android usb主机异步中断传输

Question

public boolean OpenDevice() {
    _usbManager = (UsbManager) _context.getSystemService(Context.USB_SERVICE);

    HashMap<String, UsbDevice> deviceList = _usbManager.getDeviceList();

    Iterator<UsbDevice> deviceIterator = deviceList.values().iterator();
    _usbDevice = null;

    // Iterate all the available devices and find ours.
    while(deviceIterator.hasNext()){
        UsbDevice device = deviceIterator.next();

        if (device.getProductId() == _productId && device.getVendorId() == _vendorId) {
            _usbDevice = device;
            _deviceName = _usbDevice.getDeviceName();
        }
    }

    if (_usbDevice == null) {
        Toast.makeText(_context,"Cannot find the device. Did you forgot to plug it?",Toast.LENGTH_SHORT).show();

        return false;
    }

    // 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);

    _usbManager.requestPermission(_usbDevice, mPermissionIntent);
            UsbInterface writeIntf = _usbDevice.getInterface(0);
            epOUT=writeIntf.getEndpoint(1);
            epIN=writeIntf.getEndpoint(0);
            mUsbDeviceConnection=_usbManager.openDevice(_usbDevice); 
               mUsbDeviceConnection.claimInterface(writeIntf, true);
    Toast.makeText(_context,"Found the device",Toast.LENGTH_SHORT).show();
    return true;
}
 public byte[] read(UsbRequest outRequest) throws UsbException {
    if (mUsbDeviceConnection == null) {
        throw new UsbException("no connection available");
    }

    ByteBuffer buffer = ByteBuffer.allocate(MAX_PACKAGE_SIZE);


    if (outRequest.equals(mUsbDeviceConnection.requestWait())) {
        UsbRequest inRequest = new UsbRequest();
        inRequest.initialize(mUsbDeviceConnection, epIN);
        if (inRequest.queue(buffer, MAX_PACKAGE_SIZE)) {
            mUsbDeviceConnection.requestWait();
            return buffer.array();
        }
    }
    return null;
}


public UsbRequest write(byte[] command) throws UsbException {
    if (mUsbDeviceConnection == null) {
        throw new UsbException("no connection available");
    }

    ByteBuffer buffer = ByteBuffer.allocate(1);

    UsbRequest outRequest = new UsbRequest();
    outRequest.initialize(mUsbDeviceConnection, epOUT);

    buffer.put(command);
    outRequest.queue(buffer, 1);

    return outRequest;
}


public byte[] sendCommand(byte[] command) throws UsbException {

    UsbRequest request = write(command);
    _textInfo.setText(_textInfo.getText()+"\n" +request );
    return read(request);
}

我正在尝试在endPointOut上推送一些命令并尝试从endPointIN接收数据，但是当我尝试使用mUsbDeviceConnection.requestWait（）应用程序读取时没有响应

以下代码说明我如何调用这些函数

byte b=(byte)'x';
            byte command[] = {b};
byte[] result=   hidBr.sendCommand(command);

我得到一个空白数组