/* Send a response to the received request.
Analyses the request and constructs a response.
If an error occurs, this function construct the response
accordingly.
*/
int modbus_reply(modbus_t *ctx, const uint8_t *req,
int req_length, modbus_mapping_t *mb_mapping)
{
int offset;
int slave;
int function;
uint16_t address;
uint8_t rsp[MAX_MESSAGE_LENGTH];
int rsp_length = 0;
sft_t sft;
if (ctx == NULL) {
errno = EINVAL;
return -1;
}
offset = ctx->backend->header_length;
slave = req[offset - 1];
function = req[offset];
address = (req[offset + 1] << 8) + req[offset + 2];
sft.slave = slave;
sft.function = function;
sft.t_id = ctx->backend->prepare_response_tid(req, &req_length);
/* Data are flushed on illegal number of values errors. */
switch (function) {
case MODBUS_FC_READ_COILS:
case MODBUS_FC_READ_DISCRETE_INPUTS: {
unsigned int is_input = (function == MODBUS_FC_READ_DISCRETE_INPUTS);
int start_bits = is_input ? mb_mapping->start_input_bits : mb_mapping->start_bits;
int nb_bits = is_input ? mb_mapping->nb_input_bits : mb_mapping->nb_bits;
uint8_t *tab_bits = is_input ? mb_mapping->tab_input_bits : mb_mapping->tab_bits;
const char * const name = is_input ? "read_input_bits" : "read_bits";
int nb = (req[offset + 3] << 8) + req[offset + 4];
/* The mapping can be shifted to reduce memory consumption and it
doesn't always start at address zero. */
int mapping_address = address - start_bits;
if (nb < 1 || MODBUS_MAX_READ_BITS < nb) {
rsp_length = response_exception(
ctx, &sft, MODBUS_EXCEPTION_ILLEGAL_DATA_VALUE, rsp, TRUE,
"Illegal nb of values %d in %s (max %d)\n",
nb, name, MODBUS_MAX_READ_BITS);
} else if (mapping_address < 0 || (mapping_address + nb) > nb_bits) {
rsp_length = response_exception(
ctx, &sft,
MODBUS_EXCEPTION_ILLEGAL_DATA_ADDRESS, rsp, FALSE,
"Illegal data address 0x%0X in %s\n",
mapping_address < 0 ? address : address + nb, name);
} else {
rsp_length = ctx->backend->build_response_basis(&sft, rsp);
rsp[rsp_length++] = (nb / 8) + ((nb % 8) ? 1 : 0);
rsp_length = response_io_status(tab_bits, mapping_address, nb,
rsp, rsp_length);
}
}
break;
case MODBUS_FC_READ_HOLDING_REGISTERS:
case MODBUS_FC_READ_INPUT_REGISTERS: {
unsigned int is_input = (function == MODBUS_FC_READ_INPUT_REGISTERS);
int start_registers = is_input ? mb_mapping->start_input_registers : mb_mapping->start_registers;
int nb_registers = is_input ? mb_mapping->nb_input_registers : mb_mapping->nb_registers;
uint16_t *tab_registers = is_input ? mb_mapping->tab_input_registers : mb_mapping->tab_registers;
const char * const name = is_input ? "read_input_registers" : "read_registers";
int nb = (req[offset + 3] << 8) + req[offset + 4];
/* The mapping can be shifted to reduce memory consumption and it
doesn't always start at address zero. */
int mapping_address = address - start_registers;
if (nb < 1 || MODBUS_MAX_READ_REGISTERS < nb) {
rsp_length = response_exception(
ctx, &sft, MODBUS_EXCEPTION_ILLEGAL_DATA_VALUE, rsp, TRUE,
"Illegal nb of values %d in %s (max %d)\n",
nb, name, MODBUS_MAX_READ_REGISTERS);
} else if (mapping_address < 0 || (mapping_address + nb) > nb_registers) {
rsp_length = response_exception(
ctx, &sft, MODBUS_EXCEPTION_ILLEGAL_DATA_ADDRESS, rsp, FALSE,
"Illegal data address 0x%0X in %s\n",
mapping_address < 0 ? address : address + nb, name);
} else {
int i;
rsp_length = ctx->backend->build_response_basis(&sft, rsp);
rsp[rsp_length++] = nb << 1;
for (i = mapping_address; i < mapping_address + nb; i++) {
rsp[rsp_length++] = tab_registers[i] >> 8;
rsp[rsp_length++] = tab_registers[i] & 0xFF;
}
}
}
break;
case MODBUS_FC_WRITE_SINGLE_COIL: {
int mapping_address = address - mb_mapping->start_bits;
if (mapping_address < 0 || mapping_address >= mb_mapping->nb_bits) {
rsp_length = response_exception(
ctx, &sft, MODBUS_EXCEPTION_ILLEGAL_DATA_ADDRESS, rsp, FALSE,
"Illegal data address 0x%0X in write_bit\n",
address);
} else {
int data = (req[offset + 3] << 8) + req[offset + 4];
if (data == 0xFF00 || data == 0x0) {
mb_mapping->tab_bits[mapping_address] = data ? ON : OFF;
memcpy(rsp, req, req_length);
rsp_length = req_length;
} else {
rsp_length = response_exception(
ctx, &sft,
MODBUS_EXCEPTION_ILLEGAL_DATA_VALUE, rsp, FALSE,
"Illegal data value 0x%0X in write_bit request at address %0X\n",
data, address);
}
}
}
break;
case MODBUS_FC_WRITE_SINGLE_REGISTER: {
int mapping_address = address - mb_mapping->start_registers;
if (mapping_address < 0 || mapping_address >= mb_mapping->nb_registers) {
rsp_length = response_exception(
ctx, &sft,
MODBUS_EXCEPTION_ILLEGAL_DATA_ADDRESS, rsp, FALSE,
"Illegal data address 0x%0X in write_register\n",
address);
} else {
int data = (req[offset + 3] << 8) + req[offset + 4];
mb_mapping->tab_registers[mapping_address] = data;
memcpy(rsp, req, req_length);
rsp_length = req_length;
}
}
break;
case MODBUS_FC_WRITE_MULTIPLE_COILS: {
int nb = (req[offset + 3] << 8) + req[offset + 4];
int nb_bits = req[offset + 5];
