If you are using the 4 port mayflash take a look at this guide: https://wiki.dolphin-emu.org/index.php?title=How_to_use_the_Official_GameCube_Controller_Adapter_for_Wii_U_in_Dolphin
[color=green]Windows 7 x64 / i5 4690k @ 3.5 GHz / GTX 970 / 8GB RAM[/color]
