Add I2c HTU21D temperature and humidity sensor for Raspberry Pi

.coveragerc

@@ -406,6 +406,7 @@ omit =
     homeassistant/components/sensor/haveibeenpwned.py
     homeassistant/components/sensor/hddtemp.py
     homeassistant/components/sensor/hp_ilo.py
+    homeassistant/components/sensor/htu21d.py
     homeassistant/components/sensor/hydroquebec.py
     homeassistant/components/sensor/imap.py
     homeassistant/components/sensor/imap_email_content.py

homeassistant/components/sensor/htu21d.py

@@ -0,0 +1,234 @@
+"""
+Support for HTU21D temperature and humidity sensor.
+
+For more details about this platform, please refer to the documentation at
+https://home-assistant.io/components/sensor.htu21d/
+"""
+import asyncio
+from datetime import timedelta
+from math import log10
+import logging
+import time
+
+import voluptuous as vol
+
+from homeassistant.components.sensor import PLATFORM_SCHEMA
+import homeassistant.helpers.config_validation as cv
+from homeassistant.const import CONF_NAME, TEMP_FAHRENHEIT
+from homeassistant.helpers.entity import Entity
+from homeassistant.util import Throttle
+from homeassistant.util.temperature import celsius_to_fahrenheit
+
+REQUIREMENTS = ['smbus-cffi==0.5.1']
+
+_LOGGER = logging.getLogger(__name__)
+
+CONF_I2C_BUS = 'i2c_bus'
+I2C_ADDRESS = 0x40
+DEFAULT_I2C_BUS = 1
+
+MIN_TIME_BETWEEN_UPDATES = timedelta(seconds=5)
+
+DEFAULT_NAME = 'HTU21D Sensor'
+
+SENSOR_TEMPERATURE = 'temperature'
+SENSOR_HUMIDITY = 'humidity'
+
+PLATFORM_SCHEMA = PLATFORM_SCHEMA.extend({
+    vol.Optional(CONF_NAME, default=DEFAULT_NAME): cv.string,
+    vol.Optional(CONF_I2C_BUS, default=DEFAULT_I2C_BUS): vol.Coerce(int),
+})
+
+# Byte codes from the data sheet
+CMD_READ_TEMP_HOLD = 0xE3
+CMD_READ_HUM_HOLD = 0xE5
+CMD_READ_TEMP_NOHOLD = 0xF3
+CMD_READ_HUM_NOHOLD = 0xF5
+CMD_WRITE_USER_REG = 0xE6
+CMD_READ_USER_REG = 0xE7
+CMD_SOFT_RESET = 0xFE
+MEASUREMENT_WAIT_TIME = 0.055
+
+
+# noinspection PyUnusedLocal
+@asyncio.coroutine
+def async_setup_platform(hass, config, async_add_devices, discovery_info=None):
+    """Set up the HTU21D sensor."""
+    name = config.get(CONF_NAME)
+    bus_number = config.get(CONF_I2C_BUS)
+    temp_unit = hass.config.units.temperature_unit
+    try:
+        # noinspection PyUnresolvedReferences
+        import smbus
+        bus = smbus.SMBus(bus_number)
+    except ImportError as exc:
+        _LOGGER.error("ImportError: %s", exc)
+        return False
+
+    sensor = yield from hass.async_add_job(HTU21D, bus)
+    if not sensor.detected:
+        _LOGGER.error("HTU21D sensor not detected in bus %s", bus_number)
+        return False
+
+    dev = [HTU21DSensor(sensor, name, SENSOR_TEMPERATURE, temp_unit),
+           HTU21DSensor(sensor, name, SENSOR_HUMIDITY, '%')]
+    async_add_devices(dev)
+
+
+class HTU21D:
+    """Implement HTU21D communication."""
+
+    def __init__(self, bus):
+        """Initialize the sensor handler."""
+        self._bus = bus
+        self._ok = self._soft_reset()
+        self.temperature = -255
+        self.humidity = -255
+        if self._ok:
+            self.update()
+
+    def _soft_reset(self) -> bool:
+        try:
+            self._bus.write_byte(I2C_ADDRESS, CMD_SOFT_RESET)
+            time.sleep(MEASUREMENT_WAIT_TIME)
+            return True
+        except OSError as exc:
+            _LOGGER.error("Bad writing in bus: %s", exc)
+            return False
+
+    @property
+    def detected(self) -> bool:
+        """Sensor is working ok."""
+        return self._ok
+
+    @staticmethod
+    def _calc_temp(sensor_temp) -> float:
+        t_sensor_temp = sensor_temp / 65536.0
+        return -46.85 + (175.72 * t_sensor_temp)
+
+    @staticmethod
+    def _calc_humid(sensor_humid) -> float:
+        t_sensor_humid = sensor_humid / 65536.0
+        return -6.0 + (125.0 * t_sensor_humid)
+
+    @staticmethod
+    def _temp_coefficient(rh_actual, temp_actual) -> float:
+        return rh_actual - 0.15 * (25 - temp_actual)
+
+    @staticmethod
+    def _crc8check(value) -> bool:
+        # Ported from Sparkfun Arduino HTU21D Library:
+        # https://github.com/sparkfun/HTU21D_Breakout
+        remainder = ((value[0] << 8) + value[1]) << 8
+        remainder |= value[2]
+
+        # POLYNOMIAL = 0x0131 = x^8 + x^5 + x^4 + 1
+        # divisor = 0x988000 is the 0x0131 polynomial shifted to farthest
