Repurposing A Toy Computer From The 1990s

Our more youthful readers are fairly likely to have owned some incarnation of a VTech educational computer. From the mid-1980s and right up to the present day, VTech has been producing vaguely laptop shaped gadgets aimed at teaching everything from basic reading skills all the way up to world history. Hallmarks of these devices include a miserable monochrome LCD, and unpleasant membrane keyboard, and as [HotKey] found, occasionally a proper Z80 processor.

It started, as such things often do, with eBay. [HotKey] found that the second hand market is flooded with these decades-old educational gadgets, often selling for just a few bucks. As it turns out, children of the smartphone and tablet era don’t seem terribly interested in a “laptop” from 1991. At any rate, he ordered about a dozen different models and started tearing into them to see what made them tick.

He found that the VTech machines of around 20+ years old were using the Z80 processor, and what’s more, they shared a fairly standardized external cartridge interface for adding additional software or saving data. Upon attempting to dump some data from the cartridge port, [HotKey] discovered that it was actually connected to the computer’s main bus. He realized that with a custom designed cartridge, it should be able to take over the system and have it run his own code.

After more than a year of tinkering and talking to other hackers in the Z80 scene, [HotKey] has made some impressive headway. He’s not only created a custom cartridge that lets him load new code and connect to external devices, but he’s also added support for a few VTech machines to z88dk so that others can start writing their own C code for these machines. So far he’s created some very promising proof of concept programs such as a MIDI controller and serial terminal, but ultimately he hopes to create a DOS or CP/M like operating system that will elevate these vintage machines from simple toys to legitimate multi-purpose computers.

We’ve seen VTech hardware hacked in the past, but it’s generally been focused on the company’s more recent hardware such as the Linux-powered InnoTab. It will be interesting to see if these educational toys can fulfill some hacker’s dreams of having a cheap and portable box for Z80 tinkering.

20 thoughts on “Repurposing A Toy Computer From The 1990s

    1. Why Minix, when you could make it run a *proper* operating system, such as CP/M or (if you feel you need multi-tasking) MP/M?

      If you’re looking for something more unixy, UZI, perhaps.

      1. Minix won’t run on Z80, but note the guy in the post is mostly interested in later VTech products, that run Linux.

        Minix was a proper operating system. It was created to teach internels (it being easier to create a Linux-like OS to show off the source code than try to get permission to show Unix source code), but lots of people got excited about it at the time. It was a way to get “Unix” without the cost, and by that late eighties or early nineties one could get enough hardware, cheap enough, to run it. In essence people bought the book to get the OS, I was tempted too, to run it on my Atari ST.

        It wasn’t the only option. Tgere had been variius Linux-like operating systems, of varying cost and compatibility. Mark Williams had one, I think Dennis Ritchie said it was actually very Linux-compatible.

        The problem with Minix was itcame “early” so never had the range of software drivers that Linux eventually had. And it was never mainstream, so BSD and Linux overrode Minux.

        There’s also XINU, a book with software, that came out around the time of Minix.

        Michael

          1. Sorry, indded I did give thought to that. I am aware that it has been kept current, so it has advanced since it came out, with drivers for more recent hardware.

            But I’ve not checked the newsgroup in some time. And even ten years back, I wasn’t sure of the point by then, when I have used Linux since 2001 and it’s more popular and easier to find.

            Michael

      1. Or what about Collapse OS, as featured in hackaday recently? Z80 processor – check, in an expedient piece of e waste – check, a cartridge port that would not be impossible to program with discarded parts (perfboard and diode ROM, ETC) – check. Just might need to be re-written for less ram and limited peripherals.
        https://collapseos.org

  1. Hi there!
    I am not sure about the legal issues about publishing my ROMs.

    For my experiments I just searched “well known” ROM sites on the web and found dumps of most of the ROMs. There is also already a working emulation using MAME (which I found out *AFTER* I did the reverse engineering… Just look for the machine ids pc1000 / pc2000 / gl2000 / gl4000 / …. )

    The emulation source (2009 by Sandro Ronco) can be found in the source tree:
    https://github.com/mamedev/mame/blob/master/src/mame/drivers/pc2000.cpp

  2. That’s awesome! I still have one of these from my younger days. Aside from the games and stuff, it actually has a complete (though primitive) BASIC interpreter! I knew there was a Z80 inside and thought about reverse engineering it and making add on cartridges, etc. but never had the time. Glad someone actually did.

  3. I paid $1 for a VTech PreComputer 1000 at a thrift shop, with the intention of gutting it, adding a screen, and shoving a Raspberry Pi inside with some other widgets. Pulling it apart, I noticed all the chips were through-hole and mostly DDIP.

    Then I noticed the CPU was a Z80, and very similar to the systems [HotKey] has taken apart. I don’t have the heart to destroy it, knowing it’s a genuine computer. Now it sits on a shelf next to the TRS-80 and TI-99.

  4. I have been looking at these for a month or two now and re purposing them into a e-paper writer. Basically I want to update my blogs and write up articles for pages and maybe a book someday. I have been eyeballing a 7 inch e-paper display that refreshes every 1/3 second. That is much better speed than the $400 e-paper blog writer machine Free Writer.
    The motherboard section is a Old School VGA PC Kit which I can directly wire its output VGA to the e-paper display input VGA breakout board.

    If I build it with the low end tech It will cost a total of $130.

    I have a sneaking suspicion that they are using something similar to a z80 anyway.

    I just need to find or come up with a program that can send the text out to the blog/website or just upload it to the cloud.

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.