HP262x keyboard to HP120 interface

[Rik Bos]

Nice work !
I've some 125/120 Software and some doc's (some Dutch (translated from
english))
Most of the software is on the hpmuseum website to, but I also have the
technical system manual for HP150 (got it this week ;-) with all the
diagrams of the HP150 and the HP150-II .
What I don't have is a sheetfeeder for my scanner so scanning the whole
manual is a bit to much but scanning the diagrams or other special info
isn't a problem.



> -----Oorspronkelijk bericht-----
> Van: cctalk-bounces at classiccmp.org 
> [mailto:cctalk-bounces at classiccmp.org] Namens Tony Duell
> Verzonden: zaterdag 11 april 2009 20:17
> Aan: cctalk at classiccmp.org
> Onderwerp: HP262x keyboard to HP120 interface
> 
> For those who are still interested in this (Rik?), I've now 
> built the interface from an HP262x keybaord (actually one 
> 'borrowed' from my HP2623
> terminal) to my HP120.
> 
> The differenve between the 2 keyboard interfaces is quite 
> simple. The HP120 puts the scan counter in the keyboard, the 
> interface being the clock and reset lines for this counter, 
> along with an active-high 'current key pressed' siganl. The 
> HP262x puts the scan counter in the terminal, the inteface is 
> the 7 key select lines (basically the outputs of the counter) 
> and an active-low 'key pressed' signal (open-collector). 
> Although the Hp262x runs the keybaord at 5V, it's all 4000 
> series logic interally, and can be run at the 12V of the 
> HP120 interface.
> 
> So the interface between this keyoard and the HP120 is little 
> more than a
> 7 it counter. 

Just like you sayd, the same hardware just placed different.
> 
> I've now built it, it's a little box with a DA15 socket on 
> one end to take the plug from the unmodified HP2623 keyboard 
> (I obviously wanted to leave the keyoard unchanged so I can 
> still use it with the 2623 terminal) and a short cable coming 
> out of the other end ending in an RJ11 plug to go into the HP120.
> 
> Inside are 3 chips, all common 4000 series CMOS parts. : 
> 
> A 4024 (7 bit counter). This is linked to the clock and reset 
> lines from the HP120 via the resisotr/diode protection 
> networks as used in an HP150 keyboard.
> 
> The bottom 6 outputs of this counter are buffred by a 4050 
> chip and then fed via a 16 pin header plug nad socket to the 
> DA15 socket for the keyboard. This chip may not be necessary, 
> but some counters don't like driving long cables (glitches on 
> the outputs can change the state of the flip-flops). I dout 
> the 4024 sufferes from this, but adding one chip to be sure 
> seems worth it.
Yes  a cents(pence, cents are dutch befrom before the euro) to prevent a lot
of trouble.

> 
> The last output from that counter is buffered bu 2 sections 
> of a 4049 in cascade. The reason I used that chip is that I 
> needed a NOT gate to invert the open-collector key-pressed/ 
> signal from the HP2623 keyboard. 
> This I did,, after pulling said signal high with a 3k3 
> resistor. The output of that NOT gate is again given a 
> diode/resistor protection circuit and fed to the HP120
> 
> And it works. It worked first time actually (well, I did test 
> as I went along, but after fitting the last connection , 
> plugging everything in and powering up, it worked). I can 
> type on the keyboard, the correct [1] characters come up. I 
> can use the function keys, configuration screen, etc.

Great most of the time I have to debug something like this, because I always
do several things together...
 

> [1] Modulo the fact that I have Danish/Norwegian ROMs in my HP120 (!)

I've a HP9836 and HP9826 with Swedish keyboards not very different from
standaard US-int keyboards.

> 
> I am now looking at modifying an HP150 keyboard to work with 
> the HP120. 
> More news if I get that working!
> 
> -tony


Have fun,
Rik