How does IR work in DS games?

[Red2503]

Does someone know how the IR transceiver works in DS game cartridges, for example in Pokémon HeartGold/SoulSilver? Are the IR LED and IR transistor connected (almost) directly to the cartridge pins, or is there a device (e.g. microcontroller) inbetween which controls the LED and transistor? I want to know this because I'm wondering how difficult it would be to add IR features to DS flash cards.

 

[Ryccardo]

It has some weird coprocessor/mapper thing (connected via SPI like the save chip, indeed save backups from IR games used to be a problem back then): https://i.redd.it/cb98j376def71.jpg

I guess it could be high level simulated with some effort? It's documented in gbatek http://problemkaputt.de/gbatek-ds-cart-infrared-pedometers.htm but maybe because of the time I'm finding it harder to understand it than other parts of gbatek