Anyone down to help me with this project :)?

User avatar
Lalaland124

10 Feb 2021, 12:03

I recently got my hands on an old typewriter with alps SKFF switches.
I really like the switches and as far as I know there are no PCBs I can buy for them. So I wanted to use the PCB from the typewriter itself to turn it into a USB keyboard.

However, I am relatively new to the whole soldering thing so I guess this will be quite a challenge.

So I wanted to know if there is any tutorial on how to do it :)?
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User avatar
TNT

10 Feb 2021, 12:18

Findecanor wrote:
10 Feb 2021, 00:10
It is likely that the ribbon cable connects directly to the rows and columns of the keyboard matrix, with some other lines instead going to the LEDs.

You would have to figure out the matrix, hook up a microcontroller board and then program your own version of firmware for this microcontroller+keyboard combination.
A lot of people have done this before with various keyboards: do check the Workshop subforum! It is a bit of a tedious process though.

From the last picture I would guess that the PCB is one-sided with all traces on the bottom of the keyboard module, with solder holes exposed. That should make it easier to trace the matrix.
A multimeter in continuity mode could be a great help here.

With electronics at this age, the LED circuits are probably made to run at 5V: look for resistors for them! The Teensy++ might be a good choice for microcontroller board: it has 45 GPIO pins, runs at 5V and is supported by the TMK firmware. If the keyboard does not a diodes for each switch then you would have to enable ghost key detection.
Hey, I don't mean to be rude or anything, but Findecanor already did a great job explaining this beneath your previous post. Do you have a multimeter?

Good explanations about keyboard matrices are all over the net, for example this one.

Your first job now should be to find out which row and column correspond to which pinhole on your ribbon connector. After that, you'll have to wire up a controller. Same thing as with a hand-wired matrix. You'll find plenty of tutorials on YouTube, or you just can refer to this one.

Finde jetzt spontan nix auf Deutsch, aber bei mehr Fragen kannste dich gerne melden ;)

User avatar
Lalaland124

10 Feb 2021, 13:29

Thx a lot, I know I just wanted to post it again in the right category :-)

__red__

11 Feb 2021, 00:06

I wouldn't be so sure, look at this section:
possibleic.png
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Looks like a 14 pin DIP.

__red__

11 Feb 2021, 00:15

Hmm, I keep looking at that section and I wonder if it's a series of DIP switches and not an IC.

Can you get a peek under that frame to see what, if any components are hiding under there?

User avatar
TNT

11 Feb 2021, 01:09

__red__ wrote:
11 Feb 2021, 00:15
Hmm, I keep looking at that section and I wonder if it's a series of DIP switches and not an IC.

Can you get a peek under that frame to see what, if any components are hiding under there?
He's right, you should better check to make sure. I thought the whole time you had a brainless board, might not be the case :/

MMcM

11 Feb 2021, 03:15

I wouldn't rule out jumpers, either. Notice how the signals from the right and top switches loop around to get to the connector. Which means the ones from the left need a way over. If you have a multi-meter, do a quick check whether they're all seven shorted straight across.

Findecanor

11 Feb 2021, 10:44

The topmost pair of solder points is a jumper wire. You can see that in the bottom picture.
I suspect there to be an ICs near each of the four levers/slide-switches though.

I noticed that at least one LED is marked with a symbol on the PCB. The direction of the symbol should indicate the correct polarity of the LED.
All LEDs are likely to share a common ground or Vcc. Each LED should also have a resistor in series: best to check where these are, if they are present at all.

It does not look like any diodes for switches though, so no NKRO. Ghost-key detection is necessary.
On many keyboards without diodes, Shift keys (and other modifiers) have their own direct lines not part of the main matrix, so do check for that!

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