int mapping_address = address - mb_mapping->start_bits;
if (nb < 1 || MODBUS_MAX_WRITE_BITS < nb || nb_bits * 8 < nb) {
/* May be the indication has been truncated on reading because of
* invalid address (eg. nb is 0 but the request contains values to
* write) so it's necessary to flush. */
rsp_length = response_exception(
ctx, &sft, MODBUS_EXCEPTION_ILLEGAL_DATA_VALUE, rsp, TRUE,
"Illegal number of values %d in write_bits (max %d)\n",
nb, MODBUS_MAX_WRITE_BITS);
} else if (mapping_address < 0 ||
(mapping_address + nb) > mb_mapping->nb_bits) {
rsp_length = response_exception(
ctx, &sft,
MODBUS_EXCEPTION_ILLEGAL_DATA_ADDRESS, rsp, FALSE,
"Illegal data address 0x%0X in write_bits\n",
mapping_address < 0 ? address : address + nb);
} else {
/* 6 = byte count */
modbus_set_bits_from_bytes(mb_mapping->tab_bits, mapping_address, nb,
&req[offset + 6]);
rsp_length = ctx->backend->build_response_basis(&sft, rsp);
/* 4 to copy the bit address (2) and the quantity of bits */
memcpy(rsp + rsp_length, req + rsp_length, 4);
rsp_length += 4;
}
}
break;
case MODBUS_FC_WRITE_MULTIPLE_REGISTERS: {
int nb = (req[offset + 3] << 8) + req[offset + 4];
int nb_bytes = req[offset + 5];
int mapping_address = address - mb_mapping->start_registers;
if (nb < 1 || MODBUS_MAX_WRITE_REGISTERS < nb || nb_bytes != nb * 2) {
rsp_length = response_exception(
ctx, &sft, MODBUS_EXCEPTION_ILLEGAL_DATA_VALUE, rsp, TRUE,
"Illegal number of values %d in write_registers (max %d)\n",
nb, MODBUS_MAX_WRITE_REGISTERS);
} else if (mapping_address < 0 ||
(mapping_address + nb) > mb_mapping->nb_registers) {
rsp_length = response_exception(
ctx, &sft, MODBUS_EXCEPTION_ILLEGAL_DATA_ADDRESS, rsp, FALSE,
"Illegal data address 0x%0X in write_registers\n",
mapping_address < 0 ? address : address + nb);
} else {
int i, j;
for (i = mapping_address, j = 6; i < mapping_address + nb; i++, j += 2) {
/* 6 and 7 = first value */
mb_mapping->tab_registers[i] =
(req[offset + j] << 8) + req[offset + j + 1];
}
rsp_length = ctx->backend->build_response_basis(&sft, rsp);
/* 4 to copy the address (2) and the no. of registers */
memcpy(rsp + rsp_length, req + rsp_length, 4);
rsp_length += 4;
}
}
break;
case MODBUS_FC_REPORT_SLAVE_ID: {
int str_len;
int byte_count_pos;
rsp_length = ctx->backend->build_response_basis(&sft, rsp);
/* Skip byte count for now */
byte_count_pos = rsp_length++;
rsp[rsp_length++] = _REPORT_SLAVE_ID;
/* Run indicator status to ON */
rsp[rsp_length++] = 0xFF;
/* LMB + length of LIBMODBUS_VERSION_STRING */
str_len = 3 + strlen(LIBMODBUS_VERSION_STRING);
memcpy(rsp + rsp_length, "LMB" LIBMODBUS_VERSION_STRING, str_len);
rsp_length += str_len;
rsp[byte_count_pos] = rsp_length - byte_count_pos - 1;
}
break;
case MODBUS_FC_READ_EXCEPTION_STATUS:
if (ctx->debug) {
fprintf(stderr, "FIXME Not implemented\n");
}
errno = ENOPROTOOPT;
return -1;
break;
case MODBUS_FC_MASK_WRITE_REGISTER: {
int mapping_address = address - mb_mapping->start_registers;
if (mapping_address < 0 || mapping_address >= mb_mapping->nb_registers) {
rsp_length = response_exception(
ctx, &sft, MODBUS_EXCEPTION_ILLEGAL_DATA_ADDRESS, rsp, FALSE,
"Illegal data address 0x%0X in write_register\n",
address);
} else {
uint16_t data = mb_mapping->tab_registers[mapping_address];
uint16_t and = (req[offset + 3] << 8) + req[offset + 4];
uint16_t or = (req[offset + 5] << 8) + req[offset + 6];
data = (data & and) | (or & (~and));
mb_mapping->tab_registers[mapping_address] = data;
memcpy(rsp, req, req_length);
rsp_length = req_length;
}
}
break;
case MODBUS_FC_WRITE_AND_READ_REGISTERS: {
int nb = (req[offset + 3] << 8) + req[offset + 4];
uint16_t address_write = (req[offset + 5] << 8) + req[offset + 6];
int nb_write = (req[offset + 7] << 8) + req[offset + 8];
int nb_write_bytes = req[offset + 9];
int mapping_address = address - mb_mapping->start_registers;
int mapping_address_write = address_write - mb_mapping->start_registers;
if (nb_write < 1 || MODBUS_MAX_WR_WRITE_REGISTERS < nb_write ||
nb < 1 || MODBUS_MAX_WR_READ_REGISTERS < nb ||
nb_write_bytes != nb_write * 2) {
rsp_length = response_exception(
ctx, &sft, MODBUS_EXCEPTION_ILLEGAL_DATA_VALUE, rsp, TRUE,
"Illegal nb of values (W%d, R%d) in write_and_read_registers (max W%d, R%d)\n",
nb_write, nb, MODBUS_MAX_WR_WRITE_REGISTERS, MODBUS_MAX_WR_READ_REGISTERS);
} else if (mapping_address < 0 ||
(mapping_address + nb) > mb_mapping->nb_registers ||
mapping_address < 0 ||
(mapping_address_write + nb_write) > mb_mapping->nb_registers) {
rsp_length = response_exception(
ctx, &sft, MODBUS_EXCEPTION_ILLEGAL_DATA_ADDRESS, rsp, FALSE,
"Illegal data read address 0x%0X or write address 0x%0X write_and_read_registers\n",
mapping_address < 0 ? address : address + nb,
mapping_address_write < 0 ? address_write : address_write + nb_write);
} else {
int i, j;
rsp_length = ctx->backend->build_response_basis(&sft, rsp);
rsp[rsp_length++] = nb << 1;
/* Write first.
