Android USB MIDI Driver

To use the MIDIDriver library in your Android application, follow these steps:

1. Clone the repository.
2. Import the MIDIDriver library project into your IDE (e.g., Eclipse or Android Studio) and build it.
3. Create a new Android project and add the MIDIDriver project as a library dependency.
4. Configure your AndroidManifest.xml to include the USB host feature and set the launchMode of your MIDI activity to singleTask.

Important: The launchMode must be singleTask to ensure the activity handles USB connection intents correctly.

<uses-feature android:name="android.hardware.usb.host" /> 

<application>
    <activity
        android:name=".MyMidiMainActivity"
        android:label="@string/app_name"
        android:launchMode="singleTask" >
        <intent-filter>
            <category android:name="android.intent.category.LAUNCHER" />
            <action android:name="android.intent.action.MAIN" />
        </intent-filter>
    </activity>
</application>

Use AbstractSingleMidiActivity when your application only needs to connect to one MIDI device at a time.

Receiving MIDI Events

Implement the corresponding onMidi... methods (e.g., onMidiNoteOn).

Warning: These methods are called from a background thread, not the UI thread. To update your UI, you must use a Handler and Callback to communicate with the UI thread.

Sending MIDI Events

1. Call getMidiOutputDevices() to get an instance of MIDIOutputDevice.
2. If no device is connected, getMidiOutputDevices() returns null.
3. Call the sendMidi... method on the returned instance to transmit MIDI data.

public class SampleActivity extends AbstractSingleMidiActivity {

    // This field belongs to the UI thread
    final Handler uiThreadEventHandler = new Handler(new Callback() {
        @Override
        public boolean handleMessage(Message msg) {
            if ("note on".equals(msg.obj)) {
                textView.setText("note on event received.");
            }
            return true;
        }
    });

    // This method is called from a background thread
    @Override
    public void onMidiNoteOn(final MidiInputDevice sender, int cable, int channel, int note, int velocity) {
        // Send a message to the UI thread to update views
        String message = "note on";
        uiThreadEventHandler.sendMessage(Message.obtain(uiThreadEventHandler, 0, message));
    }
}

If your device is detected by the Android host but not by the driver, you may need to manually add its VendorId to the project's device_filter.xml file.

Steps to modify the filter:

1. Clone the repository and open the library project in your IDE.
2. Open res/xml/device_filter.xml.
3. Add a new <usb-device /> entry using the VendorId you identified during troubleshooting.

CRITICAL: Conversion Requirement The VendorId displayed in USB diagnostic tools is typically in Hexadecimal, but the device_filter.xml file requires the value in Decimal.

Testing the modification:

1. Uninstall the existing sample application from your Android device.
2. Build and run your modified version of the sample app.
3. Launch the app, then connect the USB MIDI device.
4. Verify detection in the app and test MIDI message bidirectional transfer (sending and receiving).

<!-- Example of adding a device to res/xml/device_filter.xml -->
<!-- If your Hex VendorId is 0x0483, use decimal 1155 -->
<usb-device vendor-id="1155" />

If the sample application cannot detect your USB MIDI device, follow these diagnostic steps to identify if the issue is with Android connectivity, device standards, or driver configuration.

1. Verify Android Host Connectivity

Use the USB Device Info app to ensure the Android host sees the hardware:

• Open the app and select the Android tab (do not use the Linux tab).
• Tap Refresh, connect your USB MIDI device, and tap Refresh again.
• If the device information does not appear, the Android host is not detecting the hardware at all.

2. Verify USB Interface Class

In the USB Device Info app, check the Interface section. A standard USB MIDI device must have one or more interfaces with the following class:

• Audio Device (0x1)

If the device only shows other classes (like CDC or HID), it is not a standard USB MIDI device. The driver may still work if the device uses a USB MIDI compatible protocol.

3. Verify USB Endpoints

Check the Endpoint information in the USB Device Info app. A compatible device must have one or more endpoints that meet these criteria:

• Type: Must be Bulk or Interrupt.
• Direction: Must be Inbound, Outbound, or both.

If these conditions are met, note the device's VendorId for the next step.