Building an AT2XTKB (AT to XT) keyboard adapter on prototype board

If you like me you find yourself wanting an AT2XT adapter, you may have also discovered that they are not too easy to buy pre-made.

Project information here

Here is one I built on prototype board, using an AT to PS/2 Keyboard cable:


Without the IC Socket on it, it looks like this:

Once the IC Socket is fitted, the tails from the AT to PS/2 Keyboard can be attached like so:


I forgot to preserve a trace to connect the shield on mine, so I’ve had to connect that through that black wire separately.

Here is the underside:


In my case I used a PIC12F675 (which needs different code)

The last thing to do is wrap it in heatshrink tube:


A modified and compiled version for PIC12F675 can be downloaded here. I just fired it in with my Universal programmer, plugged it in and it worked perfectly first go.

If yours is using a PIC12F629 like the original design, get the firmware from the original project information page.

Posted in Vintage PC

12 thoughts on “Building an AT2XTKB (AT to XT) keyboard adapter on prototype board

  1. Hi!
    Great job you’ve done with this adapter.
    I need to make one for my project. However, what I need is exactly the opposite you’ve done here. I need to connect an XT keyboard to an AT motherboard…
    Do you think your design can be modified to do this?

    1. First of all, it is not my design. Secondly –

      Of course this is possible, but the firmware would have to be completely re-written. Given that I’ve never even looked at the source code, I wouldn’t have the faintest clue what effort this would involve.

      I suspect quite a lot.

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