Question

I’m a beginner android programmer who is trying to set up some USB functionality with my tablet and a device. My program uses an Intent filter to find the device. I took the Android’s MissileLauncherActivity.java example and rewrote it. I am getting a “could not find endpoint” error in logcat. Is there something wrong with my code, or could it be my device? LogCat is finding the error in the setDevice method where it is trying to find the OUT endpoint. Here is the code:

public class UsbTestActivity extends Activity implements Runnable {

private UsbManager mUsbManager;
private UsbDevice mDevice;
private UsbDeviceConnection mConnection;
private UsbEndpoint mEndpointIntr;
private static final String TAG = "UsbTestActivity";

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    mUsbManager = (UsbManager)getSystemService(Context.USB_SERVICE);
}

@Override
public void onPause(){
    super.onPause();
}

@Override
public void onResume(){
    super.onResume();

    Intent intent = getIntent();
    Log.d(TAG, "intent: " + intent);
    String action = intent.getAction();
    UsbDevice device = (UsbDevice)intent.getParcelableExtra(UsbManager.EXTRA_DEVICE);
    if (UsbManager.ACTION_USB_DEVICE_ATTACHED.equals(action)) {
        setDevice(device);
    } else if (UsbManager.ACTION_USB_DEVICE_DETACHED.equals(action)) {
        if (mDevice != null && mDevice.equals(device)) {
            setDevice(null);
        }
    }
}

@Override
public void onDestroy() {
    super.onDestroy();
}

public void setDevice(UsbDevice device){
    Log.d(TAG, "setDevice " + device);
    if (device.getInterfaceCount() != 1) {
        Log.e(TAG, "could not find interface");
        return;
    }
    UsbInterface intf = device.getInterface(0);
    // device should have one endpoint
    if (intf.getEndpointCount() != 1) {
        Log.e(TAG, "could not find endpoint");
        return;
    }
    System.out.println("Got endpoint");
    // endpoint should be of type interrupt
    UsbEndpoint ep = intf.getEndpoint(0);
    if (ep.getType() != UsbConstants.USB_ENDPOINT_XFER_INT) {
        Log.e(TAG, "endpoint is not interrupt type");
        return;
    }
    mDevice = device;
    mEndpointIntr = ep;
    if (device != null) {
        UsbDeviceConnection connection = mUsbManager.openDevice(device);
        if (connection != null && connection.claimInterface(intf, true)) {
            Log.d(TAG, "open SUCCESS");
            mConnection = connection;
            Thread thread = new Thread(this);
            thread.start();

        } else {
            Log.d(TAG, "open FAIL");
            mConnection = null;
        }
     }
}


private void sendCommand(int control) {
    synchronized (this) {
        if (mConnection != null) {
            byte[] message = new byte[1];
            message[0] = (byte)control;
            // Send command via a control request on endpoint zero
            if(mConnection.controlTransfer(0x21, 0x9, 0x200, 0, message, message.length, 0) > 0){
                Log.d(TAG, "Sending Failed");
        }
    }
}
}

public void run() {
    ByteBuffer buffer = ByteBuffer.allocate(1);
    UsbRequest request = new UsbRequest();
    request.initialize(mConnection, mEndpointIntr);
    byte status = -1;
    while (true) {
        // queue a request on the interrupt endpoint
        request.queue(buffer, 1);
        // send poll status command
        if (mConnection.requestWait() == request) {
            byte newStatus = buffer.get(0);
            if (newStatus != status) {
                Log.d(TAG, "got status " + newStatus);
                status = newStatus;
                sendCommand(7);

            }
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {
            }
        } else {
            Log.e(TAG, "requestWait failed, exiting");
            break;
        }
    }
}

}

Answer 1

// device should have one endpoint
    if (intf.getEndpointCount() != 1) {
        Log.e(TAG, "could not find endpoint");
        return;
    }

Looks like you are trying to work with a USB HID device and its OUT endpoint. But HID mandates the IN endpoint to be present – so getEndpointCount() will most likely return 2 instead of one. You will need to check which is the IN and which is OUT.