10 and 11 are the offset of the first values to write */
for (i = mapping_address_write, j = 10;
i < mapping_address_write + nb_write; i++, j += 2) {
mb_mapping->tab_registers[i] =
(req[offset + j] << 8) + req[offset + j + 1];
}
/* and read the data for the response */
for (i = mapping_address; i < mapping_address + nb; i++) {
rsp[rsp_length++] = mb_mapping->tab_registers[i] >> 8;
rsp[rsp_length++] = mb_mapping->tab_registers[i] & 0xFF;
}
}
}
break;
default:
rsp_length = response_exception(
ctx, &sft, MODBUS_EXCEPTION_ILLEGAL_FUNCTION, rsp, TRUE,
"Unknown Modbus function code: 0x%0X\n", function);
break;
}
/* Suppress any responses when the request was a broadcast */
return (ctx->backend->backend_type == _MODBUS_BACKEND_TYPE_RTU &&
slave == MODBUS_BROADCAST_ADDRESS) ? 0 : send_msg(ctx, rsp, rsp_length);
}
int modbus_reply_exception(modbus_t *ctx, const uint8_t *req,
unsigned int exception_code)
{
int offset;
int slave;
int function;
uint8_t rsp[MAX_MESSAGE_LENGTH];
int rsp_length;
int dummy_length = 99;
sft_t sft;
if (ctx == NULL) {
errno = EINVAL;
return -1;
}
offset = ctx->backend->header_length;
slave = req[offset - 1];
function = req[offset];
sft.slave = slave;
sft.function = function + 0x80;
sft.t_id = ctx->backend->prepare_response_tid(req, &dummy_length);
rsp_length = ctx->backend->build_response_basis(&sft, rsp);
/* Positive exception code */
if (exception_code < MODBUS_EXCEPTION_MAX) {
rsp[rsp_length++] = exception_code;
return send_msg(ctx, rsp, rsp_length);
} else {
errno = EINVAL;
return -1;
}
}
/* Reads IO status */
static int read_io_status(modbus_t *ctx, int function,
int addr, int nb, uint8_t *dest)
{
int rc;
int req_length;
uint8_t req[_MIN_REQ_LENGTH];
uint8_t rsp[MAX_MESSAGE_LENGTH];
req_length = ctx->backend->build_request_basis(ctx, function, addr, nb, req);
rc = send_msg(ctx, req, req_length);
if (rc > 0) {
int i, temp, bit;
int pos = 0;
int offset;
int offset_end;
rc = _modbus_receive_msg(ctx, rsp, MSG_CONFIRMATION);
if (rc == -1)
return -1;
rc = check_confirmation(ctx, req, rsp, rc);
if (rc == -1)
return -1;
offset = ctx->backend->header_length + 2;
offset_end = offset + rc;
for (i = offset; i < offset_end; i++) {
/* Shift reg hi_byte to temp */
temp = rsp[i];
for (bit = 0x01; (bit & 0xff) && (pos < nb);) {
dest[pos++] = (temp & bit) ? TRUE : FALSE;
bit = bit << 1;
}
}
}
return rc;
}
/* Reads the boolean status of bits and sets the array elements
in the destination to TRUE or FALSE (single bits). */
int modbus_read_bits(modbus_t *ctx, int addr, int nb, uint8_t *dest)
{
int rc;
if (ctx == NULL) {
errno = EINVAL;
return -1;
}
if (nb > MODBUS_MAX_READ_BITS) {
if (ctx->debug) {
fprintf(stderr,
"ERROR Too many bits requested (%d > %d)\n",
nb, MODBUS_MAX_READ_BITS);
}
errno = EMBMDATA;
return -1;
}
rc = read_io_status(ctx, MODBUS_FC_READ_COILS, addr, nb, dest);
if (rc == -1)
return -1;
else
return nb;
}
/* Same as modbus_read_bits but reads the remote device input table */
int modbus_read_input_bits(modbus_t *ctx, int addr, int nb, uint8_t *dest)
{
int rc;
if (ctx == NULL) {
errno = EINVAL;
return -1;
}
if (nb > MODBUS_MAX_READ_BITS) {
if (ctx->debug) {
fprintf(stderr,
"ERROR Too many discrete inputs requested (%d > %d)\n",
nb, MODBUS_MAX_READ_BITS);
}
errno = EMBMDATA;
return -1;
}
rc = read_io_status(ctx, MODBUS_FC_READ_DISCRETE_INPUTS, addr, nb, dest);
if (rc == -1)
return -1;
else
return nb;
}
/* Reads the data from a remove device and put that data into an array */
static int read_registers(modbus_t *ctx, int function, int addr, int nb,
uint16_t *dest)
{
int rc;
int req_length;
uint8_t req[_MIN_REQ_LENGTH];
uint8_t rsp[MAX_MESSAGE_LENGTH];
if (nb > MODBUS_MAX_READ_REGISTERS) {
if (ctx->debug) {
fprintf(stderr,
"ERROR Too many registers requested (%d > %d)\n",
nb, MODBUS_MAX_READ_REGISTERS);
}
errno = EMBMDATA;
return -1;
}
req_length = ctx->backend->build_request_basis(ctx, function, addr, nb, req);
rc = send_msg(ctx, req, req_length);
if (rc > 0) {
int offset;
int i;
rc = _modbus_receive_msg(ctx, rsp, MSG_CONFIRMATION);
if (rc == -1)
return -1;
rc = check_confirmation(ctx, req, rsp, rc);
if (rc == -1)
return -1;
offset = ctx->backend->header_length;
for (i = 0; i < rc; i++) {
/* shift reg hi_byte to temp OR with lo_byte */
dest[i] = (rsp[offset + 2 + (i << 1)] << 8) |
rsp[offset + 3 + (i << 1)];
}
}
return rc;
}
/* Reads the holding registers of remote device and put the data into an
array */
int modbus_read_registers(modbus_t *ctx, int addr, int nb, uint16_t *dest)
{
int status;
if (ctx == NULL) {
errno = EINVAL;
return -1;
}
if (nb > MODBUS_MAX_READ_REGISTERS) {
if (ctx->debug) {
fprintf(stderr,
"ERROR Too many registers requested (%d > %d)\n",
nb, MODBUS_MAX_READ_REGISTERS);
}
errno = EMBMDATA;
return -1;
}
status = read_registers(ctx, MODBUS_FC_READ_HOLDING_REGISTERS,
addr, nb, dest);
return status;
}
/* Reads the input registers of remote device and put the data into an array */
int modbus_read_input_registers(modbus_t *ctx, int addr, int nb,
uint16_t *dest)
{
int status;
if (ctx == NULL) {
errno = EINVAL;
return -1;
}
if (nb > MODBUS_MAX_READ_REGISTERS) {
fprintf(stderr,
"ERROR Too many input registers requested (%d > %d)\n",
nb, MODBUS_MAX_READ_REGISTERS);
errno = EMBMDATA;
return -1;
}
status = read_registers(ctx, MODBUS_FC_READ_INPUT_REGISTERS,
addr, nb, dest);
return status;
}
/* Write a value to the specified register of the remote device.
