tream(fd);  // use this to receive messages
  mOS = new FileOutputStream(fd); // use this to send commands
}
</pre>

<p>Review the <code>UsbConnection.java</code> file provided in the ADK 2012 source code for more
implementation details.</p>

<h2 id="audio-dock">USB Audio Dock Implementation</h2>

<p>One of the important new features introduced with the ADK 2012 is the ability to play audio over
a USB connection. This innovation was introduced as an update to Android Open Accessory (AOA)
<a href="http://sou