嵌入式开源库之libmodbus学习笔记

socat

1. 安装sudo apt-get install socat
2. 创建终端 socat -d -d pty,b115200 pty,b115200
3. 查看终端 ls /dev/pts/

minicom

1. 安装 sudo apt-get install minicom
2. 链接虚拟终端 sudo minicom -D /dev/pts/3
3. 以十六进制显示 minicom -D /dev/pts/1 -H
4. 设置波特率 minicom -D /dev/pts/1 -b B115200
5. 设置回显 Ctrl+A->Z->E
6. 设置自动换行 Ctrl+A->W
7. 清屏 Ctrl+A->C
8. 退出 Ctrl+A->X

交叉编译

1. 生成配置文件./autogen.sh
2. 配置./configure --host=arm-linux-gnueabihf --prefix=$(pwd)/__install
3. 编译 make(如果遇到C++版本问题请升级交叉编译器)
4. 安装 make install
5. 查看生成的库文件类型file libmodbus.so.5.1.0
libmodbus.so.5.1.0: ELF 32-bit LSB shared object, ARM, EABI5 version 1 (SYSV), dynamically linked, BuildID[sha1]=d30e9af8a0ccc675f8549abbfa88e8df5574b196, with debug_info, not stripped
6. 将库文件放到开发板的库文件目录下
   cd /usr/lib
mv /root/libmodbus.so.5.1.0 ./
7. 创建软连接
   ln -s libmodbus.so.5.1.0 libmodbus.so.5

./libmodbus.exe: /lib/libstdc++.so.6: version `GLIBCXX_3.4.21’ not found (required by ./libmodbus.exe)

Ubuntu编译

/usr/bin/ld: 找不到 -lmodbus collect2: error: ld returned 1 exit status

./a.out: error while loading shared libraries: libmodbus.so.5: cannot open shared object file: No such file or directory

将库文件的路径添加到 /etc/ld.so.conf 文件中，并运行 sudo ldconfig 命令来更新库缓存。例如，如果库文件位于 /home/lux/OpenSource/libmodbus/__install/lib 目录中，您可以将以下行添加到 /etc/ld.so.conf 文件的末尾：
/home/lux/OpenSource/libmodbus/__install/lib
保存文件后，运行 sudo ldconfig 命令。

测试

tcp_client

#include "modbus_tcp.hpp"
#include <unistd.h>int main(int argc, char *argv[])
{uint8_t read_buffer[1024];uint8_t write_buffer[1024];uint16_t read_buffer_16[3];uint16_t write_buffer_16[1024];uint8_t ret = 0;modbus::modbus_tcp modbus("192.168.2.200",60000);  //创建一个modbus_tcp对象for (int i = 0; i < 10; i++){ret = modbus.read_coil_status(0x0000, 5, read_buffer);//00 01 00 00 00 06 01   01 67 89 00 05 if (ret > 0){printf("read_coil_status:%d\r\n",ret);for (int j = 0; j < ret; j++){printf("%02x ",read_buffer[j]);}printf("\r\n");}usleep(1000*100);ret = modbus.read_input_status(0x0000, 5, read_buffer);//00 01 00 00 00 06 01    01 67 89 00 05 if (ret > 0){printf("read_input_status:%d\r\n",ret);for (int j = 0; j < ret; j++){printf("%02x ",read_buffer[j]);}printf("\r\n");}usleep(1000*100);ret = modbus.read_holding_register(0x0000, 5, read_buffer_16);//00 01 00 00 00 06 01   01 67 89 00 05if (ret > 0){printf("read_holding_register:%d\r\n",ret); for (int j = 0; j < ret; j++){printf("%02x ",read_buffer_16[j]);}printf("\r\n");}usleep(1000*100);ret = modbus.read_input_register(0x0000, 5, read_buffer_16);//00 01 00 00 00 06 01    04 67 89 00 05  if (ret > 0){printf("read_input_register:%d\r\n",ret);for (int j = 0; j < ret; j++){printf("%02x ",read_buffer_16[j]);}printf("\r\n");}usleep(1000*100);// printf("write_single_coil:%d\r\n",modbus.write_single_coil(0x0000, 0x1234));// usleep(1000*100);// printf("write_single_register:%d\r\n",modbus.write_single_register(0x0000, 0x1234));//0x06：写单个保持寄存器: 00 01 00 00 00 06 01    06 67 89 12 34// usleep(1000*100);// printf("write_multiple_coil:%d\r\n",modbus.write_multiple_coil(0x0000, 5, write_buffer));//0x0F（15）：写多个线圈: 00 01 00 00 00 08 01     0F 67 89 00 05 01 1F// usleep(1000*100);// printf("write_multiple_registers:%d\r\n",modbus.write_multiple_registers(0x0000, 5,  write_buffer_16));//0x10（16）：写多个保持寄存器: 00 01 00 00 00 11 01   10 67 89 00 05 0A 00 00 00 00 00 00 00 00 00 05 // usleep(1000*100);}usleep(1000*500);
}

modbus_slave