Bulktransfer returns -1

Question

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. 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. As far as I am aware there is no such driver for Android so I need to write directly to the USB. Garmin publishes this documentation: http://www8.garmin.com/support/pdf/USBAddendum.pdf Basically it says you must transmit on bulk out: 00 00 00 00 05 00 00 00 00 00 00 00 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. 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?…

Accepted Answer

It was a problem with me mixing up my endpoints. Here is the corrected code, now I am having an issue with getting a response but I will probably create another post.

```
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 0 Bulk Out ************/
        // 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 3 Bulk in *************/
        // 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 input endpoint");
            return;             
        }

mEndpointBulkIn = ep2;

mDevice = device;

if (device != null) {
            UsbDeviceConnection connection = mUsbManager.openDevice(device);
            if (connection != null && 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;
            }
         }
    }

}
```

Bulktransfer returns -1

Solution

Problem