expo-juce

Realtime DSP w/C++ & JUCE

Quick Start

Installation

npm install expo-juce

iOS Setup

After installing, run:

npx pod-install

Android Setup

No additional setup required.

Basic Usage

Playing a Tone

import { Button } from 'react-native';
import * as ExpoJuce from 'expo-juce';

function App() {
  const playTone = () => {
    const frequency = 440; // A4 note (Hz)
    const duration = 0.5;  // seconds
    ExpoJuce.playTone(frequency, duration);
  };

  return <Button title="Play Tone" onPress={playTone} />;
}

Available Functions

• hello() - Returns a greeting string
• getApiKey() - Returns the API key
• playTone(frequency: number, duration: number) - Plays a sine wave tone at the specified frequency for the given duration
• setValueAsync(value: string) - Async function that emits a change event
• PI - Constant value of π

Events

Listen to change events:

import { addChangeListener } from 'expo-juce';

const subscription = addChangeListener((event) => {
  console.log('Value changed:', event.value);
});

// Clean up
subscription.remove();

Low-Latency Audio

The module is configured for low-latency audio playback:

• 5ms buffer size
• Real-time audio processing thread
• AVAudioEngine on iOS
• Optimized for minimal latency

Development

Running the Example App

cd example
yarn install
yarn ios  # or yarn android

Building the Module

npm run build

Testing & Distribution

For End Users to Test

Since this is a native module, users cannot test it with Expo Go. You have several options:

Option 1: Expo EAS Build (Recommended)

Install prebuilt version from EAS https://expo.dev/accounts/aaronsmulktis/projects/expo-juce-example/builds/a8f46b6b-60a4-4bfa-98fc-5c5458b45c60

Create a development build that users can install on their devices:

cd example
eas build --profile development --platform ios

This creates a custom development client with your native module. Share the build URL from EAS.

Option 2: TestFlight (iOS)

1. Create a production build:

   cd example
   eas build --profile production --platform ios

2. Submit to TestFlight:

   eas submit --platform ios

3. Invite testers via App Store Connect

Option 3: Internal Distribution (iOS)

1. Build an ad-hoc IPA:

   cd example/ios
   xcodebuild -workspace expojuceexample.xcworkspace \
              -scheme expojuceexample \
              -configuration Release \
              -archivePath build/expojuceexample.xcarchive \
              archive

2. Export and share the IPA file
3. Users install via device provisioning profiles

Option 4: GitHub Releases

1. Build APK/IPA files
2. Create a GitHub Release
3. Attach builds as release assets
4. Add installation instructions in release notes

Note: Native modules require a custom development build. Users cannot simply scan a QR code like with Expo Go.

API documentation

• Documentation for the main branch
• Documentation for the latest stable release

Installation in managed Expo projects

For managed Expo projects, please follow the installation instructions in the API documentation for the latest stable release. If you follow the link and there is no documentation available then this library is not yet usable within managed projects — it is likely to be included in an upcoming Expo SDK release.

Installation in bare React Native projects

For bare React Native projects, you must ensure that you have installed and configured the expo package before continuing.

Add the package to your npm dependencies

npm install expo-juce

Configure for iOS

Run npx pod-install after installing the npm package.

Configure for Android

Running the Example App

1. cd example
2. cd ios
3. npx pod-install
4. Open workspace in XCode
5. Update ENABLE_USER_SCRIPT_SANDBOXING to NO in Build Settings

Contributing

Contributions are very welcome! Please refer to guidelines described in the contributing guide.