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What would make a great classic ACSII keyboard layout?

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dfnr2

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What is the best general purpose 1970's style ASCII keyboard layout?

For example, using the starting point of an ADM-3A, which is an ASR-33 derivative like many keyboards of the time:

adm3a.jpg

The HERE IS key is more of a terminal function than a keyboard function, so I think I would use the space for something else.
Perhaps the same might be said for the BREAK key.
I'd be inclined to keep the LINE FEED key.

How about a TAB key, should there be one, and if so, should it be wide like a shift key? Where would it go?

Best position of other special keys?

Dave
 
It's hard to say what's best since the 1970's is the period when keyboards were switching from bit-paired layouts to typewriter-paired layouts (these are the terms Wikipedia has). By "bit-paired" I mean layouts like on the ASR-33, ADM-3A and VT05, which were set up so that the difference between a shifted and unshifted key was a single toggled bit. So unshifted 2 is hex 32 in ASCII, and shifted 2 (") is hex 22 (the 0x10 bit being toggled). Likewise, unshifted ; is hex 3B and shifted ; (+) is hex 2B. And of course by "typewriter-paired" I mean primarily the electric typewriter layouts that had the ' and " keys on the same physical key, with IBM's Selectric being a particularly famous example.

It has been my experience that going back to older keyboard layouts is a big nuisance because keys are no longer where your muscle memory expects them to be. In other words, "best" may be simply the layout that people are most quickly able to learn, which means the layout that's closest to what they already know. So unless you have a specific reason to authentically reproduce a particular layout I would just stick with the modern typewriter-paired layout that people are used to. The VT52 from 1975 may be a good starting layout in that case.

If you expect the keyboard to be usable in serial applications, I would definitely keep the BREAK key. BREAK has no ASCII code so it really needs its own key (or if not a keyboard key, some kind of pushbutton near the keyboard). Ideally a keyboard that's useful for 1970's-era serial communications should be able to generate every ASCII code from 0 to 127 inclusive, plus BREAK. If you can fit an ALT or META key in somewhere allowing codes from 128-255 to be generated that would be interesting but I wouldn't say it's required. That's more of an 80's/90's thing anyway.

I would consider ESC and RUBOUT (aka DELETE) must-haves, and TAB and LINE FEED nice-to-haves (this is for a keyboard intended for use with a CRT -- for a printing terminal LINE FEED and BACKSPACE become more important). I'd expect ESC to be in the upper left, either to the left of 1 or the left of Q. RUBOUT should be on the right, somewhere above RETURN. If you handle key repeat in the firmware you can drop REPEAT. SHIFT and CTRL are of course mandatory (the modern positions of Caps Lock and Left Ctrl being good spots for CTRL), but I have no idea about CAPS LOCK. Are there any ASCII systems out there that don't support lower case and *require* input to be in upper case? In case such systems (or applications) exist it's probably a good idea to include CAPS LOCK too. Some people prefer Ctrl and Caps to be swapped from where they appear on PC keyboards.
 
I'm planning on going with this, except the ESC is moved up next to the "1", and a 1x TAB is placed next to the "Q" key. The two keys in the lower right corner will be left and right arrow keys. The key in the left lower corner will be (optionally) a power indicator, and "free" key, in case someone wants capslock there, or a meta/alt key. 62 keys in all.

keyboard_test.jpg

I think REPEAT is kind of extraneous, but it's in lots of retro keyboards. The

I am going with the ASR-33 style layout because ASR-33 style keycaps are hard to come by. If someone wants a selectric-style layout, then it is easy to buy a keycap set that works with the keyboard.

The keycaps are SA profile, I thought about ordering the full spherical profile (so each row has a different angle), but decided it's better to order the center row profile (level spherical) for all keys, so they are easy to swap around. (Apple II has the arrow keys on the second from bottom row, for example, and ESC next to the "Q" key.

I'm looking at a dark gray color, which is period appropriate and would be the most versatile for pairing with various machines, even if not a perfect match for the originals.

Any thoughts?
 
dfnr2 said:
I'm looking at a dark gray color, which is period appropriate and would be the most versatile for pairing with various machines, even if not a perfect match for the originals.

Any thoughts?
Click to expand...

are you having a set of double-shot cherry compatible keycaps made with the font in the picture?
 
Yes. The keycaps also work with the Futaba MD-4-PCS keys, which are used in the picture.

The pictured set is designed for OSI reproductions with a few ADM extensions. The unused Shift Lock and 1.5x Tab keys are not shown. The new set will trim the Tab to 1x and will have a few additional keys for flexibility: RESET, G/BEL, N/^, and a white POWER cap for apple II; and Shift Lock for OSI. With the right keys populated (and right interface module), this keyboard is a perfect functional and mechanical drop-in for OSI and Apple II, including mounting holes.

