I have a mechanical keyboard from a lunchbox laptop (1990), it has 5 connectors (2 are ground). I've figured out VCC and I can get the lights flash on, like it's switched on properly. For the life of me I cannot get the clock and data to work via a PS/2 to USB converter.

The Keeb:

I think it may be 'PC/AT', I've removed all caps and they're all fine, also the microcontroller is working too. So I'm going to see what I can do for PC/AT to USB conversion. This is crucial for my Cyberdeck build, if I can reuse the keyboard, then it's off the cards for now.

I have looked at the keyboard's microcontroller datasheet and identified clock input and the clock output pins, then the identified the correct clock output to the PC.

T0 and XTAL 1

The microcontroller is fed by a ceramic 6Mhz resonator, which I have verified is doing its job correctly:

Time to do some logic analysis:

D0 is Clock output to the computer.
D1 is Clock input from the resonator.
The keyboard is not switching on as it's not being told to buy the computer.
So it's confirmed that this is most likely to be an AT based keyboard (I don't think it's XT as it was a 386 laptop).

A standard active PS/2 to USB is not going to cut it, it's most likely waiting for a command from the computer to switch on. Here's the AT hex codes sent from PC to keyboard:

To progress it looks like I'm going to have to make a USB converter with Manak1n's software, using at ATmega32U4. Hopefully this does the trick and the laptop wasn't sending some unknown commands, that I have no way of knowing:

I've flashed Soarer's Converter software onto my ATmega32U4, confirmed it's working, connected up my vintage lunchbox PC keyboard and nothing, it still won't work.

Mechanical Lunchbox PC keyboard to usb update:
I tested the original cable for continuity and it seemed fine, zoom forward to today when I realised that it does have an intermittent fault, so I decided to hook up straight to the board:
We have some AT / PS_2 activity! ️

Well it's receiving HID codes which is fantastic, but they're all wrong, so it looks like I'll have to remap it all, key by key, but hey it's all part of the fun! ️

@Gammitin it's not that uncommon for laptop keyboards to send internal scancodes, in my experience. They just put the matching decode table in the bios

@foone thanks for that bit of info, just out of interest, I'm assuming they would just be hex codes? I'm hoping to reprogram my Soarer's Converter to work fully with it, I've kind of got to the point where I'm hoping I can just configure the controller and it's not going to be impossible with the firmware.

@Gammitin yeah. They should work the same as ps/2 scancodes, you'll just need to program them into your converter. I've not used Soarer (I just write my own keyboard firmware usually) but if you can enter your own scancode table it should be fine

@foone cheers, what kind of hardware are you using for the base of your own converters?

@Gammitin good question. I've been doing teensys for them, but they're no longer available so I might need to shift to something else. Probably the pi pico, as annoying as I find it

@foone i think the Pico would be a good platform, having the ability to debug everything over WiFi or Serial would be amazing. Also how cool would it be to have a little web interface so that you can see codes being sent/received, or even being able to change key codes with it too. I wish I had more programming skills!

@Gammitin the thing about the pico is that it's very capable hardware (other than not being 5v) but I just hate programming and debugging for it. It's always a nightmare