NKRO keyboards for art installation

[SFR75]

Hello,

I've been designing an art installation around keyboards and computers. It consists of a room filled with keyboars and where people can walk, sit, lie down. All keyboards are connected via usb hubs to computer, which then processes which keyboard and which keys are pressed and projects an image on the wall - a snapshot or a print if you like. So basically these keyboards become a large matrix of buttons.

However... soon I've realized that computer keyboards only support 6 keys pressed at once at most. Which is a huge problem for me. Then I've learned that they are N-Key rollover keyboards, however they are rare and expensive. From what I understand the limitation on number key pressed is not at all related to interface (PS/2 vs USB), but how keyboards are constructed and their firmware (for example IBM Model F and Model M both are PS/2, both are mechanical.. however F is NKRO and M is 2KRO).

Anyway. I wonder if there is a list somewhere of vintage/old keyboards USB or PS/2, that are full NKRO.

This is somewhat unique feature, but as you can see I really need these keyboards in order for this installation to work.

Needless to say I don't care about any other features, such as quality, look, mechanism...

Sincerely
M

[Muirium]

From what I understand the limitation on number key pressed is not at all related to interface (PS/2 vs USB), but how keyboards are constructed

You're close to correct. USB is more of a bottleneck for NKRO than PS/2 (for complex and rather cynical backwards compatibility reasons), though both are perfectly capable of delivering n-key rollover. 6KRO is a USB thing. But 2KRO is almost universally caused by using membranes to sense keypresses, as the vast majority of keyboards do. (Including the actually rather mediocre IBM Model M.)

So yes, you primarily need to avoid membrane keyboards.

Capsense keyboards (IBM Model F, Topre, and many more) are intrinsically NKRO. So are a lot of keyboards with discrete key-switches (the typical modern sense of "mechanical keyboards"), like Alps and Cherry switches. However, switches need a diode matrix to be NKRO, and some of those mechanical keyboards are just as 2KRO as their membrane peers.

A lot of vintage stuff is inherently NKRO, and it needn't cost a fortune, but knowledge is required to know before you buy it. You don't have to buy a modern board with NKRO in its marketing, though that is likely the fastest way to get what you want.

How many keyboards do you have in mind, anyway?

[SFR75]

How many keyboards do you have in mind, anyway?

thanks for a detailed answer.

Well 1 square meter corresponds to 16 keyboards

I have 15 square meters.. to give an idea -)

Now what I don't fully understand is where this 6-key limitation comes from. Correct me if I'm wrong, but apparently it's a way to keep the cost down and avoid ghosting effect, right ? So if somehow I take cheap keyboard and remove anti-ghosting feature, then it will become a NKRO keyboard with lot's of errors, when you press keys. Right ?

Thanks
M

[Muirium]

Nope.

6KRO is hideously complex to explain, because it's a policy issue, not a physical barrier like ghosting. In short: most USB keyboards are 6KRO so they don't have to duplicate their controller design work and present two different "reports" to the host computer. Why? Because PC BIOS is limited to 6KRO, and just won't accept an NKRO "report descriptor". Unless you present a 6KRO "report" from your keyboard, it will appear bricked if ever hooked up to a PC in BIOS. Customers do not like that!

So all NKRO USB keyboards (which wish to work with PCs in BIOS) must present two parallel logical representations of state: one for BIOS compatibility and one for all other uses. To my knowledge, no USB keyboards forgo the 6KRO report, even Apple's. And so almost all USB keyboards just produce a 6KRO report and let that suffice, end of story. NKRO is opt-in.

But honestly, your real obstacle is membrane keyboards. Unless you were poking keys in the 80s, It is quite likely every single keyboard you've ever touched in your entire life is a membrane keyboard! And they are all 2KRO*, whatever the electronics. :O

Notably: PS/2 (actually AT) has no such issue. It's always the same rollover, because it's so damn simple even BIOS understands it. Those of us without the port often run our vintage keyboards through converters**, which take their AT NKRO and turn it into USB NKRO just nicely. But it does need an inherently NKRO keyboard. You're always limited by the weakest link in the chain.


