Add MQTT Home Assistant script with auto-discovery

Reads BME280 (temperature, humidity, pressure) and SI1132 (UV index,
visible light, IR) and publishes to MQTT with HA discovery. All six
sensors appear under a single 'Weather Board' device in the Office room.

MQTT broker: 192.168.1.135:1883 (co2meter/co2meter)
Publishes a shared JSON state topic every 10 seconds.
Discovery configs are retained so HA picks them up on restart.

1 files changed, 213 insertions, 0 deletions

diff --git a/mqtt_ha.py b/mqtt_ha.py
new file mode 100644
index 0000000..5fa9197
--- /dev/null
+++ b/mqtt_ha.py
@@ -0,0 +1,213 @@
+#!/usr/bin/env python3
+"""
+Weather Board → Home Assistant via MQTT with auto-discovery.
+
+Reads BME280 (temperature, humidity, pressure) and SI1132 (UV index,
+visible light, IR) over I2C and publishes to an MQTT broker using
+Home Assistant's MQTT discovery protocol.
+
+Usage:
+    python3 mqtt_ha.py
+"""
+
+import json
+import signal
+import sys
+import time
+
+import paho.mqtt.client as mqtt
+
+import BME280
+import SI1132
+
+# ── MQTT settings ────────────────────────────────────────────────────────────
+MQTT_HOST = "192.168.1.135"
+MQTT_PORT = 1883
+MQTT_USER = "co2meter"
+MQTT_PASS = "co2meter"
+
+# ── I2C bus ──────────────────────────────────────────────────────────────────
+I2C = "/dev/i2c-1"
+
+# ── Home Assistant discovery identifiers ─────────────────────────────────────
+DEVICE_ID = "weather_board_office"
+DEVICE_NAME = "Weather Board"
+ROOM = "Office"
+HA_DISCOVERY_PREFIX = "homeassistant"
+STATE_TOPIC = f"{HA_DISCOVERY_PREFIX}/sensor/{DEVICE_ID}/state"
+
+# How often to read & publish (seconds)
+PUBLISH_INTERVAL = 10
+
+# ── Sensor definitions for HA auto-discovery ─────────────────────────────────
+# Each entry maps to one Home Assistant sensor entity.
+SENSORS = [
+    {
+        "key": "temperature",
+        "name": "Temperature",
+        "device_class": "temperature",
+        "unit": "°C",
+        "icon": None,
+        "state_class": "measurement",
+    },
+    {
+        "key": "humidity",
+        "name": "Humidity",
+        "device_class": "humidity",
+        "unit": "%",
+        "icon": None,
+        "state_class": "measurement",
+    },
+    {
+        "key": "pressure",
+        "name": "Pressure",
+        "device_class": "atmospheric_pressure",
+        "unit": "hPa",
+        "icon": None,
+        "state_class": "measurement",
+    },
+    {
+        "key": "uv_index",
+        "name": "UV Index",
+        "device_class": None,
+        "unit": "UV index",
+        "icon": "mdi:sun-wireless",
+        "state_class": "measurement",
+    },
+    {
+        "key": "visible_light",
+        "name": "Visible Light",
+        "device_class": "illuminance",
+        "unit": "lx",
+        "icon": None,
+        "state_class": "measurement",
+    },
+    {
+        "key": "ir",
+        "name": "Infrared",
+        "device_class": None,
+        "unit": "lx",
+        "icon": "mdi:sun-wireless-outline",
+        "state_class": "measurement",
+    },
+]
+
+# ── Shared HA device block (appears once per entity, links them together) ────
+HA_DEVICE = {
+    "identifiers": [DEVICE_ID],
+    "name": DEVICE_NAME,
+    "manufacturer": "ODROID",
+    "model": "Weather Board",
+    "suggested_area": ROOM,
+}
+
+
+def publish_discovery(client: mqtt.Client) -> None:
+    """Publish MQTT discovery config messages for every sensor entity."""
+    for sensor in SENSORS:
+        uid = f"{DEVICE_ID}_{sensor['key']}"
+        config_topic = (
+            f"{HA_DISCOVERY_PREFIX}/sensor/{DEVICE_ID}/{sensor['key']}/config"
