c++ modbus rtu

下面是一个基于C++的Modbus RTU通信代码示例： ```cpp #include <iostream> #include <cstring> #include <cerrno> #include <cstdlib> #include <cstdio> #include <unistd.h> #include <fcntl.h> #include <termios.h> using namespace std; int open_port(const char* port) { int fd = open(port, O_RDWR | O_NOCTTY | O_NDELAY); if (fd == -1) { perror("open_port: Unable to open serial port"); } else { fcntl(fd, F_SETFL, 0); } return (fd); } int set_port(int fd, int baud_rate, int data_bits, int stop_bits, char parity) { struct termios options; if (tcgetattr(fd, &options) == -1) { perror("set_port: Unable to get port settings"); return (-1); } cfsetispeed(&options, baud_rate); cfsetospeed(&options, baud_rate); options.c_cflag |= (CLOCAL | CREAD); options.c_cflag &= ~CSIZE; switch (data_bits) { case 5: options.c_cflag |= CS5; break; case 6: options.c_cflag |= CS6; break; case 7: options.c_cflag |= CS7; break; case 8: options.c_cflag |= CS8; break; default: fprintf(stderr, "Unsupported data size\n"); return (-1); } switch (parity) { case 'n': case 'N': options.c_cflag &= ~PARENB; options.c_iflag &= ~INPCK; break; case 'o': case 'O': options.c_cflag |= (PARODD | PARENB); options.c_iflag |= INPCK; break; case 'e': case 'E': options.c_cflag |= PARENB; options.c_cflag &= ~PARODD; options.c_iflag |= INPCK; break; default: fprintf(stderr, "Unsupported parity\n"); return (-1); } switch (stop_bits) { case 1: options.c_cflag &= ~CSTOPB; break; case 2: options.c_cflag |= CSTOPB; break; default: fprintf(stderr, "Unsupported stop bits\n"); return (-1); } options.c_cc[VTIME] = 0; options.c_cc[VMIN] = 1; tcflush(fd, TCIFLUSH); if (tcsetattr(fd, TCSANOW, &options) == -1) { perror("set_port: Unable to set port settings"); return (-1); } return (0); } int modbus_read_registers(int fd, unsigned char slave_addr, unsigned short start_addr, unsigned short count, unsigned short* values) { unsigned char buf[256]; int i, len; buf[0] = slave_addr; buf[1] = 0x03; buf[2] = start_addr >> 8; buf[3] = start_addr & 0xff; buf[4] = count >> 8; buf[5] = count & 0xff; len = 6; unsigned short crc = 0xFFFF; for (i = 0; i < len; i++) { crc ^= buf[i]; for (int j = 0; j < 8; j++) { if (crc & 1) { crc >>= 1; crc ^= 0xA001; } else { crc >>= 1; } } } buf[len++] = crc & 0xff; buf[len++] = crc >> 8; int n = write(fd, buf, len); if (n != len) { perror("modbus_read_registers: Unable to write to port"); return (-1); } usleep(10000); len = read(fd, buf, 256); if (len < 5) { perror("modbus_read_registers: Error reading from port"); return (-1); } crc = 0xFFFF; for (i = 0; i < len - 2; i++) { crc ^= buf[i]; for (int j = 0; j < 8; j++) { if (crc & 1) { crc >>= 1; crc ^= 0xA001; } else { crc >>= 1; } } } if (crc != (buf[len - 2] | (buf[len - 1] << 8))) { perror("modbus_read_registers: CRC error"); return (-1); } if (buf[1] & 0x80) { perror("modbus_read_registers: Exception response"); return (-1); } for (i = 0; i < count; i++) { values[i] = buf[3 + i * 2] << 8 | buf[4 + i * 2]; } return (0); } int main() { const char* port = "/dev/ttyUSB0"; int baud_rate = B9600; int data_bits = 8; int stop_bits = 1; char parity = 'N'; int fd = open_port(port); if (fd == -1) { return (EXIT_FAILURE); } if (set_port(fd, baud_rate, data_bits, stop_bits, parity) == -1) { return (EXIT_FAILURE); } unsigned short values[256]; if (modbus_read_registers(fd, 1, 0, 10, values) == -1) { return (EXIT_FAILURE); } for (int i = 0; i < 10; i++) { cout << values[i] << endl; } close(fd); return (EXIT_SUCCESS); } ``` 这个代码示例使用Linux系统提供的串口设备文件进行通信，并且实现了读取Modbus RTU从设备的寄存器的功能。需要注意的是，Modbus RTU通信需要进行CRC校验，这个代码示例中使用了一个CRC计算函数来实现校验。在实际使用中，你需要根据自己的具体需求进行修改。

你可以在GitHub上找到一个名为"modbuspp"的C++库，它是用于Modbus TCP客户端协议的库。你可以在这个链接上找到该库的详细信息和使用方法：\[1\]。 此外，你还可以在CSDN博客上找到有关C++ Modbus通信中Long和Float数据解析的实例和教程。这篇博客文章提供了关于如何解析Long和Float数据的详细说明：\[2\]。 Modbus是一种串行通信协议，最初由Modicon于1979年发布，用于可编程逻辑控制器（PLC）的通信。它是工业领域通信协议的行业标准，并且在工业电子设备之间非常常用。Modbus协议在OSI7层模型中位于数据链路层和物理层之间，使用的物理层可以是RS485/RS422/RS232等。Modbus帧格式也有一定的规范和格式要求。如果你需要更多关于Modbus协议的信息，你可以参考相关资料和文档。\[3\] #### 引用[.reference_title] - *1* *2* [【modbus.h使用】C++ Modbus Tcp实例-读写float](https://blog.csdn.net/cxyhjl/article/details/124750399)[target="_blank" data-report-click={"spm":"1018.2226.3001.9630","extra":{"utm_source":"vip_chatgpt_common_search_pc_result","utm_medium":"distribute.pc_search_result.none-task-cask-2~all~insert_cask~default-1-null.142^v91^control_2,239^v3^insert_chatgpt"}} ] [.reference_item] - *3* [modbus rtu协议 认知篇](https://blog.csdn.net/qq_39854159/article/details/123330612)[target="_blank" data-report-click={"spm":"1018.2226.3001.9630","extra":{"utm_source":"vip_chatgpt_common_search_pc_result","utm_medium":"distribute.pc_search_result.none-task-cask-2~all~insert_cask~default-1-null.142^v91^control_2,239^v3^insert_chatgpt"}} ] [.reference_item] [ .reference_list ]