*2KRO doesn't mean "you can't press 3 keys", or even 6. But it does mean you can't press any arbitrary combination of 3 keys. 2KRO keyboards typically support all 4 modifiers being chorded with an alphanumeric key, as their membranes are optimised for exactly that. But try mashing letters…

**NOT to be confused with those passive adapters you'll find everywhere. Converters are active. They run electronics (typically an ATmega 32u4 processor) to translate the protocol. Passive adapters are just wires; and will only work on keyboards which internally support both PS/2 and USB. A universal mistake!

[SFR75]

But honestly, your real obstacle is membrane keyboards. Unless you were poking keys in the 80s, It is quite likely every single keyboard you've ever touched in your entire life is a membrane keyboard! And they are all 2KRO, whatever the electronics. :O

Ok it's more clear now.

80s keyboards are now museum pieces and that's why they sell for 250 euros )

so.. you are saying that all those cheap office keyboards .. can detect only 2 keys being pressed and ignore all others (with the exception of alt-ctrl-shift...). That really sucks.

I hoped that at least 6KRO keyboards are easy to get...

ps. regarding PS/2 keyboards.. is there any advantage if I use them ? or let's say connect to RS232 interface ?

for example those:

https://www.leboncoin.fr/informatique/2188970085.htm

[Muirium]

so.. you are saying that all those cheap office keyboards .. can detect only 2 keys being pressed and ignore all others (with the exception of alt-ctrl-shift...). That really sucks.

More or less. They can't guarantee to keep responding to more simultaneous key presses. Plenty often, more keys will get through, but it's entirely down to the arbitrary routing of the membrane. Pretty soon, you'll always be blocked. It's just how they work.

I hoped that at least 6KRO keyboards are easy to get...

A lot of old Cherry keyboards could do the trick. Many of them aren't sought after: especially the mushy feeling Cherry MY family, used in G81s. You might have some luck sourcing those on the cheap. Maybe one of our Cherry aficionados can tell you what to look for to score NKRO.

Another option:

viewtopic.php?f=50&t=26878

Inosenz may even have enough keyboards for your entire project!

Edit: The lot you linked look like a bunch of rubber-domes to me, which are membrane based and inherently 2KRO.

Spoiler:

They will typically be quite light, however. Mechanical keyboards are often quite heavy, by modern standards: good ones are around a kilo. Hopefully not a problem for your installation.

[SFR75]

Thanks.

I wonder how do you know if keyboard is mechanical or membrane just by looking at their photos ? )

Please teach me.

I looked at your link by "Inosenz", but I don't understand exactly what he is selling. Space Invaders .. ?

SO:

I'm looking for 200 6KRO keyboards!!!

[photekq]

A lot of old Cherry keyboards could do the trick. Many of them aren't sought after: especially the mushy feeling Cherry MY family, used in G81s. You might have some luck sourcing those on the cheap. Maybe one of our Cherry aficionados can tell you what to look for to score NKRO.

Not a viable option for what OP needs. NKRO Cherries are rarely worthless.

Another option:

viewtopic.php?f=50&t=26878

Inosenz may even have enough keyboards for your entire project!

I don't think he has anywhere near 200 left, if any at all; the vast majority were spoken for.

I'm looking for 200 6KRO keyboards!!!

What would your total budget be?

[SFR75]

What would your total budget be?

Good question.

Sounds like more than I expected

Open to proposals..

(I thought of using cheap used 2 euros keyboards).

here what I got from Alibaba manufacturer

[Muirium]

Photekq is who I had in mind when I mentioned Cherry earlier. Definitely worth talking with him.

