哪位告诉一下CRC校验！！！给我解释一下这个吧。

只看该作者 · 2010-9-3 18:22

/************************************************************************/
/************************CRC高位和地位字节值表***************************/
uchar code  chCRCHTalbe[] =                               // CRC 高位字节值表
{
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
};
uchar code chCRCLTalbe[] =                               // CRC 低位字节值表
{
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
};

/************************************************************************/
/***************************CRC校验**************************************/
int CRC16_1(char* pchMsg, int wDataLen)
{
uchar chCRCHi = 0xFF; // 高CRC字节初始化
uchar chCRCLo = 0xFF; // 低CRC字节初始化
int wIndex;          // CRC循环中的索引

while (wDataLen--)
{
  // 计算CRC
  wIndex = chCRCLo ^ *pchMsg++ ;
  chCRCLo = chCRCHi ^ chCRCHTalbe[wIndex];
  chCRCHi = chCRCLTalbe[wIndex] ;
}

return ((chCRCHi << 8) | chCRCLo) ;
}
。。
void uart2_pro()
{
int crc2=0;
int crc3=0;
uchar k=0;
k=S2CON;
k=k&0x01;//串口2的接收标志位
if((k)&&(shuju_finish_flag==0))
{
  rec_485[i_485] =S2BUF;
  i_485++;
  if(i_485==21)//(收到21个返回的数据然后进行数据处理)
  {
i_485=0;
crc2=CRC16_1(rec_485,19);//计算所收到的前19个数据的crc校验码
crc3=rec_485[19]+(rec_485[20]*256);//所得到的crc校验码
if(crc2==crc3)//相等则说明接收数据没错误
{
。。
其中crc2=crc3中的crc3不懂怎么回事，哪位告诉一下吧。。。。。。。

2万 · 2010-9-3 20:40

CRC3是源数据包里的CRC域通过在本地对数据包的数据域进行CRC计算然后与源数据的CRC域作比较相等表示校验通过
至于为什么是
crc3=rec_485[19]+(rec_485[20]*256);//所得到的crc校验码
那是由通讯协定决定的数据打包的时候把CRC结果的高8位放在rec_485[20] 低八位放在rec_485[19]

只看该作者 · 2010-9-3 20:59

2# 原野之狼
您好我还想问一下，关于发出来的时候源数据包里的CRC域第19和20个数怎么计算啊！！！我也是刚学单片机不久的小新手请教了

2万 · 2010-9-3 21:52

由源数据端设备根据CRC算法计算出来的

2万 · 2010-9-3 22:01

这是个crc16，前19个字节的crc结果为crc2，crc3是应该得到的校验和，若相等表示数据传送正确。假如把19改为21，则crc2应该为0，则crc3就是多余的。

