Bulktransfer returns -1
<p>First let me state that I am brand new to Android Development so maybe USB is a bit complex for a first app but it is my only reason for wanting to write an app in the first place.</p>

<p>I would like to communicate to a Garmin GPS over USB.   I have done so in the past with success from the PC but it was via a driver supplied by Garmin.</p>

<p>As far as I am aware there is no such driver for Android so I need to write directly to the USB.</p>

<p>Garmin publishes this documentation:</p>

<p><a href="http://www8.garmin.com/support/pdf/USBAddendum.pdf" rel="nofollow">http://www8.garmin.com/support/pdf/USBAddendum.pdf</a></p>

<p>Basically it says you must transmit on bulk out:
00 00 00 00 05 00 00 00 00 00 00 00</p>

<p>to tell the device to  prepare for a transfer.   When I do so, my bulktransfer fails with -1.  If I have a 0 for the timeout then bulktransfer never returns.   I assume becuase there is no response from the gps.</p>

<p>I have included my code below.  The code detects the GPS and opens it.  But the first bulktransfer never completes. I am certain I am sending to the bulk out endpoint.  Can anyone get me started?</p>

<pre><code>    public class MainActivity extends Activity {

     private static final String TAG = "TestGarmin";
     private UsbManager mUsbManager;
     private UsbDevice mDevice;
     private UsbDeviceConnection mConnection;
     private UsbEndpoint mEndpointIntr;
     private UsbEndpoint mEndpointBulkOut;
     private UsbEndpoint mEndpointBulkIn;
     private static int TIMEOUT = 0;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

         mUsbManager = (UsbManager)getSystemService(Context.USB_SERVICE);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

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

            Intent intent = getIntent();
            Log.d(TAG, "intent: " + intent);
            String action = intent.getAction();
            String s = UsbManager.ACTION_USB_DEVICE_ATTACHED;           


            UsbDevice device = (UsbDevice)intent.getParcelableExtra(UsbManager.EXTRA_DEVICE);
            if (UsbManager.ACTION_USB_DEVICE_ATTACHED.equals(action)) 
                setDevice(device);

     }

     private 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 three endpoints
            if (intf.getEndpointCount() != 3) {
                Log.e(TAG, "could not find endpoint");
                return;
            }           
            // endpoint 0 should be of type interrupt
            UsbEndpoint ep0 = intf.getEndpoint(0);
            if (ep0.getType() != UsbConstants.USB_ENDPOINT_XFER_INT) {
                Log.e(TAG, "endpoint 0 is not interrupt type");
                return;
            }


            if (ep0.getDirection() != UsbConstants.USB_DIR_IN) {

                Log.e(TAG, "endpoint 0 is not an input endpoint");
                return;             
            }


            mEndpointIntr = ep0;

            // endpoint 1 should be of type bulk
            UsbEndpoint ep1 = intf.getEndpoint(1);
            if (ep1.getType() != UsbConstants.USB_ENDPOINT_XFER_BULK) {
                Log.e(TAG, "endpoint 1 is not bulk type");
                return;
            }

            if (ep1.getDirection() != UsbConstants.USB_DIR_OUT) {

                Log.e(TAG, "endpoint 1 is not an output endpoint");
                return;             
            }

            mEndpointBulkOut = ep1;

            // endpoint 2 should be of type bulk
            UsbEndpoint ep2 = intf.getEndpoint(2);
            if (ep2.getType() != UsbConstants.USB_ENDPOINT_XFER_BULK) {
                Log.e(TAG, "endpoint 2 is not bulk type");
                return;
            }

            if (ep2.getDirection() != UsbConstants.USB_DIR_IN) {

                Log.e(TAG, "endpoint 2 is not an output endpoint");
                return;             
            }




            mEndpointBulkOut = ep2;


            mDevice = device;

            if (device != null) {
                UsbDeviceConnection connection = mUsbManager.openDevice(device);
                if (connection != null &amp;&amp; connection.claimInterface(intf, true)) {
                    Log.d(TAG, "open SUCCESS");
                    mConnection = connection;

                    byte[] init = {0x00,0x00,0x00,0x00,0x05,0x00,0x00,0x00,0x00,0x00,0x00,0x00};

                    //14 00 00 00 FE 00 00 00 00 00 00 00
                    int x = connection.bulkTransfer(mEndpointBulkOut,init, init.length, 100);

                    Log.e(TAG, "BulTransfer returned " + x);




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

}
</code></pre>
