Thomas Ashworth / PololuQik2

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CRC7.cpp@3:01272a06e922, 2014-04-05 (annotated)

Committer:
tashworth
Date:
Sat Apr 05 07:25:28 2014 +0000
Revision:
3:01272a06e922
Parent:
0:511d65ef1276 
4-5-2014

Who changed what in which revision?

UserRevisionLine numberNew contents of line
srsmitherman 0:511d65ef1276 1 /**
srsmitherman 0:511d65ef1276 2 * @file CRC7.cpp
srsmitherman 0:511d65ef1276 3 * @author Edward Wilson (edwilson1989@gmail.com)
srsmitherman 0:511d65ef1276 4 * @date Dec 16, 2010
srsmitherman 0:511d65ef1276 5 * @brief The CRC7 checksum code.
srsmitherman 0:511d65ef1276 6 *
srsmitherman 0:511d65ef1276 7 *
srsmitherman 0:511d65ef1276 8 */
srsmitherman 0:511d65ef1276 9
srsmitherman 0:511d65ef1276 10 #include "CRC7.h"
srsmitherman 0:511d65ef1276 11
srsmitherman 0:511d65ef1276 12 CRC7::CRC7()
srsmitherman 0:511d65ef1276 13 {
srsmitherman 0:511d65ef1276 14 GenerateCRCTable();
srsmitherman 0:511d65ef1276 15
srsmitherman 0:511d65ef1276 16 }
srsmitherman 0:511d65ef1276 17
srsmitherman 0:511d65ef1276 18 unsigned char CRC7::GetCRC(unsigned char val)
srsmitherman 0:511d65ef1276 19 {
srsmitherman 0:511d65ef1276 20 int j;
srsmitherman 0:511d65ef1276 21 for (j = 0; j < 8; j++) {
srsmitherman 0:511d65ef1276 22 if (val & 1)
srsmitherman 0:511d65ef1276 23 val ^= CRC7_POLY;
srsmitherman 0:511d65ef1276 24 val >>= 1;
srsmitherman 0:511d65ef1276 25 }
srsmitherman 0:511d65ef1276 26 return val;
srsmitherman 0:511d65ef1276 27 }
srsmitherman 0:511d65ef1276 28
srsmitherman 0:511d65ef1276 29 unsigned char CRC7::CRC(unsigned char message[], unsigned int length)
srsmitherman 0:511d65ef1276 30 {
srsmitherman 0:511d65ef1276 31 unsigned char i, crc = 0;
srsmitherman 0:511d65ef1276 32
srsmitherman 0:511d65ef1276 33 for (i = 0; i < length; i++)
srsmitherman 0:511d65ef1276 34 crc = CRCTable[crc ^ message[i]];
srsmitherman 0:511d65ef1276 35 return crc;
srsmitherman 0:511d65ef1276 36 }
srsmitherman 0:511d65ef1276 37
srsmitherman 0:511d65ef1276 38 void CRC7::GenerateCRCTable()
srsmitherman 0:511d65ef1276 39 {
srsmitherman 0:511d65ef1276 40 int i;
srsmitherman 0:511d65ef1276 41 // generate a table value for all 256 possible byte values
srsmitherman 0:511d65ef1276 42 for (i = 0; i < 256; i++) {
srsmitherman 0:511d65ef1276 43 CRCTable[i] = GetCRC(i);
srsmitherman 0:511d65ef1276 44 }
srsmitherman 0:511d65ef1276 45 }
srsmitherman 0:511d65ef1276 46