Arduino-USBMIDI VS Control-Surface

But generally speaking MIDI and USB MIDI are based on fundamentally different communication protocols and always require a MCU to do the conversion. An Arduino Micro can do the job well and there are even Libraries with example code that does exactly this. See here: https://github.com/lathoub/Arduino-USBMIDI/blob/master/examples/MIDI_DIN2USB/MIDI_DIN2USB.ino

Option 3 - Arduino USB MIDI

hmm..yes you would have to code a little bit. But, cool learning experience? The examples are pretty good. This simple one: https://github.com/lathoub/Arduino-USBMIDI/blob/master/examples/Basic_IO/Basic_IO.ino shows part of the code that would replace the serial code in your original sketch. Note the library itself is handling the code that advertises the controller to Linux as a MIDI device. That's an important benefit.

I was in a similar boat to you, though I have a lot of experience programming outside of the arduino/midi controller context. I was pretty happy to just use https://github.com/tttapa/Control-Surface as a library to handle connecting an arduino with a pot to my PC as a midi controller. The docs and examples the codebase has were very useful.

Wow, what a pretty project! If you end up expanding this, you might look at the Control-Surface lib; seems like it's made for this kind of thing.

https://github.com/tttapa/Control-Surface

I've been working on this beasty project together with a friend. We did some liveshows back then and decided that we needed some more control gear. But not just a laptop focusing launchpad, we wanted to forget there was even a laptop (or other hardware) attached to this controller, so that all our attention and focus would be on the music and the crowd, and above all: we wanted something that would instantly announce your presence on stage.

I used this library with an Arduino and several multiplexers. It worked very well and was easy to use. https://github.com/tttapa/Control-Surface

Should be fixed in https://github.com/tttapa/Control-Surface/commit/eb7a468a0a73584b93be16d978404b25401ce66f, you can increase the SELECT_LINE_DELAY constant if necessary.

The PCB was an entirely new endeavour for me, but it was essential in making the project footprint as small as possible. Never done any kind of electronics design outside of hobbyist arduino stuff and the initial prototype. I used [KiCAD 6] to design the PCB. KiCAD might be the single greatest GUI-based open-source software I have ever used, its a shame FreeCAD is so far behind it in terms of stability. It is also free and open source. I went with a simple 2 layer design with all through-hole components to keep things as simple as possible so people didnt have to mess around with heat guns or toaster ovens to solder the board. It turned out great. I also elected to use a teensy to do the heavy lifting. Sticking to an arduino platform means its a lot easier for people to contribute to the firmware. It also meant I could use the greatest arduino library ever written, Control Surface. Control surface is what makes it so easy to write the midi logic for the firmware. It is the backbone of the firmware and really is incredible.

Take a look at tttapa's control surface github! It's an extremely robust MIDI library so all you really need is a little Arduino/C knowledge and you should be able to get the inputs worked out. I'm a little fuzzy in my output understanding with MIDI, but this library supports that too! Understanding Keyboard matrices isn't hard once you wrap your head around the basics (I recommend looking up computer keyboard handwiring guides and/or qmk as there's a lot there and the wiring is the same)