Thing is: we're keyboard collectors, so of course we're going to point you to nice stuff that we like. But let's step back a bit: you're really after the overwhelming impression of being surrounded by random keyboards, right? Your project is more about a sense of being face to face with a whole wall of keys.

See, I'm thinking… does rollover really matter? Aren't people likely to put their hands on different keyboards at the same time? If it was just one keyboard you had to play with, sure, limited rollover sucks. But if there's dozens and dozens and dozens of the things all around you, you're going to fool around pressing buttons all over the place, on different keyboards, aren't you.

200 limited keyboards still adds up to an enormous instrument, to me. Maybe you could just try it with freebie junk and see if anyone notices but you?

Edit: now I've seen your Chinese offer, how about this question: which is better for your installation? The same design of keyboard over and over, like tiles, or random ones, with a post-apocalyptic e-waste vibe? I can see advantages in either. The Chinese boards would be clean and new, and those colours are intense; they'll tile well but also emphasise your geometry. Meanwhile, a whole mess of old keyboards is going to feel like walking into a survivalist's cave, and it'll be grungy with dirt, you bet! There's less a sense of rigid space when you're wall to wall with different objects, as any hoarder can attest.

It's a matter of picking an aesthetic.

[SFR75]

Photekq is who I had in mind when I mentioned Cherry earlier. Definitely worth talking with him.

Thing is: we're keyboard collectors, so of course we're going to point you to nice stuff that we like. But let's step back a bit: you're really after the overwhelming impression of being surrounded by random keyboards, right? Your project is more about a sense of being face to face with a whole wall of keys.

See, I'm thinking… does rollover really matter? Aren't people likely to put their hands on different keyboards at the same time? If it was just one keyboard you had to play with, sure, limited rollover sucks. But if there's dozens and dozens and dozens of the things all around you, you're going to fool around pressing buttons all over the place, on different keyboards, aren't you.

200 limited keyboards still adds up to an enormous instrument, to me. Maybe you could just try it with freebie junk and see if anyone notices but you?

Correct! however I planned to put them on the floor and allow people to walk over them and roll and sit...
So when you walk you will be either pressing two keys.. or many keys. If you press many keys I can almost find the shape of your feet. If you lie down, I can get the shape of your body. So it's a question of resolution. Of course with 2KRO I can somewhat deduce what's going on .. maybe create a cloud around those pixels and make sort of moving mass. It's getting more complicated..

Edit: now I've seen your Chinese offer, how about this question: which is better for your installation? The same design of keyboard over and over, like tiles, or random ones, with a post-apocalyptic e-waste vibe? I can see advantages in either. The Chinese boards would be clean and new, and those colours are intense. A whole mess of old keyboards is going to feel like walking into a survivalist's cave, and it'll be grungy with dirt, you bet!

It's a matter of picking an aesthetic.

You are absolutely right and I'm trilled that you see it the same way. Of course it's MUCH better to have bunch of old, useless, random keyboards. It's much more interesting and it corresponds much better to the idea of "survivalist cave" as you put it! With new chinese keyboards it's not at all the same image and same experience.

[jsheradin]

I think modern generic cherry clone stuff might be your best option. Gaudy gamer boards are easy to come by for cheap and should be NKRO USB. Aliexpress has loads of them new, eBay has plenty used as well.

One option if you're dead set on vintage could be low profile Keytronic foam and foil boards. I'm pretty sure they're all NKRO. Most of them are AT or PS/2 so USB adapters are cheap. They're pretty horrific to type on (particularly the tactile variant) so I don't think you'll anger too many people by using them for artistic purposes. They're prone to foam degrading but the few I've come across worked OK enough for this application.

Keep in mind that walking on a keyboard exerts some pretty insane forces. Switch stems are tiny and a 100kg person turning on the ball of their foot will break just about any board.

[SFR75]

I think modern generic cherry clone stuff might be your best option. Gaudy gamer boards are easy to come by for cheap and should be NKRO USB. Aliexpress has loads of them new, eBay has plenty used as well.

