I can also use my 3DS to play Nintendo DS games online. I currently have Mario Kart DS, but I am going to purchase a flashcart soon. I will most likely go with an Acekard 2i as I have had interest in it for a long time and I have good reason to use it over alternatives. Once I can get a flashcart, I will more seriously play DS games rather than just 3DS.
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CzarVine
SylverReZ
You're going to need a modded 3DS to use the AK2i as the last update only supported below v4.4.