3 Apr
2009
3 Apr
'09
7:50 p.m.
And using a 2392A keyboard ?
I don't think I have one of those. What machine does it go with? It also uses the HP150 keyboard interface..
The original keyboard looks a lot like the small HP 9816 keyboard..
Maybe you could modify one of those.
No, the HP9816 keyboard is very different. it's a 5V
interface on 4 wires (+5V, ground, clock, data (from
keyboard)/reset (to keyboard). It also has the twiddleknob
(which is addressed as 1 column of keys -- 7 bits of motion
and 1 of direction IIRC). Interestingly the 9816 keysiwtches
are not wired as a matrix, rather one side of each switch is
grounded, the other goes to a multiplexer input. Scheamtics
are on hpmuseum.net.
The closest keyboard i have electrically is the HP150 one.
And not realy the right style.
It is the same interface, similar circuitry, but with
differnt
key matrix layout. I think I can hackl that by replacing the
scan counter chip in the keyboard (a 4024) with a little
circuit of about half a dozen chips.
The closest keyboard I have for having the right keys is the
one for the
HP2623 terminal -- after all a similar keyboard was used on
the HP125, which as you know is a very similar machine to the
HP120 (to the extent that the firmware ROMs are the same, for
example). Of course the interface is quite differen, but a
conversion circuit shouldn't be too hard to buiold (probably
cost more for case/connectors than for logic chips!).
In a lot of cases the right HP keyboards are difficult to find even HIL
keyboards are not always easy (reasonable priced) to find.
If I was you I should go for the interface and the HP2623 keyboard, it looks
better when using the HP120 ;-)
-Rik