How to Fix DS Cartridge Slots! Repair DS and GBA

Why won't my son's Nintendo DS read any games? ds with gameboy slot From Nintendo DS Accessories - Scott The Woz ds lite gameboy slot Load the GBA game , then load the DS game If done correctly, the DS bios will have the option for Start GBA

ds lite gba slot My goal is to reverse engineer the protocol, but I have no idea where to even start Specifically: How does the DS game know which GBA game is