Hacking Ds roms on a 3ds flashcart

[DiscostewSM]

By the time the cartridge gets accessed a register will be set that determines whether it's a DS or 3DS card, changing it in software will be improbable, best solution would be to have 2 bootloaders, one for DS and one for 3DS and a stitch on the top of the cartridge to switch between the two, the micro SD card used can be the same assuming the software on the card is good enough to be able to do so, chances are you would need 2 card slots one for a fat16/32 for DS and the other as RAW for 3DS, one game at a time until homebrew is working on 3DS

Having a kind of switch on the flashcard itself for that operation is actually not a bad idea, as long as it makes a momentary connection drop when changed. When removing the cards from a 3DS, 3DS games bring up a warning that the card was removed and that the user should return to the Home menu by pressing Home. DS games just freeze, but the Home button still operates as normal for that type of game (giving the option to continue or close the game).

Now that I think about it, if a spot was reserved for the 1:1 duplicate of a 3DS game, who is to say the DS menu system couldn't do the job of copying a valid 3DS game from the memory card in the flashcard to that spot? Then, just reset to the Home menu, flip the switch to 3DS mode, and run the game?

 

[Immortal_no1]

You won't have to, all you need to do is drop the connection on pin 7 which detects the removal of the card. perhaps also pin 8 for the voltage should also be dropped while switching. that can all be done via a button rather than a switch all the card needs is a little EEPROM to store the internal settings for the next time it's booted up / switched from DS to 3DS mode.

 

[Immortal_no1]

Now that I think about it, if a spot was reserved for the 1:1 duplicate of a 3DS game, who is to say the DS menu system couldn't do the job of copying a valid 3DS game from the memory card in the flashcard to that spot? Then, just reset to the Home menu, flip the switch to 3DS mode, and run the game?

It's as simple as that, quite literally. Just 1GB or 2GB (for possible future proofing) of NAND flash on the card and a microSD card slot, ds mode can transfer the game to the NAND and the button/switch changes to 3DS mode to play the game. the act of copying a game to the NAND must first have a gamesave backup feature to backup your previous progress.

Problem with NAND is the number of times data can be written to it and read from it, around 100,000 times is average i think, so still that's plenty. but if we had the capability to take apart the cartridge via a screw or something and then replace the NAND ourself that would be nice. all we would need is a NAND socket to place the NAND chip in so we don't have to solder anything. These could be sold separately via flash cart retailers for this use. But still you would be looking at getting about 20 years of average use from one flash chip unless you swap out the games lots of times a day 365 days a year. Not likely, but would be a great opportunity for expansion to more than 1 -2 GB of games come out that are enormous...

That would be the first implementation of cards until homebrew is sorted for the 3DS