Sorry man. If you're going to be replacing the USB stick with an external HD, and the external DS doesn't have it's own power source, you can get a USB Y-cable. One end will go into the external HD and the other 2 ends will go into the Wii U. That's what I'm using. The extra power needed will come from the extra cable plugged into the Wii U. If you use only a single cable, the Wii U will detect the external HD but will fail to format it to Wii U OS format.
3DS: tolu619
Wii U: FoyehBoys
Vita, PS3 and PS4: FoyehBoys
XBoxOne: Tolu619
Switch: Tolu619
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