Modbus协议学习第六篇之基于libmodbus库的示例程序（可以联合Modbus模拟仿真软件进行调试）

前置工作

学了这么多Modbus的知识，如果不进行实际的操作，总感觉懂的不透彻。基于此，本篇博文就带各位读者来了解下如何通过编写程序来模拟与Modbus Slave仿真软件的通讯。当然了，这里有两个前提，如下：

1.请确保读者跟随我的第五篇博文进行了同等的操作，编译生成了modbus库。第五篇博文地址：libmodbus库的编译

2.使用VSPD创建一对串口：COM3和COM4。可参考：Modbus poll & slave仿真软件初体验

具体步骤

代码侧具体步骤

1.启动Visual Studio，创建一个新的工程项目:【File】→【New】→【Project】。在弹出的新建对话框左边中选择【Visual C++】→【Win32 Console Application】项，输入你自定义的应用程序名，设置完成后单击【确定】按钮。继续点击下一步后，具体项目配置勾选如下图：

2.工程创建完成后，找到第五篇博客中编译的libmodbus库文件，将之前生成的lib和dll文件以及几个必要的头文件都复制到本项目所在的目录，如图：

3.来到VS的主界面，在项目下的文件夹【源文件】上右键，选择【添加】→【现有项】，在弹出的对话框中，选中modbus.h和modbus.lib文件（按住ctrl键多选），再点击【添加】按钮将这两个文件添加进项目中，如下图所示：

4.添加完之后，我们就可以使用libmodbus库中的各种接口函数了。接下来，我们在【源文件】文件夹上右键，【添加】→【新建项】，添加自己的Demo程序，暂且命名为SimRtuMaster.cpp吧，如下图：