So, is it worth spending about $10 more per set to get duplicate arrow and ESC keys for different row profiles? I'd like to go that way. That would allow a spherical profile for a nicer overall keyboard experience, but would restrict arbitrary swapping. Or just stick with the flat keyboard profile? I'd really like to go with the spherical profile, but want to make this keyboard as generally useful and appealing as possible, with the hope of getting a price break buying 100 sets, and getting rid of them instead of getting stuck with an expensive brick in my storage locker.
 
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dfnr2 said:
Yes. This set is designed for OSI replicas with a few ADM extensions. The unused Shift Lock and 1.5x Tab keys are not shown. The new set will trim the Tab to 1x and will have a few additional keys for flexibility: RESET, G/BEL, N/^, and a white POWER cap for apple II; and Shift Lock for OSI. The keys also work with the Futaba MD-4-PCS keys, which are used in the picture.

So, is it worth spending about $10 more per set to get duplicate arrow and ESC keys for different row profiles? I'd like to go that way. That would allow a spherical profile for a nicer overall keyboard experience, but would restrict arbitrary swapping. Or just stick with the flat keyboard profile? I'd really like to go with the spherical profile, but want to make this keyboard as generally useful and appealing as possible, with the hope of getting a price break buying 100 sets, and sharing the savings instead of getting stuck with them in my storage locker.
Click to expand...

I think what you show in the picture is period correct for key sculpture. Maybe the option of an inverted T for cursor keys, but that blows period correctness
 
Here is the gray selection (ABC plastic). I'm leaning toward the darker grays, with some of my preferences circled. Any thoughts?

grays.jpg
 
Al Kossow said:
I think what you show in the picture is period correct for key sculpture. Maybe the option of an inverted T for cursor keys, but that blows period correctness
Click to expand...

That's what I hope is the consensus.
 
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I agree, but not black, which would look out of place in an Apple II. But not too light, which would look weird on a C4P. A shade of gray that looks good in both systems will work anywhere. I'm leaning toward GEW (2nd row, third from left)
 
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What's the general preference in the alpha key legends? A larger font centered in the middle of the key like the ADM-3A, or a smaller font centered on the bottom half of the key, like the Apple 2 and Sol keyboards? I like the larger centered position, but am leaning toward the smaller, lower position to make the key set work in more different situations (for example, with the Apple II Bel-G and ^-N keys).

Thoughts?
 
FYI, just remembered this Tektronix keyboard patent, 4106011 which has N-key rollover without diodes

Screen Shot 2020-01-15 at 10.21.15 AM.png

The circuit is used on the tek 4052 with cherry keyswitches
Screen Shot 2020-01-15 at 10.18.19 AM.png
 
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I think this was a pretty common architecture for keyboard scanning. However, without the diodes, the keyboard is still susceptible to "ghosting" artifacts if three keys are pressed forming three corners of a rectangle in the matrix.

One way to prevent ghosting without diodes is the use capacitive keys. The issue would be sourcing the keys, though. Another method involves checking each key separately, either through multiplexers (like the HP 9816 keyboard), or using an I/O line for each key (if there are 64 or so I/O lines available). The issue with multiplexers is the large number of chips required, and the issue with direct I/O lines is that it would require a chip (microprocessor or FPGA) with a large number of pins.

The current keyboard uses a similar scanning method to the one described in the patent, with debouncing and n-key rollover in software. The main reason my circuit uses a bunch of chips is because I chose to avoid a large surface mount chip in favor of a small DIP chip that is popular with hobbyists.
 
Al Kossow said:
Larger, in the center. With double-shots, wear on the label isn't an issue.
anyone else like bumps on f and j ?
Click to expand...

I am thinking of going with "deep dish" F and J keys. I also like bumps, but they are controversial, and out of place on most vintage machines. Deep dish is a bit more subtle, and actually feels very good.
 
I don't know how you'd ever find out who made these, but I bought two sets of keytops and they are VERY well made ABS double-shots
https://www.ebay.com/itm/322915402230
They almost look like the keys on Heath/Zenith Z2x terminals
There was one weird key included in the kit, have no idea what it means
1962.JPG
 
@Al, good to know of a good source of keycaps. Many vintage layouts, including DEC terminals and HP machines, used the Selectric-style layout, and these keycaps can be the basis for keyboards with that style of layout, perhaps supplemented with a few custom keycaps if needed.
 
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