WTF is a Totodile?

Posted 2010.03.17 22.34 in Computers/Internet/Technology

So there’s this new game that just came out for the DS, called Pokemon. I don’t really get it. There’s these wild semi-magical beasties that you catch, squish them down into little balls, then release them now and then and force them to fight each other for entertainment and money.

Anyhow, it came with a pedometer that connects wirelessly to the game card, and I wanted to know how it worked.

Before I got out the magic screwdrivers and scalpel, I did play with it for a bit. I got a Totodile, and I named him Bungee. He defeated a bunch of other wild creatures. He can scratch and squirt water and glare menacingly.

But then I got bored and started prying things apart…

The cartridge casing looks black, but it’s transparent – you can shine light through it. The big chip is the ROM, it’s 1Gb (128MB). The smaller chip above that is a flash ram for the game saves, it’s 4Mb (512kB). At the top is the IR transceiver bit, below that is an oscillator. The chip on the right is some kind of microprocessor.

I also took apart the pokewalker, to see what it’s like inside – after all if you’re going to stuff a pokemon into it, you want to be sure it’s comfortable and has all the necessary ammenities.

(Click on the thumbnails for a larger view.)

The pokewalker contains a handful of parts… there’s a microprocessor very similar to the one in the cartridge, what looks like a 512kB flash chip, the IR transceiver, what I think is a controller chip for the IR, and a handful of discrete SMT components. Unlike other pedometers I’ve disassembled, this one doesn’t have an obvious pendulum or weighted switch, for detecting steps. I’m not sure what it uses, one component looked possible as a very small pendulum switch, or the thing that I think might be the IR controller chip might be a solid state gyroscope-type thingy.

Either way, it does seem to work when you shake it. Though that gives the imprisoned pokemon a headache as he bounces around inside.


  1. Stephanie says:

    Update: I must have been half asleep when I was examining the pokewalker… gyroscope-type thingy indeed. It uses a solid state 3-axis accelerometer to detect walking movements. This allows it to function whether on a belt, in a pocket, or even hanging from a string. (Although it is more prone to missing steps when not on a belt – as per instructions.)

    I’m not sure yet which chip is the accelerometer though – it’s either the small one next to the IR transceiver, or it’s the small one on the other side. At the moment I’m thinking it’s the one by the IR transceiver… I still think the one on the other side is memory.

    Also, there’s lots of nice silkscreened test points in there, you can see them in the pics. The most interesting would be the RX and TX ones – it might be possible to capture and maybe decode the communications by tapping into those two signals then doing some communications between the pokewalker and the game cart.

  2. The chips in the pokewalker are as follows:

    The TSSOP-8 chip on the back is a EEPROM manufactured by STMicroelectronics.

    The 10-pin chip is a solid state accelerometer of non-determininant origins. There is no telling how many axis it can actually read on, it is very likely that it only reads on one (since it just need to know it is moving, it doesn’t much care where)

    The 32 pin chip is a microcontroller of unknown origins. It is unknown if the chip is mask rom, flash, OTP-EPROM, or whatever. it is also unknown what the chipset is, but it also likely custom.

    The long black ‘chip’ is a crystal, while the 6bit silver thing is an oscillator. One is likely used for time keeping, while the other is used for timing the microcontroller’s logic.

    Most of the test points are fairly obvious: MISO MOSI SCLK are wired into the EERPOM, TX and RX are wired to the IR, There is a EEP-CS (eeprom chip select) as well as well as some power points. The only other is NMI (non maskable interrupt) and E7-0 through E7-2, which I suspect are GPIO on the microcontroller.

  3. Stephanie says:

    Thanks for the info Bryon!

    I’m pretty sure the accelerometer is a 3-axis as I tested and verified the pokewalker counts steps when it is moved in any one of the three axis. A single-axis would only function if the pokewalker were being moved along the one axis being measured.


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