deskthority

So for years I've hated keyboards, and just wanted a "proper" like we had when I was young and pretty. I bought some stuff at an auction and there was this keyboard for a Quantel Paintbox, I got for £10.

It's brand new and in it's original box, the date code is 1989, it's made by a company called access keyboards, which is based in Reading, it has Cherry switches and it's basically perfect as far as I'm concerned.

The connections were an RJ plug that went to a header on the board .. Originally there were four wires but one was connected to a reset switch and that just drew that line to ground .. so there were three actually connected .. on a five pin header.

5.NC (but pin reads 5V when power connected)
4.Data
3.NC (but pin reads 5V when power connected)
2.+5V
1. GND

When connected to an arduino it reads two byes when pressed and three bytes when released. But they are not recognised. But this suggests to me that it is something like (if not actually) AT scancodes. The microcontroller is an 8040 which is the same family as the AT keyboards.

What I want is to take the scan code from the keyboard and feed it into the Arduino then feed the scancode out of the arduino as a USB keyboard.

Now I could do this with the PS2 code for the arduino, except that there is no strobe to trigger the interrupt line (and it doesn't work by using one of the other pins, a scope says they stay high when a key is pressed.

I've trawled through lots of the internet but I can't find anyone who has gone down this road before. Has anyone here seen some code I could use as a starting point ?

There are a couple firmwares for PS/2 - to USB protocol converters that work with some Arduino: those based on 8-bit Atmel microcontrollers (only ATmega32u4?) which have a built-in USB device controller on the chip.
Arduinos that have a serial-to-USB chip in them don't work: that USB port can only be used for programming the board and nothing else.

* TMK Firmware Collection: Thread here, Geekhack thread.
The firmware is a large framework that can be used as firmware for lots of keyboards, and there are protocol "converters" for several protocols. Open Source (GPL2)
* Soarer's Converter firmware. Only available has a binary blob, because the source is closed. Has not been updated for a long time, and the author is not reachable.

There are a lot of people around here who use either or both of these.

If your keyboard does not talk PS/2, then it could be IBM's terminal protocol. That should also be supported by the firmwares I mentioned above. Both above should also support remapping keys.
TMK would need to be (re-)compiled to get another keymap, and with the AVR-GCC toolchain, not Arduino's IDE.

TMK supports also some ARM-based microcontrollers, but I'm not sure about PS/2 support on those. The hardware would first need to be capable the 5V signals that PS/2 uses.

Other than that, you may still be able to find a commercial PS/2-to-USB converter / "active adaptor" out there to buy. I've also seen converters preloaded with Soarer's or TMK firmware on eBay.

... and BTW: Welcome to Deskthority!
Beware that the forum has a problem with spam right now.

As this keyboard is to a custom system it is basically a terminal board. The RJ connector and lack of lock lights almost always indicate a terminal board. With terminal boards you get into the realm of custom protocols like you are seeing and not good documentation available about those custom protocols.

Usually in this case it is easier to remap the key matrix if possible as opposed to trying to reverse engineer the protocol. This means that you would connect a controller with some standard mapping code configured to that matrix and just bypass the existing controller entirely. Still some work walking through the matrix but once done much easier to implement.