crctest.c

一种crc的写法已经测试

//与富马一致得校验
unsigned short CalcCRC16(unsigned char * pPtr,unsigned int nCount)
{
	unsigned short  wCRC,i;
	wCRC = 0;

	while (nCount > 0)
	{
		nCount--; 
		wCRC = wCRC ^ (unsigned short)(0xFF&*pPtr++);
		for (i=0; i<8; i++)
		{
			if (wCRC & 0x0001)
				wCRC = wCRC >> 1 ^ 0x8408;
			else
				wCRC = wCRC >> 1;
		}
	}
	wCRC = (wCRC<< 8) | ((wCRC >> 8) & 0xFF);
    return wCRC;
}

//ok 
int main(void)
{

 	unsigned char beforecrc[20];
    unsigned char  aftercrc[20];
   // Cmd[0]=0x7E;
   unsigned int len;
   unsigned short crc;
   int i;
   crc=0;
    
   len=10;
 						beforecrc[0]=1;
						beforecrc[1]=1;
						beforecrc[2]=1;
						beforecrc[3]=1;
						beforecrc[4]=0;
						beforecrc[5]=0;
						beforecrc[6]=0x21;
						
						beforecrc[7]=0;//if success set 0; or set not 0;
						
						beforecrc[8]=0;
						beforecrc[9]=0;
    printf("test the function of crc :: \n");
    printf("Befor crc:: \n");	
      if(len>0)
    {
        for(i=0;i<len;i++)
        printf("*%2X*",beforecrc[i]);
    }
    
    crc=CalcCRC16(beforecrc,len);
    beforecrc[11]=crc%256;
    beforecrc[10]=crc/256;
    
    
    printf("After crc:: \n");	
    len=len+2;
      if(len>0)
    {
        for(i=0;i<len;i++)
        printf("*%2X*",beforecrc[i]);
    }
    
    return 1;
}