I realize few games used it, but the GBC did have a infra-red port on it. Anyone know if there is a way to add an infra-red LED to a GBA for use in GBC games?
Considering the IR port needs to be basically touching another IR port for it to function, the practicality of that on a GBA is not very practical. That aside though, You would need to create your own software and hardware and replace/mod the GBA with that. I would say it's not possible to be honest.
According to Martin Korth's excellent GBA documentation, IR functionality was at one point planned, and a separate IR adapter was released together with a single Japanese game, Cyberdrive Zoids: http://img.photobucket.com/albums/v664/ClawGrip/ir-zoids.jpg That is all in GBA mode, however. If you really wanted to add back IR functionality to old Game Boy games, you'd not only have to find a way to implant an IR communication port in the GBA, but also re-program the CGB compatiblity mode to route the appropriate MMIO/calls/interrupts to said adapter if it's done in software, or way hardware modification things if it's implemented in hardware. It's probably not impossible if the compatibility stuff is done in the BIOS, but if it's actually a hardware feature it's going to get real hard real fast.
