¡Funciona perfectamente!
How to update your DSTWO's firmware on a 3DS
Good news for those of you who accidentally updated before updating your DSTwo, it is possible to update from your 3DS, however this method is risky, and not recommended if you can use the normal method in the above spoiler.
In order for this method to work, your 3DS must already recognize the DSTwo and show this icon (if it doesn't show up you're gonna have to use the normal upgrade method in the above spoiler).
1. Download firmware 1.17.
2. Extract "dstwoupdate.dat" to the root of your microsd card and rename it to "dstwoupdateb.dat".
3. Put your microsd card into your DSTwo and insert it into your 3DS.
4. Turn on the 3DS and launch the DSTwo, you will see this screen.
Stay on this screen, DO NOT TOUCH ANYTHING, and just wait and wait for 3 minutes, IF YOU TOUCH ANYTHING YOU MAY BRICK YOUR DSTWO.
5. After the 3 minutes is up, turn off the 3DS, then put the microsd card back into your computer and delete "dstwoupdateb.dat".
6. You can now put your microsd card back into your DSTwo, and back into your 3DS, and now your DSTwo should be on firmware 1.17, and it should work normally on your 3DS on the latest firmware.
LINK:
http://gbatemp.net/topic/290190-the-sup ... the-dstwo/