Hi I have a pair of cheap chinese wireless Gamepad Controller with one reciever and two gamepad . The gamepad is connected to my samsung S20 FE phone via USB OTG.  

There are two problem I encounter.

first, in the Android App it only detect one gamepad instead of two why does it happen?

second, it show unmapped Joystick warning what does it mean? & how to solve it?

Hi, thanks for your detailed message; I will try to help.

Firstly, I apologise for that huge advert! it's not supposed to be that large - Google are only supposed to make it 10% of the height of your screen -  something's going strange there, I'll try to look into that.

An unmapped joystick means that the Android system cannot identify what type of game controller it is, so it doesn't know what the buttons or axis should be. Basically, Android doesn't have the driver for this controller. I do remember this controller - I used to have 2 of them - and they were horrible. I have some suggestions:

Do you have access to a PC or laptop? Can you compare what the Windows version of my app does with these controllers? Windows should be able to load the correct drivers and map the buttons and axis correctly, and also show both controllers. It'll show you that they're not compatible with Android. If you also get the unmapped warning on the Windows version of the app, you can submit information about the controller using an app called "SDL Gamepad Tool". This will help include the mapping for them controllers in SDL applications / games, and also Steam games in the future.

In conclusion, this yellow message means that the gamepad is not compatible with Android, so it doesn't know which button is which, so it makes a guess. Games may not work with it. This is also the reason why both controllers aren't showing. Without a driver, it can only see one USB device.

Keep in mind that my app is showing you exactly what the Android system can see. It's a diagnostic tool. If a controller doesn't appear to work, then the app has performed its task.