In this section, you will examine the example Android app that performs GPIO interfacing on BBB. The purpose of this application is to demonstrate how to use PacktHAL to perform GPIO read and write processes from within an actual app. PacktHAL provides a set of interfacing functions that you will use to work with GPIOs from within your Android apps. These functions allow you to read the values of input GPIOs and set the values of output GPIOs. The low-level details of the hardware interfacing are implemented in PacktHAL, so you can quickly and easily get your apps interacting with GPIOs.

Before digging through the GPIO app's code, you must install the code to your development system and install the app to your Android system. The source code for the app, as well as a precompiled .apk package, are located in the chapter3.tgz file, which is available for download from the book's website.