Used by write_bit and write_register */
static int write_single(modbus_t *ctx, int function, int addr, const uint16_t value)
{
int rc;
int req_length;
uint8_t req[_MIN_REQ_LENGTH];
if (ctx == NULL) {
errno = EINVAL;
return -1;
}
req_length = ctx->backend->build_request_basis(ctx, function, addr, (int) value, req);
rc = send_msg(ctx, req, req_length);
if (rc > 0) {
/* Used by write_bit and write_register */
uint8_t rsp[MAX_MESSAGE_LENGTH];
rc = _modbus_receive_msg(ctx, rsp, MSG_CONFIRMATION);
if (rc == -1)
return -1;
rc = check_confirmation(ctx, req, rsp, rc);
}
return rc;
}
/* Turns ON or OFF a single bit of the remote device */
int modbus_write_bit(modbus_t *ctx, int addr, int status)
{
if (ctx == NULL) {
errno = EINVAL;
return -1;
}
return write_single(ctx, MODBUS_FC_WRITE_SINGLE_COIL, addr,
status ? 0xFF00 : 0);
}
/* Writes a value in one register of the remote device */
int modbus_write_register(modbus_t *ctx, int addr, const uint16_t value)
{
if (ctx == NULL) {
errno = EINVAL;
return -1;
}
return write_single(ctx, MODBUS_FC_WRITE_SINGLE_REGISTER, addr, value);
}
/* Write the bits of the array in the remote device */
int modbus_write_bits(modbus_t *ctx, int addr, int nb, const uint8_t *src)
{
int rc;
int i;
int byte_count;
int req_length;
int bit_check = 0;
int pos = 0;
uint8_t req[MAX_MESSAGE_LENGTH];
if (ctx == NULL) {
errno = EINVAL;
return -1;
}
if (nb > MODBUS_MAX_WRITE_BITS) {
if (ctx->debug) {
fprintf(stderr, "ERROR Writing too many bits (%d > %d)\n",
nb, MODBUS_MAX_WRITE_BITS);
}
errno = EMBMDATA;
return -1;
}
req_length = ctx->backend->build_request_basis(ctx,
MODBUS_FC_WRITE_MULTIPLE_COILS,
addr, nb, req);
byte_count = (nb / 8) + ((nb % 8) ? 1 : 0);
req[req_length++] = byte_count;
for (i = 0; i < byte_count; i++) {
int bit;
bit = 0x01;
req[req_length] = 0;
while ((bit & 0xFF) && (bit_check++ < nb)) {
if (src[pos++])
req[req_length] |= bit;
else
req[req_length] &=~ bit;
bit = bit << 1;
}
req_length++;
}
rc = send_msg(ctx, req, req_length);
if (rc > 0) {
uint8_t rsp[MAX_MESSAGE_LENGTH];
rc = _modbus_receive_msg(ctx, rsp, MSG_CONFIRMATION);
if (rc == -1)
return -1;
rc = check_confirmation(ctx, req, rsp, rc);
}
return rc;
}
/* Write the values from the array to the registers of the remote device */
int modbus_write_registers(modbus_t *ctx, int addr, int nb, const uint16_t *src)
{
int rc;
int i;
int req_length;
int byte_count;
uint8_t req[MAX_MESSAGE_LENGTH];
if (ctx == NULL) {
errno = EINVAL;
return -1;
}
if (nb > MODBUS_MAX_WRITE_REGISTERS) {
if (ctx->debug) {
fprintf(stderr,
"ERROR Trying to write to too many registers (%d > %d)\n",
nb, MODBUS_MAX_WRITE_REGISTERS);
}
errno = EMBMDATA;
return -1;
}
req_length = ctx->backend->build_request_basis(ctx,
MODBUS_FC_WRITE_MULTIPLE_REGISTERS,
addr, nb, req);
byte_count = nb * 2;
req[req_length++] = byte_count;
for (i = 0; i < nb; i++) {
req[req_length++] = src[i] >> 8;
req[req_length++] = src[i] & 0x00FF;
}
rc = send_msg(ctx, req, req_length);
if (rc > 0) {
uint8_t rsp[MAX_MESSAGE_LENGTH];
rc = _modbus_receive_msg(ctx, rsp, MSG_CONFIRMATION);
if (rc == -1)
return -1;
rc = check_confirmation(ctx, req, rsp, rc);
}
return rc;
}
int modbus_mask_write_register(modbus_t *ctx, int addr, uint16_t and_mask, uint16_t or_mask)
{
int rc;
int req_length;
/* The request length can not exceed _MIN_REQ_LENGTH - 2 and 4 bytes to
* store the masks. The ugly substraction is there to remove the 'nb' value
* (2 bytes) which is not used. */
uint8_t req[_MIN_REQ_LENGTH + 2];
req_length = ctx->backend->build_request_basis(ctx,
MODBUS_FC_MASK_WRITE_REGISTER,
addr, 0, req);
/* HACKISH, count is not used */
req_length -= 2;
req[req_length++] = and_mask >> 8;
req[req_length++] = and_mask & 0x00ff;
req[req_length++] = or_mask >> 8;
req[req_length++] = or_mask & 0x00ff;
rc = send_msg(ctx, req, req_length);
if (rc > 0) {
/* Used by write_bit and write_register */
uint8_t rsp[MAX_MESSAGE_LENGTH];
rc = _modbus_receive_msg(ctx, rsp, MSG_CONFIRMATION);
if (rc == -1)
return -1;
rc = check_confirmation(ctx, req, rsp, rc);
}
return rc;
}
/* Write multiple registers from src array to remote device and read multiple
registers from remote device to dest array. */
int modbus_write_and_read_registers(modbus_t *ctx,
int write_addr, int write_nb,
const uint16_t *src,
int read_addr, int read_nb,
uint16_t *dest)
{
int rc;
int req_length;
int i;
int byte_count;
uint8_t req[MAX_MESSAGE_LENGTH];
uint8_t rsp[MAX_MESSAGE_LENGTH];
if (ctx == NULL) {
errno = EINVAL;
return -1;
}
if (write_nb > MODBUS_MAX_WR_WRITE_REGISTERS) {
if (ctx->debug) {
fprintf(stderr,
"ERROR Too many registers to write (%d > %d)\n",
write_nb, MODBUS_MAX_WR_WRITE_REGISTERS);
}
errno = EMBMDATA;
return -1;
}
if (read_nb > MODBUS_MAX_WR_READ_REGISTERS) {
if (ctx->debug) {
fprintf(stderr,
"ERROR Too many registers requested (%d > %d)\n",
read_nb, MODBUS_MAX_WR_READ_REGISTERS);
}
errno = EMBMDATA;
return -1;
}
req_length = ctx->backend->build_request_basis(ctx,
MODBUS_FC_WRITE_AND_READ_REGISTERS,
read_addr, read_nb, req);
req[req_length++] = write_addr >> 8;
req[req_length++] = write_addr & 0x00ff;
req[req_length++] = write_nb >> 8;
req[req_length++] = write_nb & 0x00ff;
