The function key is controlled via the integrated GPIO. 



Programming under Windows


AA15: 0xFED84C00, this is the address of this GPIO.

AA15: 0xFED84C00 High: Bit0=0x8201, Low: Bit0=0x8200 (input/custom scan key).



Further Infos: https://docs.microsoft.com/en-us/windows-hardware/drivers/gpiobtn/gpio-buttons-and-indicators-implementation-guide-for-windows-8-1 



Programming under Android


Power button: KeyCode=26

Definition button 1: KeyCode=27

Definition button 2: KeyCode=123 


Weitere Infos: https://developer.android.com/things/sdk/pio/gpio