Re: Chip for PC Keyboard buffer

From: Tauno Voipio (tauno.voipio_at_iki.fi.NOSPAM.invalid)
Date: 03/18/04 

Date: Thu, 18 Mar 2004 07:16:00 GMT

Michael Joosten wrote:
> Max wrote:
>
>>I want make a PC keyboard buffer to use PC keyboard with a long cable in an
>>industrial enviroment.
>>Does anyone suggest any chip to use?
>
>
> Since I just read a data *** of an I2C repeater chip, and as it looks
> like that the 8042/41 protocol looks very like the SCL/SDA signaling I2C
> uses, why not just such a thingy?
> The keyboard itself seems to have the pullup resistors, and on an old
> keyboard controller there seem to be a 2k2 each. So, perhaps even two of
> such repeater chips on each side, with resistors as pullup/terminators
> between these repeaters?
>

PC keyboard is *not* compatible with I2C. The protocol uses clock
clamping, but in other ways it's nearer the asynchronous serial
communication (commonly mis-called RS-232), but not compatible
with that, either.

If the repeater trusts on I2C protocol, it will not work with the
keyboard.

Tauno Voipio
tauno voipio @ iki fi