Trouble with MIDI controller code

Projects Programming
1

I'm building a MIDI controller using an arduino pro micro, but Im pretty much new to all of this and I don't know from where I should start the code. I made the circuit with help of people here in the forum, so that part is correct.
I did some basic arduino exercises, but I feel disoriented as what I should learn next, basically Im having trouble in filtering the information. From what I've understood (correct if im wrong), I will be using the MIDIUSB library and MIDI language.

The circuit is composed by:

  • 4x4 matrix with diodes connected to 8 digital pins, acting as note triggers;
  • 8 pots connected to 8 analog pins, acting as effect controllers;
  • 6 buttons with series resistors connected to 1 analog pin, acting as "PLAY", "STOP", "REC", "LOOP" " "+/- OCTAVE"
  • 1 apa106 LED connected to 1 digital pin, acting as an octave indicator.

MIDI CONTROLLER CIRCUIT 3.png
MIDI CONTROLLER CIRCUIT 3.png4961×3508 1.24 MB

MIDI CONTROLLER CIRCUIT 3.png
MIDI CONTROLLER CIRCUIT 3.png4961×3508 1.24 MB

2

So you built some hardware but don’t have requirements for the software piece? What is the code supposed to do?

Where you can start is learn to detect events happening on the buttons or pots without blocking the loop. Write a piece of code that detects and print a message upon press and upon release of each button or when the value of a pot changes for example.

Whatever you’ll want to do later on, you’ll need something like this.

3

You could use the Control Surface library I maintain. You can find the links to the documentation and “Getting Started” guide here. It supports button matrices and potentiometers out of the box, it debounces the buttons and filters the analog inputs so you don't have to worry about that.

For the button matrix, see the NoteButtonMatrix.ino example. For the potentiometers, see the Control-Change-Potentiometer.ino example for the potentiometers.

For the resistor ladder of your buttons, you'll have to write some code yourself. You can send MIDI messages using

Control_Surface.sendNoteOn(notenumber, velocity); // default channel 1
Control_Surface.sendNoteOff(notenumber, velocity);
Control_Surface.sendNoteOn({notenumber, CHANNEL_10}, velocity); // specific channel

You can find a full list of MIDI sending functions in the MIDI_Sender documentation.

If you want to change the octave of the notes of the buttons, you can use the Bankable::NoteButtonMatrix with a Transposer that you control yourself in your main loop:

#include <Control_Surface.h>

USBMIDI_Interface midi;

// Transpose up to 2 octaves down or up (steps of 12 semitones = 1 octave)
Transposer<-2, +2> transposer{12};

// The note numbers corresponding to the buttons in the matrix
const AddressMatrix<4, 3> addresses = {{
  {0x3C, 0x3D, 0x3E},
  {0x3F, 0x40, 0x41},
  {0x42, 0x43, 0x44},
  {0x45, 0x46, 0x47},
}};
Bankable::NoteButtonMatrix<4, 3> buttons {
  transposer,   // determines the offset
  {2, 3, 4, 5}, // row pins
  {6, 7, 8},    // column pins
  addresses,    // address matrix
  CHANNEL_1,    // channel and optional cable number
};

void setup() {
  Control_Surface.begin();
}

void loop() {
  Control_Surface.loop();
  if (/* some button pressed */) {
    // You can set the transposition using transposer.select(i),
    // where i is the index of the octave to select: i = 0 is
    // the lowest octave (-2 in this case), i = 1 is the second
    // octave (-1 here), i = 2 is the third octave (no transposition
    // here) etc.
    transposer.select(0); // selects transposition of -2
  }
}

Pieter

4

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