crc16.c

dsp tmslf2407a 汇编,c的原代码,包括i2c,scitimer,fir等的很多程序.

#include "typedef.h" 
#include "global.h" 
extern uchar deviceAddr;     
extern uchar pcdata[Len];

#define POLYNOMIAL  0x8408   /*x^16+x^12+x^5+1*/
#define PRESET_VALUE 0xFFFF
#define CHECK_VALUE 0xF0B8
#define CALC_CRC     1
#define CHECK_CRC    0  


uchar crc16Calculate(uchar *pBuf, uchar byLen);  
uchar verifyType();   
uchar chkCRC_re(uchar * cBuf,uchar cLen);

/*
	计算字符数组的CRC校验，pBuf 为字符数组首地址，byLen为长度
*/
uchar crc16Calculate(uchar *pBuf, uchar byLen)
{
	unsigned int current_crc_value;
	uchar i,j; 	 

 	current_crc_value = PRESET_VALUE;
 	for(i=0;i<byLen;i++)
  	{   
  		current_crc_value = current_crc_value^pBuf[i];
	   	for(j=0;j<8;j++)
   		{
     			if(current_crc_value & 0x0001)     			
       				current_crc_value = (current_crc_value>>1)^POLYNOMIAL;      		
     			else      		
        			current_crc_value = (current_crc_value>>1);      		
    		}   
	}
	current_crc_value = ~current_crc_value;		
 	return(current_crc_value);
}    
 
uchar verifyType()  
{               
   	uchar type;
   	
   	if( deviceAddr == pcdata[1] ){ type = 1;} 	/*地址合法*/
   	else if(pcdata[1] == 0xfe)  { type = 2;}     /*广播地址*/
   	else if(pcdata[1] == 0xff)  { type = 3;}     /**/
   	else                        { type = 0;}
	
   	if(type)   	
      		if(!chkCRC_re(pcdata,pcdata[0]))type = 0;      /*CRC校验正确*/	
   	return(type);
}    

uchar chkCRC_re(uchar * cBuf,uchar cLen)
{
   	uchar flag=1 ; 
   	uchar j; 
   	j = ~ crc16Calculate(cBuf,cLen-2);
   	flag  = (cBuf[cLen-2] == (j&0x00ff) );	//crc MSByte
   	flag &= (cBuf[cLen-1] == (j>>8) );	//crc LSByte
   	return(flag);
}