(Note: I read about this on Hackaday, but their article didn't actually explain the project very well at all, calling this a flash cartridge, when in fact it is not really anything of the kind.)
So, a fellow who goes by the name Godzil has been working to reverse engineer the Bandai 200x chip. This is the chip responsible for allowing the Wonderswan to boot up, and was likely meant to prevent bootleggers from making pirate or unlicensed Wonderswan games. The fact that it has never been properly documented or reverse engineered is the primary reason why Wonderswan homebrew has so far been limited to the WonderWitch and thus a very, very small community in Japan.
He made himself a fairly simple looking passive breakout board, and began probing the pins until he learned how the chip's handshake worked, then coded up a replacement in VHDL and put it onto a CPLD. He's planning to release the VHDL with an open source license, though for the moment it's CC-BY-ND. He's also apparently planning to design a flash cart around this work which is currently called WonderMadeline, though he doesn't explain any details about this. Also, this is just my understanding from reading his broken English. You should definitely check it out if you like WonderSwan, it looks cool.
(For those looking for the "Take my money already!" approach, he appears to be selling some of the extra breakout boards he ordered for the project, although unless you have a logic analyzer and a bunch of other fancy tools you probably won't find it super useful. Yet.)
http://www.986-studio.com/2014/10/28/finally/
Last edited by arfink (Oct 29, 2014 5:54 am)