The Accessory Development Kit (ADK) is a reference implementation for hardware manufacturers and hobbyists to use as a starting point for building accessories for Android. Each ADK release is provided with source code and hardware specifications to make the process of developing your own accessories easier. Creating new and alternative hardware based on the ADK is encouraged!
Android accessories can be audio docking stations, exercise machines, personal medical testing devices, weather stations, or any other external hardware device that adds to the functionality of Android.
Accessories use the Android Open Accessory (AOA) protocol to communicate with Android devices, over a USB cable or through a Bluetooth connection. If you are building an accessory that uses USB, make sure you understand how to implement the AOA protocol to establish communication between your accessory hardware and Android. For more information, see the Android Open Acessory protocol.
The following sections provide more information about the Android Accessory Development Kits, how to use them, and how to get started building your own accessories for Android.