[sdiy] WinTel Keyboard by 2

Batz Goodfortune batzman at all-electric.com
Fri Jun 28 04:29:42 CEST 2002

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 

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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