Recycling an old USB keyboard

[Machine]

Since I use my Filco Majestouch I miss some extra keys like "sleep" or media keys. I know, they can be easily mapped in Linux, but it's a little harder to do that in Windows. And - another key combo to learn.

Then came the idea: special keys on 3.5" front panel! Just imagine: "REBOOT", "SHUTDOWN", "HIBERNATE", "SLEEP" keys on front panel, beside "RESET" button.

But how to connect them? I would need USB keyboard controller chip. They are small SMD parts and would require quite a small lab at home. No - I think it's not the way to go, there must be an easier option. I have plenty of old USB keyboards, they all have working USB controller chips mounted on nice little PCB with connectors (and even USB cable).

The problem is - I want specific keystrokes to be generated. Codes of standard media keys would be perfect - but how to do it? Is any USB controller able to generate such codes? And how to figure out which keyboard connector pins to use? Connect the chip to PC, try all combinations observing which codes are generated? Anyone tried this? Anyone knows is it possible to solder wires to those black PCB connectors? (I think the black thingie could be removed, there should be copper under the black contact layer, but I'm not sure).

[alaricljs]

No, not just any KB can be a donor for this, it would need the keys that you want already present, then it's a matter of mapping the matrix to figure out which pins get shorted for each key needed.  You can't reprogram a KB controller, unless it supports that feature (which is rare).

However, you can get a teensy from pjrc.com and load up any of a number of available KB firmwares.

[Machine]

Thanks, Teensy seems like the thing to do the job, though it's a pity theres nothing cool I could use my old keyboards to

[hoggy]

Would a cherry g84-4700 do?

[Findecanor]

A Teensy might be unnecessary. If you want to build a tiny keyboard with only these keys, and you already have a spare USB keyboard with  all the keys that you want then yes, you should be able to reuse the controller board from that keyboard. You need to figure out the part of the matrix where these keys are and then build the keyboard. When your keyboard is done, then you just connect it via USB to your computer. Your computer should have no problems coping with multiple connected USB keyboards.

Of course, using a programmable keypad would be much easier than building your own keyboard.