This is an Arduino Sketch for a simple arcade button MIDI Controller using the Control Surface library and Raspberry Pi Pico

PicoMIDI.ino

#include <Control_Surface.h>

//
USBMIDI_Interface midi;
using namespace MIDI_Notes;

// Button Rows
NoteButton button1  = { 2, {note(Eb, 3), CHANNEL_1}};
NoteButton button2  = { 3, {note( D, 3), CHANNEL_1}};
NoteButton button3  = { 4, {note(Db, 3), CHANNEL_1}};
NoteButton button4  = { 5, {note( C, 3), CHANNEL_1}};

NoteButton button5  = { 6, {note( B, 2), CHANNEL_1}};
NoteButton button6  = { 7, {note(Bb, 2), CHANNEL_1}};
NoteButton button7  = { 8, {note( A, 2), CHANNEL_1}};
NoteButton button8  = { 9, {note(Ab, 2), CHANNEL_1}};

NoteButton button9  = {10, {note( G, 2), CHANNEL_1}};
NoteButton button10 = {11, {note(Gb, 2), CHANNEL_1}};
NoteButton button11 = {12, {note(F_, 2), CHANNEL_1}};
NoteButton button12 = {13, {note(E , 2), CHANNEL_1}};

NoteButton button13 = {18, {note(Eb, 2), CHANNEL_1}};
NoteButton button14 = {19, {note( D, 2), CHANNEL_1}};
NoteButton button15 = {20, {note(Db, 2), CHANNEL_1}};
NoteButton button16 = {21, {note( C, 2), CHANNEL_1}};


void setup() {
    // Initialize everything
    Control_Surface.begin();
}

void loop() {
    // Update the Control Surface (check whether the potentiometer's input has 
    // changed since last time, if so, send the new value over BLE MIDI).
    Control_Surface.loop();
}