byte_count = write_nb * 2;
req[req_length++] = byte_count;
for (i = 0; i < write_nb; i++) {
req[req_length++] = src[i] >> 8;
req[req_length++] = src[i] & 0x00FF;
}
rc = send_msg(ctx, req, req_length);
if (rc > 0) {
int offset;
rc = _modbus_receive_msg(ctx, rsp, MSG_CONFIRMATION);
if (rc == -1)
return -1;
rc = check_confirmation(ctx, req, rsp, rc);
if (rc == -1)
return -1;
offset = ctx->backend->header_length;
for (i = 0; i < rc; i++) {
/* shift reg hi_byte to temp OR with lo_byte */
dest[i] = (rsp[offset + 2 + (i << 1)] << 8) |
rsp[offset + 3 + (i << 1)];
}
}
return rc;
}
/* Send a request to get the slave ID of the device (only available in serial
communication). */
int modbus_report_slave_id(modbus_t *ctx, int max_dest, uint8_t *dest)
{
int rc;
int req_length;
uint8_t req[_MIN_REQ_LENGTH];
if (ctx == NULL || max_dest <= 0) {
errno = EINVAL;
return -1;
}
req_length = ctx->backend->build_request_basis(ctx, MODBUS_FC_REPORT_SLAVE_ID,
0, 0, req);
/* HACKISH, addr and count are not used */
req_length -= 4;
rc = send_msg(ctx, req, req_length);
if (rc > 0) {
int i;
int offset;
uint8_t rsp[MAX_MESSAGE_LENGTH];
rc = _modbus_receive_msg(ctx, rsp, MSG_CONFIRMATION);
if (rc == -1)
return -1;
rc = check_confirmation(ctx, req, rsp, rc);
if (rc == -1)
return -1;
offset = ctx->backend->header_length + 2;
/* Byte count, slave id, run indicator status and
additional data. Truncate copy to max_dest. */
for (i=0; i < rc && i < max_dest; i++) {
dest[i] = rsp[offset + i];
}
}
return rc;
}
void _modbus_init_common(modbus_t *ctx)
{
/* Slave and socket are initialized to -1 */
ctx->slave = -1;
ctx->s = -1;
ctx->debug = FALSE;
ctx->error_recovery = MODBUS_ERROR_RECOVERY_NONE;
ctx->response_timeout.tv_sec = 0;
ctx->response_timeout.tv_usec = _RESPONSE_TIMEOUT;
ctx->byte_timeout.tv_sec = 0;
ctx->byte_timeout.tv_usec = _BYTE_TIMEOUT;
ctx->indication_timeout.tv_sec = 0;
ctx->indication_timeout.tv_usec = 0;
}
/* Define the slave number */
int modbus_set_slave(modbus_t *ctx, int slave)
{
if (ctx == NULL) {
errno = EINVAL;
return -1;
}
return ctx->backend->set_slave(ctx, slave);
}
int modbus_get_slave(modbus_t *ctx)
{
if (ctx == NULL) {
errno = EINVAL;
return -1;
}
return ctx->slave;
}
int modbus_set_error_recovery(modbus_t *ctx,
modbus_error_recovery_mode error_recovery)
{
if (ctx == NULL) {
errno = EINVAL;
return -1;
}
/* The type of modbus_error_recovery_mode is unsigned enum */
ctx->error_recovery = (uint8_t) error_recovery;
return 0;
}
int modbus_set_socket(modbus_t *ctx, int s)
{
if (ctx == NULL) {
errno = EINVAL;
return -1;
}
ctx->s = s;
return 0;
}
int modbus_get_socket(modbus_t *ctx)
{
if (ctx == NULL) {
errno = EINVAL;
return -1;
}
return ctx->s;
}
/* Get the timeout interval used to wait for a response */
int modbus_get_response_timeout(modbus_t *ctx, uint32_t *to_sec, uint32_t *to_usec)
{
if (ctx == NULL) {
errno = EINVAL;
return -1;
}
*to_sec = ctx->response_timeout.tv_sec;
*to_usec = ctx->response_timeout.tv_usec;
return 0;
}
int modbus_set_response_timeout(modbus_t *ctx, uint32_t to_sec, uint32_t to_usec)
{
if (ctx == NULL ||
(to_sec == 0 && to_usec == 0) || to_usec > 999999) {
errno = EINVAL;
return -1;
}
ctx->response_timeout.tv_sec = to_sec;
ctx->response_timeout.tv_usec = to_usec;
return 0;
}
/* Get the timeout interval between two consecutive bytes of a message */
int modbus_get_byte_timeout(modbus_t *ctx, uint32_t *to_sec, uint32_t *to_usec)
{
if (ctx == NULL) {
errno = EINVAL;
return -1;
}
*to_sec = ctx->byte_timeout.tv_sec;
*to_usec = ctx->byte_timeout.tv_usec;
return 0;
}
int modbus_set_byte_timeout(modbus_t *ctx, uint32_t to_sec, uint32_t to_usec)
{
/* Byte timeout can be disabled when both values are zero */
if (ctx == NULL || to_usec > 999999) {
errno = EINVAL;
return -1;
}
ctx->byte_timeout.tv_sec = to_sec;
ctx->byte_timeout.tv_usec = to_usec;
return 0;
}
/* Get the timeout interval used by the server to wait for an indication from a client */
int modbus_get_indication_timeout(modbus_t *ctx, uint32_t *to_sec, uint32_t *to_usec)
{
if (ctx == NULL) {
errno = EINVAL;
return -1;
}
*to_sec = ctx->indication_timeout.tv_sec;
*to_usec = ctx->indication_timeout.tv_usec;
return 0;
}
int modbus_set_indication_timeout(modbus_t *ctx, uint32_t to_sec, uint32_t to_usec)
{
/* Indication timeout can be disabled when both values are zero */
if (ctx == NULL || to_usec > 999999) {
errno = EINVAL;
return -1;
}
ctx->indication_timeout.tv_sec = to_sec;
ctx->indication_timeout.tv_usec = to_usec;
return 0;
}
int modbus_get_header_length(modbus_t *ctx)
{
if (ctx == NULL) {
errno = EINVAL;
return -1;
}
return ctx->backend->header_length;
}
int modbus_connect(modbus_t *ctx)
{
if (ctx == NULL) {
errno = EINVAL;
return -1;
}
return ctx->backend->connect(ctx);
}
void modbus_close(modbus_t *ctx)
{
if (ctx == NULL)
return;
ctx->backend->close(ctx);
}
void modbus_free(modbus_t *ctx)
{
if (ctx == NULL)
return;
ctx->backend->free(ctx);
}
int modbus_set_debug(modbus_t *ctx, int flag)
{
if (ctx == NULL) {
errno = EINVAL;
return -1;
}
ctx->debug = flag;
return 0;
}
/* Allocates 4 arrays to store bits, input bits, registers and inputs
registers. The pointers are stored in modbus_mapping structure.
