[sdiy] WinTel Keyboard by 2

phillip m gallo philgallo at attglobal.net
Fri Jun 28 16:48:42 CEST 2002


Batz,

start here;

http://www.beyondlogic.org/keyboard/keybrd.htm

-----Original Message-----
From: owner-synth-diy at dropmix.xs4all.nl
[mailto:owner-synth-diy at dropmix.xs4all.nl]On Behalf Of Batz Goodfortune
Sent: Thursday, June 27, 2002 7:30 PM
To: synth-diy at dropmix.xs4all.nl
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 butchering
it one into a custom function layout. One of my audio recorders (Creamware)
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 collision
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 at
all.

I'm thinking that by putting a diode in the path of the second keyboard, it
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 ends
then we're laughing. If it's at the keyboard end only then I guess I'd have
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 move.
- 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.

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