Attached is my first DS app. It's a file manager for managing homebrew files on your DS card. It's most useful feature is that it allows you to transfer files from your PC to your DS card via your home wifi (thanks to Pete Lockwood for help on this bit) - this was the main reason I developed it - I got fed up unplugging microSD cards all the time
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You can navigate folders/rename/delete/move files/create directories etc.
Via nifi you can send files from one DS to another.
There are some config options to setup when you run it, to set;
root dir (hopefully will allow other DS type cards to use this - I use R4s)
PC ip address (for PC->DS comms)
Wifi AP (default wifi access point)
There are some screenshots on my website - www.greenacorn.co.uk (go to NDS section & look for FileManager article)
To use the PC->DS wifi transfer you will need the files in the 2nd attachment (PCwififiles.zip), this include executables for the PC along with C/C++ source if you want to compile yourselves. The files named copy2nds.* are for ubuntu, the send_to_ds*/main.cpp is the windows version. For windows you drag a file onto the .exe to run the PC side. For ubuntu use the shell script which will send the .nds file from the current directory (you will need to edit the dir named in the .sh for where you place the .exe file)
It will run under the no$gba emulator - but wifi/file functions won't work, so not v. useful, apart from viewing the screen.