Before you begin developing software that communicates using GPIOs, you must first construct a hardware circuit for the GPIOs to interface with. For this chapter, you will build a simple circuit that consists of a 1k ohm resistor, an LED, and a pushbutton switch. Part numbers and suppliers for these components were listed in Chapter 1, Introduction to Android and the BeagleBone Black. Before getting started, be sure that you have all of the proper parts and remove all power sources from your BBB (unplug the power supply and USB cables) prior to connecting anything to the BBB's P8/P9 connector.
Tip
Don't disassemble your circuit!
The GPIO circuit in this chapter is part of a much larger circuit used in Chapter 6, Creating a Complete Interfacing Solution. If you build the circuit as it is positioned in the following diagram (towards the top of the breadboard), you can simply leave the GPIO components and wires in place as you build the remaining circuits...