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Hi people, if you had any version of Nintendo DS with the Acekard2i card, I will teach you in this tutorial how to use the same card on the 3DS in order to play Nintendo DS homebrews. I know that there’s on the market many new linkers that allow more functionalities but if you, like me, have already own Acekard2i for your old DS, this will allow you to play Nintendo DS homebrews without paying any extra fees on new linkers.

You will need:
-A Acekard2i
-A DS / DS lite / DSi or DSi XL
-A computer
-A micro SD
-A USB or SD adapter

1-So to begin, download this file : https://www.mediafire.com/?v43ku9mtw3iyb9v

2-Once downloaded, extract the 2 files with WinRar to where you want.

3-Now format your micro SD using your computer (if you have games in it I suggest you move them to the desktop and then put them back on the micro SD after formatting).

4-Put the two files you extracted earlier at the root of your micro SD.

5-Then insert your micro SD in your Acekard2i, and put your Acekard2i in a DS / DS lite / DSi / DSi XL, but not yet in your 3DS.

6-Turn on your console, and once in the menu of your Acekard2i click on "Micro SD Card".

7-Go into the content of your micro SD, select "ak2ifw_update_3ds_v1_DSi" if you're with a DSi / DSi XL or "ak2ifw_update_3ds_v1_DSL" if you're with a DS Lite.

8-Press the "Start" button and wait for "Progress" is completed at 100%.

9-Once this done, you can put your Acekard2i in your 3DS and use it normally.

Enjoy !

I guess you should specify that this tutorial only works for 3DS on firmware 4.4.0-10 and below.
Acekard 2i lacks hardware that is checked on newer firmware, rendering it useless, and no software update can fix this.