ahoy/tools/esp8266/crc.cpp

//-----------------------------------------------------------------------------
// 2022 Ahoy, https://www.mikrocontroller.net/topic/525778
// Creative Commons - http://creativecommons.org/licenses/by-nc-sa/3.0/de/
//-----------------------------------------------------------------------------

#include "crc.h"

uint8_t crc8(uint8_t buf[], uint8_t len) {
    uint8_t crc = CRC8_INIT;
    for(uint8_t i = 0; i < len; i++) {
        crc ^= buf[i];
        for(uint8_t b = 0; b < 8; b ++) {
            crc = (crc << 1) ^ ((crc & 0x80) ? CRC8_POLY : 0x00);
        }
        yield();
    }
    return crc;
}

uint16_t crc16(uint8_t buf[], uint8_t len, uint16_t start) {
    uint16_t crc = start;
    uint8_t shift = 0;

    for(uint8_t i = 0; i < len; i ++) {
        crc = crc ^ buf[i];
        for(uint8_t bit = 0; bit < 8; bit ++) {
            shift = (crc & 0x0001);
            crc = crc >> 1;
            if(shift != 0)
                crc = crc ^ CRC16_MODBUS_POLYNOM;
        }
        yield();
    }
    return crc;
}