sensor: Improve reported value precision

Casting the measured values to `int` loses a lot of precision.  Sending
the raw values, however, results in uselessly over-precise values.
Thus, we need to compromise by truncating the values at the tenths
place.

src/thermostat/sensor.py

@@ -96,9 +96,9 @@ class Daemon:
             while 1:
                 data = bme280.sample(bus, SENSOR_ADDR, params)
                 values = {
-                    "temperature": int(data.temperature),
-                    "pressure": int(data.pressure),
-                    "humidity": int(data.humidity),
+                    "temperature": adj(data.temperature),
+                    "pressure": adj(data.pressure),
+                    "humidity": adj(data.humidity),
                 }
                 client.publish(TOPIC, json.dumps(values))
                 ready = select.select((self.quitpipe[0],), (), (), 10)[0]
@@ -142,6 +142,10 @@ class Daemon:
         print("Message", client, userdata, msg)
 
 
+def adj(value, p=10):
+    return int(value * p) / p
+
+
 def main():
     logging.basicConfig(level=logging.DEBUG)
     daemon = Daemon()