hi,
i did some tests, so if you are getting the same ideas you don't have to test them again.
my idea was, that the tp is able to check if the cartridge is already
powered or not.so I searched the 5v plane for connections with the LESH-NUS and found out, that there are 3 connections.
i was hoping, that one of them is a sense pin, but it seams like they are just 3 vcc input pins, they are all connected inside the ic.
i lifted them and connected them to the 3.3v enable signal for the step up circuit, so they are only powered if the tp wants to power the cart, but nothing changed.
my next idea was, that it is checking for a
reset state or something.
i powered the cartridge itself externally, set it to game mode, shut off the n64 and even reconnected the controller.
guess what.. it didn't work. ^^
(maybe i hold the les-nus state powered from the cartridge side)
i could monitor all tp comamnds with my modded mupen64 emulator and retry them on real hardware, to
look for the diffs in the response packages.
but even if the real tp reacts in a different way, the solution would be still rom patching only. :/
i'm getting out of ideas, maybe i'm not the right person to dig into that any further. ^^
bailing out, you are on your own. good luck