  PCA9555 chips, but other I2C-compatible chips of completely different
   types.  Pinscape supports a number of I2C-based chips: PWM controllers,
   ADCs, accelerometers, and various plunger sensors.  You only have to
   define the i2c0/i2c1 section <i>once</i> for all of the chips that share
   that bus.
</p>
<p>
   Once the bus is configured, you can configure the PCA9555 itself.  This
   is done via the <a href="JSONConfigRef.htm#pca9555"><tt>pca9555</tt></a>
   property, where you specify the chip's bu