Once the interface factors are determined, one of the three interface options can be used. The first interface option is using Android Open Accessory (AOA) mode. Google introduced AOA in May 2011 to address the dilemma of wanting to control a much simpler peripheral from the Android platform using the USB device port. AOA allows peripherals to use the USB Embedded Host as their interface to the Android platform. At the physical layer and through the establishment of the USB connection (aka Enumeration), a traditional host-peripheral connection is made. The power arrangement is also maintained. The peripheral platform could provide the full 500 mA to the Android device. One can think of the two entities, Android host and AOA peripheral, as swapping logical functions. The Android platform (USB device) is now controlling the peripheral (USB host) through an installed application (APK). The only requirement to use AOA is that the Android platform be running OS version 3.1 onward.