[sdiy] WinTel Keyboard by 2

John L Marshall john.l.marshall at gte.net
Fri Jun 28 05:40:53 CEST 2002


Keyboard wedges have been around for decades years. The application that I
am most familiar with is for bar code wands and scanning guns. Keyboard
wedges fit in series with the keyboard so that they may send characters to
the computer directly. Keyboard characters pass through the wedge. Responses
from the computer enter the wedge first and then are passed on to the
keyboard. I will check my archives and see if I have more details.

Take care,
Pacific Northwest DIY Synthesizer meeting, July 20, 2002
See: www.sound-photo.com

----- Original Message -----
From: "Batz Goodfortune" <batzman at all-electric.com>
To: <synth-diy at dropmix.xs4all.nl>
Sent: Thursday, June 27, 2002 7:29 PM
Subject: [sdiy] WinTel Keyboard by 2

> Y-ellow all.
>          If someone out there is privy to the inner workings of a standard
> (5pin DIN) keyboard, would you at all be able to advise me.
> I want to add a second keyboard to the I/Face for the purpose of
> it one into a custom function layout. One of my audio recorders
> has always had an awful layout and isn't really conducive to quick
> operations. Especially when you're miles away at the time and you need to
> stop/start it recording.
> As I recall, the keyboard I/Face is an open collector drive at each end.
> The protocol wakes up and sends a special req to the keyboard which
> responds by sending a special (Yes I'm awake) ack. in return. The problem
> as I see it, is that with two keyboards on the same I/Face, both are going
> to try and respond at the same time. Undoubtedly there would be a
> and the BIOS/OS (Or whatever feels the need to do a keyboard check) will
> get a trashed response. Probably deciding that there's no keyboard there
> all.
> I'm thinking that by putting a diode in the path of the second keyboard,
> would be able to pull the line down but never receive the REQ from the
> boxen and therefore never send an "I'm awake" Ack.
> Is that a fair assumption? Or is there something more to it? I guess it
> rather depends on where the pullup resistor is. If there's one at both
> then we're laughing. If it's at the keyboard end only then I guess I'd
> to add another one on the boxen side of the diode? And I'd assume it would
> probably be the standard 4K7 TTL type pullup?
> Anyway, a comment or 2 on the off-topic-ness of the post would be most
> welcome. And for those interested, I literally was frothing at the mouth
> this morning and I can now say from experience, - mainly for Harry's
> benefit who seemed to be suggesting that "frothing" was a good career
> - that frothing isn't worth it.
> I am going to have to try and stop mistaking the tube of shaving cream for
> toothpaste in future.
> Thanks in advance.
> Be absolutely Icebox.
>   _ __        _       ____Happiness is a warm penguin____
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> |  _ \ / _` | __|___ |  Geek music by geeks for geeks
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