Here is a app note of motorola called "Interfacing MC68HC05
Microcontrollers to the IBM AT Keyboard Interface "

http://e-www.motorola.com/files/microcontrollers/doc/app_note/AN1723.pdf

They add some thermometer capabilities to a PC by connecting their card
between the PC and the keyboard.
It is well documented. (how PS/2 works....etc)

SamB

-----Message d'origine-----
De : pic microcontroller discussion list [mailto:PICLIST@MITVMA.MIT.EDU]
De la part de Mike Hord
Envoy=E9 : jeudi 25 mars 2004 19:58
=C0 : PICLIST@MITVMA.MIT.EDU
Objet : Re: [PICLIST] [PIC]: keyboard emulator + pc keyboard


I'm afraid I don't know too much about PS/2.  Take a look at
www.beyondlogic.org for more info.  It appears based on a bit of info
they have there that the data/clock lines are open collector (on a
keyboard), but your PIC (unless you work it as
such) will NOT have OC I/O.

Okay, a little more searching produced this:
http://panda.cs.ndsu.nodak.edu/~achapwes/PICmicro/PS2/ps2.htm
from my own alma mater, North Dakota State University.

There is a little on there about connecting a microcontroller and KB
concurrently.  I think, anyway, but I didn't read it too hard.

They suggest making your own OC drivers for the PIC.  May be worth a
read.

Mike H.

>thanks for your idea, what I know is that you can buy a simple "Y"=20
>Cable at any pc shop. I don't have one, I know it molded and maybe it=20
>contain any tiny circuit inside, or connected pin-to-pin without any=20
>circuit. and if so, I wonder how
>2 ordinary keyboards can work together.
>
>Tal

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