EXPS/2 Keyboard Adapter Translates PS/2 And USB To MSX

Say what you will about suitcase computers, but at least most of them still have their keyboards with them. [danjovic] has this vintage Brazilian computer from the 1980s called a Gradiente Expert. These were MSX machines with Z80 chips that ran BASIC, DOS, and CP/M, and they looked like state-of-the-art dual-deck stereo systems. You can still find them pretty easily, but sadly, most of them have lost their rad mechanical keyboard with its giant arrow keys and proprietary connector.

If you now want to get one of these awesome pieces of computing history and would like to be able to talk to it, [danjovic] has you covered with the open-source EXPS/2 keyboard adapter. It will allow you to connect either a PS/2 keyboard or a USB keyboard in fallback mode to the Expert using an ATMega328P and a bespoke DIN-13 to DB-13 cable. As it turns out, there’s a wealth of information on MSX keyboard matrices out there.

How much do you know about the USB keyboard interface? If you want a warehouse of information delivered to your brain in the most pleasant way possible, go watch [Ben Eater] break it down with pen and paper.

9 thoughts on “EXPS/2 Keyboard Adapter Translates PS/2 And USB To MSX

  1. Interesting.

    When I acquired my SGI Indigo, I had the same problem: no (proprietary interface) keyboard or mouse. Thankfully, the SGI is a bit more popular here, and someone had built an intelligent PC-to-SGI keyboard & mouse adapter, for which I was happy to pay $50 or so.

    1. I’m planning to make a controller for my custom keyboard that supports the Indigo protocol. Sadly no information can be found on this. Years ago there was some guy posted an converter with source code but that’s gone as well, pretty hopeless.

      1. That’s pretty much where I’m stuck as well. The source code for the PIC converter seems to be lost. The 50 buck converters aren’t made anymore and the person/company who made them can’t be reached anymore. There was somebody selling old stock through email but they are out of the old keyboards too now. Sometimes there were keyboard with the old proprietary SGI interface on ebay, but always for around 200 € or more. I hoped for a cheaper opportunity, but instead now none have been on ebay in at least a year. I’d pay 200 € for an original now just so that I can record each key press and combinations once so I can build my own adapter and share that. But nobody seems to be willing to lend one out, let alone sell one.

        It’s frustrating because there are many of these still around and some are still in regular use and owned by not just collectors but fans. It feels like it should be pretty easy to find one and reverse engineer the protocol. It can’t be that complicated, right?

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