arduino_midi_library VS relay-bypass

take a look here

The Arduino MIDI Library [1]. Back in 2009, I learned C++ to build it and control my guitar effects pedals with custom electronics as part of my engineering degree.

[1] https://github.com/FortySevenEffects/arduino_midi_library

Your project can be broken up into a number of subprojects. For keyscanning you don't need additional hardware, just the pins from the ribbon cables going to the arduino's digital pins and ground. Since the keys are just switches (two per key, the time difference between the two switches closing giving the source of velocity), you could start with some examples from the Arduino MIDI library (https://github.com/FortySevenEffects/arduino_midi_library). To test MIDI sending you don't even need to start from the keybed just yet, and if you do, you can start with a single key. Once you've got that part figured out end to end (key press/release generates note on/off events) you can work on iterating through the matrix, CC controls etc. MIDI out can be done in different ways. With a 5 pin DIN plug you'd just need two 220 ohm resistors.

On an Arduino compatible platform the configuration of the baud rate at the bare metal layer is taken care of by the library when you call its begin() method. Looking at the example code included with the library it appears that there are no timer interrupts or anything like that required of you in order to use it. Another thing that jumps out is that the call to read() returns a non-zero value if anything has been received that you should use to predicate whether any further attention needs to be spent on it by your code. You may know this but it wasn't apparent from the loop() { MIDI.read\`() }` example that you gave above.

As i have started to combine this with Midi Implementation from FourtySevenEffects lib, i only have done a quick test with two/three strips and did discover follwing issue(s):

Using a library for the midi shield you can register two functions as callbacks. One callback for NoteOn(...) messages and one for NoteOff(...) messages. But thre is much more. In the end the source of truth should always be the docs for the library itself.

Click the link to github (second link in the article) and there's all the source code: https://github.com/FortySevenEffects/arduino_midi_library

Here’s a library that might work.

Solution from GitHub here:

Not to discourage it, but FYI on what's already out there for AVR: https://github.com/mstratman/relay-bypass

All open source: https://github.com/mstratman/relay-bypass

u/cedarcedar If you're curious you can see its code here: https://github.com/mstratman/relay-bypass/blob/main/relay-bypass/relay-bypass.ino

if you find momentary buttons that are suitable, use them to control a relay. e.g. with this kit or from scratch.

An alternate option, which you probably also won't find an off-the-shelf solution for, is to use a microcontroller and a couple of relays. You can steal 90% of the bones from my project here: https://github.com/mstratman/relay-bypass Switch to an attiny84 or something else with more pins, add a second foot switch, get rid of the muting, and add the toggle logic.

Tonight I added an EQD-style relay bypass using a MAS Effects kit to somebody's pedal and took a few pics to share in case anyone's interested in seeing how you do this sort of upgrade (disclaimer, shameless self promotion, but FYI it's also open source). It's a good first project for anyone wanting to dip their toe in the DIY pedal waters.

Or if you want to completely DIY the MAS Effects one without a kit, all the code and schematics are here: https://github.com/mstratman/relay-bypass (but again, check parts availability first since the relays and AVR are hard to find).

[schematics, code, etc are all here] [kits here]

The footswitch controls a relay that's powered by the code from this project: https://github.com/mstratman/relay-bypass (from which you can buy drop-in kits to get soft touch true bypass on your pedals). This one has a bigger, cheaper relay since space wasn't at a premium the way it is on those drop-in kits.

Schematic: https://github.com/mstratman/relay-bypass/blob/main/relay-bypass-schematic-1.3.png