5.现在就可以在SimRtuMaster.cpp中编写程序了，在此将代码分享如下：

#include <stdio.h>
#ifndef _MSC_VER
#include <unistd.h>
#endif#include <string.h>
#include <stdlib.h>
#include <errno.h>#include "modbus.h"#define LOOP           1    //循环次数
#define SERVER_ID     17    //从端设备地址
#define ADDRESS_START  0    //测试寄存器起始地址
#define ADDRESS_END   99    //测试寄存器结束地址int main(void) {modbus_t *ctx;int rc;int nb_fail;int nb_loop;int addr;int nb;uint8_t *tab_rq_bits;		// 用于保存发送或接收的数据uint8_t *tab_rp_bits;uint16_t *tab_rq_registers;uint16_t *tab_rp_registers;uint16_t *tab_rw_rq_registers;// RTUctx = modbus_new_rtu("COM3", 19200, 'N', 8, 1);		// 创建一个RTU类型的容器modbus_set_slave(ctx, SERVER_ID);					// 设置从端地址modbus_set_debug(ctx, TRUE);							// 设置debug模式if (modbus_connect(ctx) == -1)		// 建立连接{fprintf(stderr, "Connection failed: %s\n", modbus_strerror(errno));modbus_free(ctx);return -1;}nb = ADDRESS_END - ADDRESS_START;					// 计算需要测试的寄存器个数// 以下申请内存块用来保存发送和接收各数据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_rq_registers = (uint16_t *)malloc(nb * sizeof(uint16_t));memset(tab_rw_rq_registers, 0, nb * sizeof(uint16_t));nb_loop = nb_fail = 0;while (nb_loop++ < LOOP){// 从起始地址开始顺序测试for (addr = ADDRESS_START; addr < ADDRESS_END; addr++){int i;// 生成随机数, 用于测试for (i = 0; i < nb; i++) {tab_rq_registers[i] = (uint16_t)(65535.0 * rand() / (RAND_MAX + 1.0));tab_rw_rq_registers[i] = ~tab_rq_registers[i];tab_rq_bits[i] = tab_rq_registers[i] % 2;}nb = ADDRESS_END - addr;// 测试线圈寄存器的单个读写rc = modbus_write_bit(ctx, addr, tab_rq_bits[0]);			// 写线圈寄存器if (rc != 1){printf("ERROR modbus_write_bit (%d) \n", rc);printf("Address = %d, value = %d\n", addr, tab_rq_bits[0]);nb_fail++;}else{// 写入之后，再读取并比较rc = modbus_read_bits(ctx, addr, 1, tab_rp_bits);if (rc != 1 || tab_rq_bits[0] != tab_rp_bits[0]){printf("ERROR modbus_read_bits single (%d) \n", rc);printf("address = %d\n", addr);nb_fail++;}}// 测试线圈寄存器的批量读写rc = modbus_write_bits(ctx, addr, nb, tab_rq_bits);if (rc != nb) {printf("ERROR modbus_write_bits (%d) \n", rc);printf("Address = %d, nb = %d\n", addr, nb);nb_fail++;}else {// 写入之后，再读取并比较rc = modbus_read_bits(ctx, addr, nb, tab_rp_bits);if (rc != nb) {printf("ERROR modbus_read_bits\n");printf("Address = %d, nb = %d\n", addr, nb);nb_fail++;}else {// 进行比较for (i = 0; i < nb; i++) {if (tab_rp_bits[i] != tab_rq_bits[i]){printf("ERROR modbus_read_bits\n");printf("Addr = %d, Val = %d (0x%X) != %d (0x%X\n", addr, tab_rq_bits[i], tab_rq_bits[i], tab_rp_bits[i], tab_rp_bits[i]);nb_fail++;}}}}// 测试保持寄存器的单个读写rc = modbus_write_register(ctx, addr, tab_rq_registers[0]);if (rc != 1) {printf("ERROR modbus_write_register (%d) \n", rc);printf("Addr = %d, Val = %d (0x%X) \n", addr, tab_rq_registers[0], tab_rq_registers[0]);nb_fail++;}else {// 写入后进行读取rc = modbus_read_registers(ctx, addr, 1, tab_rp_registers);if (rc != 1) {printf("ERROR modbus_write_registers (%d) \n", rc);printf("Address = %d\n", addr);nb_fail++;}else {// 读取后进行比较if (tab_rq_registers[0] != tab_rp_registers[0]) {printf("ERROR modbus_write_registers\n");printf("Addr = %d, Val = %d (0x%X) != %d (0x%X\n", addr, tab_rq_registers[i], tab_rq_registers[i], tab_rp_registers[i], tab_rp_registers[i]);nb_fail++;}}}// 测试线圈寄存器的批量读写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++;}else {// 进行读取测试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 ( i = 0; i < nb; i++){if (tab_rq_registers[i] != tab_rp_registers[i]) {printf("ERROR modbus_read_registers\n");printf("Addr = %d, Val = %d (0x%X) != %d (0x%X)\n", addr, tab_rq_registers[i], tab_rq_registers[i], tab_rp_registers[i], tab_rp_registers[i]);nb_fail++;}}}}// 功能码23(0x17)读写多个寄存器的测试rc = modbus_write_and_read_registers(ctx,addr, nb, tab_rw_rq_registers,addr, nb, tab_rp_registers);if (rc != nb) {printf("ERROR modbus_write_and_read_registers(%d)\n", rc);printf("Address = %d, nb = %d\n", addr, nb);nb_fail++;}else {for (i = 0; i < nb; i++) {if (tab_rp_registers[i] != tab_rw_rq_registers[i]){printf("ERROR modbus_read_and_write_registers READ\n");printf("Addr = %d, Val = %d (0x%X) != %d (0x%X)\n", addr, tab_rp_registers[i], tab_rw_rq_registers[i], tab_rp_registers[i], tab_rw_rq_registers[i]);nb_fail++;}}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 (i = 0; i < nb; i++){if (tab_rw_rq_registers[i] != tab_rp_registers[i]) {printf("ERROR modbus_read_and_write_registers READ\n");printf("Addr = %d, Val = %d (0x%X) != %d (0x%X)\n", addr, tab_rp_registers[i], tab_rw_rq_registers[i], tab_rp_registers[i], tab_rw_rq_registers[i]);nb_fail++;}}}}}printf("Test: ");if (nb_fail) {printf("%d Fails\n", nb_fail);}else{printf("Success\n");}}// Free the memoryfree(tab_rq_bits);free(tab_rq_bits);free(tab_rq_registers);free(tab_rp_registers);free(tab_rw_rq_registers);// Close the connectionmodbus_close(ctx);modbus_free(ctx);return 0;
}