In the last chapter, you prepared your development PC and BBBAndroid system for the development of hardware-interfacing Android apps. Now that your development environment is set up and ready to go, you will begin exploring your very first app that is capable of direct communication with hardware connected to the BBB.

General-Purpose Input/Output (GPIO) is one of the most basic interfaces in digital electronics. In the examples within this chapter, you will be working with GPIOs to receive digital input signals from the outside world and send digital output signals back in response. While this is a small start, it is the first step in developing and understanding hardware-interfacing apps that are much more complex. GPIOs can be used to implement complex and powerful interfacing logic. We will discuss both the hardware and software sides of GPIO interfacing and explain how calling Java methods in Android apps can interface with low-level...