I’ve been working on my keyboard again today. ML62 is the name of the project and is something that I’ve been working on for almost 18 months now.

The idea is rather simple, but the implementation is a lot more complex so I’ll avoid details and let you look at the GitHub project if you’re interested.

What I wanted was a keyboard that I could hack. Something that I had total control over in hardware, and not depend on software to be installed to modify the keycodes as they come in.

About six months ago I put a few 3.5mm plugs in the back of my keyboard with the intention of plugging my footswitch directly into the keyboard rather than as a separate USB device.

Back of Keyboard

The original footswitch was basically a keyboard with a single button. It connected to the computer via USB and was ridiculously excessive for what it was.

Original Footswitch

About a month ago I finally got around to actually connecting it up the way I’d always intended. To have it treated as just another button on the keyboard. I stripped out the Teensy and connected it to the keyboard as another button.

The reason that there were two plugs was because I wanted to experiment with different functions. When I’m coding it may be useful to have my footswitch do something different than other times. I also expect that I may want a second switch in the future. For now, I just want to be able to plug into the other port try a different setting to see if I like it better.

A month ago that wasn’t really possible because I ran out of pins on my connector. I decided yesterday that it was time to redo the wiring in the keyboard so that I can connect both ports. Again, it’s something that I’ve wanted to do for a while. I’ve iterated too many times and it’s well overdue for a refactor.

There was a little board on the underside of the keyboard that had the resistors for the LEDs. There was a connector for the USB port. There was another little board to connect the keyboard to the chassis. All of that needed to be merged together into something far more extendable.

USB Connector

This one is the USB connector. A massive hack but it worked good enough to allow me to patch into the power and ground.

Keyboard Connector

And this is the connector between the chassis and the keyboard. This picture is pretty old. I used the two empty pins to get the footswitch plug running.

New Circuit Board

After a bit of work I merged it all together like that.

The USB connector back to the Teensy is only linked into the signal pins. I’m pulling the +5V and GND out of the USB cable because I need it in the chassis circuit. I send it back to the Teensy over the 8pin connector.

And the finished keyboard (at this stage) looks like this.

Keyboard Inside

Keyboard Outside