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- /****************************************************************************
- * drivers/1wire/1wire_crc.c
- *
- * Copyright (C) 2018 Haltian Ltd. All rights reserved.
- * Author: Juha Niskanen <juha.niskanen@haltian.com>
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- *
- * 1. Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- * notice, this list of conditions and the following disclaimer in
- * the documentation and/or other materials provided with the
- * distribution.
- * 3. Neither the name NuttX nor the names of its contributors may be
- * used to endorse or promote products derived from this software
- * without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
- * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
- * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
- * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
- * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
- * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
- * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
- * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
- * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
- * POSSIBILITY OF SUCH DAMAGE.
- *
- ****************************************************************************/
- /****************************************************************************
- * Included Files
- ****************************************************************************/
- #include <stdint.h>
- #include <stdbool.h>
- #include <string.h>
- #include "1wire_internal.h"
- /****************************************************************************
- * Public Functions
- ****************************************************************************/
- /* Compute a Dallas Semiconductor 8 bit CRC. */
- uint8_t onewire_crc8(FAR const uint8_t *input, uint8_t len)
- {
- uint8_t crc = 0;
- while (len-- > 0)
- {
- int i;
- uint8_t inbyte = *input++;
- for (i = 0; i < 8; i++)
- {
- uint8_t mix = (crc ^ inbyte) & 0x01;
- crc >>= 1;
- if (mix)
- crc ^= 0x8c;
- inbyte >>= 1;
- }
- }
- return crc;
- }
- /* Compute a Dallas Semiconductor 16 bit CRC. This is used to check
- * the integrity of received data from many 1-wire devices.
- *
- * Note: the CRC-16 computed here is not what you'll get from the 1-wire
- * network, because:
- * - The CRC-16 is transmitted bitwise inverted.
- * - The binary representation of the return value may have a different
- * byte order than the two bytes you get from 1-wire due to endian-ness.
- */
- uint16_t onewire_crc16(FAR const uint8_t *input, uint16_t len,
- uint16_t initial_crc)
- {
- uint16_t crc = initial_crc;
- while (len-- > 0)
- {
- int i;
- uint8_t inbyte = *input++;
- for (i = 0; i < 8; i++)
- {
- uint8_t mix = ((crc & 0xff) ^ inbyte) & 0x01;
- crc >>= 1;
- if (mix)
- {
- crc ^= 0xa001;
- }
- inbyte >>= 1;
- }
- }
- return crc;
- }
- /****************************************************************************
- * Name: onewire_valid_rom
- *
- * Description:
- * Check CRC-8 of received input
- *
- * Input Parameters:
- * rom - 64-bit rom code
- *
- * Returned Value:
- * true if CRC-8 of rom matches
- *
- ****************************************************************************/
- bool onewire_valid_rom(uint64_t rom)
- {
- uint8_t crc;
- uint8_t buf[8];
- memcpy(buf, &rom, sizeof(buf));
- crc = onewire_crc8(buf, 7);
- return crc == buf[7];
- }
- /****************************************************************************
- * Name: onewire_check_crc16
- *
- * Description:
- * Check CRC-16 of received input
- *
- * Input Parameters:
- * input - Array of bytes to checksum
- * len - Length of input
- * inverted_crc - The two CRC16 bytes in the received data
- *
- * Returned Value:
- * true if CRC-16 matches
- *
- ****************************************************************************/
- bool onewire_check_crc16(FAR const uint8_t *input, uint16_t len,
- FAR const uint8_t *inverted_crc)
- {
- uint16_t crc;
- crc = ~onewire_crc16(input, len, 0);
- return (crc & 0xff) == inverted_crc[0] && (crc >> 8) == inverted_crc[1];
- }
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