crc8.c

00001 //================ File Despciption =========================================//
00002 //=== File name : crc8.c
00003 //=== 
00004 //#include "crc8.h"
00005 //===========================================================================//
00006 
00007 //================ Index ====================================================//
00008 //
00009 //================ Include Header ===========================================//
00010 //
00011 //================ PUBLIC METHOD ============================================//
00012 // extern function from another file
00013 //
00014 //================ PRIVATE METHOD ===========================================//
00015 // non extern function
00016 //
00017 //================ PUBLIC DATA ==============================================//
00018 // extern data
00019 //
00020 //================ PRIVATE DATA =============================================//
00021 // non extern data
00022 //
00023 //================ PRIVATE DEFINE ===========================================//
00024 //
00025 //================ PRIVATE MACRO ============================================//
00026 //
00027 //================ SOURCE CODE ==============================================//
00028 //
00029     //This procedure calculates the cumulative Dallas Semiconductor
00030 // 1-Wire CRC of all bytes passed to it. The result
00031 //accumulates in the global variable CRC.
00032 const unsigned char crc8_table[256]={
00033 0x00,0x07,0x0E,0x09,0x1C,0x1B,0x12,0x15,0x38,0x3F,0x36,0x31,0x24,0x23,0x2A,0x2D,
00034 0x70,0x77,0x7E,0x79,0x6C,0x6B,0x62,0x65,0x48,0x4F,0x46,0x41,0x54,0x53,0x5A,0x5D,
00035 0xE0,0xE7,0xEE,0xE9,0xFC,0xFB,0xF2,0xF5,0xD8,0xDF,0xD6,0xD1,0xC4,0xC3,0xCA,0xCB,
00036 0x90,0x97,0x9E,0x99,0x8C,0x8B,0x82,0x85,0xA8,0xAF,0xA6,0xA1,0xB4,0xB3,0xBA,0xBD,
00037 0xC7,0xC0,0xC9,0xCE,0xDB,0xDC,0xD5,0xD2,0xFF,0xF8,0xF1,0xF6,0xE3,0xE4,0xED,0xEA,
00038 0xB7,0xB0,0xB9,0xBE,0xAB,0xAC,0xA5,0xA2,0x8F,0x88,0x81,0x86,0x93,0x94,0x9D,0x9A,
00039 0x27,0x20,0x29,0x2E,0x3B,0x3C,0x35,0x32,0x1F,0x18,0x11,0x16,0x03,0x04,0x0D,0x0A,
00040 0x57,0x50,0x59,0x5E,0x4B,0x4C,0x45,0x42,0x6F,0x68,0x61,0x66,0x73,0x74,0x7D,0x7A,
00041 0x89,0x8E,0x87,0x80,0x95,0x92,0x9B,0x9C,0xB1,0xB6,0xBF,0xB8,0xAD,0xAA,0xA3,0xA4,
00042 0xF9,0xFE,0xF7,0xF0,0xE5,0xE2,0xEB,0xEC,0xC1,0xC6,0xCF,0xC8,0xDD,0xDA,0xD3,0xD4,
00043 0x69,0x6E,0x67,0x60,0x75,0x72,0x7B,0x7C,0x51,0x56,0x5F,0x58,0x4D,0x4A,0x43,0x44,
00044 0x19,0x1E,0x17,0x10,0x05,0x02,0x0B,0x0C,0x21,0x26,0x2F,0x28,0x3D,0x3A,0x33,0x34,
00045 0x4E,0x49,0x40,0x47,0x52,0x55,0x5C,0x5B,0x76,0x71,0x78,0x7F,0x6A,0x6D,0x64,0x63,
00046 0x3E,0x39,0x30,0x37,0x22,0x25,0x2C,0x2B,0x06,0x01,0x08,0x0F,0x1A,0x1D,0x14,0x13,
00047 0xAE,0xA9,0xA0,0xA7,0xB2,0xB5,0xBC,0xBB,0x96,0x91,0x98,0x9F,0x8A,0x8D,0x84,0x83,
00048 0xDE,0xD9,0xD0,0xD7,0xC2,0xC5,0xCC,0xCB,0xE6,0xE1,0xE8,0xEF,0xFA,0xFD,0xF4,0xF3
00049 
00050 };
00051 
00052 
00053 inline unsigned char crc8Compute(unsigned char *p,unsigned char length)   
00054 {   
00055     unsigned char crc8;   
00056     unsigned char i;   
00057     unsigned char offset;   
00058    
00059     crc8 = 0;   
00060     for(i = 0; i < length; i++)   
00061     {   
00062         offset = crc8 ^ *(p + i);   
00063         crc8 = crc8_table[offset];   
00064     }   
00065     return crc8;
00066     //return crc8 ^ 0x55;   
00067 }   
00068 /*
00069 * Function: Do_CRC8
00070 * * Description:
00071 * Computes the CRC value given the byte and the old CRC value as a static value
00072 *
00073 * Return Value: CRC value
00074 * Parameters: Input data byte to be CRC'ed
00075 * Remarks:
00076 * uses a table driven method to speed things up.
00077 *
00078 * */
00079 inline unsigned char crc8OneByte(unsigned char xx,unsigned char ucCRC)
00080 {
00081     ucCRC = crc8_table[ucCRC ^ xx];
00082 
00083     return (ucCRC);
00084 }
00085 
00086 unsigned char Crc8(unsigned char* xx,const int size, unsigned char ucCRC)
00087 {
00088 
00089     int i;
00090     for(i=0; i<size; i++)
00091     {
00092         ucCRC=crc8OneByte(xx[i],ucCRC);
00093     }
00094     return ucCRC;
00095 }
00096 //================ END OF FILE ==============================================//
00097 //
00098 
00099