4.c. Pushbuttons

The expansion PCB has designated connection points for three pushbuttons: a push-on/push-off power button connected in parallel with the power button on the 3pi base, a general-purpose pushbutton connected to mbed pin P21 on one side and ground on the other, and a general-purpose pushbutton that is not connected to anything except a set of prototyping pins on each side. This last button can be connected to an arbitrary mbed or Wixel I/O line to create a second user-interface pushbutton.

General-purpose pushbutton on the m3pi expansion PCB.

A ground pad is conveniently placed next to the pads connected to the right side of this general-purpose pushbutton, which makes it easy to connect one side of the button to ground.