+        # left of three bytes
+        divisor = 0x988000
+
+        for i in range(0, 16):
+            if remainder & 1 << (23 - i):
+                remainder ^= divisor
+            divisor >>= 1
+
+        if remainder == 0:
+            return True
+        else:
+            _LOGGER.error("Bad CRC: remainder=%s", remainder)
+            return False
+
+    @property
+    def valid_measurement(self) -> bool:
+        """Return True for a valid measurement data."""
+        return self._ok and self.temperature > -100 and self.humidity > -1
+
+    @property
+    def dew_point_temperature(self) -> float:
+        """Get the dew point temperature in ºC for the last measurement."""
+        if self.valid_measurement:
+            coef_a, coef_b, coef_c = 8.1332, 1762.39, 235.66
+            part_press = 10 ** (coef_a - coef_b / (self.temperature + coef_c))
+            dewp = - coef_c
+            dewp -= (coef_b /
+                     (log10(self.humidity * part_press / 100.) - coef_a))
+            return dewp
+        return -255
+
+    @Throttle(MIN_TIME_BETWEEN_UPDATES)
+    def update(self):
+        """Read raw data and calculate temperature and humidity."""
+        try:
+            self._bus.write_byte(I2C_ADDRESS, CMD_READ_TEMP_NOHOLD)
+            time.sleep(MEASUREMENT_WAIT_TIME)
+            buf_t = self._bus.read_i2c_block_data(
+                I2C_ADDRESS, CMD_READ_TEMP_HOLD, 3)
+
+            self._bus.write_byte(I2C_ADDRESS, CMD_READ_HUM_NOHOLD)
+            time.sleep(MEASUREMENT_WAIT_TIME)
+            buf_h = self._bus.read_i2c_block_data(
+                I2C_ADDRESS, CMD_READ_HUM_HOLD, 3)
+        except OSError as exc:
+            self._ok = False
+            _LOGGER.error("Bad reading: %s", exc)
+            return
+
+        if self._crc8check(buf_t):
+            temp = (buf_t[0] << 8 | buf_t[1]) & 0xFFFC
+            self.temperature = self._calc_temp(temp)
+
+            if self._crc8check(buf_h):
+                humid = (buf_h[0] << 8 | buf_h[1]) & 0xFFFC
+                rh_actual = self._calc_humid(humid)
+                # For temperature coefficient compensation
+                rh_final = self._temp_coefficient(rh_actual, self.temperature)
+                rh_final = 100.0 if rh_final > 100 else rh_final  # Clamp > 100
+                rh_final = 0.0 if rh_final < 0 else rh_final  # Clamp < 0
+                self.humidity = rh_final
+            else:
+                self.humidity = -255
+        else:
+            self.temperature = -255
+        _LOGGER.debug("HTU21D values: %.2f ºC, %.2f %%. Dew point: %.2f",
+                      self.temperature, self.humidity,
+                      self.dew_point_temperature)
+
+
+class HTU21DSensor(Entity):
+    """Implementation of the HTU21D sensor."""
+
+    def __init__(self, htu21d_client, name, variable, unit):
+        """Initialize the sensor."""
+        self._name = '{}_{}'.format(name, variable)
+        self._variable = variable
+        self._unit_of_measurement = unit
+        self._client = htu21d_client
+        self._state = None
+
+    @property
+    def name(self) -> str:
+        """Return the name of the sensor."""
+        return self._name
+
+    @property
+    def state(self) -> int:
+        """Return the state of the sensor."""
+        return self._state
+
+    @property
+    def unit_of_measurement(self) -> str:
+        """Return the unit of measurement of the sensor."""
+        return self._unit_of_measurement
+
+    @asyncio.coroutine
+    def async_update(self):
+        """Get the latest data from the HTU21D sensor and update the state."""
+        yield from self.hass.async_add_job(self._client.update)
+        if self._client.valid_measurement:
+            if self._variable == SENSOR_TEMPERATURE:
+                value = round(self._client.temperature, 1)
+                if self.unit_of_measurement == TEMP_FAHRENHEIT:
+                    value = celsius_to_fahrenheit(value)
+            else:
+                value = round(self._client.humidity, 1)
+            self._state = value

requirements_all.txt

@@ -784,6 +784,7 @@ sleekxmpp==1.3.2
 sleepyq==0.6
 
 # homeassistant.components.sensor.envirophat
+# homeassistant.components.sensor.htu21d
 # smbus-cffi==0.5.1
 
 # homeassistant.components.media_player.snapcast