A Proof Of Concept Flash Cart For The WonderSwan

Unless you’ve been to Japan or are fairly deep into the retro game collecting, you’ve probably never heard of the WonderSwan. It’s a handheld console, released after the Game Boy Color was beginning to show its age, and a bit before the introduction of the Game Boy Advance. It sold rather well in the only country it was released in, the game library is somewhat impressive, and there are quite a few homebrew games. Actually running these homebrew games is a challenge, though: each WonderSwan has a memory controller that maps the game ROM into the CPU’s memory. Without knowing how this controller chip works, the only way to run a homebrew cartridge is to turn on the machine with a real cart, go to the system menu, and swap the carts out. It turns out there’s a better solution, that includes programming CPLDs and looking at the output of a logic analyzer.

The first step towards [Godzil]’s efforts to create a Flash cart for the WonderSwan is to figure out the pinout of the cartridge connector – something that isn’t well documented for a system without a homebrew hardware scene. This was done in the usual way; with a lot of ribbon cable and patience This only provided an incomplete picture of how the WonderSwan interfaced with its carts, but after digging up an official development board, [Godzil] was able to make sense of all the signals.

After building a breakout board for the cartridge port, [Godzil] connected a DE0 Nano FPGA board and looked at all the signals. With just a little bit of VHDL, the memory controller could be reverse engineered and reimplemented. [Godzil] has his proof of concept working – video below – and the next part of his project will be to turn this into a proper Flash cart.

22 thoughts on “A Proof Of Concept Flash Cart For The WonderSwan

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  2. The WonderSwan was yet another handheld game system superior to the GameBoy that just could not beat the Nintendo giant.

    Nintendo made its fortune selling games to the rest of the world that were outdated in Japan. The NES hit the USA in 1985 yet the innards have Copyright 1983 on them, the year the Famicom was released in Japan. Similarly, the Super Famicom was already two years old when the SNES was released.

    How the GameBoy didn’t immediately succumb to the first wave of color handhelds that were technically better in every way, I’ve no idea. Then the Color Gameboy dropped and it was all over for all the other handhelds, until the PSP.

    It’s like Apple products. A lot of people will buy whatever Nintendo tosses out onto the market, no matter how much better anyone else’s gear is.

    ‘Course Nintendo has been around since 1889.

    1. My theory is that the primary problem with systems like the NGPC and WonderSwan was that the market for games in Japan and the market for games in the US were vastly different at the time. In the 90s in Japan it was somewhat more commonn for adults to be “gamers,” but in the US games were marketed and sold primarily to children. Marketing to children is largely driven by fads and what is popular can be as fickle and idiotic as children themselves can often be. Pokemon happened to have a fanatical following in Japan and the US and as a result, any handheld system which couldn’t run Pokemon would be summarily spurned. It took the waning of the popularity of the Pokemon series before other handhelds began to unseat that fad.

    2. Different market back then. Presenting the NES to the United States in 1983 – the height of the video game crash – would’ve been an absolute flop. By properly timing their entry to the market, they were able to spark a real recovery in the industry.

    1. The WonderSwan Color/Crystal is able to last for more than 10Hr with a single AA battery.. A B&W stay for more than 15Hr with the same battery.
      The original gameboy need 4 battery, was only between 10 to 20 Hr of battery life, and the next version of the GameBoy (the Lite, or the color) was not able to keep much more even with the optimisation, but they use only two battery, which was a good weight improvement.

      BTW something not said in this article, the WonderSwan was originally design by Koto Laboratory, founded by Gunpei Yokoi, the man who created the GameBoy (and the Virtual Boy)

      (Oh and the FPGA board on the video is a DE0, not a DE0 nano, but this is not a real issue there ;))

  3. The original GB was 30-35 hours with LR6 battery but it was 10 hours with rechargeable AA.
    Ok 10hours of Wonderswan is fair but for who travels a lot : 35 hours….think…..35 HOURS !!!!!!! lol

    1. Compare apples to apples. GB= 35 hours on 4 batteries. Wonderswan= 40 hours on 4 batteries. You don’t really have an argument. Any traveler would have a case to hold extra batteries the handheld and games anyways. It is moot.

  4. Sorry, I was wrong with the time I gave:

    >The WonderSwan series are all powered by a single AA battery, with the original
    >monochrome version having a battery life of 40 hours.

    The color/crystal have a shorter battery life, wikipedia say 15hr for the Crystal, but I’m sure it’s a bit more, the difference with the B&W is just too big.

    What have killed the WonderSwan is not it’s power as competing directly with the GameBoy / Lite / Color line, it is far superior in number of points, but it came too late as Nintendo was ready to launch the Gameboy Advance that was far ahead of the WS power.

    Also Bandai did a poor sales management, they get nearly no contract with major studio for the B&W launch, the Color launch was a bit better as they get SquareSoft for porting Final Fantasy on it but it was too late, they mainly released game based their own licence portfolio (lots of games are Bandai licences like One Piece, Digimon, …) they were unable to get enough third party studio to work on it.

  5. I think I am the only one excited about this. I got my b&w wonderswan and swancrystal back in the early aughts. I haven’t used them in years, but this may make me bring them out again.

    1. I assure you, you are not the only one who’s excited about this! I came across my SwanCrystal just the other day, and was thinking “I need to use this more.” I totally would if I didn’t have to carry around umpteen cartridges!

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