The modbus_mapping_new_start_address() function shall return the new allocated
structure if successful. Otherwise it shall return NULL and set errno to
ENOMEM. */
modbus_mapping_t* modbus_mapping_new_start_address(
unsigned int start_bits, unsigned int nb_bits,
unsigned int start_input_bits, unsigned int nb_input_bits,
unsigned int start_registers, unsigned int nb_registers,
unsigned int start_input_registers, unsigned int nb_input_registers)
{
modbus_mapping_t *mb_mapping;
mb_mapping = (modbus_mapping_t *)malloc(sizeof(modbus_mapping_t));
if (mb_mapping == NULL) {
return NULL;
}
/* 0X */
mb_mapping->nb_bits = nb_bits;
mb_mapping->start_bits = start_bits;
if (nb_bits == 0) {
mb_mapping->tab_bits = NULL;
} else {
/* Negative number raises a POSIX error */
mb_mapping->tab_bits =
(uint8_t *) malloc(nb_bits * sizeof(uint8_t));
if (mb_mapping->tab_bits == NULL) {
free(mb_mapping);
return NULL;
}
memset(mb_mapping->tab_bits, 0, nb_bits * sizeof(uint8_t));
}
/* 1X */
mb_mapping->nb_input_bits = nb_input_bits;
mb_mapping->start_input_bits = start_input_bits;
if (nb_input_bits == 0) {
mb_mapping->tab_input_bits = NULL;
} else {
mb_mapping->tab_input_bits =
(uint8_t *) malloc(nb_input_bits * sizeof(uint8_t));
if (mb_mapping->tab_input_bits == NULL) {
free(mb_mapping->tab_bits);
free(mb_mapping);
return NULL;
}
memset(mb_mapping->tab_input_bits, 0, nb_input_bits * sizeof(uint8_t));
}
/* 4X */
mb_mapping->nb_registers = nb_registers;
mb_mapping->start_registers = start_registers;
if (nb_registers == 0) {
mb_mapping->tab_registers = NULL;
} else {
mb_mapping->tab_registers =
(uint16_t *) malloc(nb_registers * sizeof(uint16_t));
if (mb_mapping->tab_registers == NULL) {
free(mb_mapping->tab_input_bits);
free(mb_mapping->tab_bits);
free(mb_mapping);
return NULL;
}
memset(mb_mapping->tab_registers, 0, nb_registers * sizeof(uint16_t));
}
/* 3X */
mb_mapping->nb_input_registers = nb_input_registers;
mb_mapping->start_input_registers = start_input_registers;
if (nb_input_registers == 0) {
mb_mapping->tab_input_registers = NULL;
} else {
mb_mapping->tab_input_registers =
(uint16_t *) malloc(nb_input_registers * sizeof(uint16_t));
if (mb_mapping->tab_input_registers == NULL) {
free(mb_mapping->tab_registers);
free(mb_mapping->tab_input_bits);
free(mb_mapping->tab_bits);
free(mb_mapping);
return NULL;
}
memset(mb_mapping->tab_input_registers, 0,
nb_input_registers * sizeof(uint16_t));
}
return mb_mapping;
}
modbus_mapping_t* modbus_mapping_new(int nb_bits, int nb_input_bits,
int nb_registers, int nb_input_registers)
{
return modbus_mapping_new_start_address(
0, nb_bits, 0, nb_input_bits, 0, nb_registers, 0, nb_input_registers);
}
/* Frees the 4 arrays */
void modbus_mapping_free(modbus_mapping_t *mb_mapping)
{
if (mb_mapping == NULL) {
return;
}
free(mb_mapping->tab_input_registers);
free(mb_mapping->tab_registers);
free(mb_mapping->tab_input_bits);
free(mb_mapping->tab_bits);
free(mb_mapping);
}
#ifndef HAVE_STRLCPY
/*
* Function strlcpy was originally developed by
* Todd C. Miller <Todd.Miller@courtesan.com> to simplify writing secure code.
* See ftp://ftp.openbsd.org/pub/OpenBSD/src/lib/libc/string/strlcpy.3
* for more information.
*
* Thank you Ulrich Drepper... not!
*
* Copy src to string dest of size dest_size. At most dest_size-1 characters
* will be copied. Always NUL terminates (unless dest_size == 0). Returns
* strlen(src); if retval >= dest_size, truncation occurred.
