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What is the proper way to close a connection to a UsbAccessory in Android? It seems the even in the stock Google example, if I connect and accessory, exit the app and then go back to it, the connection is not re-established.
Looking closely, it seems that after calling close() on the FileDescriptor, it won't open again, and a "could not open /dev/usb_accessory" log is emitted. NOT calling close() is a bad option, as a thread blocking on read() will not be released. Upon physical disconnection / reconnection of the device everything is OK.
It seems really surprising that the simple use-case of exiting the app and then opening it again does not work in the reference application and even more surprising if it is not feasible.
I'm using a Nexus S running stock Android 2.3.6.
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USB accessory mode allows users to connect USB host hardware specifically designed for Android-powered devices. The accessories must adhere to the Android accessory protocol outlined in the Android Accessory Development Kit documentation.
When you connect USB the first time (with already installed app), system call permission dialog. Then another time at start app usb will get permission automatically.
Open Accessory API or Open Accessory Framework - this is the API/framework in the Android development environment that allows the Android applications to transmit data in and out of the available USB port. This is provided by Google through the Android SDK.
The problem is that the reading thread never exits, thus the file descriptor stays open, and cannot be opened again when the app is resumed.
This has been confirmed to be a bug: http://code.google.com/p/android/issues/detail?id=20545
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