单片机模块化程序: CRC校验
前言
这一节说明一下数据传输中常用的CRC校验
所谓CRC校验,说白了就是对数据做下计算,然后把计算结果放到最后面
平时用的最多的算是CRC16
直接上菜
计算CRC
/**
* @brief calculate CRC
* @param *modbusdata: Source data address
* @param length: data length
* @param
* @retval CRC16 Value
* @example
**/
int crc16_modbus(u8 *modbusdata, int length)
{
int i, j;
int crc = 0xffff;//0xffff or 0
for (i = 0; i < length; i++)
{
crc ^= modbusdata[i];
for (j = 0; j < 8; j++)
{
if ((crc & 0x01) == 1)
{
crc = (crc >> 1) ^ 0xa001;
}
else
{
crc >>= 1;
}
}
}
return crc;
}
判断接收的数据CRC是否正确
/**
* @brief check CRC for data
* @param *modbusdata: Read data address
* @param length: Read data length
* @param
* @retval 1:CRC16 OK
* @example
**/
int crc16_flage(u8 *modbusdata, int length)
{
int Receive_CRC=0,calculation=0;
if(length<=2)
{
return 0;
}
Receive_CRC = crc16_modbus(modbusdata, length-2);
calculation = modbusdata[length-2];
calculation <<= 8;
calculation += modbusdata[length-1];
if(calculation != Receive_CRC)
{
return 0;
}
return 1;
}
发送的数据加上CRC
我想发送 01 00 55 aa 数据
最终发送的数据
说明:
1.最后两位 F7 和 BE就是经过CRC16计算之后的数据;高位在前,低位在后
2.整个数据发给另一个设备以后,另一个设备用同样的方式计算 01 00 55 aa 的CRC16值
然后判断下自己计算的值是不是 F7,BE
判断接收的数据CRC是否正确
上位机(C# / JAVA)CRC16校验程序
/// <summary>
/// calculate CRC
/// </summary>
/// <param name="modbusdata">Source data address</param>
/// <param name="length">data length</param>
/// <returns></returns>
private int crc16_modbus(byte[] modbusdata, int length)
{
int i, j;
int crc = 0xffff; //0xffff or 0
try
{
for (i = 0; i < length; i++)
{
crc ^= modbusdata[i]&0xff;
for (j = 0; j < 8; j++)
{
if ((crc & 0x01) == 1)
{
crc = (crc >> 1) ^ 0xa001;
}
else
{
crc >>= 1;
}
}
}
}
catch (Exception)
{
throw;
}
return crc;
}
/// <summary>
///
/// </summary>
/// <param name="modbusdata"></param>
/// <param name="length"></param>
/// <returns></returns>
private int crc16_flage(byte[] modbusdata, int length)
{
int Receive_CRC = 0, calculation = 0;//接收到的CRC,计算的CRC
if(length<=2) return 0;
Receive_CRC = crc16_modbus(modbusdata, length-2);
calculation = modbusdata[length -2];
calculation <<= 8;
calculation += modbusdata[length-1];
if (calculation != Receive_CRC)
{
return 0;
}
return 1;
}
注:对于上位机byte类型需要&0xff
JavaScript CRC校验
