sgp40_crc
args[2] = sgp40_crc(&args[0], 2);
args[5] = sgp40_crc(&args[3], 2);
crc = sgp40_crc(&buf[0], 2);
static uint8_t sgp40_crc(uint8_t *, size_t);
sn_crc1 = sgp40_crc(&buf[0], 2);
sn_crc2 = sgp40_crc(&buf[3], 2);
sn_crc3 = sgp40_crc(&buf[6], 2);
fs_crc = sgp40_crc(&buf[0], 2);
tstcrc = sgp40_crc(&buf[0], 2);