crc8.cpp

00001 /* please read copyright-notice at EOF */
00002 
00003 #include "crc8.h"
00004 
00005 #define CRC8INIT    0x00
00006 #define CRC8POLY    0x18              //0X18 = X^8+X^5+X^4+X^0
00007 
00008 char    crc8 ( char *data_in, int number_of_bytes_to_read )
00009 {
00010     char     crc;
00011     int loop_count;
00012     char  bit_counter;
00013     char  data;
00014     char  feedback_bit;
00015     
00016     crc = CRC8INIT;
00017 
00018     for (loop_count = 0; loop_count != number_of_bytes_to_read; loop_count++)
00019     {
00020         data = data_in[loop_count];
00021         
00022         bit_counter = 8;
00023         do {
00024             feedback_bit = (crc ^ data) & 0x01;
00025     
00026             if ( feedback_bit == 0x01 ) {
00027                 crc = crc ^ CRC8POLY;
00028             }
00029             crc = (crc >> 1) & 0x7F;
00030             if ( feedback_bit == 0x01 ) {
00031                 crc = crc | 0x80;
00032             }
00033         
00034             data = data >> 1;
00035             bit_counter--;
00036         
00037         } while (bit_counter > 0);
00038     }
00039     
00040     return crc;
00041 }
00042 
00043 /*
00044 This code is from Colin O'Flynn - Copyright (c) 2002 
00045 only minor changes by M.Thomas 9/2004
00046 oonverted to mbed library by Erik van Wijk 10/2010
00047 
00048 Permission is hereby granted, free of charge, to any person obtaining a copy of
00049 this software and associated documentation files (the "Software"), to deal in
00050 the Software without restriction, including without limitation the rights to
00051 use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
00052 the Software, and to permit persons to whom the Software is furnished to do so,
00053 subject to the following conditions:
00054 
00055 The above copyright notice and this permission notice shall be included in all
00056 copies or substantial portions of the Software.
00057 
00058 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
00059 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
00060 FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
00061 COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
00062 IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
00063 CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
00064 */