*/
size_t strlcpy(char *dest, const char *src, size_t dest_size)
{
register char *d = dest;
register const char *s = src;
register size_t n = dest_size;
/* Copy as many bytes as will fit */
if (n != 0 && --n != 0) {
do {
if ((*d++ = *s++) == 0)
break;
} while (--n != 0);
}
/* Not enough room in dest, add NUL and traverse rest of src */
if (n == 0) {
if (dest_size != 0)
*d = '\0'; /* NUL-terminate dest */
while (*s++)
;
}
return (s - src - 1); /* count does not include NUL */
}
#endifLibModbus库实际工程应用
首先要下载安装VisualStudio2019或者VisualStudio2022，下载连接如下：
1、TIA中新建项目插入PLC 1214C,PLC属性设置如上所示IP地址为192.168.1.214。DB块中数据如下图所示，远程连接地址设置为192.168.1.106，不设置代表任何客户端都可连接。
2、编写ModbusTCP Server端程序，程序如下图所示。
3、Modbus通信数据地址隐射为M100，如下图所示数据长度映射600个字。
4、监控表中添加M100开始的数据监控表。如下图所示。
5、打开VisualStudio2019新建名为"MFCApplicationMultiLineTest"的MFC项目。将modbus.h头文件增加到项目MFCApplicationMultiLineTest.CPP文件中，如下图所示。
6、新建如下全局变量用于通信和线程管理。
cpp
#define LOOP 1
#define CLIENT_ID 20
#define ADDRESS_START 40001
#define ADDRESS_END 40101
#define ADDRESS_MAX 40201
#define ADDRESS_SUPERMAX 40301
#define PI 3.1415926
threadInfo Info;
CMutex cmtex;
BOOL ThreadKiller = FALSE;
BOOL ForKiller = FALSE;
HANDLE hMyThread;
BOOL ModbusThreadKiller = FALSE;
BOOL ModbusLoop = FALSE;
BOOL ServerConnectFailedFlag = FALSE;
int nb_fail;
int nb_loop;
int addr;
int addr_float = 100;
int addr_float_supermax = 200;
int nb;
int sel;
int flnb;
int spnb;
int nCount;
CString strfloat;
modbus_t* ctx;
uint8_t * tab_rq_bits;
uint8_t * tab_rp_bits;
uint16_t* tab_rq_registers;
uint16_t* tab_rp_registers;
uint16_t* tab_rw_registers;
uint16_t* tab_float_registers;
uint16_t* tab_float_write_registers;
float * read_float_registers;
float * write_float_registers;
CRect rcClientOld;
CRect rcClientNew;7、在OnInitDialog()初始化函数中加入如下代码。窗口打开后即可连接ModbusTCP服务器端。
cpp
ctx = modbus_new_tcp("192.168.1.214", 502);
modbus_set_debug(ctx, TRUE);
modbus_set_slave(ctx, CLIENT_ID);
modbus_set_response_timeout(ctx, 10, 1000000);
if (modbus_connect(ctx) == -1)
{
fprintf(stderr, "Connection failed: %s\n", modbus_strerror(errno));
printf("Connection failed: %s\n", modbus_strerror(errno));
OutputDebugString(_T("Connection failed : % s\n"));
AfxMessageBox(_T("Modbus Server Conneect Failed!"), MB_ICONINFORMATION);
modbus_close(ctx);
modbus_free(ctx);
ServerConnectFailedFlag = TRUE;
return -1;
}
else
{
AfxMessageBox(_T("Modbus Server Conneect Success!"), MB_ICONINFORMATION);
ServerConnectFailedFlag = FALSE;
}
SetTimer(1, 1000, NULL);
/*ModbusTCP通讯寄存器内存分配和内存空间初始化*/
nb = ADDRESS_END - ADDRESS_START;//40001-4101为int
flnb = ADDRESS_MAX - ADDRESS_END;//40101-40201为float
spnb = ADDRESS_SUPERMAX - ADDRESS_MAX;//40201-40301为float
tab_rq_bits = (uint8_t*)malloc(nb * sizeof(uint8_t));
memset(tab_rq_bits,0, nb * sizeof(uint8_t));
tab_rp_bits = (uint8_t*)malloc(nb * sizeof(uint8_t));
memset(tab_rp_bits,0, nb * sizeof(uint8_t));
tab_rq_registers = (uint16_t*)malloc(nb * sizeof(uint16_t));
memset(tab_rq_registers,0, nb * sizeof(uint16_t));
tab_rp_registers = (uint16_t*)malloc(nb * sizeof(uint16_t));
memset(tab_rp_registers,0, nb * sizeof(uint16_t));
tab_rw_registers = (uint16_t*)malloc(nb * sizeof(uint16_t));
memset(tab_rw_registers,0, nb * sizeof(uint16_t));
tab_float_registers = (uint16_t*)malloc(2 * flnb * sizeof(uint16_t));
memset(tab_float_registers,0, 2 * flnb * sizeof(uint16_t));
read_float_registers = (float*)malloc(flnb * sizeof(float));
memset(read_float_registers,0, flnb * sizeof(float));
write_float_registers = (float*)malloc((flnb) * sizeof(float));
memset(write_float_registers,0, (flnb) * sizeof(float));
tab_float_write_registers = (uint16_t*)malloc(2 * flnb * sizeof(uint16_t));
memset(tab_float_write_registers,0, 2 * flnb * sizeof(uint16_t));
//**********************************************************************
GetClientRect(&rcGetold);
OldClientPoint.x = rcGetold.right - rcGetold.left;
OldClientPoint.y = rcGetold.bottom - rcGetold.top;8、编写相关的通信线程函数ModBusCommunication(LPVOID* pParam)。Libmodbus库函数说明在Libmodbus官网有详细的说明。
cpp
UINT CMFCApplicationMultiLineTestDlg::ModBusCommunication(LPVOID* pParam)
{
CMFCApplicationMultiLineTestDlg* modbustcp = (CMFCApplicationMultiLineTestDlg*)pParam;
int rc=0;
int n=0;
int qw=0;
int rq=0;
int wf = 0;
float rfloat = 0;
//COLORREF RGB;
BOOL sendmsg = FALSE;
BOOL dspmsg = FALSE;
CWnd* thHwnd = AfxGetApp()->GetMainWnd();
CSingleLock modbuslock(&cmtex);
modbuslock.Lock();
if (ServerConnectFailedFlag == FALSE)
{
while (ModbusLoop==FALSE)
{
if(ServerConnectFailedFlag==FALSE)
{
if (ModbusThreadKiller)//最好让线程自行退出。
{
DWORD dwExitCode;
GetExitCodeThread(modbustcp->ModbusTcpThread,&dwExitCode);
AfxEndThread(dwExitCode,TRUE);
}
else
{
for (int q = 0; q <= 9; q++)
{
rc = modbus_write_bit(ctx, q, 0);
if (rc != 1)
{
printf("Error modbus_write_bit(%d)\n", rc);
