As someone with some computer engineering experience, the best way to handle this would likely be to get two GBAs and a digital oscilloscope, and read the data that's sent. Then you could ideally spoof that data/reverse engineer that. You may be able to get VBAlink to print that data instead of using actual hardware, which would save a lot of time, money, and troubleshooting. Beyond that, once you have a binary dump, try reading it for known binary data (Pokemon IDs, etc). You could also try hooking up an arduino or a version of vblink and sending that data to the games and see what happens.
NStephenH changed their profile photo