LED-BOARD/client/MQTT.md

MQTT Configuration

This project can publish weather and public transport data to an MQTT broker. To enable MQTT, follow these steps:

1. Install dependencies

Ensure you have Rust and Cargo installed. The MQTT support uses the Paho MQTT client crate. Run:

cargo update

2. Set the MQTT_BROKER environment variable

Before running the client, define MQTT_BROKER to your broker address.

• Without URI scheme (defaults to TCP):

  export MQTT_BROKER=localhost:1883
  

• With URI scheme:

  export MQTT_BROKER=tcp://broker.example.com:1883
  

3. Run the LED board client

Pass the LED board IP address as the only argument:

export MQTT_BROKER=localhost:1883
cargo run --bin ledboard_client -- 192.168.1.50

Topics and Payloads

The client publishes two topics:

weather

JSON payload with fields:

• dt: timestamp (Unix seconds)
• temp: temperature in °C
• weather: object with main, description, icon
• rain: rain volume in last 3h (optional)
• pop: probability of precipitation
• wind: object with speed, deg, gust

straba

JSON payload with fields:

• outbound_station: name of outbound station
• outbound_diff: seconds until outbound departure
• inbound_station: name of inbound station
• inbound_diff: seconds until inbound departure

Customization

You can adjust MQTT topics, QoS, and message formats in client/bin/src/main.rs under the publish_to_mqtt function.