ardxp

This project provides an Arduino framework that connects physical cockpit controls to the X-Plane flight simulator over UDP using an Arduino Ethernet Shield.

COMPONENTS Hardware components

Arduino - Arduino Ethernet Shield

x 1

PROJECT DESCRIPTION

A reusable Arduino communication framework that connects physical cockpit controls (switches, rotary encoders, potentiometers) to the X-Plane flight simulator over UDP, using an Arduino Ethernet Shield (W5500).

1. The Problem

X-Plane isn't a typical flight game — it models aircraft systems in professional-grade detail and exposes two things over the network for external hardware to interact with:

Commands — trigger simulator actions (landing gear, autopilot functions, etc.)
DataRefs — represent internal simulator variables (airspeed, altitude, switch states, etc.)

The catch: every new cockpit hardware project would otherwise need to reimplement X-Plane's UDP protocol from scratch. ardxp abstracts that networking layer away, so developers can focus on the cockpit hardware itself instead of the wire protocol.

Typical uses: home cockpit panels, flight training simulators, DIY instrument clusters, switch/annunciator panels, throttle quadrants, autopilot panels.

2. What It Provides

Three core operations are supported:

Function	Purpose
`sendCommand()`	Send a command to the simulator (CMND)
`writeDataref()`	Write a value to a simulator variable (DREF)
`subscribeDataref()`	Subscribe to a simulator variable (RREF)

The standout feature is automatic simulator discovery — the framework listens for X-Plane's multicast beacon (BECN) instead of requiring a manually configured IP address.

IPAddress BECN_ip(239,255,1,1); udp.beginMulticast(BECN_ip, BECN_port);

The included example reads a potentiometer and writes its normalized value directly into an X-Plane DataRef:

const int zone_1_pot = A3; writeDataref(PSTR("cl300/gshldl_h"), pot_value / 1023.0);

3. How It Works (at a glance)

Arduino boot
   → Get IP via DHCP
   → Listen for X-Plane beacon (auto-discovery)
   → Open UDP channel
   → Read hardware input (switch / potentiometer)
   → Build & send X-Plane packet
   → Receive simulator updates → refresh LEDs/displays
   → (repeat, bidirectionally)

Unlike simple one-way UDP examples, ardxp is bidirectional — it sends hardware input to the simulator while simultaneously receiving state updates back, keeping physical cockpit indicators in sync.

4. Implementation Notes

Ethernet init (DHCP)

Serial.println(F("Waiting for DHCP.")); Ethernet.begin(mac); Serial.println(Ethernet.localIP());

UDP send

udp.beginPacket(xplane_ip, xplane_port); udp.write(packetBuffer, n_bytes); udp.endPacket();

Networking is delegated entirely to the standard Arduino Ethernet library (Ethernet.h, EthernetUdp.h), so application code only needs to deal with simulator logic, not raw Ethernet plumbing.

5. Practical Checklist

Confirm the Ethernet Shield is detected first — easy to mistake this for a simulator communication issue
The X-Plane PC and Arduino must be on the same subnet for multicast beacon discovery to work
If the beacon isn't found, check firewall settings first
Use exact, valid Command/DataRef names (typos fail silently)
When subscribing to many DataRefs, tune update rates to avoid flooding the network
Keep hardware input handling separate from protocol logic for easier maintenance

Related Projects

Project	WIZnet Product	Why It's Similar
Home Cockpit Simulator for X-Plane	W5500	The most closely related project. It uses Arduino and Ethernet to build a physical cockpit interface that communicates directly with the X-Plane flight simulator.
Home Automation Control Devices Remotely Through Internet Using Arduino	W5100/W5500	Demonstrates Arduino-based Ethernet control of physical devices over a network, following a similar hardware-to-network communication architecture.
Arduino Ethernet Servo Motor	W5100	Controls physical hardware through Ethernet using an Arduino and WIZnet Ethernet module. While not X-Plane-specific, it shares the same pattern of remotely controlling real-world devices over Ethernet.

6. FAQ

Q. Why an Ethernet Shield specifically? It plugs directly into the Arduino Ethernet library, letting the framework speak X-Plane's native UDP protocol without extra translation layers.

Q. Is this beginner-friendly? Yes. Networking is encapsulated in helper functions, so the real learning curve is understanding X-Plane's Command/DataRef naming — not the Ethernet implementation.

Q. Can it scale to a full cockpit build? Yes — it's designed as reusable infrastructure, not a one-off demo. Multiple Arduino panels, switches, encoders, and displays can all share the same UDP communication layer.

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