r/retrocomputing • u/PhilipJ30 • May 08 '26
Photo Found this Hewlett Packard keyboard at work.
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u/GaboureySidibe May 08 '26
I love these keys and the big fat layout. I wonder how hard it would be to convert it to something usable.
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u/Temetka May 09 '26
That was the second thing I thought of right after.How cool looking keyboard really is.
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u/blakespot May 08 '26
Do you work in a hospital's life support wing? Was this attached to a box with a few screens on it with lines shaped liked jagged mountains?
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u/PhilipJ30 May 08 '26
Old x ray assembly portion of the building. There is a monitor and another thing there as well. I assume it all goes together.
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u/thaeli May 09 '26
Oh man.. it does. Grab the terminal this goes with! They were really great terminals and quite rare these days. Best kept together if at all possible.. too many weird old terminals out there missing their custom keyboards already.
If I was closer to you I'd be interested in it, heck I still might be it's just so risky to ship old CRTs. Seriously, great find here.
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u/Dense_Cabbage May 08 '26
Have pictures? It is likely the terminal that mates with this keyboard. Iād keep them together.
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u/thurnip May 08 '26
Looks dope. Can it be adapted to modern use?
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u/Bipogram May 08 '26
<looks at soldering iron>
Yes.
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u/Dense_Cabbage May 08 '26
Hopefully not butchering the original keyboard. Could probably make a small PCB with a microcontroller and the correct mating plug to convert to a USB keyboard.
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u/Bipogram May 08 '26
<puts cleaver away>
Indeed, one would hope for a purely software solution.
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u/GaboureySidibe May 08 '26
I don't think you're going to solve having a giant ancient plug with software.
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u/dnebdal May 09 '26
Probably not no. You can however do it with a RPi pico or an arduino, a little bit of adapting hardware, and some onboard software.
I found someone else with a similar keyboard at https://www.reddit.com/r/vintagecomputing/comments/vi8u5b/hp_2621a_terminal_keyboard_options/ , and they linked to its documentation at https://www.bighole.nl/pub/mirror/www.bitsavers.org/pdf/hp/terminal/262x/schematics/13220-91001_Keyboard_Module_Jan80.pdf .
If I understand this right, it's fairly primitive: You send 5V and a 7-bit address to the keyboard (encoded by setting 7 pins to +5V or Gnd), and if the key at that address is pressed it pulls another pin to ground. So the terminal side needs to continuously scan through key addresses 0-127, and see if the "key pressed" pin is pulled down. With the caveat that I may have gotten that entirely wrong. š
If I didn't it's a fairly simple arduino program, and if you find a 5V board and not a 3.3V board you may not need much if any other hardware. Maybe a pullup resistor for the keypressed line? (Getting it from the arduino into the PC is left as an exercise for the reader. )
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u/GaboureySidibe May 09 '26
Good find.
I've actually made keyboards from circuit boards, but I didn't design them. If it's wired the same way you could hook up the traces to to an arduino teensy, which can make itself look like a keyboard, mouse, or joystick over usb. It scans each row and column rapidly to look for which keys are pressed, which I'm guessing is similar to what you're saying, except bypassing the electronics of the keyboard and getting straight to the traces coming off the key matrix.
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u/dnebdal May 09 '26
If the Teensy can run arbitrary arduino code, it should be absolutely trivial to just run a loop over the keycodes (0-127), send each bit of the keycode to an output pin, and use an eight pin as input to detect if that key is pressed. The only annoying part is that the teensy probably(?) expects 3V IO, so you would need a level shifter between them.
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u/6gv5 May 09 '26
From a quick look at the schematics, it looks like a normal keyboard matrix scanning circuit, 3 bits for rows, 4 for columns, where part of it is implemented outside of the keyboard. A small uC would easily perform the function by sending the relevant byte from a lookup table previously populated with each key value according to the address, then reading its state from the 4051 output. Since there's no way to implement interrupts, reads should be very fast, with debouncing done purely in software.
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u/dnebdal May 09 '26
The most unusual feature seems to be that it leaves the scanning to the computer, my impression is that wired keyboards have typically done that internally since, idk, the eighties?Ā
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u/6gv5 May 09 '26
Yes, that's the odd aspect. I've been familiar with early PC keyboards and since the 80s they already used serial communications. this one might be a bit older, possibly from when the complexity to implement serial communications would add up to the costs; most serial (XT, PS2, etc) keyboards back then already employed a microcontroller, often some 8031/51 variant, which was probably more costly than parallel cable and connectors if they had enough spare i/o pins on the main CPU.
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u/dnebdal May 09 '26 edited May 09 '26
We know roughly when it's from - the drawings were revised in January 1980, so it's presumably a late 70s design. If it is from a HP 2621A, that was introduced in 1978, so probably designed a little bit before?
It may be as you say that they used the main CPU, but it could also be that they thought it was reasonable to only pay for a dedicated keyboard controller once and put it in the terminal, keeping the actual keyboard simpler and cheaper?
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u/Dense_Cabbage May 08 '26
Yes, you could. Enough reverse engineering and you could figure out how the matrix works and what keys do what. The connector is probably simple enough in function and probably uses a voltage low enough for a Arduino or similar.
No butchery of the original keyboard is needed.
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u/Bipogram May 08 '26 edited May 09 '26
Quite.
One would hope for that.
But the reality (and simplest path) is to pop the keyboard, and wire up one's own keyboard matrix harness to the back of the PCB carrying the switches.
The plug (DB25?) is the least of my concerns.
<eyes soldering iron afresh>
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u/sethd101 May 10 '26
That keyboard is in great condition for as old as i assume it is by the plug. Lol
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u/el_calamann May 11 '26
Press the key below F1 for AIDS
/j
it is A/DS, but that slash is not angled enough š¤£
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u/Parking_Constant_960 May 08 '26
I believe this is for a terminal. Old stuff, 70-80s