PrusaLink MQTT Bridge

This application acts as a bridge between a PrusaLink-enabled 3D printer and an MQTT broker. It periodically fetches the printer's status via the PrusaLink API and publishes it to a specified MQTT topic.

This allows for easy integration into various home automation systems like Home Assistant, Node-RED, or any other system that can subscribe to MQTT topics.

Features

• Fetches printer status from the PrusaLink API.
• Publishes status data to an MQTT broker.
• Configurable exclusively via environment variables.
• Structured, configurable logging (text or JSON).
• Easy to run with Docker and Docker Compose.
• Lightweight and efficient, built with Go.

Getting Started

These instructions will get you a copy of the project up and running on your local machine for development and testing purposes.

Prerequisites

• A Prusa 3D printer with PrusaLink enabled.
• Go (version 1.24 or later) for local development.
• Docker and Docker Compose (or Podman and Podman Compose) for running the containerized application.

Configuration

The application is configured exclusively via environment variables. The library go-envconfig is used to parse them.

Variable	Required	Default	Description
PRUSALINK_HOST	Yes	-	Hostname or IP address of the printer
PRUSALINK_APIKEY	Yes	-	API key from PrusaLink settings
PRUSALINK_INTERVAL	No	10	Fetch interval in seconds
MQTT_BROKER	Yes	-	Hostname or IP address of the MQTT broker
MQTT_PORT	No	1883	Port of the MQTT broker
MQTT_USERNAME	No	-	MQTT username (optional)
MQTT_PASSWORD	No	-	MQTT password (optional)
MQTT_TOPIC	No	prusa-link	MQTT topic to publish to
LOG_LEVEL	No	INFO	Log level (DEBUG, INFO, WARN, ERROR)
LOG_FORMAT	No	text	Log format (text or json)

Important Notes

• Printer Availability: The PrusaLink-enabled printer must be online and accessible when the bridge starts. The application fetches the printer's serial number on startup to use it in the MQTT topic, ensuring a unique identifier for each printer. If the printer is not available, the application will exit with an error.

Usage

Running with Docker Compose (Recommended)

This is the easiest way to run the application, as it includes a pre-configured MQTT broker (Eclipse Mosquitto).

1. Create a .env file in the project root with your PrusaLink credentials and any desired overrides:

   # Required
   PRUSALINK_HOST=your-prusa-link-host
   PRUSALINK_APIKEY=your-prusa-link-api-key
   
   # Optional - for debugging
   LOG_LEVEL=DEBUG

2. Start the services:

   # With Docker
   docker compose up --build
   
   # With Podman
   podman compose up --build

The bridge will start, connect to the included Mosquitto broker, and begin publishing data.

Running Locally

1. Install dependencies:

   go mod tidy

2. Set the required environment variables in your shell:

   export PRUSALINK_HOST="your-prusa-link-host"
   export PRUSALINK_APIKEY="your-prusa-link-api-key"
   export MQTT_BROKER="your-mqtt-broker" # e.g., localhost

3. Run the application:

   go run cmd/prusa-link-mqtt-bridge/main.go

Development

Project Structure

• cmd/prusa-link-mqtt-bridge: Main application entry point.
• pkg/config: Configuration loading logic (go-envconfig).
• pkg/prusalink: Logic for interacting with the PrusaLink API.
• pkg/mqtt: Logic for publishing data to MQTT.
• Dockerfile: Defines the multi-stage Docker build.
• docker-compose.yml: Defines the application and MQTT broker services.

Running Tests

To run the unit tests and see the coverage report, use the following command:

go test -v -coverprofile=coverage.out ./...

The detailed code coverage report can be found in the CI workflow logs under the "Show Coverage Summary" step.

MQTT Data

The application publishes a JSON payload to the configured MQTT topic. The full MQTT topic path will include the printer's serial number to ensure uniqueness, formatted as MQTT_TOPIC/SERIAL_NUMBER/status. For example, if MQTT_TOPIC is prusa-link and the printer's serial number is XYZ123, the status will be published to prusa-link/XYZ123/status.

Additionally, the application publishes an availability status to MQTT_AVAILABILITY_TOPIC/SERIAL_NUMBER/availability. It sends online when the bridge starts and offline when it disconnects.

Here is an example of the status data payload:

{
  "state_text": "PRINTING",
  "temp_nozzle": 215.2,
  "target_nozzle": 215.0,
  "temp_bed": 60.1,
  "target_bed": 60.0,
  "axis_z": 3.1,
  "flow": 95,
  "speed": 100,
  "fan_hotend": 4939,
  "fan_print": 5632,
  "progress": 19.0,
  "print_time_left": 11520,
  "print_time": 2913
}

License

This project is licensed under the GNU Affero General Public License v3 (AGPLv3) - see the LICENSE.md file for details.