Help me resurrect a keyboard?

[Platokrates]

I have this old electric typewriter keyboard that I took apart that I want to get working over usb or ps2, and I've tried a couple things, but nothing has worked. It's a Smith Corona typewriter, and it has a ribbon cable with 24 soldering points. I've tried to hook it up to the controller out of an old HP USB keyboard, but I can't get any symbols out of it even if I jump the inputs on the controller with a wire. Do I need another part of the membrane keyboard I gutted? Or a teensy?

[Daniel Beardsmore]

You won't get it working without making a custom controller because the keyboard matrix of each will be different. The first thing you need to do is trace the matrix. Maybe you should post a photos of it so that we can see what you are working with.

Surely you don't mean this thing?

:-)

[rich1051414]

That thing isn't in a case and is rolling everywhere, but that looks like an spongy horrible nightmare to type on.

[Platokrates]

No, it uses linear switches that use rubber jumpers. I'll see if I can find pictures.

[Platokrates]

https://imgur.com/a/8bosd
I uploaded some pictures to imgur. Sorry that they're not the best quality...

[Daniel Beardsmore]

Ah, it's a Mitsumi keyboard. In case you don't know what a keyboard matrix is, see:

wiki/Keystroke_sensing#Conductive

All the keys are placed into a grid of wires. The controller is programmed to know which key corresponds to which grid position, so that when it senses that current can pass through that grid position, it knows which key to report. This is all keyboard-specific. Also, the number of columns and rows in the matrix is specific to each keyboard.

So if you connect the Mitusmi matrix to the HP controller, it won't work. At best, it will type complete nonsense.

The first thing you need to do is figure out which of the lines are rows and which are columns and draw up a grid, and then determine which key appears at each position in the matrix. Then, connect it to something like a Teensy and compile a new controller programmed for the matrix that that keyboard uses. Then, each grid position will cause the correct key to be output.

[rich1051414]

No, it uses linear switches that use rubber jumpers. I'll see if I can find pictures.

Do these have the rubber sleeves that give the tactility? I have one of these, those feel surprisingly good for a rubber dome, but the membrane ones are a little infuriating, it is very easy to have a misalignment which can cause half the keyboard to not work. It looks like yours uses a proper PCB though. I ended up harvesting the rubber sleeves and throwing the rest away, but yeah, it was just a membrane