An accessory that connects with Android over USB connection must use the Android Open Accessory (AOA) protocol version 2.0. This version of the AOA protocol is supported on Android 4.1 (API Level 16) and higher. Once an Android device connects to an accessory that supports this protocol, the Android system treats it as a standard audio output device and routes all audio to that accessory. No secondary software application is required on the Android device.
Note:
什么是AOA 和AOA2 呢?
http://source.android.com/tech/accessories/aoap/aoa.html
http://source.android.com/tech/accessories/aoap/aoa2.html
AOA2 还可以支持hid , 就很方便了,即使是android 的手机和平板做usb device , 也可以支持hid 哦。只要支持AOA2 就可以。xmos 的usb audio 就可以远程操作android 手机播放暂停...
AOA 2.0 allows the accessory to register one or more USB Human Interface Devices (HID) with an Android device. This approach reverses the direction of communication for typical USB HID devices like USB mice and keyboards. Normally, the HID device is a peripheral connected to a USB host like a personal computer. But in the case of the AOA protocol, the USB host acts as one or more input devices to a USB peripheral.
HID support in AOA 2.0 is simply a proxy for standard HID events. The implementation makes no assumptions about the content or type of events and merely passes it through to the input system, so an AOA 2.0 accessory can act as any HID device (mouse, keyboard, game controller, etc.). It can be used for something as simple as the play/pause button on a media dock, or something as complicated as a docking station with a mouse and full QWERTY keyboard.
如果你想启用USB音频设备通过任何Android4.0官方固件/内核,在这里请投票:
http://code.google.com/p/android/issues/detail?id=24614
星:点击星投票
根据Android3.1的规格,Android 4.0的设备可以支持USB音频功能,即Android的4.0设备和USB_CLASS_AUDIO的兼容标准的USB DAC可互操作的设备,如:
http://developer.android.com/guide/t...usb/index.html
http://developer.android.com/reference/and...bConstants.html
标准的USB DAC的USB_CLASS_AUDIO兼容的设备,不需要特殊的USB设备驱动程序。相反,他们使用的操作系统的标准驱动程序。
Android标准的USB音频驱动程序是通用的USB音频驱动ALSA(高级Linux声音架构)。
最新的Android 4.0包括card.c,USB音频驱动器,用于ALSA这应该是符合USB音频类设备,允许24位/192千赫。
https://bitbucket.org/paulobrien/android_ke...ound/usb/card.c
如果你需要了解详细的情况,请到这个链接
5)客户产品点评
google 有一个社区专门讨论usb audio on android 。
http://code.google.com/p/android/issues/detail?id=24614&sort=-stars&colspec=ID Type Status Owner Summary Stars