question: public void write ( Command command , int value , int index , ByteBuffer buffer ) throws UsbException { if ( mDeviceHandle != null ) { int transferred = LibUsb . controlTransfer ( mDeviceHandle , USB_REQUEST_OUT , command . getValue ( ) , ( short ) value , ( short ) index , buffer , USB_TIMEOUT_MS ) ; if ( transferred < 0 ) { throw new LibUsbException ( "error writing byte buffer" , transferred ) ; } else if ( transferred != buffer . capacity ( ) ) { throw new LibUsbException ( "transferred bytes [" + transferred + "] is not what was expected [" + buffer . capacity ( ) + "]" , transferred ) ; } } else { throw new LibUsbException ( "device handle is null" , LibUsb . ERROR_NO_DEVICE ) ; } }
target:  Writes the buffer contents to the device