Connecting a USB keyboard to One Chip MSX

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By Grauw

Enlighted (7454)

Grauw's picture

19-06-2014, 14:23

Until now I’ve been using a Sansun mini-keyboard with my 1chipMSX and Zemmix Neo. It’s small and it works with PS/2 as the One Chip MSX requires, but it’s very uncomfortable for typing because the keys are wobbly and not organised well.

So I set out looking for a new keyboard, but there isn’t much choice in the PS/2 space anymore nowadays and I wasn’t able to find a keyboard that suited me. I was looking for a quality low-travel keyboard, and most PS/2 keyboards available nowadays are either really cheap, or mechanical gaming keyboards with high travel.

The more I was looking at it, my Logitech Illuminated keyboard seemed more and more of a good fit. In addition of having a great feel, the keyboard layout is also similar to the MSX. And, I already own two of them. Only one problem: it does not support PS/2, only USB.

After searching for a while, I found there is one “active” USB to PS/2 converter on the market: the StarTech PS22USB. It isn’t cheap, but then again buying another quality keyboard wouldn’t be cheap either. For the Dutch, here’s the tweakers.net listing.

It arrived today and I’m happy to report it’s working like a charm. It’s quite compact, looks good and does not require external power. More importantly, it also seems to function without a hitch.

Now people mentioned in other threads to be aware of key ghosting. Note that key ghosting will be a property of the keyboard, not the PS/2 to USB converter. As for the Logitech Illuminated keyboard, it doesn’t have n-key rollover, but it passes the Nemesis test (diagonal + fire), and also in Synthesix I was able to play a bunch of chords without issues (on Mac OS X in emulator, I can’t). So, no key ghosting issues encountered yet, better than a real MSX keyboard so far.

So I can recommend this solution, maybe someone will find these experiences useful.

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By sd_snatcher

Prophet (2865)

sd_snatcher's picture

19-06-2014, 15:19

Thanks for the tip!

But I wonder: Doesn't it add any lag?

By Grauw

Enlighted (7454)

Grauw's picture

19-06-2014, 16:18

I didn’t notice any.

Peering through the semitransparent casing, it seems to be using a microcontroller of sorts to do the conversion; it will no doubt introduce a tiny bit of lag, but as it’s got a dedicated controller, plus the fact that USB is many times faster than serial PS/2, it is probably negligibly small.

Also consider that MSX generally only reads the keyboard 60 times / second, it’s easy to keep up with.

By MichelM

Expert (69)

MichelM's picture

28-12-2016, 18:16

It seems the Startech PS22USB is discontinued. Are there any other known adapters that will allow a USB keyboard to work with a 1chipMSX?

By AxelStone

Prophet (2637)

AxelStone's picture

02-01-2017, 18:15

Question: can't you use a normal ps2 to usb converter? They are quite cheap.

By Grauw

Enlighted (7454)

Grauw's picture

02-01-2017, 18:39

Those cheap adapters only work on keyboards which support PS/2 (most don't nowadays).

I think it should be fairly easy to create an adapter with an Arduino board?

By Meits

Scribe (5178)

Meits's picture

02-01-2017, 20:21

Not even every PS/2 keyboard will get support of the OCM. Tried a few at work. Don't remember which Logitechs they were.
I've got an old white microsoft one here which doesn't ghost with nemesis either.

By Samor

Paragon (1986)

Samor's picture

14-02-2018, 20:45

I came across this issue with my Zemmix Neo.

The Steelseries G6v2 (which supports ps/2) unfortunately does not work. When connecting it the leds (num, caps, scroll) blink but it does not react.

I'm not sure if we could identify reasons for a keyboard not working, but the Steelseries has a distinct media button in place of one of the Windows keys which could render it incompatible, or it might have to do with the amount of power it requires (it's capable of booting my pc with a keypress too, which might be a non-standard feature).

I did happen to have a Cherry G83-6104 USB keyboard which fortunately does work (without me knowing it in advance), but it sadly doesn't pass the "nemesis test".
I checked and it's still available today (on bol.com), in ps/2 and usb versions (both would work on the OCM/Zemmix as I have the USB one).
While I'm lucky to have a working keyboard at all (it's a decent one too save for the ghosting) I'd still like to find one that doesn't have the issue, but it might be difficult nowadays (I don't really want to gamble on expensive gaming keyboards which may or may not work).

I know the (cheap) Logitech K120 passes the "nemesis test", but it's USB only... at least, new versions are.

By sdsnatcher73

Master (209)

sdsnatcher73's picture

14-02-2018, 21:46

I am using a DELL PS/2 keyboard, working fine on OCM. Passes nemesis test.

I also have an HP PS/2 keyboard that works but does not pass nemesis test.

By Samor

Paragon (1986)

Samor's picture

14-02-2018, 21:50

Thanks for the info. Smile

By Pencioner

Paladin (685)

Pencioner's picture

15-02-2018, 00:31

Currently i use the cheap usb keyboard which has ps/2 and i haven't tested with nemesis yet. But i'm going to buy this one: anti-ghost keyboard and once i buy it i will report if it is that good as described ;)

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