n inputs to the Pico, and converts button
   presses into PC input, using the USB keyboard, gamepad, and XBox controller
   emulations described above.  The <a href="JSONConfigRef.htm#buttons"><tt>buttons</tt></a>
   property in the config file sets up the mappings between the physical buttons
   and the PC actions they invoke when pressed.
</p>
<p>
   In terms of the electrical wiring, there are a few ways to connect buttons
   to the Pico:
</p>
<ul>
   <li>GPIO ports
   <li>PCA9555 GPIO Extender chips
   