嵌入式Libmodbus源码分析-RTU相关函数分析
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00. 目录
01. RTU模式概述
RTU模式相关源码文件为modbus-rtu.h、modbus-rtu-private.h和modbus-rtu.c文件。
02. modbus-rtu-private.h文件
RTU模式私有的数据类型和函数声明
/*
* Copyright © 2001-2011 Stéphane Raimbault <stephane.raimbault@gmail.com>
*
* SPDX-License-Identifier: LGPL-2.1-or-later
*/
#ifndef MODBUS_RTU_PRIVATE_H
#define MODBUS_RTU_PRIVATE_H
#ifndef _MSC_VER
#include <stdint.h>
#else
#include "stdint.h"
#endif
#if defined(_WIN32)
#include <windows.h>
#else
#include <termios.h>
#endif
#define _MODBUS_RTU_HEADER_LENGTH 1
#define _MODBUS_RTU_PRESET_REQ_LENGTH 6
#define _MODBUS_RTU_PRESET_RSP_LENGTH 2
#define _MODBUS_RTU_CHECKSUM_LENGTH 2
#if defined(_WIN32)
#if !defined(ENOTSUP)
#define ENOTSUP WSAEOPNOTSUPP
#endif
/* WIN32: struct containing serial handle and a receive buffer */
#define PY_BUF_SIZE 512
struct win32_ser {
/* File handle */
HANDLE fd;
/* Receive buffer */
uint8_t buf[PY_BUF_SIZE];
/* Received chars */
DWORD n_bytes;
};
#endif /* _WIN32 */
typedef struct _modbus_rtu {
/* Device: "/dev/ttyS0", "/dev/ttyUSB0" or "/dev/tty.USA19*" on Mac OS X. */
char *device;
/* Bauds: 9600, 19200, 57600, 115200, etc */
int baud;
/* Data bit */
uint8_t data_bit;
/* Stop bit */
uint8_t stop_bit;
/* Parity: 'N', 'O', 'E' */
char parity;
#if defined(_WIN32)
struct win32_ser w_ser;
DCB old_dcb;
#else
/* Save old termios settings */
struct termios old_tios;
#endif
#if HAVE_DECL_TIOCSRS485
int serial_mode;
#endif
#if HAVE_DECL_TIOCM_RTS
int rts;
int rts_delay;
int onebyte_time;
void (*set_rts) (modbus_t *ctx, int on);
#endif
/* To handle many slaves on the same link */
int confirmation_to_ignore;
} modbus_rtu_t;
#endif /* MODBUS_RTU_PRIVATE_H */
03. modbus-rtu.h文件
RTU模式对外开放的API函数声明
/*
* Copyright © 2001-2011 Stéphane Raimbault <stephane.raimbault@gmail.com>
*
* SPDX-License-Identifier: LGPL-2.1-or-later
*/
#ifndef MODBUS_RTU_H
#define MODBUS_RTU_H
#include "modbus.h"
MODBUS_BEGIN_DECLS
/* Modbus_Application_Protocol_V1_1b.pdf Chapter 4 Section 1 Page 5
* RS232 / RS485 ADU = 253 bytes + slave (1 byte) + CRC (2 bytes) = 256 bytes
*/
#define MODBUS_RTU_MAX_ADU_LENGTH 256
//创建RTU类型的结构体
//device: "COM1 ~ COM9" /dev/ttyS0 /dev/ttyUSB0 /dev/ttyUSB1等等
//baud 波特率的设置值 9600 19200 57600 115200
//parity:奇偶校验位 'N' 'E' 'O'
//data_bit: 数据位 5 6 7 8
//stop_bit: 停止位 1 2
MODBUS_API modbus_t* modbus_new_rtu(const char *device, int baud, char parity,
int data_bit, int stop_bit);
#define MODBUS_RTU_RS232 0
#define MODBUS_RTU_RS485 1
//设置串口模式
MODBUS_API int modbus_rtu_set_serial_mode(modbus_t *ctx, int mode);
//获取串口模式
MODBUS_API int modbus_rtu_get_serial_mode(modbus_t *ctx);
#define MODBUS_RTU_RTS_NONE 0
#define MODBUS_RTU_RTS_UP 1
#define MODBUS_RTU_RTS_DOWN 2
//以下函数一般不常用
MODBUS_API int modbus_rtu_set_rts(modbus_t *ctx, int mode);
MODBUS_API int modbus_rtu_get_rts(modbus_t *ctx);
MODBUS_API int modbus_rtu_set_custom_rts(modbus_t *ctx, void (*set_rts) (modbus_t *ctx, int on));
MODBUS_API int modbus_rtu_set_rts_delay(modbus_t *ctx, int us);
MODBUS_API int modbus_rtu_get_rts_delay(modbus_t *ctx);
MODBUS_END_DECLS
#endif /* MODBUS_RTU_H */
04. modbus-rtu.c文件
modbus-rtu.c 通信层实现，RTU模式相关的函数定义，主要是串口的设置、连接及消息的发送和接收等等。
/*
* Copyright © 2001-2011 Stéphane Raimbault <stephane.raimbault@gmail.com>
*
* SPDX-License-Identifier: LGPL-2.1-or-later
*/
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <fcntl.h>
#include <string.h>
#ifndef _MSC_VER
#include <unistd.h>
#endif
#include <assert.h>
#include "modbus-private.h"
#include "modbus-rtu.h"
#include "modbus-rtu-private.h"
#if HAVE_DECL_TIOCSRS485 || HAVE_DECL_TIOCM_RTS
#include <sys/ioctl.h>
#endif
#if HAVE_DECL_TIOCSRS485
#include <linux/serial.h>
#endif
/* Table of CRC values for high-order byte */
static const uint8_t table_crc_hi[] = {
0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,
