MOTU Simple Control Panel (Unofficial)

This is a basic control panel I wrote for my MOTU UltraLite AVB audio interface.

The whole app is based on Tauri, with a Next.js frontend.

This is a rewrite of my previous version made with Flutter

Keep in mind that this app talks to my interface based on how I configured my input/output/mixer channels, your configuration will surely be different.

How to use

On first launch, the app will show an alert notifying about the missing API URL inside the app settings. Head to the settings and insert the full MOTU AVB API Datastore URL in the dedicated field.

The URL will have a format similar to this:
http://localhost:1280/0001f2fffe012d80/datastore

Once saved, return to the app home to use the interface.

How it works

MOTU AVB audio interfaces have a build-in API you can use to get or set values. Since they don't have a WebSocket, I had to use a Long Polling approach, that's exactly how the official webapp works.

Reading from the API

• For each request, the API sends an "ETag" Header, that represents the number of times any parameter changed since boot.
• After each request, we save that ETag locally, then in the next request we send a "If-None-Match=<that_etag>", and if it does not match with the ETag the interface has, it means something changed, so the interface will reply back ONLY with the parameters that changed since the tag we sent.
  If the ETag is the same, the interface will hang for 15 seconds waiting for possible changes, if nothing changes it will reply with a status code 304.
• Since we receive only "incremental data" from the API, we save everything in a datastoreState variable, and merge into that on every update.

Writing to the API

• For the Faders, the API expects Amplitude Ratio values from a minimum of 0 (-∞dB) to a maximum of 4 (+12dB), so a conversion is needed, ad it's done with methods contained in the lib/decibelUtils.js file.
  In this app, I've adjusted faders to have a value that spans between a minimum of -6dB and a maximum of 6dB.
• Toggle buttons in the API are 0 (OFF) or 1 (ON).

References:

• MOTU AVB API Documentation
• Decibel Amplitude Ratio example table
• Decibel to Amplitude Ratio formula

Development

# Install Node dependencies
npm i

# Install Rust dependencies
cd src-tauri
cargo update

# Development server
npm run tauri dev

# Build release
npm run tauri build

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