HassMic

Hassmic (HM) is an Android application and Home Assistant designed to run on devices acting as Home Assistant voice assistant satellites. It does this with two parts:

• The HassMic App runs a Wyoming satellite, which can be auto-detected and set up by Home Assistant. This can be used entirely independently of the HassMic Integration if you want.
• The HassMic App also listens for a connection from the HassMic integration, which can be installed by adding this repository in HACS (or by copying the custom_components/hassmic directory into the appropriate place in your configuration directory). This provides a few advantages:
  • Using the integration, you can control the volume of the text-to-speech responses.
  • The integration also provides a media_player with its own independent volume control, which will automatically pause and resume when the voice assist is activated
  • The integration provides more sensors about the state of the client, including instrumentation that can help with debugging or deeper integration of a HM device.

The following features are planned, but not currently implemented:

• Timer support
• Local wakeword support

Some caveats to using the app include:

• Automatically starting on Android 12+ fails in an annoying way: the service auto-starts, but can't access the microphone. This is a security feature added to Android that I don't have a great solution for (no auto-start services can access the microphone unless they also start a UI).
• There's not really a "UI" to speak of. Opening the app gives some diagnostic information and a single toggle switch. You must enable running in the background, since that's where all the work happens. If running in the background isn't enabled, the app does nothing.

License

This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

Dev Tips

This project is built on React Native and uses a substantial amount of native code. Vestiges of expo infrastructure still exist, but expo commands won't work.

To build an APK use,

cd android
./gradlew assembleRelease

The built APK will be at android/app/build/outputs/apk/release/app-release.apk

You can also use installRelease instead of assembleRelease to install the built package to a device connected via adb.

HM Protocol Notes

The HassMic client and server communicate using a slightly strange paradigm based on protocol buffers (defined in the proto/ directory). The server sends ServerMessage messages to the client, and the client sends ClientMessages to the server. Because of a strange bug that I never quite got to the bottom of with sending raw binary data back and forth, these protos are marshalled to their binary forms and then base64-encoded, and sent over the wire as newline-separated strings. There is no handshaking involved; client messages and server messages are handled by separate threads on both ends. The client also sends a periodic ping to let the server know it's still connected, even if it's not sending audio data.

If you're reading the code and come across the name Cheyenne, you've found the HassMic integration protocol. That name is an outdated pun -- in early versions of Hassmic, the protocol was based around the core of the Wyoming protocol. It has since been rewritten and no longer resembles Wyoming, but for the moment the name persists.