USB HID on Android

Question

I'm trying to read data from the custom made USB device (working as slave) in Android. I was able to write the data to the device with this code:

UsbRequest request = new UsbRequest();
request.initialize(_outConnection, _outEndpoint);

int bufferDataLength = _outEndpoint.getMaxPacketSize();

ByteBuffer buffer = ByteBuffer.allocate(bufferDataLength + 1);
buffer.put(bytes);
if (request.queue(buffer, bufferDataLength)) {
            UsbRequest req = _outConnection.requestWait(); }

I see the result on the debug board that my device is connected to. I'm trying the same approach for reading data, but apparently that doesn't work:

int siz = 1; 
ByteBuffer res = ByteBuffer.allocate(siz + 1);
UsbRequest request = new UsbRequest();
request.initialize(_inConnection, _inEndpoint);
request.queue(res, siz); // This return false always

What am I doing wrong? I have no idea of the size of the packet sent back - but I assume that 1 byte I would be always able to read.

My device has HID interface with two interrupt endpoints (IN and OUT)

Yes, but I'm not sure what fixed the problem. I will write as the answer what I did — Archeg
can you share me the code please @Archeg. It will be helpful for me. I am also searching the same nearly a week. I ll be gone mad if i dont find. — Sathish
I'm sorry to bump an old question, but it seems that your final post is the only reference to our problem on SO. Did you manage to reset the connection to the HID device, we are running into the same problem as mentioned in your last post. We've tried the releaseInterface(UsbInterface intf) class but this does not function because our HID device (Motorola LS2208) doesn't have a deviceID. — Rick
Here is the code that was working on the real device: gist.github.com/archeg/8333021 I must say, that this code was test code, that is not meant to get to production, so I just tried different stuff until it worked. There are some strange things that are happening there, but it worked and that was ok for me. — Archeg

Archeg Archeg · Accepted Answer · 2013-04-04T08:33:39

I have no idea what fixed the problem, but now it works. I have rewritten everything from scratch. I think I didn't use this code (I thought it is for user notification and I don't need that. But appears it is something else) - and that was the main reason why it didn't work:

// Create and intent and request a permission.
    PendingIntent mPermissionIntent = PendingIntent.getBroadcast(_context, 0, new Intent(ACTION_USB_PERMISSION), 0);
    IntentFilter filter = new IntentFilter(ACTION_USB_PERMISSION);
    _context.registerReceiver(mUsbReceiver, filter);

Several things that I did and which helped me to implement stable connection are:

1) Closing and opening the connection each time I need it. I know this is sounds strange, but this is the only way I could make it stable. If I try to use long-living connection, for some reason it gets corrupted and stops from working after some time.

2) Reading continously in never-ending while loop. I also put some short sleeps in all my threads - that helped to read in more real time manner.

3) Locking the device (synchronized). I do not open both write and read connections simultaneously.

I didn't have much hours assigned for this project, and this project is only a demo - so all of this suited us well. I think if spent a little more time, some of these things could have been rewritten to more nice ones.

USB HID on Android

1 Answers