Ok, it's all new to me...) I will look up Cherry keyboards. for Gaudy I'm not sure what it is.. but for my purposes the larger keyboard - the better!

One option if you're dead set on vintage could be low profile Keytronic foam and foil boards. I'm pretty sure they're all NKRO. Most of them are AT or PS/2 so USB adapters are cheap. They're pretty horrific to type on (particularly the tactile variant) so I don't think you'll anger too many people by using them for artistic purposes. They're prone to foam degrading but the few I've come across worked OK enough for this application.

Well.. I hope people won't get angry. After all it's an installation about keyboards! What could be better ?

Keep in mind that walking on a keyboard exerts some pretty insane forces. Switch stems are tiny and a 100kg person turning on the ball of their foot will break just about any board.

Yep. I thought of that of course. I guess heavy people need to be more careful. But I assume (this needs to be tested), that simple walking shouldn't break the board, since weight will be distributed evenly. According to website it's 3lbs/square inch.

[photekq]

I'm with j's suggestions. Generic USB models from alibaba etc. will probably be the fastest, easiest and cheapest option. Look for "anti-ghosting keyboard", since NKRO seems to be used less commonly there. They usually list how many keys anti-ghosting they support.

The Keytronic route is a good one for vintage, since those keyboards are about as close to worthless as vintage keyboards come. But that said, I think finding 200 of them will be quite a challenge.

[SFR75]

I'm with j's suggestions. Generic USB models from alibaba etc. will probably be the fastest, easiest and cheapest option. Look for "anti-ghosting keyboard", since NKRO seems to be used less commonly there. They usually list how many keys anti-ghosting they support.

Ok.. so "anti-ghosting" is the right term ? It's true that NKRO they don't use that much.

The Keytronic route is a good one for vintage, since those keyboards are about as close to worthless as vintage keyboards come. But that said, I think finding 200 of them will be quite a challenge.

correct... plus Keytronic are way too vintage even for me. I was thinking of simplest HP, Dell etc keyboards as visual reference. Something that everybody is familiar with...

Thanks for your help!

[Johnbo]

I planned to put them on the floor and allow people to walk over them and roll and sit...

lol those keyboards are going to be instantly destroyed. Have you tried stomping, standing on one foot and wheeling in place, etc. on a test keyboard to see how it fares?

If you really want the keyboard aesthetic, something like this might be able to handle that abuse for a bit:
https://www.aliexpress.com/item/3256802146625794.html
https://www.aliexpress.com/item/3256804143092411.html

[AnnoyedWalrus]

I have to agree with mr Johnbo, I can't see how it would be possible to build this with keyboards, vintage or modern, without it breaking the first day of the exhibition. How important is the keyboards in the installation? It could be possible to build it by building a floor of frosted glass with webcams pointing up on it from below. It would still be pretty expensive but it should be more rugged.

[SFR75]

I have to agree with mr Johnbo, I can't see how it would be possible to build this with keyboards, vintage or modern, without it breaking the first day of the exhibition. How important is the keyboards in the installation? It could be possible to build it by building a floor of frosted glass with webcams pointing up on it from below. It would still be pretty expensive but it should be more rugged.

Hmm.. I will do some tests, but I don't feel that walking bare feet would destroy the keyboards if they are placed on flat rigid surface (floor). Apparently the pressure is 4.4 N/cm2.. which corresponds to 400gm per cm2.

also found this:
"Another study at the University of Michigan determined that the overall mean peak reaction force during a typing task is 2.54 Newtons (263.1 grams), which is 5.4 times the minimum key actuation make-force of . 47 Newtons (47.6 grams) (4)."


Building a frosted glass floor seems to be very complicated! You would need an array of webcams or need to have fewer cameras and more distance. Complicated!

