Android app that implements the OpenDisplay WiFi protocol, turning any Android device into an OpenDisplay-compatible screen.

Built for the AValue EPD-42S (42" e-ink display running Android 5.1), but works on any Android 5.0+ device.

Note: OpenDisplay over WiFi is still under development. This app currently only works with the OpenDisplay Wi-Fi app for Home Assistant.

1. App discovers OpenDisplay servers on the local network via mDNS (_opendisplay._tcp)
2. Connects over TCP and announces display capabilities (resolution, color scheme)
3. Receives images from the server and renders them full-screen
4. Polls for updates at the interval specified by the server

opendisplay-android/
├── opendisplay-java/     # Standalone Java library (pure Java, no Android deps)
│   └── src/main/java/org/opendisplay/
│       ├── OpenDisplayProtocol.java   # Packet framing, CRC16, encode/decode
│       ├── OpenDisplayClient.java     # TCP client with polling loop
│       ├── ImageDecoder.java          # Image bytes → ARGB pixel array
│       └── DisplayConfig.java        # Display capabilities config
├── app/                  # Android app
│   └── src/main/java/org/opendisplay/android/
│       ├── MainActivity.java          # Full-screen display + lifecycle
│       └── MdnsDiscovery.java         # Android NsdManager mDNS discovery

The opendisplay-java library is a standalone Java library with zero Android dependencies. It can be used in any Java application — the Android app is just one consumer. The library is tested against py-opendisplay's WiFi server.

• minSdkVersion: 22 (Android 5.1 Lollipop)
• targetSdkVersion: 28
• Java 7 source/target for maximum device compatibility
• Tested on the AValue EPD-42S (NXP i.MX 7Dual, Android 5.1)

./gradlew assembleDebug
# APK at app/build/outputs/apk/debug/app-debug.apk

The Java library has unit tests and integration tests that automatically start a py-opendisplay WiFi server:

./gradlew :opendisplay-java:test

Requires uv and Python 3.11+ for the integration tests. If py-opendisplay is checked out somewhere else, set PY_OPENDISPLAY_DIR=/path/to/py-opendisplay.

Use py-opendisplay to serve images:

cd py-opendisplay
uv run opendisplay-serve photo.png

Implements the OpenDisplay Basic Standard WiFi protocol with uint32 frame lengths for large display support. Supports all 5 color schemes (monochrome, BW+red, BW+yellow, BW+red+yellow, 6-color).

MIT