I've wanted to build a KIM-1 like computer for a long time. Something that Chuck Peddle would have gladly called his own. However, I'm not looking to build a clone of anything. I'll get to some design questions later.

So, what will my trainer computer be used for? Well, I say "trainer" in that it would be like some of the first 6502 SBC's. Computers that helped people learn 6502 programming. At a minimum, it will have the keypad, 7-segment displays, 20x4 LCD display, UART and a VIA or two. So, quite a bit more than a KIM-1 but not quite an Apple II.


Anyway, one thing I'm wondering about are the button arrangements.
The KIM-1 (at least, the one on Wikipedia) has a 6x4 keypad arrangement with one missing key that is a switch.

For my computer, I'm thinking of doing something similar but maybe a little more intuitive. I thought about going really old-school and use octal format but I'm not insane...not yet. LMAO!!

1) 0-9, A-F (16) keys for hexadecimal input
2) Control keys. Suggestions needed here. I assume "Enter", "Delete", etc.
3) Status keys. Suggestions needed here. I assume "Address" (show the current PC), status flags? Etc.
4) What else?

BTW, I will be putting a PS/2 port on this computer. I love the novelty of the keypad entry but having to use it for a few hours isn't ideal. So the user will be able to use either/or. But I do want the keypad to be intuitive and useful.

Suggestions are appreciated.

Thanks!

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Cat; the other white meat.

Grab something like this:
https://www.amazon.com/exec/obidos/ASIN ... ezvid02-20

Then apply a hammer, pliers, welder, and/or blowtorch as appropriate liberally until you get it wired the way you want.

Or, you can hunt down the mechanical keyboard folks that like to build them from scratch to see how they make their plates, and PC board, and buy their switches, and build their own.

But for < $20, I bet this is a pretty good start. You're not going to be able to buy keys, case, PC Board for that much.

I was thinking about testing a budget ($1.20) 24-key IR keypad (NEC protocol) with a plastic laminated overlay;

Thanks guys.

I do plan on integrating my own keypad. Either a couple Grayhill keypads or something else.

Maybe I should have asked a little differently. I'm also looking for some suggestions on functionality (that will eventually get a key).

For example, 0-9A-F will be for entering data, addresses, etc.
Then, I will need some "OK" or "Enter" key. Along with a backspace or DEL key to correct mistakes.

What else would you suggest?

I'm thinking total key count should be 16 for the 0-9A-F, and either 4 or 8 more buttons for control, etc.

Oh, maybe an UP and DOWN key (arrows). Etc.

Something like:



That would be a 4x4 matrix next to a 1x4. BUT, I'm thinking it should be a 2x4 instead. Which would be 24 keys total.

Thoughts?

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Cat; the other white meat.

See the "Keypads and keyboards" part of the "Potpourri" page of the 6502 primer, at http://wilsonminesco.com/6502primer/potpourri.html#KBD .

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http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

I've always liked the KIM-1 keypad functions & layout. The only thing I'd change is the SST (Single Step) switch. I'd make it a push button (& flip-flop) with a Red/Green LED to indicate Single Step or Run mode.

Those tactile switches are pretty good: if you have a suitable enclosure, you can put printed card over them and have the feel of a keyboard without the keys. You can laminate the card with librarian's tape and it still works and should be durable.

Here's an example:
https://www.flickr.com/photos/pbnelson/ ... 493134393/

And here's another:
http://www.kswichit.com/8080kit/8080kit.htm

Those are great examples! In fact, I like the idea of having two functions on the keypads. Like a shift key that can be used to run macros, etc.

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Cat; the other white meat.

In my experience, these things have a very short life span. I'm using them to control RGB LED strip, and already worn out two of them with less than 1000 presses each. It's good that they're cheap.

One thing to consider is something they use from the VAX days and the EDT editor.

On that editor, it was (pretty much) entirely driven from the VT100 numeric keypad, which is essentially 18 keys plus the arrow keys.

The singular concept that stands out about how they use this is they designate one of the keys as the "Gold" key.

And it's simply a shift key.

Not like a normal shift key, it's not a chording thing, it's a toggle.

This Gold key basically doubles your available keys, so you don't have to have a lot of keys on your keypad.

It's just a nice concept to consider.

The only thing close to what you're after that I've had is the Elektor Junior computer. I no-longer have most of it because when (at uni) I started to make other 6502 systems it was more or less consigned to the recycling bin (and I now kick myself every time I remind myself of that) However I still have some of the keyswitches and the 7-segment LED displays.

Last project I did with the keyswitches was to make a matrix keypad with them on stripboard.

Those keyswitches. They're the best. Not sure if you can still get them. But googling about, I find this in this very site:

http://www.6502.org/users/dieter/xp/x32/x32.htm

which is a Junior computer, so you can see those keyswitches.

More googling and they might be Digitast Microminiature SPDT, Key Switches

e.g. https://uk.rs-online.com/web/p/keyboard ... s/2112335/

They're not cheap compared to the little regular push-buttons, but for a personal project I think having good buttons is worth it. Some nice lettraset and a light cover spray/varnish to seal it in and you're good to go.

I'd not go octal though - 8/16 bits just don't go well with 3-bit octal grouping. I did find that somewhat weird on the PDP11 and it wasn't until relatively recently that I got into PDP8's where it makes more sense, being a 12-bit machine.

Good luck with it - hope it goes well!

Cheers,

-Gordon

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Gordon Henderson.
See my Ruby 6502 and 65816 SBC projects here: https://projects.drogon.net/ruby/

One thing that would be nice is a CRC function key. When entering a long program ( original or from a book ), it would be nice to generate a CRC. Also, if you know what the correct CRC is, it is possible to even correct and single byte error with a good CRC. The math isn't too hard. I find the easiest way to handle correction is to play is backwards until you find the syndrome. Most text talk about using things like the Chinese remainder theorem and prim factors of the polynomial. Playing the CRC backwards is trivial in comparison.
Don't use check sums as they're are biased and poor at finding problems and useless for repairing code.
Dwight