[SFR75]

I planned to put them on the floor and allow people to walk over them and roll and sit...

lol those keyboards are going to be instantly destroyed. Have you tried stomping, standing on one foot and wheeling in place, etc. on a test keyboard to see how it fares?

If you really want the keyboard aesthetic, something like this might be able to handle that abuse for a bit:
https://www.aliexpress.com/item/3256802146625794.html
https://www.aliexpress.com/item/3256804143092411.html

well of course if you jump on one foot you can probably destroy it. But I would suggest people use it gently. It will be exposed at the gallery not a public venue. From my experience with interactive installation people are usually overcautious and not the other way around...

vandal-proof metal keyboards look very sturdy, but it has a particular look.. and it costs waaaay to much. 16000 bucks in keyboards )

[Johnbo]

I feel like you're looking at static pressure and ignoring the dynamic pressures that come from walking, jumping, stomping, tripping and stumbling and falling onto them, etc.

Sure, 99% of people might be careful. But there's always that one person, and also accidents happen. People would trip, stumble, get their name called and wheel around quickly, etc. Plus, when the caps start inevitably snapping off, you now have a floor full of sharp, broken plastic.

[Muirium]

Yes, I must also agree. Keyboards break too often in shipping not to fear for a world of hurt for a keyboard floor. Bare feet and sharp, broken plastic don't sound like fun!

People can still smoosh keyboards, I think, it's just the matter of full body weight and movement which is too much. I can definitely picture keyboard walls with people mushing into those. It would be quite dynamic, especially if angled back a little bit, but the key is to keep their weight in their legs and on the floor I think.

[SFR75]

I feel like you're looking at static pressure and ignoring the dynamic pressures that come from walking, jumping, stomping, tripping and stumbling and falling onto them, etc.

true that..
here is an article which describes pressure on walking and standing...

https://ard.bmj.com/content/annrheumdis ... 6.full.pdf

looks like at worse it's 4x. So.. 1.6kg/cm2 )
I think I can put that much pressure with my finger.

Sure, 99% of people might be careful. But there's always that one person, and also accidents happen. People would trip, stumble, get their name called and wheel around quickly, etc. Plus, when the caps start inevitably snapping off, you now have a floor full of sharp, broken plastic.

Ok. Maybe I would need to glue caps or choose keyboards with flatter caps.
But i agree - it's a good idea to test this. I will put 10 keyboards and walk and jump and see what happens )
My weight is 83kg.

Will give visitors slippers to protect them from broken plastic

[SFR75]

Yes, I must also agree. Keyboards break too often in shipping not to fear for a world of hurt for a keyboard floor. Bare feet and sharp, broken plastic don't sound like fun!

People can still smoosh keyboards, I think, it's just the matter of full body weight and movement which is too much. I can definitely picture keyboard walls with people mushing into those. It would be quite dynamic, especially if angled back a little bit, but the key is to keep their weight in their legs and on the floor I think.

Yes a wall would be another possibility although from artistic point I like it less.. Will do a stress test this week and let you know

[Johnbo]

What about this?

https://www.aliexpress.com/item/3256804337611582.html

[Johnbo]

The problem with all those pressure studies is that that's going to be for pressure on a flat, even surface. Keyboards are not that. If the entire weight of my body is spread over the surface area of my foot, yeah, it won't be too bad. But if I'm standing on a few switches, now the entire weight of my body is 100% directed through the stems of those keyswitches. That pressure per square cm is going to be much, MUCH different.

I think I can put that much pressure with my finger.

Think about it this way. 10 of your finger tips are roughly the surface area of 10 keycaps, right? Now, picture holding someone above your head on just you fingertips. Think it still sounds the same as pressing down on a keyboard with your fingers? Now picture someone dancing on these (of course people are going to want to dance on an exhibit like this). If someone jumped and landed on your fingertips with the ball one of their feet, think you could easily catch that person on just your fingertips?

