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.

pyproject.toml

@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "thermostat"
-version = "0.2.0"
+version = "0.3.0dev2"
 description = ""
 authors = ["Dustin C. Hatch <dustin@hatch.name>"]
 

src/thermostat/sensor.py

@@ -1,7 +1,9 @@
 import json
 import logging
 import os
+import select
 import signal
+import threading
 import time
 from contextlib import closing
 from types import FrameType
@@ -20,30 +22,45 @@ PORT = 8883
 USERNAME = os.environ.get("MQTT_USERNAME", "")
 PASSWORD = os.environ.get("MQTT_PASSWORD", "")
 TOPIC = "homeassistant/sensor/thermostat"
+AVAILABILITY_TOPIC = f"{TOPIC}/availability"
 
 I2CPORT = 1
 SENSOR_ADDR = 0x77
 
+DEVICE = {
+    "manufacturer": "Dustin C. Hatch",
+    "name": "RPi Thermostat Display",
+    "model": "RPi Thermostat Display",
+    "identifiers": [
+        os.uname().nodename,
+    ],
+}
 
 SENSOR_CONFIG = {
     "thermostat_temperature": {
         "device_class": "temperature",
         "name": "Thermostat Temperature",
+        "device": DEVICE,
         "state_topic": TOPIC,
+        "availability_topic": AVAILABILITY_TOPIC,
         "unit_of_measurement": "°C",
         "value_template": r"{{ value_json.temperature }}",
     },
     "thermostat_pressure": {
         "device_class": "pressure",
         "name": "Thermostat Pressure",
+        "device": DEVICE,
         "state_topic": TOPIC,
+        "availability_topic": AVAILABILITY_TOPIC,
         "unit_of_measurement": "hPa",
         "value_template": r"{{ value_json.pressure }}",
     },
     "thermostat_humidity": {
         "device_class": "humidity",
         "name": "Thermostat Humidity",
+        "device": DEVICE,
         "state_topic": TOPIC,
+        "availability_topic": AVAILABILITY_TOPIC,
         "unit_of_measurement": "%",
         "value_template": r"{{ value_json.humidity }}",
     },
@@ -52,18 +69,20 @@ SENSOR_CONFIG = {
 
 class Daemon:
     def __init__(self) -> None:
-        self.running = True
+        self.quitpipe = os.pipe()
+        self._ready = threading.Event()
 
     def on_signal(self, signum: int, frame: FrameType) -> None:
         log.debug("Got signal %d at %s", signum, frame)
         log.info("Stopping")
-        self.running = False
+        os.close(self.quitpipe[1])
 
     def run(self):
         signal.signal(signal.SIGINT, self.on_signal)
         signal.signal(signal.SIGTERM, self.on_signal)
 
         client = mqtt.Client()
+        client.will_set(AVAILABILITY_TOPIC, "offline", retain=True)
         client.on_connect = self.on_connect
         client.on_message = self.on_message
         client.on_disconnect = self.on_disconnect
@@ -73,15 +92,20 @@ class Daemon:
         client.loop_start()
         with closing(smbus2.SMBus(I2CPORT)) as bus:
             params = bme280.load_calibration_params(bus, SENSOR_ADDR)
-            while self.running:
+            self._ready.wait()
+            while 1:
                 data = bme280.sample(bus, SENSOR_ADDR, params)
                 values = {
-                    "temperature": int(data.temperature),
+                    "temperature": adj(data.temperature),
-                    "pressure": int(data.pressure),
+                    "pressure": adj(data.pressure),
-                    "humidity": int(data.humidity),
+                    "humidity": adj(data.humidity),
                 }
                 client.publish(TOPIC, json.dumps(values))
-                time.sleep(10)
+                ready = select.select((self.quitpipe[0],), (), (), 10)[0]
+                if self.quitpipe[0] in ready:
+                    os.close(self.quitpipe[0])
+                    break
+        client.publish(AVAILABILITY_TOPIC, "offline", retain=True)
         client.disconnect()
         client.loop_stop()
 
@@ -94,9 +118,14 @@ class Daemon:
     ):
         log.info("Successfully connected to MQTT broker")
         for key, value in SENSOR_CONFIG.items():
+            value["unique_id"] = f"sensor.{key}"
             client.publish(
-                f"homeassistant/sensor/{key}/config", json.dumps(value)
+                f"homeassistant/sensor/{key}/config",
+                json.dumps(value),
+                retain=True,
             )
+        client.publish(AVAILABILITY_TOPIC, "online", retain=True)
+        self._ready.set()
 
     def on_disconnect(self, client, userdata, rc):
         log.error("Lost connection to MQTT broker")
@@ -113,6 +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()