+        )
+        payload = {
+            "name": sensor["name"],
+            "unique_id": uid,
+            "object_id": uid,
+            "state_topic": STATE_TOPIC,
+            "value_template": "{{ value_json." + sensor["key"] + " }}",
+            "unit_of_measurement": sensor["unit"],
+            "state_class": sensor["state_class"],
+            "device": HA_DEVICE,
+        }
+        if sensor["device_class"]:
+            payload["device_class"] = sensor["device_class"]
+        if sensor["icon"]:
+            payload["icon"] = sensor["icon"]
+
+        client.publish(config_topic, json.dumps(payload), retain=True)
+        print(f"  discovery: {config_topic}")
+
+
+def read_sensors(bme: BME280.BME280, si: SI1132.SI1132) -> dict:
+    """Read all sensors and return a dict ready for JSON serialisation."""
+    # Temperature must be read first — it sets t_fine used by humidity/pressure
+    temperature = bme.read_temperature()
+    humidity = bme.read_humidity()
+    pressure = bme.read_pressure() / 100.0  # Pa → hPa
+
+    uv_index = si.readUV() / 100.0
+    visible_light = si.readVisible()
+    ir = si.readIR()
+
+    return {
+        "temperature": round(temperature, 2),
+        "humidity": round(humidity, 2),
+        "pressure": round(pressure, 2),
+        "uv_index": round(uv_index, 2),
+        "visible_light": round(visible_light, 1),
+        "ir": round(ir, 1),
+    }
+
+
+def main() -> None:
+    # ── Initialise I2C sensors ───────────────────────────────────────────
+    print("Initialising sensors...")
+    si = SI1132.SI1132(I2C)
+    # Normal mode, 2× oversampling for humidity, pressure, temperature
+    bme = BME280.BME280(I2C, 0x03, 0x02, 0x02, 0x02)
+    print("  BME280 + SI1132 ready")
+
+    # ── Connect to MQTT broker ───────────────────────────────────────────
+    client = mqtt.Client(client_id=DEVICE_ID)
+    client.username_pw_set(MQTT_USER, MQTT_PASS)
+
+    def on_connect(cl, _userdata, _flags, rc):
+        if rc == 0:
+            print(f"  connected to MQTT broker at {MQTT_HOST}:{MQTT_PORT}")
+            publish_discovery(cl)
+        else:
+            print(f"  MQTT connection failed (rc={rc})")
+
+    client.on_connect = on_connect
+    client.will_set(STATE_TOPIC, payload="", retain=False)
+
+    print("Connecting to MQTT...")
+    client.connect(MQTT_HOST, MQTT_PORT, keepalive=60)
+    client.loop_start()
+
+    # ── Graceful shutdown ────────────────────────────────────────────────
+    running = True
+
+    def _stop(signum, _frame):
+        nonlocal running
+        print(f"\nCaught signal {signum}, shutting down...")
+        running = False
+
+    signal.signal(signal.SIGINT, _stop)
+    signal.signal(signal.SIGTERM, _stop)
+
+    # ── Main loop ────────────────────────────────────────────────────────
+    print("Publishing sensor data...\n")
+    while running:
+        try:
+            data = read_sensors(bme, si)
+            payload = json.dumps(data)
+            client.publish(STATE_TOPIC, payload, retain=False)
+            print(f"  {payload}")
+        except Exception as e:
+            print(f"  sensor read error: {e}")
+
+        # Sleep in small increments so we can react to signals promptly
+        for _ in range(PUBLISH_INTERVAL * 10):
+            if not running:
+                break
+            time.sleep(0.1)
+
+    # ── Cleanup ──────────────────────────────────────────────────────────
+    client.loop_stop()
+    client.disconnect()
+    print("Done.")
+
+
+if __name__ == "__main__":
+    main()