Erik van Wijk
crc8 Library - Original copyright: Colin O'Flynn - Copyright (c) 2002
crc8.cpp@0:cc65a6cec1a1, 2010-10-21 (annotated)
- Committer:
- evwijk
- Date:
- Thu Oct 21 17:11:49 2010 +0000
- Revision:
- 0:cc65a6cec1a1
Who changed what in which revision?
| User | Revision | Line number | New contents of line |
|---|---|---|---|
| evwijk | 0:cc65a6cec1a1 | 1 | /* please read copyright-notice at EOF */ |
| evwijk | 0:cc65a6cec1a1 | 2 | |
| evwijk | 0:cc65a6cec1a1 | 3 | #include "crc8.h" |
| evwijk | 0:cc65a6cec1a1 | 4 | |
| evwijk | 0:cc65a6cec1a1 | 5 | #define CRC8INIT 0x00 |
| evwijk | 0:cc65a6cec1a1 | 6 | #define CRC8POLY 0x18 //0X18 = X^8+X^5+X^4+X^0 |
| evwijk | 0:cc65a6cec1a1 | 7 | |
| evwijk | 0:cc65a6cec1a1 | 8 | char crc8 ( char *data_in, int number_of_bytes_to_read ) |
| evwijk | 0:cc65a6cec1a1 | 9 | { |
| evwijk | 0:cc65a6cec1a1 | 10 | char crc; |
| evwijk | 0:cc65a6cec1a1 | 11 | int loop_count; |
| evwijk | 0:cc65a6cec1a1 | 12 | char bit_counter; |
| evwijk | 0:cc65a6cec1a1 | 13 | char data; |
| evwijk | 0:cc65a6cec1a1 | 14 | char feedback_bit; |
| evwijk | 0:cc65a6cec1a1 | 15 | |
| evwijk | 0:cc65a6cec1a1 | 16 | crc = CRC8INIT; |
| evwijk | 0:cc65a6cec1a1 | 17 | |
| evwijk | 0:cc65a6cec1a1 | 18 | for (loop_count = 0; loop_count != number_of_bytes_to_read; loop_count++) |
| evwijk | 0:cc65a6cec1a1 | 19 | { |
| evwijk | 0:cc65a6cec1a1 | 20 | data = data_in[loop_count]; |
| evwijk | 0:cc65a6cec1a1 | 21 | |
| evwijk | 0:cc65a6cec1a1 | 22 | bit_counter = 8; |
| evwijk | 0:cc65a6cec1a1 | 23 | do { |
| evwijk | 0:cc65a6cec1a1 | 24 | feedback_bit = (crc ^ data) & 0x01; |
| evwijk | 0:cc65a6cec1a1 | 25 | |
| evwijk | 0:cc65a6cec1a1 | 26 | if ( feedback_bit == 0x01 ) { |
| evwijk | 0:cc65a6cec1a1 | 27 | crc = crc ^ CRC8POLY; |
| evwijk | 0:cc65a6cec1a1 | 28 | } |
| evwijk | 0:cc65a6cec1a1 | 29 | crc = (crc >> 1) & 0x7F; |
| evwijk | 0:cc65a6cec1a1 | 30 | if ( feedback_bit == 0x01 ) { |
| evwijk | 0:cc65a6cec1a1 | 31 | crc = crc | 0x80; |
| evwijk | 0:cc65a6cec1a1 | 32 | } |
| evwijk | 0:cc65a6cec1a1 | 33 | |
| evwijk | 0:cc65a6cec1a1 | 34 | data = data >> 1; |
| evwijk | 0:cc65a6cec1a1 | 35 | bit_counter--; |
| evwijk | 0:cc65a6cec1a1 | 36 | |
| evwijk | 0:cc65a6cec1a1 | 37 | } while (bit_counter > 0); |
| evwijk | 0:cc65a6cec1a1 | 38 | } |
| evwijk | 0:cc65a6cec1a1 | 39 | |
| evwijk | 0:cc65a6cec1a1 | 40 | return crc; |
| evwijk | 0:cc65a6cec1a1 | 41 | } |
| evwijk | 0:cc65a6cec1a1 | 42 | |
| evwijk | 0:cc65a6cec1a1 | 43 | /* |
| evwijk | 0:cc65a6cec1a1 | 44 | This code is from Colin O'Flynn - Copyright (c) 2002 |
| evwijk | 0:cc65a6cec1a1 | 45 | only minor changes by M.Thomas 9/2004 |
| evwijk | 0:cc65a6cec1a1 | 46 | oonverted to mbed library by Erik van Wijk 10/2010 |
| evwijk | 0:cc65a6cec1a1 | 47 | |
| evwijk | 0:cc65a6cec1a1 | 48 | Permission is hereby granted, free of charge, to any person obtaining a copy of |
| evwijk | 0:cc65a6cec1a1 | 49 | this software and associated documentation files (the "Software"), to deal in |
| evwijk | 0:cc65a6cec1a1 | 50 | the Software without restriction, including without limitation the rights to |
| evwijk | 0:cc65a6cec1a1 | 51 | use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of |
| evwijk | 0:cc65a6cec1a1 | 52 | the Software, and to permit persons to whom the Software is furnished to do so, |
| evwijk | 0:cc65a6cec1a1 | 53 | subject to the following conditions: |
| evwijk | 0:cc65a6cec1a1 | 54 | |
| evwijk | 0:cc65a6cec1a1 | 55 | The above copyright notice and this permission notice shall be included in all |
| evwijk | 0:cc65a6cec1a1 | 56 | copies or substantial portions of the Software. |
| evwijk | 0:cc65a6cec1a1 | 57 | |
| evwijk | 0:cc65a6cec1a1 | 58 | THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
| evwijk | 0:cc65a6cec1a1 | 59 | IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS |
| evwijk | 0:cc65a6cec1a1 | 60 | FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR |
| evwijk | 0:cc65a6cec1a1 | 61 | COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER |
| evwijk | 0:cc65a6cec1a1 | 62 | IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN |
| evwijk | 0:cc65a6cec1a1 | 63 | CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. |
| evwijk | 0:cc65a6cec1a1 | 64 | */ |