User manual

AOAA Kit - User’s Guide
Page 16
Copyright 2012 © Embedded Artists AB
4 The AOAA Board Design
This chapter describes the design of the AOAA Kit both from a conceptual and hardware perspective.
Android Open Accessory allows connecting Accessories to an Android device. The Accessory and
Android device communicates over USB. The Accessory has to implement a USB Host interface, while
the Android acts as a USB client (also called USB Device). For more information about Android Open
Accessory, see [3].
The AOAA Kit supports the requirements to implement an Android Accessory and much more!
4.1 AOA Use Cases
Typical basic Accessory use cases are outlined below. There are many application where connecting
(typically) a phone to an isolated system has great benefits. It can give the system a user interface for
information readout or control of the system. It can also allow for the system to get Internet access.
Figure 7 – Basic Android Accessory Use Cases
There are two ways of viewing the relationship between the Android device and the accessory:
 A traditional view is that the application in the Android device contains the intelligence and
basically only uses the accessory for input/output. In a master/slave analogy, the Android
device would be the master and the accessory the slave.
 An alternative is to view the Android device as (an alternative) user interface to the accessory.
The intelligence is embedded in the accessory and the application running on the Android
device creates a graphical user interface to the accessory. Possibly in combination with a
communication channel with the Internet.
The AOAA kit is much more than just a platform for prototyping and developing basic Android Open
Accessory applications. The hardware has a network centric design, meaning that there is provision for
creating both wired and wireless networks. Figure 8 below illustrated the three types of networks
directly supported by the AOAA board.
Android
Accessory
Device
Graphical User Interface
- For status readout from Accessory
- For control of Accessory
Phone is Internet gateway
- For downloading new
profiles/settings
- For upgrading system
- For buying new features
- For accessing remote information
- For allowing remote access of
system, for example diagnostic
service
Accessory is gateway to wireless
remote accessory, like pulse meter,
pedometer, etc.