Round mFi sensor values to reasonable levels of precision

Most of the mFi sensors are able to reasonably provide accurate
readings to a tenth of a unit or so. This patch rounds them for
better display in the UI. Normally, I would expect this to be a view
action instead of altering the actual data emitted, but since these
values are reasonable for sensor precision, we're not really losing
anything. I followed the model from the openweathermap component, which
rounds for readability in the backend.

homeassistant/components/sensor/mfi.py

@@ -20,6 +20,12 @@ _LOGGER = logging.getLogger(__name__)
 
 STATE_ON = 'on'
 STATE_OFF = 'off'
+DIGITS = {
+    'volts': 1,
+    'amps': 1,
+    'active_power': 0,
+    'temperature': 1,
+}
 SENSOR_MODELS = [
     'Ubiquiti mFi-THS',
     'Ubiquiti mFi-CS',
@@ -76,7 +82,8 @@ class MfiSensor(Entity):
         if self._port.model == 'Input Digital':
             return self._port.value > 0 and STATE_ON or STATE_OFF
         else:
-            return self._port.value
+            digits = DIGITS.get(self._port.tag, 0)
+            return round(self._port.value, digits)
 
     @property
     def unit_of_measurement(self):

homeassistant/components/switch/mfi.py

@@ -98,6 +98,6 @@ class MfiSwitch(SwitchDevice):
     @property
     def device_state_attributes(self):
         attr = {}
-        attr['volts'] = self._port.data.get('v_rms', 0)
-        attr['amps'] = self._port.data.get('i_rms', 0)
+        attr['volts'] = round(self._port.data.get('v_rms', 0), 1)
+        attr['amps'] = round(self._port.data.get('i_rms', 0), 1)
         return attr