Research And Implementation Of Android Audio Accessory Based On AOA Protocol

As Android open accessory (AOA) protocol is released, Android-powered device and its peripherals can access each other contributing to an Android ecosystem easily. Android audio accessory is more and more popular to consumers and thus AOA protocol specially gives support to it.This thesis provides a new Android audio accessory solution by a deep research for AOA protocol and audio accessory technology. AOA protocol specifies that Android-powered device can communicate with accessory and accessories implementing AOA API can access Android-powered device. This thesis studys AOA protocol core content, technology and application scenarios, analyzes auido accessory’ demands and then designs and implements the feature of playing Android audio to audio accessory through USB interface. Besides, by studying technologys such as Bluetooth, USB mass storage and SD, Android audio accessory in this thesis also supports Bluetooth play, USB disk play and SD card play. So, there are four audio sources for Android audio accessory, that is, AOA audio, Bluetooth audio, USB disk audio and SD card audio. By software decoding to respective audio source, Android audio accessory afterwards streams available PCM data to high-quality codec. According the distinction of audio sources, Android audio accessory supports four play modes. Each paly mode has a static priority which is eventually used by Android audio accessory to select audio source. This thesis analyses demands of hardward and software development platform, taking several alternatives of different semiconductor vendors into account, and eventually selects Freescale Kenitis k70 microcontroller and SGTL 5000 stereo audio codec.This thesis brings AOA protocol into Android audio accessory and a new method of playing Android audio through USB is implemented, breaking out the situation of current audio accessory market which is dominated by Bluetooth and local playback. This thesis involves several key technologys including AOA protocol, Bluetooth advanced audio distribution profile, USB mass storage protocol and SD protocol.