dealchars.c

PIC18F4620、TIS6700下RFID程序

#include "dealchars.h"
////////////////////////////////////////////////////////////////////////
//Cyclic Redundancy Check (CRC). According to ISO/IEC 13239
////////////////////////////////////////////////////////////////////////
uint CRC16CheckSum(uchar *cBuffer,uchar iBufLen) 
{
	uchar i,j;
	uint wCrc = CRC16_PRESET;
	
	for (i=0; i<iBufLen; i++) 
	{
		wCrc ^= (uint)cBuffer[i];
		for (j=0; j<8; j++) 
		{
			if (wCrc & 0x0001)
				wCrc = (uint) (wCrc >> 1) ^ CRC16_POLYNOM;
			else
				wCrc = (uint)(wCrc >> 1);
		}
	}
	wCrc = ~wCrc;
	return wCrc;
}
///////////////////////////////////////////////////////////////////////////////
//Reverse the bits of a byte, 7-0, 6-1, 5-2, 4-3
///////////////////////////////////////////////////////////////////////////////
uchar reverse_byte(uchar original_byte) 
{
	uchar i, ret_byte = 0;
	
	for (i=0; i<8; i++) 
	{
		ret_byte >>= 1;
		if (original_byte & 0x80) 
			ret_byte |= 0x80;
		original_byte <<= 1;
	}	
	return ret_byte;
}
///////////////////////////////////////////////////////////////////////////////
//convers two char to a HEX 
///////////////////////////////////////////////////////////////////////////////
uchar char_to_hex(uchar high_char, uchar low_char)
{
        uchar high_temp,low_temp;
        if(high_char <= 0x39)
        {
              high_temp = high_char - 0x30;
        }
        else
        {
              high_temp = high_char - 0x37;
        }
        if(low_char <= 0x39)
        {
              low_temp = low_char - 0x30;
        }
        else
        {
              low_temp = low_char - 0x37;
        }
        return high_temp*16 +low_temp;
}
///////////////////////////////////////////////////////////////////////////////
//convers HEX to a two char 
///////////////////////////////////////////////////////////////////////////////
uint hex_to_char(uchar a_hex)
{
        uint temp;
        uchar high_temp,low_temp;
        
        high_temp = a_hex/16;
        if(high_temp<=9)
        {
              high_temp += 0x30;
        }
        else
        {
              high_temp += 0x37;
        } 
        
        low_temp = a_hex%16;
        if(low_temp<=9)
        {
              low_temp += 0x30;
        }
        else
        {
              low_temp += 0x37;
        }
        
        temp = (uint)high_temp;
        temp = (temp<<8) + (uint)low_temp;
        return temp;
}