i still have concerns, but do hope i'm proven wrong.

have been doing some research, and found two paths that may be worth following up if anyone is interested:

1. $1 USB host, a hardware solution using the CH559:
https://www.youtube.com/watch?v=po3FBdY0GS4
a small development board for the CH559 is available here:
https://www.electrodragon.com/product/ch559-mini-dev-board-ch55x-series/

2. USB host/device implementation using PIO of the RP2040. note that this does not use the onboard USB hardware:
https://github.com/sekigon-gonnoc/Pico-PIO-USB

addendum:
3. the CH375/CH376 also looks like an option,available on a small PCB for around $5 on ebay:
https://www.ebay.com/itm/164195409955
https://www.ebay.com/itm/165027473834  
(note: the CH376 may be an updated version of the CH375, and so a better choice)
while the main target is reading USB flash drives, it appears to also produce results from USB keyboards and mouses. it can connect directly to a TTL serial port, and requires to be sent commands and returns packets of data containing keypress information - NOT ASCII codes; some interpretation is required.
see also:
https://github.com/djuseeq/Ch376msc/issues/13
and:
http://www.electronicsfaq.com/2016/11/interface-usb-mouse-to-your-arduino.html  


cheers,
rob   :-)
Edited 2022-05-15 22:06 by robert.rozee

I got some 6 pin mini din plugs and fitted on to one of my 1993 vintage Honeywell keyboards. Some keys worked and some didn't, so I pulled it apart and gave it a clean but still not all keys working. At least I know the Pico is a goer.
Two keyboards that have been mentioned the Logitech K120 and the Microsoft 600 both fail to work. There are some on EBay for around $20 but with another $20 postage Altronics also charge $20 postage, so before going down that path I will try some Computer repair shops.

Salvos and other op shops are worth a try too. I have a couple of keyboards from 'Savers' if you have any near you.

The mini keyboard from Altronics works with the CMM2 as a USB keyboard but I have not tried it as a PS2 one yet. This is it here as described on the packaging, cheaper.

Bill

There are quite a few PS/2 keyboards on ebay.com.au especially if you can afford $25 or so. If you buy "untested" you might be taking a risk, but not always. Not everyone has something to test them with now.

It's worth trying a cheap Chinese USB keyboard with an adapter. Just a plain one, nothing fancy with USB ports, lights or anything like that. The code used in them was copied many years ago and won't have been changed since.

Also look for keyboards by Chicony. They have been in business for a long time and make generic keyboards for just about all computers. There are usually some on ebay, but prices can get expensive for the vintage mechanical versions. The cheaper "bubble" contact ones aren't that bad though.
Edited 2022-05-16 16:49 by Mixtel90

We discussed PS2 keyboards and USB keyboards that have PS2-USB firmware built in in relation to the F4 in this thread;
https://www.thebackshed.com/Forum/ViewTopic.php?TID=13440&PID=163787#163787
I have since purchased three PS2 keyboards from Amazon UK that work perfectly for me with the PS/2 keyboard connection to MM plus, PicoMite, F4 and other designs.
https://www.amazon.co.uk/gp/product/B01M4GIVOY/ref=ppx_yo_dt_b_asin_title_o07_s00?ie=UTF8&psc=1

Looking around, as Geoff has said, I see plenty of new PS/2 keyboards for sale.

  palcal said  

I got some 6 pin mini din plugs and fitted on to one of my 1993 vintage Honeywell keyboards. Some keys worked and some didn't, so I pulled it apart and gave it a clean but still not all keys working. At least I know the Pico is a goer.

Palcal

can you please post an image of that Honeywell Keyboard, I'm interested to see if it's a Re-Badged IBM Model M, in which case it'll never work the encoder Chip needs a study 5 volts

@ Rickard5..... The keyboard works just some keys not working. I have 3 more to test yet, then I will crawl town to see if I can find one. Just don't want to pay $20 postage if it is not necessary.

"The keyboard works just some keys not working."

If it's a "plastic bubble" type it may be possible to clean the contacts.

Many years ago I managed to fix one by separating the layers and carefully wiping the contacts with isopropyl alcohol. Metho would probably work too.

@ phil99....I pulled it apart and cleaned with ISO, some more of the keys worked but not all.

I see lots of new HP PS/2 keyboards on eBay for $10 to $18. In the US. Seems like lots of schools and companies acquired a surplus of spares over the years and are now selling them.

I ended up buying the Altronics Keyboard Cat. D2111.
Works great, thanks all.

If I were a person who knew what they were doing I'd probably not need to ask this, but:

Will a PS/2 keyboard only work if you're powering from USB? My two keyboards only work if they get 5 V power from USB. If I use a power adapter through the 3.3 V LDO regulator, neither of them do anything.

Otherwise, my colourful PicoMite VGA works great.

Thanks!

  scruss said  

Will a PS/2 keyboard only work if you're powering from USB? My two keyboards only work if they get 5 V power from USB. If I use a power adapter through the 3.3 V LDO regulator, neither of them do anything.

Generally speaking, yes.
ALL keyboards - USB and PS/2 - expect a 5v supply.  Trying to run them on 3v3 USUALLY results in no-talkie, and even for those that will talk, it is probably marginal and the board could stop and start working at random.  Much better to always feed KB's 5v DC and use level-shifting on the DAT and CLK lines as per the manual.

I have two or three PS2 keyboards that are fine on 3V3. The only thing I notice is that the LEDs are slightly dimmer!. However, I design my boards to power the keyboard from 5V and include some sort of level shifting for the PicoMite. It's not worth doing otherwise.

That looks so cool, scruss... and no clash with the purple PCB at all. LOL!

Ah, thanks. Looks like this one is going to be USB powered from now on. Just as well, as I can't source any other 3.3 V regulators affordably.