32 lines
667 B
C
32 lines
667 B
C
/*
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* crc.c
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*
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* Created on: Jun 9, 2021
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* Author: user
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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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