146 lines
3.9 KiB
C
146 lines
3.9 KiB
C
/****************************************************************************
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* drivers/1wire/1wire_crc.c
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <stdint.h>
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#include <stdbool.h>
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#include <string.h>
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#include <nuttx/1wire/1wire_crc.h>
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#include "1wire_internal.h"
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/* Compute a Dallas Semiconductor 8 bit CRC. */
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uint8_t onewire_crc8(FAR const uint8_t *input, uint8_t len)
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{
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uint8_t crc = 0;
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while (len-- > 0)
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{
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int i;
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uint8_t inbyte = *input++;
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for (i = 0; i < 8; i++)
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{
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uint8_t mix = (crc ^ inbyte) & 0x01;
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crc >>= 1;
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if (mix)
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crc ^= 0x8c;
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inbyte >>= 1;
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}
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}
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return crc;
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}
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/* Compute a Dallas Semiconductor 16 bit CRC. This is used to check
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* the integrity of received data from many 1-wire devices.
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*
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* Note: the CRC-16 computed here is not what you'll get from the 1-wire
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* network, because:
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* - The CRC-16 is transmitted bitwise inverted.
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* - The binary representation of the return value may have a different
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* byte order than the two bytes you get from 1-wire due to endian-ness.
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*/
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uint16_t onewire_crc16(FAR const uint8_t *input, uint16_t len,
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uint16_t initial_crc)
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{
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uint16_t crc = initial_crc;
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while (len-- > 0)
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{
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int i;
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uint8_t inbyte = *input++;
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for (i = 0; i < 8; i++)
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{
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uint8_t mix = ((crc & 0xff) ^ inbyte) & 0x01;
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crc >>= 1;
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if (mix)
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{
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crc ^= 0xa001;
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}
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inbyte >>= 1;
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}
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}
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return crc;
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}
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/****************************************************************************
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* Name: onewire_valid_rom
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*
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* Description:
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* Check CRC-8 of received input
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*
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* Input Parameters:
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* rom - 64-bit rom code
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*
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* Returned Value:
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* true if CRC-8 of rom matches
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*
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****************************************************************************/
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bool onewire_valid_rom(uint64_t rom)
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{
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uint8_t crc;
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uint8_t buf[8];
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memcpy(buf, &rom, sizeof(buf));
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crc = onewire_crc8(buf, 7);
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return crc == buf[7];
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}
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/****************************************************************************
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* Name: onewire_check_crc16
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*
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* Description:
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* Check CRC-16 of received input
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*
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* Input Parameters:
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* input - Array of bytes to checksum
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* len - Length of input
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* inverted_crc - The two CRC16 bytes in the received data
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*
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* Returned Value:
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* true if CRC-16 matches
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*
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****************************************************************************/
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bool onewire_check_crc16(FAR const uint8_t *input, uint16_t len,
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FAR const uint8_t *inverted_crc)
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{
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uint16_t crc;
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crc = ~onewire_crc16(input, len, 0);
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return (crc & 0xff) == inverted_crc[0] && (crc >> 8) == inverted_crc[1];
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}
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