crc16_modbus :function (modbusdata,length) { let i=0, j=0; let crc = 0xffff;//0xffff or 0 for (i = 0; i < length; i++){ crc = crc ^ modbusdata[i]&0xff; for (j = 0; j < 8; j++){ if ((crc & 0x01) == 1){ crc = (crc >> 1) ^ 0xa001; } else{ crc = crc >> 1; } } } // let car_hi = ((crc & 0xFF00) >> 8); //高位置 // let car_lo = (crc & 0x00FF); //低位置 // return [car_hi, car_lo];//返回一个2维数组 return crc;//返回crc校验的数据 },
扩展
大部分设备的CRC16计算方式,这个地方是 0xffff, 但是也有0的情况
补充(查表法)
const char crctableh[] = { 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40 }; const char crctablel[] = { 0x00, 0xC0, 0xC1, 0x01, 0xC3, 0x03, 0x02, 0xC2, 0xC6, 0x06, 0x07, 0xC7, 0x05, 0xC5, 0xC4, 0x04, 0xCC, 0x0C, 0x0D, 0xCD, 0x0F, 0xCF, 0xCE, 0x0E, 0x0A, 0xCA, 0xCB, 0x0B, 0xC9, 0x09, 0x08, 0xC8, 0xD8, 0x18, 0x19, 0xD9, 0x1B, 0xDB, 0xDA, 0x1A, 0x1E, 0xDE, 0xDF, 0x1F, 0xDD, 0x1D, 0x1C, 0xDC, 0x14, 0xD4, 0xD5, 0x15, 0xD7, 0x17, 0x16, 0xD6, 0xD2, 0x12, 0x13, 0xD3, 0x11, 0xD1, 0xD0, 0x10, 0xF0, 0x30, 0x31, 0xF1, 0x33, 0xF3, 0xF2, 0x32, 0x36, 0xF6, 0xF7, 0x37, 0xF5, 0x35, 0x34, 0xF4, 0x3C, 0xFC, 0xFD, 0x3D, 0xFF, 0x3F, 0x3E, 0xFE, 0xFA, 0x3A, 0x3B, 0xFB, 0x39, 0xF9, 0xF8, 0x38, 0x28, 0xE8, 0xE9, 0x29, 0xEB, 0x2B, 0x2A, 0xEA, 0xEE, 0x2E, 0x2F, 0xEF, 0x2D, 0xED, 0xEC, 0x2C, 0xE4, 0x24, 0x25, 0xE5, 0x27, 0xE7, 0xE6, 0x26, 0x22, 0xE2, 0xE3, 0x23, 0xE1, 0x21, 0x20, 0xE0, 0xA0, 0x60, 0x61, 0xA1, 0x63, 0xA3, 0xA2, 0x62, 0x66, 0xA6, 0xA7, 0x67, 0xA5, 0x65, 0x64, 0xA4, 0x6C, 0xAC, 0xAD, 0x6D, 0xAF, 0x6F, 0x6E, 0xAE, 0xAA, 0x6A, 0x6B, 0xAB, 0x69, 0xA9, 0xA8, 0x68, 0x78, 0xB8, 0xB9, 0x79, 0xBB, 0x7B, 0x7A, 0xBA, 0xBE, 0x7E, 0x7F, 0xBF, 0x7D, 0xBD, 0xBC, 0x7C, 0xB4, 0x74, 0x75, 0xB5, 0x77, 0xB7, 0xB6, 0x76, 0x72, 0xB2, 0xB3, 0x73, 0xB1, 0x71, 0x70, 0xB0, 0x50, 0x90, 0x91, 0x51, 0x93, 0x53, 0x52, 0x92, 0x96, 0x56, 0x57, 0x97, 0x55, 0x95, 0x94, 0x54, 0x9C, 0x5C, 0x5D, 0x9D, 0x5F, 0x9F, 0x9E, 0x5E, 0x5A, 0x9A, 0x9B, 0x5B, 0x99, 0x59, 0x58, 0x98, 0x88, 0x48, 0x49, 0x89, 0x4B, 0x8B, 0x8A, 0x4A, 0x4E, 0x8E, 0x8F, 0x4F, 0x8D, 0x4D, 0x4C, 0x8C, 0x44, 0x84, 0x85, 0x45, 0x87, 0x47, 0x46, 0x86, 0x82, 0x42, 0x43, 0x83, 0x41, 0x81, 0x80, 0x40 }; int crc16_modbus(unsigned char *modbusdata, int length) { unsigned char crch = 0xff; unsigned char crcl = 0xff; int index; while (length--) { index = crcl ^ *modbusdata++; crcl = crch ^ crctableh[index]; crch = crctablel[index]; } return (crch << 8 | crcl); }
