//--------------------------------------------------------------------------------- 
//crc8校驗程序 
//--------------------------------------------------------------------------------- 
unsigned char crc8(unsigned char *ptr, unsigned char len) 
{ 
unsigned char i; 
unsigned char crc=0; 
while(len--!=0) 
{ 
for(i=1; i!=0; i*=2) 
{ 
if((crc&1)!=0) {crc/=2; crc^=0x8C;} 
else crc/=2; 
if((*ptr&i)!=0) crc^=0x8C; 
} 
ptr++; 
} 
return(crc); 
}