Windows C语言 Modbus 串口通讯：发送命令帧并接收电压采样值

在Windows系统下，可以使用C语言编写Modbus通讯协议的相关代码，并通过串口发送给电脑设备。以下是一个简单的示例代码：

#include <stdio.h>
#include <stdlib.h>
#include <windows.h>

HANDLE hSerial;

void openSerialPort()
{
    hSerial = CreateFile("COM1", GENERIC_READ | GENERIC_WRITE, 0, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);

    if (hSerial == INVALID_HANDLE_VALUE)
    {
        printf("Failed to open serial port\n");
        exit(1);
    }

    DCB dcbSerialParams = {0};
    dcbSerialParams.DCBlength = sizeof(dcbSerialParams);

    if (!GetCommState(hSerial, &dcbSerialParams))
    {
        printf("Failed to get serial port state\n");
        exit(1);
    }

    dcbSerialParams.BaudRate = CBR_9600;
    dcbSerialParams.ByteSize = 8;
    dcbSerialParams.StopBits = ONESTOPBIT;
    dcbSerialParams.Parity = NOPARITY;

    if (!SetCommState(hSerial, &dcbSerialParams))
    {
        printf("Failed to set serial port state\n");
        exit(1);
    }
}

void closeSerialPort()
{
    CloseHandle(hSerial);
}

void sendModbusCommand(const unsigned char *command, int length)
{
    DWORD bytesWritten;
    WriteFile(hSerial, command, length, &bytesWritten, NULL);
}

void receiveModbusResponse(unsigned char *response, int length)
{
    DWORD bytesRead;
    ReadFile(hSerial, response, length, &bytesRead, NULL);
}

int main()
{
    openSerialPort();

    // 构建要发送的Modbus命令帧
    unsigned char modbusCommand[] = {0x01, 0x03, 0x00, 0x00, 0x00, 0x02, 0xC4, 0x0B};

    sendModbusCommand(modbusCommand, sizeof(modbusCommand));

    // 接收Modbus响应
    unsigned char modbusResponse[256];
    receiveModbusResponse(modbusResponse, sizeof(modbusResponse));

    // 处理Modbus响应，获取电压采样值等信息
    // ...

    closeSerialPort();

    return 0;
}

上述代码通过CreateFile函数打开串口设备，然后使用GetCommState和SetCommState函数配置串口参数，如波特率、数据位、停止位和校验位等。然后，可以通过WriteFile函数将Modbus命令帧发送给串口设备，使用ReadFile函数接收串口设备返回的Modbus响应。最后，可以根据Modbus响应的内容提取所需的电压采样值等信息进行处理。

请注意，上述代码中的串口设备为COM1，可以根据实际情况更改为所需的串口号。