My DIY ~26 key midi MX keyboard

I’d like to share my progress on a small project somewhat inspired by some members of this forum. I initially started designing an Organelle clone / Orac computer, but I found DIY norns / fates and while I wait to get my hands on one I’ve started building a compact midi keyboard.


Quick run down of the current setup:
5mm cast Acrylic cut on my CNC router
Switches are linear switches commonly found on mechanical keyboards. (Off label Outemu reds to be exact)
4x 10kB potentiometers for CV control
Arduino Micro will be the controller for this version, so no class complient USB midi, but I have some Atmega32u4’s on order.

To be added:
Key caps, attempting to cut or 3D print something, but might just end up buying some.
TRS Midi

Planned features:
Octive shift
Aux btn, as per Organelle
“Volca” mode, output different CC messages for controlling my Volca’s
A sequencer or arp is also a consideration
Wood or ply base

I have some good key scanning and midi code but I’m currently looking at other Arduino projects that I can borrow features from.


Freewired on the backside?

Yup, starting on hand wiring it tonight. With only 30 switches it shouldn’t be to tedious. If I decide to make more then I might look at a PCB, though the pots might need to stay hand wired.

Arduino Micro doesn’t have +26 inputs, how do you deal with this? i2c module for extra inputs/outputs?

No extra hardware, apart from an extra diode per switch, using Key scanning / key matrix. 5 rows x 6 columns = 11 pins for 30 switches.

mmm, a key matrix is good for typing keyboards, for music keyboards I think that key matrix could not work well when multiple keys are pressed.

Most commercial music keyboards use matrix scanning. The only issue is ghosting which is why you need to add a diode per switch, which is common practice.

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The monome grid uses a key matrix… Diodes take care of problems with multiple simultaneous key presses

Idly following the conversation but to satisfy my curiosity - what’s the problem and how do diodes solve it?

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If you cannot the keys in a matrix without diodes, pressing two or more buttons at the same time can appear to the controller as though you had pressed other buttons.