/* =============================================================================
 * sht30_convert.c
 * ===========================================================================*/
#include "sht30_convert.h"

uint8_t sht30_crc8(const uint8_t *data, size_t len)
{
    uint8_t crc = 0xFF;
    for (size_t i = 0; i < len; i++) {
        crc ^= data[i];
        for (int b = 0; b < 8; b++) {
            if (crc & 0x80) crc = (uint8_t)((crc << 1) ^ 0x31);
            else            crc = (uint8_t)(crc << 1);
        }
    }
    return crc;
}

int sht30_parse(const uint8_t frame[6], double *temp_c, double *rh)
{
    if (sht30_crc8(&frame[0], 2) != frame[2]) return -1;
    if (sht30_crc8(&frame[3], 2) != frame[5]) return -2;

    uint16_t raw_t  = (uint16_t)((frame[0] << 8) | frame[1]);
    uint16_t raw_rh = (uint16_t)((frame[3] << 8) | frame[4]);

    if (temp_c) *temp_c = -45.0 + 175.0 * ((double)raw_t / 65535.0);
    if (rh)     *rh     = 100.0 * ((double)raw_rh / 65535.0);
    return 0;
}