printf("Address=%d,value=%d\n", q, 0);
nb_fail++;
}
else
{
rc = modbus_read_bits(ctx, q, 1, tab_rq_bits);
if (rc != 1 || tab_rq_bits[0] != 0)
{
printf("Error modbus_read_bit single(%d)\n", rc);
printf("Address=%d", q);
nb_fail++;
}
}
Sleep(10);
}
for (qw = 0; qw <= 9; qw++)
{
rc = modbus_write_bit(ctx, qw, 1);//西门子S7-1200 I/O地址对应：0对应Q0.0,1对应Q0.1,8对应Q1.0
if (rc != 1)
{
printf("Error modbus_write_bit(%d)\n", rc);
printf("Address=%d,value=%d\n", qw, 1);
nb_fail++;
}
else
{
rc = modbus_read_bits(ctx, qw, 1, tab_rq_bits);
if (rc != 1 || tab_rq_bits[0] != 1)
{
printf("Error modbus_read_bit single(%d)\n", rc);
printf("Address=%d", qw);
nb_fail++;
}
}
Sleep(10);
}
addr = 0;
//addr=0对应西门子S7-1200 modbus寄存器40001，1对应40002、40001映射S7-1200 MW100,40002映射S7-1200 MW102,
for (rq = 0; rq < nb; rq++)
{
tab_rq_registers[rq] = rq + 820 * sel;
}
//向S7-1200 MD300-MD696寄存器写入100个浮点数据，MD300对应modbus寄存器40201（200），MD696对应寄存器40301
for (wf= 0;wf<flnb; wf++)
{
write_float_registers[wf] = (wf+sel)*(float)PI;
modbus_set_float_dcba(write_float_registers[wf], tab_float_write_registers + 2 * wf);
}
rc = modbus_write_registers(ctx, addr,nb,tab_rq_registers);
if (rc != nb)
{
printf("Error modbus_write_registers(%d)\n", rc);
printf("Address=%d,nb=%d\n", addr,nb);
nb_fail++;
if (sendmsg == FALSE)
{
sendmsg = TRUE;
::PostMessage(thHwnd->GetSafeHwnd(), WM_THREAD_MONITOR, WPARAM(sendmsg), 0);
}
}
else
{
rc = modbus_read_registers(ctx,addr,nb,tab_rp_registers);
if (rc != nb)
{
printf("Error modbus_read_registers(%d)\n", rc);
printf("Address=%d,nb=%d\n", addr, nb);
nb_fail++;
}
else
{
for (int k = 0; k < nb; k++)
{
if (tab_rq_registers[k] != tab_rp_registers[k])
{
printf("Error modbus_read_registers(%d)\n",nb);
printf("Address=%d,Value %d(0x%X!=%d (0x%X))\n",addr,tab_rq_registers[k],tab_rq_registers[k],tab_rp_registers[k],tab_rp_registers[k]);
nb_fail++;
}
}
}
}
/*S7-1200浮点数据写入格式为dcba(100-200定义为float数据对应MD300-MD496，float数据需要分配2*flnb的存储空间)最大写入123个字
写入前50个浮点数据（写入100个浮点数据必须分两次写入）*/
rc = modbus_write_registers(ctx,addr_float,flnb,tab_float_write_registers);
if (rc!=flnb)
{
printf("Error modbus_write_registers(%d)\n",flnb);
printf("Address=%d,flnb=%d\n",addr_float,flnb);
nb_fail++;
}
/*S7-1200浮点数据读取格式为dcba(100-200定义为float数据对应MD300-MD496，float数据需要分配2*flnb的存储空间)最大写入123个字
写入后50个浮点数据（写入100个浮点数据必须分两次写入）*/
rc = modbus_write_registers(ctx, addr_float_supermax, spnb, tab_float_write_registers+spnb);
if (rc != spnb)
{
printf("Error modbus_write_registers(%d)\n", spnb);
printf("Address=%d,flnb=%d\n", addr_float_supermax, spnb);
nb_fail++;
}
/*S7-1200浮点数据读取格式为dcba(100-200定义为float数据对应MD300-MD496，float数据需要分配2*flnb的存储空间)最大读取125个字
读取前50个浮点数据（读取数据必须分两次读取）*/
rc = modbus_read_registers(ctx,addr_float,flnb,tab_float_registers);//读取前50个浮点
if (rc!=flnb)
{
printf("Error modbus_read_registersF(%d)\n", rc);
printf("Address=%d,nb=%d\n", addr_float, flnb);
nb_fail++;
}
rc = modbus_read_registers(ctx, addr_float_supermax, spnb, tab_float_registers+spnb);//读取后50个浮点
if (rc != spnb)
{
printf("error modbus_read_registersb(%d)\n", rc);
printf("address=%d,nb=%d\n", addr_float_supermax, spnb);
nb_fail++;
}
else
{
for (int lst = 0; lst < flnb; lst++)
{
dspmsg = TRUE;
read_float_registers[lst] = modbus_get_float_dcba(tab_float_registers+lst*2);
rfloat = read_float_registers[lst];
//Sleep(1);
::PostMessage(thHwnd->GetSafeHwnd(), WM_SHOUWDATAFROMSIEMENS,WPARAM(dspmsg),LPARAM(lst));
dspmsg = FALSE;
}
rfloat = read_float_registers[0];
strfloat.Format(_T("%.4f"), rfloat);
modbustcp->SetDlgItemText(IDC_EDITREADFLOAT,strfloat);
strfloat.Format(_T("%.4f"), read_float_registers[1]);
modbustcp->SetDlgItemText(IDC_EDITFREADLOAT4, strfloat);
strfloat.Format(_T("%.4f"), read_float_registers[2]);
modbustcp->SetDlgItemText(IDC_EDITREADFLOAT8, strfloat);
}
n++;
modbustcp->SetDlgItemInt(IDC_EDITCACULATE, n);
}
}
}
}
else
{
printf("Connection Failed: %s\n", modbus_strerror(errno));
AfxMessageBox(_T("ModbusServer Connect Failed!"), MB_ICONINFORMATION);
}
n = 0;
modbustcp->SetDlgItemInt(IDC_EDITCACULATE, n);
modbustcp->ModbusTcpThread = NULL;
sendmsg = FALSE;
dspmsg = FALSE;
modbuslock.Unlock();
return 0;
}9、增加线程启动按钮，在按钮中启动通信线程完成通信。此例程为Libmodbus和S7-1200通信测试例程，写的比较早，没有严格封装。S7-200 PLC 的程序做了严格封装，后面在做介绍。
cpp
void CMFCApplicationMultiLineTestDlg::OnBnClickedButtonstart()
{
if (ModbusTcpThread == NULL)
{
ModbusThreadKiller = FALSE;
ModbusLoop = FALSE;
UpdateData(TRUE);
sel = m_select;
SetDlgItemInt(IDC_EDITDSP,sel);
UpdateData(FALSE);
Sleep(50);
ModbusTcpThread = AfxBeginThread((AFX_THREADPROC)ModBusCommunication, this);
}
else
{
AfxMessageBox(_T("ModbusTCP通讯线程已启动，无需重启!"), MB_ICONINFORMATION);
}
}10、启动MFC程序进行仿真。如下图所示。
11、在博图变量监控表中监控变量，如下图所示。对比发现数据准确无误。
12、合信M226ES与LibModbus之间的通信。合信M226ESModbusTCP协议客户端不需要编写程序，设置好IP地址即可，端口默认502。下面是M226ES Modbus地址映射（默认隐射）。
13、下面为测试的相关视频。
C++和S7-1200 Libmodbus 通信
