54 lines
1.8 KiB
C
54 lines
1.8 KiB
C
/*
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* File: crc8.c
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* Description: Simple CRC8 library
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* Author: Jan Mrna
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* Date: 2022-06-09
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*
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*
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* Copyright (c) 2024 Veles Labs s.r.o.
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in all
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* copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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*
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*/
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#include "crc8.h"
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/* TODO add polynomial and init value to make this function
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* generic */
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/* Stolen from Sensirion SCD4x datasheet, section 3.11 */
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uint8_t crc8_calculate(const uint8_t *data, uint16_t count)
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{
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uint16_t current_byte;
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uint8_t crc = CRC8_INIT;
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uint8_t crc_bit;
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/* calculates 8-Bit checksum with given polynomial */
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for (current_byte = 0; current_byte < count; ++current_byte) {
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crc ^= (data[current_byte]);
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for(crc_bit = 8; crc_bit > 0; --crc_bit) {
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if (crc & 0x80) {
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crc =(crc << 1) ^ CRC8_POLYNOMIAL;
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} else {
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crc = (crc << 1);
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}
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}
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}
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return crc;
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}
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