STM32F103的CRC-8校验问题

571420670 · 发表于 2016-4-24 19:25:57

这是别人贴给我的一段CRC-8检验代码，生产多项式为X8+X2+X1+1.但是我看了一下午了整个代码也查了CRC的资料。。。就是没弄明白，有没有大侠能帮忙讲一下。跪谢！！！

unsigned char PEC_calculation(unsigned char pec[])
{
unsigned char crc[6];
unsigned char BitPosition=47;
unsigned char shift;
unsigned char i;
unsigned char j;
unsigned char temp;

do{
      crc[5]=0;    /* Load CRC value 0x000000000107 */
      crc[4]=0;
      crc[3]=0;
      crc[2]=0;
      crc[1]=0x01;
      crc[0]=0x07;
      BitPosition=47;    /* Set maximum bit position at 47 */
      shift=0;
      //Find first 1 in the transmited message
      i=5; /* Set highest index */
      j=0;
      while((pec[i]&(0x80>>j))==0 && i>0)
      {
      BitPosition--;
      if(j<7){ j++; }
      else{ j=0x00; i--;}
      }
shift=BitPosition-8; /*Get shift value for crc value*/

while(shift)
      {
      for(i=5; i<0xFF; i--)
         {
         if((crc[i-1]&0x80) && (i>0)){ temp=1;}
         else{ temp=0;}
         crc[i]<<=1;
         crc[i]+=temp;
         }
      shift--;
      }

      //Exclusive OR between pec and crc
      for(i=0; i<=5; i++){ pec[i] ^=crc[i];}/*End of for*/
}while(BitPosition>8);
return pec[0];