from struct import unpack as unp
from time import sleep_ms

# SHT20 default address
SHT20_I2CADDR = 64

# SHT20 Command
TRI_T_MEASURE_NO_HOLD = b"\xf3"
TRI_RH_MEASURE_NO_HOLD = b"\xf5"
READ_USER_REG = b"\xe7"
WRITE_USER_REG = b"\xe6"
SOFT_RESET = b"\xfe"


class SHT20(object):

    def __init__(self, i2c_bus):
        self._address = SHT20_I2CADDR
        self._bus = i2c_bus

    def get_SHT_temperature(self):
        self._bus.writeto(self._address, TRI_T_MEASURE_NO_HOLD)
        sleep_ms(150)
        origin_data = self._bus.readfrom(self._address, 2)
        origin_value = unp(">h", origin_data)[0]
        value = -46.85 + 175.72 * (origin_value / 65536)
        return value

    def get_SHT_relative_humidity(self):
        self._bus.writeto(self._address, TRI_RH_MEASURE_NO_HOLD)
        sleep_ms(150)
        origin_data = self._bus.readfrom(self._address, 2)
        origin_value = unp(">H", origin_data)[0]
        value = -6 + 125 * (origin_value / 65536)
        return value


# sht=SHT20(I2C(scl = Pin(22), sda = Pin(21), freq = 100000))