TrainCamp_lipengpeng_Modbus/crc.cpp

#include "crc.h"

quint16 CalculateCrc(const QByteArray &data)
{
    quint16 crc = 0xFFFF;  // MODBUS初始值
    const quint16 polynomial = 0xA001;  // MODBUS多项式（0x8005的反转）

    for (int i = 0; i < data.size(); ++i)
    {
        crc ^= static_cast<quint8>(data.at(i));

        for (int bit = 0; bit < 8; ++bit)
        {
            if (crc & 0x0001)
            {  // 检查最低位
                crc = (crc >> 1) ^ polynomial;  // 右移并异或
            } else
            {
                crc >>= 1;  // 仅右移
            }
        }
    }
    return crc;
}

bool CrcCheck(const QByteArray &data)
{
    //首先对接收报文的长度进行检验
    if (data.size() < 3)
    {
        return false;
    }
    //对接收的报文进行CRC校验
    QByteArray payload = data.left(data.length() - 2);

    //分离接收值的crc校验位
    quint8 receivedCrcLow = static_cast<quint8>(data.at(data.length() - 2));
    quint8 receivedCrcHigh = static_cast<quint8>(data.at(data.length() - 1));

    //计算返回的报文的crc
    quint16 crc = CalculateCrc(payload);
    quint8 calcCrcLow = crc & 0xFF;
    quint8 calcCrcHigh = (crc >> 8) & 0xFF;

    //比较计算的crc值和接收到的crc值是否一致
    if(calcCrcLow == receivedCrcLow && calcCrcHigh == receivedCrcHigh)
    {
        return true;
    }
    else
    {
        return false;
    }
}