Tap. Command. Move.

The DEJA Server connects to DCC-EX EX-CommandStations over USB serial at 115200 baud. Every DCC command — throttle, turnout, function — is wrapped in angle brackets and sent as text: <t 3 50 1> means "set address 3 to speed 50, forward." The command station translates these into DCC signals on the track. Simple, plain-text, and documented by DCC-EX.

MQTT is a lightweight pub/sub protocol built for constrained hardware. The DEJA Server runs a broker that Arduino, ESP32, and Pico W devices connect to over WiFi. Every message shares the same {action, payload} shape as the WebSocket protocol — publish one to a device's topic and it acts in milliseconds.

{
  "action": "pin",
  "payload": { "pin": 4, "state": true },
  "device": "arduino-1"
}

WebSocket is an IO-device transport — a wireless alternative to MQTT for ESP32 WiFi and Pico W boards. Each device dials the DEJA Server at /device with its own token, and the port opens only when your layout has a WebSocket device. No app uses it: Throttle reaches your server through DEJA Cloud, so there is nothing to open on your network for your phone or tablet. Messages are small JSON envelopes, the same shape as MQTT.

{
  "device": "esp32-yard",
  "sensor": 2,
  "state": 1
}

Yes — the DEJA Server runs its own built-in WiThrottle server, replacing JMRI for that role. ProtoThrottle hardware, Engine Driver, ThrottleCard, and other WiThrottle clients connect directly and drive locomotives right alongside the DEJA Throttle app. We encourage you to use whatever throttle — or throttles — you like best. ThrottleCard in particular is worth a look, with Apple Watch control and game-controller support (Xbox, PlayStation, MFi) built in.

Throttle signs in with Firebase Authentication. Sessions are backed by signed JWT tokens and verified on every request, and the DEJA Server links to your account and layout before it will connect. You can share a layout with guest operators without handing out your password, and revoking access is instant.

Your roster, routes, turnouts, and effects live in Firestore and Realtime Database, protected by per-layout security rules — only accounts you've granted access can read or write them. All traffic between the apps, the server, and Firebase is TLS-encrypted in transit and encrypted at rest on Google's infrastructure. No layout data ever touches a public internet path in plaintext.

Firebase provides real-time sync between your apps and the server. When you change a throttle setting on your phone, Firebase pushes that change to the server instantly — no polling, no refresh. Your roster, routes, turnout states, and effects are all stored in Firebase so they persist across sessions and devices.

Your DEJA Server opens an outbound-only connection to DEJA Cloud and streams live device telemetry to your layout's private channel whenever someone has a device log open. Throttle's Devices page reads that stream in real time — free for everyone. There are no inbound router ports to forward, no firewall rules to punch holes in, and nothing on your home network is ever exposed to the internet.

Every remote read goes through Firebase Authentication and per-layout security rules — only members of your layout can see its data. The Server itself only ever dials out; combined with account linking, that's identity + authorization before any layout data leaves your network.

The DEJA CLI is a single command that starts the entire platform. It launches the Node.js server, connects to your DCC-EX EX-CommandStation via USB serial, connects to Firebase for cloud sync, and optionally starts the MQTT broker for IO devices and the WiThrottle server. One command: deja start.