2万 · 2010-9-3 22:12

最后两个字节就是crc3。

2万 · 2010-9-5 12:28

http://www.hotpower.org/HotAjax/HotPower_HotAjax.html

//CRC位域8表(小端):
const unsigned int CRCR16_A001_Table[256] = {
  0x0000,0xC0C1,0xC181,0x0140,0xC301,0x03C0,0x0280,0xC241,0xC601,0x06C0,0x0780,0xC741,0x0500,0xC5C1,0xC481,0x0440,
  0xCC01,0x0CC0,0x0D80,0xCD41,0x0F00,0xCFC1,0xCE81,0x0E40,0x0A00,0xCAC1,0xCB81,0x0B40,0xC901,0x09C0,0x0880,0xC841,
  0xD801,0x18C0,0x1980,0xD941,0x1B00,0xDBC1,0xDA81,0x1A40,0x1E00,0xDEC1,0xDF81,0x1F40,0xDD01,0x1DC0,0x1C80,0xDC41,
  0x1400,0xD4C1,0xD581,0x1540,0xD701,0x17C0,0x1680,0xD641,0xD201,0x12C0,0x1380,0xD341,0x1100,0xD1C1,0xD081,0x1040,
  0xF001,0x30C0,0x3180,0xF141,0x3300,0xF3C1,0xF281,0x3240,0x3600,0xF6C1,0xF781,0x3740,0xF501,0x35C0,0x3480,0xF441,
  0x3C00,0xFCC1,0xFD81,0x3D40,0xFF01,0x3FC0,0x3E80,0xFE41,0xFA01,0x3AC0,0x3B80,0xFB41,0x3900,0xF9C1,0xF881,0x3840,
  0x2800,0xE8C1,0xE981,0x2940,0xEB01,0x2BC0,0x2A80,0xEA41,0xEE01,0x2EC0,0x2F80,0xEF41,0x2D00,0xEDC1,0xEC81,0x2C40,
  0xE401,0x24C0,0x2580,0xE541,0x2700,0xE7C1,0xE681,0x2640,0x2200,0xE2C1,0xE381,0x2340,0xE101,0x21C0,0x2080,0xE041,
  0xA001,0x60C0,0x6180,0xA141,0x6300,0xA3C1,0xA281,0x6240,0x6600,0xA6C1,0xA781,0x6740,0xA501,0x65C0,0x6480,0xA441,
  0x6C00,0xACC1,0xAD81,0x6D40,0xAF01,0x6FC0,0x6E80,0xAE41,0xAA01,0x6AC0,0x6B80,0xAB41,0x6900,0xA9C1,0xA881,0x6840,
  0x7800,0xB8C1,0xB981,0x7940,0xBB01,0x7BC0,0x7A80,0xBA41,0xBE01,0x7EC0,0x7F80,0xBF41,0x7D00,0xBDC1,0xBC81,0x7C40,
  0xB401,0x74C0,0x7580,0xB541,0x7700,0xB7C1,0xB681,0x7640,0x7200,0xB2C1,0xB381,0x7340,0xB101,0x71C0,0x7080,0xB041,
  0x5000,0x90C1,0x9181,0x5140,0x9301,0x53C0,0x5280,0x9241,0x9601,0x56C0,0x5780,0x9741,0x5500,0x95C1,0x9481,0x5440,
  0x9C01,0x5CC0,0x5D80,0x9D41,0x5F00,0x9FC1,0x9E81,0x5E40,0x5A00,0x9AC1,0x9B81,0x5B40,0x9901,0x59C0,0x5880,0x9841,
  0x8801,0x48C0,0x4980,0x8941,0x4B00,0x8BC1,0x8A81,0x4A40,0x4E00,0x8EC1,0x8F81,0x4F40,0x8D01,0x4DC0,0x4C80,0x8C41,
  0x4400,0x84C1,0x8581,0x4540,0x8701,0x47C0,0x4680,0x8641,0x8201,0x42C0,0x4380,0x8341,0x4100,0x81C1,0x8081,0x4040
};
//CRC位域8查表算法(小端):
unsigned int GetCRCR16_A001_FFFF_0000_Table(unsigned char *crcBuff, unsigned char crcLen) {
unsigned char i;
unsigned int crc = 0xFFFF;
  for(i = 0; i < crcLen; i ++) {
crc = (crc >> 8) ^ CRCR16_A001_Table[(crc & 0xFF) ^ crcBuff];
  }
  return crc;
}
void main() {
const unsigned char dataTable[] = "\x01\x23\x45\x67\x89\xAB\xCD\xEF";
unsigned int crc;
  crc = GetCRCR16_A001_FFFF_0000_Table((unsigned char *)dataTable, sizeof(dataTable) - 1);
  while(1);
}

2万 · 2010-9-5 12:29

http://www.hotpower.org/HotAjax/HotPower_HotAjax.html

//CRC位域4表(小端):
const unsigned int CRCR16_A001_Table[16] = {
  0x0000,0xCC01,0xD801,0x1400,0xF001,0x3C00,0x2800,0xE401,0xA001,0x6C00,0x7800,0xB401,0x5000,0x9C01,0x8801,0x4400
};
//CRC位域4查表算法(小端):
unsigned int GetCRCR16_A001_FFFF_0000_Table(unsigned char *crcBuff, unsigned char crcLen) {
unsigned char i;
unsigned int crc = 0xFFFF;
unsigned char crcTemp;
  for(i = 0; i < (crcLen * 2); i ++) {
if (i & 1) crcTemp = crcBuff[i >> 1] >> 4;
else crcTemp = crcBuff[i >> 1] & 0x0F;
crc = (crc >> 4) ^ CRCR16_A001_Table[(crc & 0x0F) ^ crcTemp];
  }
  return crc;
}
void main() {
const unsigned char dataTable[] = "\x01\x23\x45\x67\x89\xAB\xCD\xEF";
unsigned int crc;
  crc = GetCRCR16_A001_FFFF_0000_Table((unsigned char *)dataTable, sizeof(dataTable) - 1);
  while(1);
}

哪位告诉一下CRC校验！！！给我解释一下这个吧。

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