0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,
0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1,
0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1,
0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,
0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40,
0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1,
0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,
0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40,
0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,
0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,
0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,
0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,
0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40,
0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1,
0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,
0x80, 0x41, 0x00, 0xC1, 0x81, 0x40
};
/* Table of CRC values for low-order byte */
static const uint8_t table_crc_lo[] = {
0x00, 0xC0, 0xC1, 0x01, 0xC3, 0x03, 0x02, 0xC2, 0xC6, 0x06,
0x07, 0xC7, 0x05, 0xC5, 0xC4, 0x04, 0xCC, 0x0C, 0x0D, 0xCD,
0x0F, 0xCF, 0xCE, 0x0E, 0x0A, 0xCA, 0xCB, 0x0B, 0xC9, 0x09,
0x08, 0xC8, 0xD8, 0x18, 0x19, 0xD9, 0x1B, 0xDB, 0xDA, 0x1A,
0x1E, 0xDE, 0xDF, 0x1F, 0xDD, 0x1D, 0x1C, 0xDC, 0x14, 0xD4,
0xD5, 0x15, 0xD7, 0x17, 0x16, 0xD6, 0xD2, 0x12, 0x13, 0xD3,
0x11, 0xD1, 0xD0, 0x10, 0xF0, 0x30, 0x31, 0xF1, 0x33, 0xF3,
0xF2, 0x32, 0x36, 0xF6, 0xF7, 0x37, 0xF5, 0x35, 0x34, 0xF4,
0x3C, 0xFC, 0xFD, 0x3D, 0xFF, 0x3F, 0x3E, 0xFE, 0xFA, 0x3A,
0x3B, 0xFB, 0x39, 0xF9, 0xF8, 0x38, 0x28, 0xE8, 0xE9, 0x29,
0xEB, 0x2B, 0x2A, 0xEA, 0xEE, 0x2E, 0x2F, 0xEF, 0x2D, 0xED,
0xEC, 0x2C, 0xE4, 0x24, 0x25, 0xE5, 0x27, 0xE7, 0xE6, 0x26,
0x22, 0xE2, 0xE3, 0x23, 0xE1, 0x21, 0x20, 0xE0, 0xA0, 0x60,
0x61, 0xA1, 0x63, 0xA3, 0xA2, 0x62, 0x66, 0xA6, 0xA7, 0x67,
0xA5, 0x65, 0x64, 0xA4, 0x6C, 0xAC, 0xAD, 0x6D, 0xAF, 0x6F,
0x6E, 0xAE, 0xAA, 0x6A, 0x6B, 0xAB, 0x69, 0xA9, 0xA8, 0x68,
0x78, 0xB8, 0xB9, 0x79, 0xBB, 0x7B, 0x7A, 0xBA, 0xBE, 0x7E,
0x7F, 0xBF, 0x7D, 0xBD, 0xBC, 0x7C, 0xB4, 0x74, 0x75, 0xB5,
0x77, 0xB7, 0xB6, 0x76, 0x72, 0xB2, 0xB3, 0x73, 0xB1, 0x71,
0x70, 0xB0, 0x50, 0x90, 0x91, 0x51, 0x93, 0x53, 0x52, 0x92,
0x96, 0x56, 0x57, 0x97, 0x55, 0x95, 0x94, 0x54, 0x9C, 0x5C,
0x5D, 0x9D, 0x5F, 0x9F, 0x9E, 0x5E, 0x5A, 0x9A, 0x9B, 0x5B,
0x99, 0x59, 0x58, 0x98, 0x88, 0x48, 0x49, 0x89, 0x4B, 0x8B,
0x8A, 0x4A, 0x4E, 0x8E, 0x8F, 0x4F, 0x8D, 0x4D, 0x4C, 0x8C,
0x44, 0x84, 0x85, 0x45, 0x87, 0x47, 0x46, 0x86, 0x82, 0x42,
0x43, 0x83, 0x41, 0x81, 0x80, 0x40
};
/* Define the slave ID of the remote device to talk in master mode or set the
* internal slave ID in slave mode */
static int _modbus_set_slave(modbus_t *ctx, int slave)
{
/* Broadcast address is 0 (MODBUS_BROADCAST_ADDRESS) */
if (slave >= 0 && slave <= 247) {
ctx->slave = slave;
} else {
errno = EINVAL;
return -1;
}
return 0;
}
/* Builds a RTU request header */
static int _modbus_rtu_build_request_basis(modbus_t *ctx, int function,
int addr, int nb,
uint8_t *req)
{
assert(ctx->slave != -1);
req[0] = ctx->slave; //从设备ID
req[1] = function; //功能码
req[2] = addr >> 8; //地址高位
req[3] = addr & 0x00ff; //地址低位
req[4] = nb >> 8; //数量高位
req[5] = nb & 0x00ff; //数量低位
return _MODBUS_RTU_PRESET_REQ_LENGTH;
}
/* Builds a RTU response header */
static int _modbus_rtu_build_response_basis(sft_t *sft, uint8_t *rsp)
{
/* In this case, the slave is certainly valid because a check is already
* done in _modbus_rtu_listen */
rsp[0] = sft->slave;
rsp[1] = sft->function;
return _MODBUS_RTU_PRESET_RSP_LENGTH;
}
static uint16_t crc16(uint8_t *buffer, uint16_t buffer_length)
{
uint8_t crc_hi = 0xFF; /* high CRC byte initialized */
uint8_t crc_lo = 0xFF; /* low CRC byte initialized */
unsigned int i; /* will index into CRC lookup */
/* pass through message buffer */
while (buffer_length--) {
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