Hi all, this is my first post here but not the first time I've ended up here for help. I've been posting into the void on a keyboard forum and decided I needed some real nerds to help me out.
I've got a 1992 vintage Focus FK-2001 pc/AT keyboard converted to USB via a pro micro AVR board running the soarer's converter abandonware standard.
I don't have a din->ps/2 converter to test this keyboard out natively, otherwise I would have tried. I am thinking about picking one up though.
My debugging progress so far is here
https://deskthority.net/viewtopic.php?f=7&t=26186&p=492104#p492104but a short synopsis:
Certain keys apparently grouped by possibly rows or columns work perfect, a lot of keys do not, enough keys its unlikely that all the switches are failing. I borrowed a logic analyzer from work and took a peak at the ps/2 signal. The keys that behave, do just that, but the misbehaving keys are causing the host(pro-micro) to request a resend to the device.
When I looked closer, I found that the clock is averaging about 20% above the max allowable ps/2 spec. I replaced every capacitor I could find, measured the crystal oscillator at the rated 6Mhz that provides a clock to the micro controller that acts as the keyboard driver.
I'm really hoping I'm not seeing a dying keyboard driver because they're basically impossible to find and having written a keyboard driver in the past, I'd prefer to avoid doing it again.