ds18b20crc.c

/******************************************************************************
 * @file    onewirecrc.c
 * @author  Matt Anderson (mda2376@gmail.com)
 * @version V1.0.0
 * @date    27-December-2013
 * @brief   OneWire CRC calculation
 ******************************************************************************
 * Copyright (c) 2013 Matt Anderson.  All rights reserved.
 *
 * Portions auto generated by pycrc v0.8.1, http://www.tty1.net/pycrc/
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation, either
 * version 3 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this program; if not, see <http://www.gnu.org/licenses/>.
 ******************************************************************************
 */
 
#include "main-header.h"
#include "ds18b20crc.h"
 
#if defined(ONEWIRE_CRC_USE_TABLE)
static const uint8_t crc_table[256] = {
  0x00, 0x5e, 0xbc, 0xe2, 0x61, 0x3f, 0xdd, 0x83, 0xc2, 0x9c, 0x7e, 0x20, 0xa3, 0xfd, 0x1f, 0x41,
  0x9d, 0xc3, 0x21, 0x7f, 0xfc, 0xa2, 0x40, 0x1e, 0x5f, 0x01, 0xe3, 0xbd, 0x3e, 0x60, 0x82, 0xdc,
  0x23, 0x7d, 0x9f, 0xc1, 0x42, 0x1c, 0xfe, 0xa0, 0xe1, 0xbf, 0x5d, 0x03, 0x80, 0xde, 0x3c, 0x62,
  0xbe, 0xe0, 0x02, 0x5c, 0xdf, 0x81, 0x63, 0x3d, 0x7c, 0x22, 0xc0, 0x9e, 0x1d, 0x43, 0xa1, 0xff,
  0x46, 0x18, 0xfa, 0xa4, 0x27, 0x79, 0x9b, 0xc5, 0x84, 0xda, 0x38, 0x66, 0xe5, 0xbb, 0x59, 0x07,
  0xdb, 0x85, 0x67, 0x39, 0xba, 0xe4, 0x06, 0x58, 0x19, 0x47, 0xa5, 0xfb, 0x78, 0x26, 0xc4, 0x9a,
  0x65, 0x3b, 0xd9, 0x87, 0x04, 0x5a, 0xb8, 0xe6, 0xa7, 0xf9, 0x1b, 0x45, 0xc6, 0x98, 0x7a, 0x24,
  0xf8, 0xa6, 0x44, 0x1a, 0x99, 0xc7, 0x25, 0x7b, 0x3a, 0x64, 0x86, 0xd8, 0x5b, 0x05, 0xe7, 0xb9,
  0x8c, 0xd2, 0x30, 0x6e, 0xed, 0xb3, 0x51, 0x0f, 0x4e, 0x10, 0xf2, 0xac, 0x2f, 0x71, 0x93, 0xcd,
  0x11, 0x4f, 0xad, 0xf3, 0x70, 0x2e, 0xcc, 0x92, 0xd3, 0x8d, 0x6f, 0x31, 0xb2, 0xec, 0x0e, 0x50,
  0xaf, 0xf1, 0x13, 0x4d, 0xce, 0x90, 0x72, 0x2c, 0x6d, 0x33, 0xd1, 0x8f, 0x0c, 0x52, 0xb0, 0xee,
  0x32, 0x6c, 0x8e, 0xd0, 0x53, 0x0d, 0xef, 0xb1, 0xf0, 0xae, 0x4c, 0x12, 0x91, 0xcf, 0x2d, 0x73,
  0xca, 0x94, 0x76, 0x28, 0xab, 0xf5, 0x17, 0x49, 0x08, 0x56, 0xb4, 0xea, 0x69, 0x37, 0xd5, 0x8b,
  0x57, 0x09, 0xeb, 0xb5, 0x36, 0x68, 0x8a, 0xd4, 0x95, 0xcb, 0x29, 0x77, 0xf4, 0xaa, 0x48, 0x16,
  0xe9, 0xb7, 0x55, 0x0b, 0x88, 0xd6, 0x34, 0x6a, 0x2b, 0x75, 0x97, 0xc9, 0x4a, 0x14, 0xf6, 0xa8,
  0x74, 0x2a, 0xc8, 0x96, 0x15, 0x4b, 0xa9, 0xf7, 0xb6, 0xe8, 0x0a, 0x54, 0xd7, 0x89, 0x6b, 0x35
};
#endif /* defined(ONEWIRE_CRC_USE_TABLE) */
 
#if defined(ONEWIRE_CRC_USE_BIT)
static uint8_t crc_reflect(uint8_t data, uint32_t data_len) {
  unsigned int i;
  uint8_t ret;
 
  ret = data & 0x01;
  for (i = 1; i < data_len; i++) {
    data >>= 1;
    ret = (ret << 1) | (data & 0x01);
  }
  return ret;
}
#endif /* defined(ONEWIRE_CRC_USE_BIT) */
 
static inline uint8_t onewire_crc_init(void) {
  return 0;
}
uint8_t onewire_crc_update(uint8_t crc, const unsigned char *data, uint32_t data_len) {
#if defined(ONEWIRE_CRC_USE_TABLE)
  unsigned int tbl_idx;
 
  while (data_len--) {
    tbl_idx = (crc ^ *data) & 0xff;
    crc = (crc_table[tbl_idx] ^ (crc >> 8)) & 0xff;
 
    data++;
  }
  return crc & 0xff;
#elif defined(ONEWIRE_CRC_USE_BIT)
  unsigned int i;
  uint8_t bit;
  unsigned char c;
 
  while (data_len--) {
    c = crc_reflect(*data++, 8);
    for (i = 0; i < 8; i++) {
      bit = crc & 0x80;
      crc = (crc << 1) | ((c >> (7 - i)) & 0x01);
      if (bit) {
        crc ^= 0x31;
      }
    }
    crc &= 0xff;
  }
  return crc & 0xff;
#endif /* defined(ONEWIRE_CRC_USE_TABLE) */
}
 
uint8_t onewire_crc_finalize(uint8_t crc) {
#if defined(ONEWIRE_CRC_USE_TABLE)
  return crc ^ 0x00;
#elif defined(ONEWIRE_CRC_USE_BIT)
  unsigned int i;
  uint8_t bit;
 
  for (i = 0; i < 8; i++) {
    bit = crc & 0x80;
    crc = (crc << 1) | 0x00;
    if (bit) {
      crc ^= 0x31;
    }
  }
  crc = crc_reflect(crc, 8);
  return (crc ^ 0x00) & 0xff;
#endif /* defined(ONEWIRE_CRC_USE_TABLE) */
}
 
uint8_t onewire_crc(const uint8_t *data, uint32_t data_len) {
  uint8_t crc;
 
  crc = onewire_crc_init();
  crc = onewire_crc_update(crc, data, data_len);
  crc = onewire_crc_finalize(crc);
 
  return crc;
}