Keyboard hacking: Part 1



When you are broke “Neccessity is the mother of invention” couldn’t be a more true statement. I’ve been recording some guitar riffs recently, and I thought it’d be nice to control the transport (play/pause, stop, record, fwd, back) of my DAW via foot controls on my pedal board. There are controllers out there that work for this very thing, but….I’m broke. Not only that, but anytime I buy a new gadget it seems that it witll either only do about 90% of what I want it to do or it does way more than I’d ever need. So what to do? Hacking an old USB keyboard seems to be the easiest option.


99.9% of the difficulty in this job is figuring out the keyboard matrix to determine which two connections need to short in order to output the correct keystroke. There are several tutorials online, including this one, so I’ll spare the gory details.  For those that are tech savvy I’ll give you the general idea:

When you open a keyboard you’ll see two mylar sheets sandwiched together. Each sheet has a set of traces that lead to the logic board. When you press a key on the keyboard you are connecting the top layer of mylar to the bottom (which shorts two pins on the logic board). I started by numbering each pin on the logic board, 1 thru 28. I then used the continuity buzzer on my multimeter to figure out which pin on the logic board was connected to each key that I needed to use on the keyboard (do this on both mylar layers). The buzzer won’t always buzz so you need to watch for a resistance change on the multimeter. Some traces had a few hundred ohms of resistance which rendered the buzzer useless. I then sanded off PCB mask that covered the pins, soldered leads on the PCB, and tested it on my DAW by shorting the wires momentarily. It works!

The next update will have actual pictures of the project, and I’ll start experimenting with the enclosure.

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