基于51单片机的Modbus通讯Code Example

以下是基于51单片机的Modbus通讯Code Example，代码中使用了Keil C编译器和STC89C52单片机：

#include <reg52.h>

#define SlaveAddress 1      // 从机address
#define FunctionCode 3      // function code
#define RegisterAddress 0   // register address
#define RegisterLength 1    // registerLength

sbit RS485_EN = P2^7;       // RS485芯片使能控制引脚

void delay(unsigned int i)  // 延时函数
{
    while(i--);
}

void UART_Init()            // 串口初始化函数
{
    SCON = 0x50;
    TMOD = 0x20;
    TH1 = 0xFD;
    TL1 = 0xFD;
    TR1 = 1;
}

void SendByte(unsigned char dat)  // send一个byte
{
    SBUF = dat;
    while(TI == 0);
    TI = 0;
}

void SendPacket(unsigned char address, unsigned char function, unsigned char* pData, unsigned char length) // senddata包
{
    unsigned char i, crcHi, crcLo;
    crcHi = 0xFF;
    crcLo = 0xFF;
    SendByte(0xFF);
    SendByte(0xFF);
    SendByte(address);
    SendByte(function);
    SendByte(RegisterAddress / 256);
    SendByte(RegisterAddress % 256);
    SendByte(RegisterLength / 256);
    SendByte(RegisterLength % 256);
    for(i = 0; i < length; i++)
    {
        SendByte(pData[i]);
        crcHi ^= pData[i];
        for(j = 0; j < 8; j++)
        {
            if(crcHi & 0x01)
            {
                crcHi >>= 1;
                crcHi ^= 0xA0;
            }
            else
            {
                crcHi >>= 1;
            }
        }
    }
    SendByte(crcHi);
    SendByte(crcLo);
}

void Modbus() // Modbus主函数
{
    unsigned char data[2] = {0, 0};
    SendPacket(SlaveAddress, FunctionCode, data, RegisterLength);
}

void main()
{
    UART_Init();
    while(1)
    {
        RS485_EN = 0;
        delay(1000);
        Modbus();
        delay(1000);
        RS485_EN = 1;
        delay(1000);
    }
}

注：该代码仅为示例，仅供参考，具体实现需要根据实际需求进行调整。