From 890eb720d5c6194d84f5467c32b017b792cad42f Mon Sep 17 00:00:00 2001 From: Jérémy Dufour Date: Sat, 16 May 2009 01:23:06 +0200 Subject: * digital/avr/modules/utils: - add a function to compute CRC. --- digital/avr/modules/utils/crc.h | 76 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 76 insertions(+) create mode 100644 digital/avr/modules/utils/crc.h (limited to 'digital/avr/modules/utils/crc.h') diff --git a/digital/avr/modules/utils/crc.h b/digital/avr/modules/utils/crc.h new file mode 100644 index 00000000..04a3eed8 --- /dev/null +++ b/digital/avr/modules/utils/crc.h @@ -0,0 +1,76 @@ +#ifndef crc_h +#define crc_h +/* crc.h */ +/* crc - Compute CRC for data (CRC on 8 bits). {{{ + * + * Copyright (C) 2009 Dufour Jérémy + * + * APBTeam: + * Web: http://apbteam.org/ + * Email: team AT apbteam DOT org + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. + * + * }}} */ + +#ifndef HOST +#include +#endif + +#ifdef HOST +/** + * CRC i-button, 8-bit (Dallas/Maxim) for host. + */ +uint8_t +_crc_ibutton_update (uint8_t crc, uint8_t data) +{ + uint8_t i; + + crc = crc ^ data; + for (i = 0; i < 8; i++) + { + if (crc & 0x01) + crc = (crc >> 1) ^ 0x8C; + else + crc >>= 1; + } + return crc; +} +#endif + +/** + * Compute CRC. + * @param data the data on which to compute CRC. + * @param length the length of data (in byte). + * @return the computed CRC. + */ +static inline uint8_t +crc_compute (uint8_t *data, uint8_t length) +{ + uint8_t i, crc; + /* Sanity check. */ + if (!data) + return 0; + /* For each data byte. */ + for (i = 0, crc = 0; i < length; i++) + { + /* Compute CRC. */ + crc = _crc_ibutton_update (crc, data[i]); + } + /* Return computed CRC. */ + return crc; +} + +#endif /* crc_h */ -- cgit v1.2.3