Add MQTT Sensor

homeassistant/components/sensor/mqtt.py

@@ -0,0 +1,89 @@
+# -*- coding: utf-8 -*-
+"""
+homeassistant.components.sensor.mqtt
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Allows to configure a MQTT sensor.
+
+This generic sensor implementation uses the MQTT message payload as the sensor value.
+
+sensor:
+  platform: mqtt
+  name: "MQTT Sensor"
+  state_topic: "home/bedroom/temperature"
+  unit_of_measurement: "ºC"
+
+Variables:
+
+name
+*Optional
+The name of the sensor. Default is 'MQTT Sensor'.
+
+state_topic
+*Required
+The MQTT topic subscribed to receive sensor values. 
+
+unit_of_measurement
+*Optional
+Defines the units of measurement of the sensor, if any.
+
+"""
+
+import logging
+from homeassistant.helpers.entity import Entity
+import homeassistant.components.mqtt as mqtt
+
+_LOGGER = logging.getLogger(__name__)
+
+DEFAULT_NAME = "MQTT Sensor"
+
+DEPENDENCIES = ['mqtt']
+
+# pylint: disable=unused-argument
+def setup_platform(hass, config, add_devices_callback, discovery_info=None):
+    """ Add MQTT Sensor """
+    
+    if config.get('state_topic') is None:
+        _LOGGER.error("Missing required variable: state_topic")
+        return False
+        
+    add_devices_callback([MqttSensor(
+        hass,
+        config.get('name',DEFAULT_NAME),
+        config.get('state_topic'),
+        config.get('unit_of_measurement'))])
+
+
+class MqttSensor(Entity):
+    """ Represents a sensor that can be updated using MQTT """
+    def __init__(self, hass, name, state_topic, unit_of_measurement):
+        self._state = "-"
+        self._hass = hass
+        self._name = name
+        self._state_topic = state_topic
+        self._unit_of_measurement = unit_of_measurement
+
+        def message_received(topic, payload, qos):
+            self._state = payload
+            self.update_ha_state()
+
+        mqtt.subscribe(hass, self._state_topic, message_received)
+
+    @property
+    def should_poll(self):
+        """ No polling needed """
+        return False
+
+    @property
+    def name(self):
+        """ The name of the sensor """
+        return self._name
+
+    @property
+    def unit_of_measurement(self):
+        """ Unit this state is expressed in. """
+        return self._unit_of_measurement
+
+    @property
+    def state(self):
+        """ Returns the state of the entity. """
+        return self._state