
<h4>

<h4>PCA9555 inputs</h4>
<p>
   The Pico has a relatively small number of GPIO ports, which limits
   the number of buttons you can attach.  This is even more limiting
   if you're attaching anything else to the Pico, such as an accelerometer
   and plunger sensor, since those will also use up some GPIO ports.
</p>
<p>
   One way to add more ports is with a GPIO Extender chip.  These are
   special chips that are specifically designed to add extra GPIO-like
   input/output ports to a microcontroller, 