Homebrew RTC Manipulation with libnds

[MichiS97]

Hi guys,

as you all know, some games have some time travel blocks included, like the Gen 4 Pokemon games which won't let you use the Pal Park for 24 hours if you have changed your system date.
On the 3DS, such timegates can be bypassed by using homebrews such as RTChanger to actually change the "hardware clock" of the 3DS itself. That doesn't help you with Pal Park though, as a 3DS obviously doesn't have a GBA slot.

Now, I'd like to create a similar tool for the DS for the purpose of bypassing these kind of timegates and as a general programming exercise. I have some experience with C and C++ and coding on embedded systems. However, I don't quite understand how the DS works yet. AFAIK, the RTC can only be controlled by the ARM7, right? How would I be able to let the user select a time and date the RTC should be set to and have that information actually be sent to the ARM7?

I'd really appreciate some insight into this. Also, if somebody generally knows any good guides on programming on the DS, please let me know

Thanks!

 

[MichiS97]

Alright, quick update: I figured out how to read the time from the system and how to transfer data between the two CPUs. The problem is now that the "rtcSetTimeAndDate"-function in libnds apparently doesn't work.

 

[Ryccardo]

Another option would be to backup and restore the clock offset in the eeprom - if I understood the documentation correctly, it's just a record of the time being changed, instead of an actual difference applied to the hardware clock like it is on 3DS?

 

[MichiS97]

That would probably be easier, yes. I'm gonna have to so some research on that.