[SFR75]

The problem with all those pressure studies is that that's going to be for pressure on a flat, even surface. Keyboards are not that. If the entire weight of my body is spread over the surface area of my foot, yeah, it won't be too bad. But if I'm standing on a few switches, now the entire weight of my body is 100% directed through the stems of those keyswitches. That pressure per square cm is going to be much, MUCH different.

Keyboard is pretty much flat surface with keys taking shape of your feet. So the weight will be still more or less evenly distributed IMHO. Of course there is a space between keys, so this should be taken into an account.. probably -15% ?

Think about it this way. 10 of your finger tips are roughly the surface area of 10 keycaps, right? Now, picture holding someone above your head on just you fingertips. Think it still sounds the same as pressing down on a keyboard with your fingers? Now picture someone dancing on these (of course people are going to want to dance on an exhibit like this). If someone jumped and landed on your fingertips with the ball one of their feet, think you could easily catch that person on just your fingertips?

no, this picture is wrong. if there were only 10 keycaps and that's it, then yes. it would correspond to the picture you described more or less..However the surface of you feet covers easily 40 keycaps. And two feet it's around 80 if not more. Plus the keyboards I've seen when you press the keycap all the way in it's resting on the the plate below. This also distributes weight across it's surface.

[SFR75]

What about this?

https://www.aliexpress.com/item/3256804337611582.html

hmmm!! very-very interesting! let me think about this. thanks!

[thefarside]

What about this?

https://www.aliexpress.com/item/3256804337611582.html

hmmm!! very-very interesting! let me think about this. thanks!

I think something like that would be a safer option. Even if you handed out slippers if someone were to fall and damage themselves you don’t want to be liable. Something like that would probably be the safest option in the name of art. Just imagine a 160 kg person falling and their elbow digging right into a mechanical keyboard…

I’m curious how you are going to synchronize all of these keyboards. Does it all go to one computer network through USB hubs? I feel like you would hit a limit at some point and would need to use more than one computer. If you have a draft picture I’d be interested in seeing your concept and where this exhibit is going to be located when finished.

[SFR75]

I think something like that would be a safer option. Even if you handed out slippers if someone were to fall and damage themselves you don’t want to be liable. Something like that would probably be the safest option in the name of art. Just imagine a 160 kg person falling and their elbow digging right into a mechanical keyboard…

Yes I understand.... at the same time the installation will loose this mechanical/tactile feel, which certainly adds to the experience.
For the rest.. well, it's all very american (no offence, I'm an american myself ! ). However this happens in Paris/France and the justice is so notoriously slow here, that nobody sues anyone .. plus people are more thin in general. Nevertheless safety and well-being of visitors it's certainly something I need to keep in my mind. So thanks for that thought!

I’m curious how you are going to synchronize all of these keyboards. Does it all go to one computer network through USB hubs? I feel like you would hit a limit at some point and would need to use more than one computer. If you have a draft picture I’d be interested in seeing your concept and where this exhibit is going to be located when finished.

Yeah. I thought about this. So the idea is to make 1m x 1m blocks consisting of 15 keyboards connected to 16-port USB hub. The hub will be connected to RaspberryPI, which will aggregate all the data and send it via ethernet. All blocks with RaspberriPI's will be connected to a network switch/router and data will be consumed by a server (openFrameworks) running on PC. It will then aggregate data coming from modules and generate image and send it to a projector. That's the plan !)

Yep, I will be happy to share the concept/sketches when I'm done with that part.

M

[SFR75]

UPDATE 1:
So I bought some simple USB membrane dell keyboards to do the break test.
They are extremely solid.. I don't think I can break them even if I really try.

UPDATE2:

However the bad news comes once again from this ghosting/rolling thing.
I would've expected, that when you step on keyboard at least some keys would work. However if more than certain number of keys are pressed at once, they @#$() keyboard blocks everything and doesn't recognize a single key.

Now that's a huge set back..

I thought I could at least get something, but it looks like I can get NOTHING out of them.