Professional Android Sensor Programming

Chapter 10

Android Open Accessory

What's in this chapter?

Introducing AOA

Explaining how AOA works and why developers may want to use it

Presenting some of the limitations of AOA

Providing an example of code that uses AOA

Android Open Accessory (AOA) is a protocol that allows an Android device to interact with external sensors and actuators via USB. This addition to the Android SDK is exciting for both electronics hobbyists and mobile professionals because it opens up the possibilities of reacting to real-world inputs like temperature changes and controlling real-world objects such as lights without being limited to the current form-factor of a mobile phone or its current hardware sensors.

A Short History of AOA

AOA is a relatively new and underutilized feature of the Android SDK, having only been announced by Google at the Google I/O developer conference in May 2011. Official Android SDK support for external hardware such as USB devices (and, to some extent, NFC) is still in the early phases and the infancy of the APIs may help explain why some idiosyncrasies such as power requirements (to be described in a later section) exist.

At the same time as announcing the AOA APIs in the Android SDK, Google also announced the availability of an Android Development Kit (ADK) microcontroller based on the popular Arduino hardware platform. In conjunction with external hardware, it is easy to see how mobile phones have shifted away from simply being cellular-enabled phones to “little computers ...