Skip to main content
DEJA.jsDEJA.js
Sign up

🔌 IO Devices

IO devices extend your layout beyond what the DCC-EX CommandStation handles directly. They control effects like lighting, servo-driven turnouts, sensors, and animated elements — anything that isn't powered through the DCC track bus.

DEJA IO supports four firmware targets across two transports — USB serial and MQTT over WiFi — plus a generic WebSocket API for custom integrations. Pick the device type that fits your hardware and how you want it connected. See the IO Guide for the full platform overview.

🎯 Supported Device Types

Device typeHardwareTransportSketch / RuntimeSetup guide
🟢 deja-arduinoArduino Mega 2560 (or compatible AVR)USB serial @ 115200io/src/deja-arduino/ (Arduino sketch)Arduino & ESP32 Setup
🟠 deja-esp32ESP32 Dev ModuleUSB serial @ 115200io/src/deja-arduino/ (shared sketch)Arduino & ESP32 Setup
🛜 deja-esp32-wifiESP32 Dev ModuleWiFi + MQTTio/src/deja-esp32-wifi/ (Arduino sketch)Arduino & ESP32 Setup
🍓 deja-mqttRaspberry Pi Pico WWiFi + MQTTio/src/deja-pico-w/ (CircuitPython)Pico W Setup

🤝 deja-arduino and deja-esp32 share the same sketch — the only difference is the FQBN (Mega vs ESP32) and the upload speed. Same JSON-over-serial protocol, same handlers, same config file.

🛜 deja-esp32-wifi and deja-mqtt share the same MQTT topology — same topic scheme ({TOPIC_ID}/{LAYOUT_ID}/{DEVICE_ID}), same single-object command format, same publish/subscribe semantics. Pick the one that matches your hardware.

🛠️ What These Devices Can Do

All four firmware targets share the same capabilities:

  • 🎛️ PWM servos via an Adafruit PCA9685 16-channel servo driver — for turnout motors and animated elements
  • 💡 Digital outputs — for LEDs, relays, and on/off devices
  • 🚦 Signal heads — for model railroad signal aspects
  • 📡 Sensors — for detecting train presence (block detection, occupancy)
  • 🔧 Servo-driven turnouts via TurnoutPulser

The handlers are identical regardless of transport — the same pin / servo / turnout / effects / ialed actions work whether the message arrives over serial or MQTT.

📡 Picking a Transport

  • USB serial (deja-arduino, deja-esp32) — simplest setup, no networking, lowest latency. Ideal when the board lives next to the DEJA Server.
  • WiFi + MQTT (deja-esp32-wifi, deja-mqtt) — wireless, ideal for boards mounted inside scenery, under benchwork, or anywhere a USB cable is impractical. Requires an MQTT broker (Mosquitto recommended) on the same network as the server.

🚀 Setting Up a Device

  1. Register the device — In the Cloud app, go to your layout's Devices section and add a new device with a unique device ID and the matching device type.
  2. Flash the firmware — See Arduino & ESP32 Setup (for deja-arduino, deja-esp32, deja-esp32-wifi) or Pico W Setup (for deja-mqtt).
  3. Deploy configuration — Run the deploy script to push your Cloud configuration to the device. The wizard prompts for WiFi/MQTT credentials when needed.
  4. Verify — Open the Monitor app to see your device appear and respond to commands.

📚 Reference