Parallel keyboard interfacing

From: J.C. Wren <>
Date: Wed Feb 18 07:44:59 2004

Cini, Richard wrote:

>Hello, all:
> I was browsing the Mini-ITX motherboard site recently
>( and was intrigued by some of the cloaked "classic"
>PC projects. The Mini-ITX is an extremely small form-factor PC motherboard
>and this site outlines people's homebrewed projects.
> Anyway, there's a project using an Atari 800, a Commodore 64 and a
>Commodore SX-64. This got me to thinking. In these projects the keyboard is
>left in the case as a prop (non-working). I was thinking about using a
>busted Amiga 500 (more internal space to mount stuff) for a project but I
>want to find out how hard it would be to make the prototype keyboard
>"working" by connecting it to a hacked PS/2 keyboard controller.
> Does anyone have a schematic for an actual PS/2 or AT keyboard? How
>are the keys connected to the keyboard controller?
> Thanks in advance.
    With wires :) I don't have a copy around, but the original XT and
AT Technical guides have the schematics for the keyboard. I'm not sure
if the PS/2 did or not. Like most keyboard controllers, it's just a
row/column arrangement. Your biggest job would likely be cutting loose
all the matrix'ed connections on the original keyboard so you could
patch it into a matrix the PS/2 keyboard expects.

    If you look in the back of Citcuit Cellar Ink, there are several
companies that sell matrix scanners that output PS/2 codes. They're not
very expensive, and it'd be a LOT less effort than trying to re-use a
PS/2 controller. If this is the avenue your interested in, and you
don't have CCI, I'll grab one of my copies from the warehouse and look
some up for you.

    For those reading this far down, my PS/2 parallel keyboard adapter
nears completion. I turned some boards a week or so ago, but made a
misteak on them. The software is basically complete, lacking only the
check out of the Otrona interface. It also developed a couple of extra
features, such as the ability to swap the left control and capslock key,
option for backspace to send DEL instead of 0x08, CTRL+ALT+DEL now
generates an external reset, and the firmware is updatable by the user
(using XMODEM). I plan to send out for the final boards late this week
or early next week.

Received on Wed Feb 18 2004 - 07:44:59 GMT

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