摘要：
RS-485是一种半双工通信协议，通常用于工业控制模块之间的通信。由于其传输距离长，不容易出错，因此被广泛使用。这是Windows下的示例。Linux需要进行相应的修改。
RS-485是一种半双工的通信协议，经常用于工业控制模块间的通信，因其传输距离远，不容易出错的特点，应用广泛。
此为windows下示例，linux需做相应修改。
#pragma once #include <windows.h> #include <stdio.h> #include <stdlib.h> class Net485 { public: Net485(long baud_rate, wchar_t* port_name); bool send(BYTE data[], int length); protected: void set_up_serial_port(long baud); private: HANDLE serial_port; }; #include "Net485.h" #include <iostream> Net485::Net485(long baud_rate, wchar_t* port_name) { const wchar_t name[8] = L"COM4"; serial_port = CreateFile(name, GENERIC_READ | GENERIC_WRITE, 0, 0, OPEN_EXISTING, 0, 0); if (serial_port == INVALID_HANDLE_VALUE) { fprintf(stderr, "Error opening portn"); CloseHandle(serial_port); } else { set_up_serial_port(baud_rate); } } bool Net485::send(BYTE data[],int length) { if (serial_port == INVALID_HANDLE_VALUE) { printf("发送失败::INVALID_HANDLE_VALUE"); return false; } DWORD dwTx = 0; BOOL ret = FALSE; DWORD dwLength = length; Sleep(10); if (dwLength > 0) { ret = WriteFile(serial_port, data, dwLength, &dwTx, NULL); if (ret == FALSE) { printf("发送失败"); return false; } } return true; } void Net485::set_up_serial_port(long baud) { DCB properties; // 设置读写缓冲区 GetCommState(serial_port, &properties); switch (baud) { case 1200: properties.BaudRate = CBR_1200; break; case 2400: properties.BaudRate = CBR_2400; break; case 4800: properties.BaudRate = CBR_4800; break; case 9600: properties.BaudRate = CBR_9600; break; case 14400: properties.BaudRate = CBR_14400; break; case 19200: properties.BaudRate = CBR_19200; break; case 38400: properties.BaudRate = CBR_38400; break; default: fprintf(stderr, "Invalid baud rate: %ldn", baud); exit(0); break; } properties.Parity = NOPARITY; properties.ByteSize = 8; properties.StopBits = ONESTOPBIT; SetCommState(serial_port, &properties); //在读写串口前，用 PurgeComm 函数清空缓冲区 PurgeComm(serial_port, PURGE_RXCLEAR | PURGE_TXCLEAR | PURGE_TXABORT | PURGE_TXABORT); return; }
使用示例
/// 485PLC通信 Net485* net = new Net485(9600,L"COM4"); BYTE data[2]; data[0] = 0x01; if (info.th == 1) { data[1] = 0x11; } else { data[1] = 0x12; } net->send(data,sizeof(data));