First, if you�re using a non-official Adapter that offers a toggle between �Wii U� and �PC� modes, switch it to �Wii U.� Dolphin has native support for the GameCube Controller Adapter once you have installed the proper driver, so feel free to ignore the PC mode unless you wish to use the controller in other applications. You can use Wii Remotes with Dolphin, along with any other gamepad, including Xbox 360 and One Controllers. If the Dolphin Emulator couldn't detect the adapter, it's possible that you already have another one running. How to use the Official GameCube Controller Adapter for Wii U in Dolphin Insert a GameCube disc into the slot. GameCube Controller ports on the top of the Wii unit.
I am using an actual gamecube controller and a WiiU Nintendo gamecube adapter.
