HP 700/32 keyboard signals

Stan Sieler sieler at allegro.com
Tue Jun 2 13:10:47 CDT 2009


An acquaintance in (maybe) India, has dozens of HP 700/32
keyboards he'd like to continue using ... but by attaching them to
modern equipment.  He's done some initial work trying to figure
out the signals/protocol, but hasn't solved it yet.

I pointed him to CC here, but he seems reluctant to join.

He writes:
  > We have about 75 HP 700/32 terminal keyboards which we want use as input
  > devices for our quality control points. I have already constructed a PIC    
  > board to do the job but I just can not read the keyboard. What I see from
  > the osciloscope is, the keyboard requires 5V power, a 77 kHz 1:3 duty rate
  > clock, and outputs two pulses on two different lines, time between which is
  > dependent on the key pressed. For example, for the left-shift key, there is
  > always 22 clock cycles between these two pulses. 

If anyone is interested in corresponding with him, please email me offline
and I'll try to put you in contact with him.


Stan Sieler
sieler at allegro.com

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