With Slot-1 DS flash carts, you sometimes want to boot a GBA cart in Slot-2. There’s probably something already out there for this, but I couldn’t find one so I made a small and simple GBA mode switcher. It uses the setting you’ve selected in your DS firmware to determine which screen to run on. This is probably the shortest DS code I’ll ever write, so source is included in this post.
The source code is available at
Cryptosystem's Blog
Note: I have made sure to try this application prior to posting this thread. I can confirm, that it can boot GBA binaries from slot-2 cards, on the top screen, however the display is too dim to allow one to clearly see what he's doing.
GBA Slot switcher