EDIT*** I did have to rewrite this topic due to my misuse of the term OTG (On The Go) as it was rectified by a moderator ***
One feature I learned of my rockchip players (and also of Actions ATJ-2135) is the one which allows the user to work with his player while it is charging in the USB port.
Every player has its own method to put the player in such status, but in general it works when the player is plugged to USB port (obviously) but in charging mode, this is without the control of the PC over the device.
When the player is plugged appears in the PC either as a device or as a external HDD, when this status is cut (through software disconnection in the tray icon for instance) the player go into charging mode.
If in this mode is pressed the key that call MAIN MENU... the menu will appear allowing to play song or games or whatever the users wants while the player is in charge mode.
In rockchip player seems normal to have screen showing the panel of connection while the player is charging, when is called MAIN MENU it will enter too in SAVE mode switching off such screen, which will give more life to LCD screen
This is useful too when the signal is amplified to external speakers.
Nice trick of rockchip players and according with what a moderator correct me... of many others players