MQTT Integration

Any broker. Any platform that speaks MQTT.

Car 2 Home is a fully featured MQTT client. Every sensor your vehicle exposes, standard OBD, enhanced PIDs, calculated metrics, GPS, TPMS, diagnostic state, gets published to your broker, with auto-discovery payloads compatible with anything that understands the Home Assistant MQTT discovery format.

If you already run Mosquitto, EMQX, HiveMQ, or any other broker, you're a couple of fields away from a working setup. Car 2 Home does not depend on our servers for any of this, telemetry goes directly from the app to your broker.

MQTT vs. native Home Assistant

Both paths carry the same sensors. The difference is that MQTT carries continuous state, while the native Home Assistant integration also carries events (trip started, DTC found, harsh acceleration). If you only need MQTT, you'll get all the live data, but the discrete moments that drive the most interesting automations only exist in the native integration.

CapabilityMQTTNative HA
Continuous state
Sensor values published as they change.
✓✓
Events
trip_started, trip_ended, dtc_found, harsh_event, ecu_online/offline.
—✓
Bidirectional commands
Home Assistant can ask the car to scan for DTCs or re-announce sensors.
—✓

How data is published

  • Auto-discovery payloads are sent with retain=true so any broker subscriber that comes online later sees the entity catalog immediately.
  • Delta updates only: values are republished only when they change, with optional throttling, to avoid flooding the broker.
  • Enumerated PIDs are decoded: Fuel Type "1" becomes "Gasoline", commanded equivalence ratio is reported as a fraction, etc. Both raw and human-readable values are exposed as attributes.
  • Material Design icons are included in discovery payloads, so dashboards render correctly out of the box.
  • Configurable QoS per topic class. Sensor state defaults to QoS 0; lifecycle messages use QoS 1.
  • TLS and authentication supported; credentials stored in iOS Keychain / Android Keystore.

Works with

Anything that speaks MQTT. We test regularly against:

  • Home Assistant via the MQTT integration (auto-discovery picks Car 2 Home up automatically).
  • Node-RED for visual flows and complex automations.
  • openHAB, Domoticz, ioBroker.
  • Custom dashboards via Grafana + Telegraf or InfluxDB.
  • ESPHome bridges, Zigbee2MQTT setups, and any DIY MQTT consumer.

Choosing a broker

If you don't already run one, here's a starting point:

  • Mosquitto: the simplest option. Runs as a Home Assistant add-on with one click, or stand-alone in Docker. Enough for a household.
  • EMQX: clustered, scales well, has a clean web UI. Worth it if you have many devices or want detailed monitoring.
  • HiveMQ: solid commercial / cloud option if you don't want to self-host.

Quick setup

  1. 1. Have a broker reachable from your phone

    Either on your local network or via a tunnel (Tailscale, Cloudflare Tunnel, Nabu Casa). MQTT must be reachable while you're driving for telemetry to flow live.

  2. 2. Open Settings → MQTT in the app

    Enter host, port, username, password, optional TLS settings. The app validates the connection and shows status in real time.

  3. 3. Subscribe and watch the entities arrive

    Auto-discovery payloads are published immediately. In Home Assistant, the device shows up under Settings → Devices & Services → MQTT. In Node-RED or any MQTT explorer, browse the topic tree under your configured prefix.

See the step-by-step setup guide →

Matter / SmartThings / Google Home / Alexa

We're building a Matterbridge plugin that re-exports the same MQTT data as Matter devices, making your car discoverable in Apple Home, Google Home, SmartThings and Alexa with zero broker on the consumer side. Coming soon.