// Scan organ keyboard with Arduino Leonardo board (double scan for contact bounce supression)
// Using MIDIUSB library v.1.0.5 from Gary Grewal (install from the Arduino IDE Library Manaager)
// John Harvey 7 May 2023
// www.johnharvey.uk

// See these for more information:
// www.arduino.cc/en/Reference/MIDIUSB
// www.arduino.cc/en/Tutorial/MidiDevice
// github.com/arduino-libraries/MIDIUSB
// github.com/arduino/tutorials/blob/master/ArduinoZeroMidi/ArduinoZeroMidi.ino

// Code is laid out in line for ease of understanding how it works; reduction in overall size could
// be achieved using functions to encapsulate repeated code segments but with some loss of clarity

#include <MIDIUSB.h>

// Arduino output pins to drive keyboard matrix rows
const byte Row1 = 8;
const byte Row2 = 9;
const byte Row3 = 10;
const byte Row4 = 11;
const byte Row5 = A0; // Analog pins used as digital outputs
const byte Row6 = A1;
const byte Row7 = A2;
const byte Row8 = A3;

// Arduino input pins to read keyboard matrix columns
const byte Column1 = 0;
const byte Column2 = 1;
const byte Column3 = 2;
const byte Column4 = 3;
const byte Column5 = 4;
const byte Column6 = 5;
const byte Column7 = 6;
const byte Column8 = 7;

const byte ScopeSync = 12;  // Trigger oscilloscope at start of loop
const byte MidiChannel = 1; // The channel assigned to this keyboard; channels are zero-based in code, so channel 1 is 0 etc.

// Remember key state, true = key on, false = key off; only 61 keys in full 5 octave keyboard (and some have fewer keys)
// but zero-based row/column scan of 8x8 keyboard matrix goes from 0 to 63
boolean KeyState[64];       // Previous key state
boolean KeyState1[64];      // Data from first scan
boolean KeyState2[64];      // Data from second scan

void setup() {

  pinMode (Column1, INPUT_PULLUP);
  pinMode (Column2, INPUT_PULLUP);
  pinMode (Column3, INPUT_PULLUP);
  pinMode (Column4, INPUT_PULLUP);
  pinMode (Column5, INPUT_PULLUP);
  pinMode (Column6, INPUT_PULLUP);
  pinMode (Column7, INPUT_PULLUP);
  pinMode (Column8, INPUT_PULLUP);

  pinMode (Row1, OUTPUT);
  pinMode (Row2, OUTPUT);
  pinMode (Row3, OUTPUT);
  pinMode (Row4, OUTPUT);
  pinMode (Row5, OUTPUT);
  pinMode (Row6, OUTPUT);
  pinMode (Row7, OUTPUT);
  pinMode (Row8, OUTPUT);

  pinMode (A4, OUTPUT); // Set unused analog inputs as outputs so that stray noise does not trigger ADCs
  pinMode (A5, OUTPUT);

  digitalWrite(Row1, HIGH);
  digitalWrite(Row2, HIGH);
  digitalWrite(Row3, HIGH);
  digitalWrite(Row4, HIGH);
  digitalWrite(Row5, HIGH);
  digitalWrite(Row6, HIGH);
  digitalWrite(Row7, HIGH);
  digitalWrite(Row8, HIGH);

  pinMode(LED_BUILTIN, OUTPUT);   // Pin 13 is LED_BUILTIN, use for bottom C visual indication
  digitalWrite(LED_BUILTIN, LOW); // Set LED to off

  pinMode (ScopeSync, OUTPUT);
  digitalWrite(ScopeSync, LOW);

  for (byte keyNumber = 0; keyNumber <= 63; keyNumber ++) {
    KeyState[keyNumber] = false;  //
    KeyState1[keyNumber] = false; // All notes off
    KeyState2[keyNumber] = false; //
  }
}

void loop() {

  digitalWrite(ScopeSync, HIGH);  // Generate oscilloscope sync pulse at start of each keyboard scan for test purposes
  delayMicroseconds(50);
  digitalWrite(ScopeSync, LOW);

  // FIRST SCAN

  for (byte row = 1; row <= 8; row ++) {

    // Rows are normally high, set one low at a time and see which columns are pulled low by key presses

    if (row == 1) {
      digitalWrite(Row1, LOW);
      digitalWrite(Row2, HIGH);
      digitalWrite(Row3, HIGH);
      digitalWrite(Row4, HIGH);
      digitalWrite(Row5, HIGH);
      digitalWrite(Row6, HIGH);
      digitalWrite(Row7, HIGH);
      digitalWrite(Row8, HIGH);
    }

    if (row == 2) {
      digitalWrite(Row1, HIGH);
      digitalWrite(Row2, LOW);
      digitalWrite(Row3, HIGH);
      digitalWrite(Row4, HIGH);
      digitalWrite(Row5, HIGH);
      digitalWrite(Row6, HIGH);
      digitalWrite(Row7, HIGH);
      digitalWrite(Row8, HIGH);
    }

    if (row == 3) {
      digitalWrite(Row1, HIGH);
      digitalWrite(Row2, HIGH);
      digitalWrite(Row3, LOW);
      digitalWrite(Row4, HIGH);
      digitalWrite(Row5, HIGH);
      digitalWrite(Row6, HIGH);
      digitalWrite(Row7, HIGH);
      digitalWrite(Row8, HIGH);
    }

    if (row == 4) {
      digitalWrite(Row1, HIGH);
      digitalWrite(Row2, HIGH);
      digitalWrite(Row3, HIGH);
      digitalWrite(Row4, LOW);
      digitalWrite(Row5, HIGH);
      digitalWrite(Row6, HIGH);
      digitalWrite(Row7, HIGH);
      digitalWrite(Row8, HIGH);
    }

    if (row == 5) {
      digitalWrite(Row1, HIGH);
      digitalWrite(Row2, HIGH);
      digitalWrite(Row3, HIGH);
      digitalWrite(Row4, HIGH);
      digitalWrite(Row5, LOW);
      digitalWrite(Row6, HIGH);
      digitalWrite(Row7, HIGH);
      digitalWrite(Row8, HIGH);
    }

    if (row == 6) {
      digitalWrite(Row1, HIGH);
      digitalWrite(Row2, HIGH);
      digitalWrite(Row3, HIGH);
      digitalWrite(Row4, HIGH);
      digitalWrite(Row5, HIGH);
      digitalWrite(Row6, LOW);
      digitalWrite(Row7, HIGH);
      digitalWrite(Row8, HIGH);
    }

    if (row == 7) {
      digitalWrite(Row1, HIGH);
      digitalWrite(Row2, HIGH);
      digitalWrite(Row3, HIGH);
      digitalWrite(Row4, HIGH);
      digitalWrite(Row5, HIGH);
      digitalWrite(Row6, HIGH);
      digitalWrite(Row7, LOW);
      digitalWrite(Row8, HIGH);
    }

    if (row == 8) {
      digitalWrite(Row1, HIGH);
      digitalWrite(Row2, HIGH);
      digitalWrite(Row3, HIGH);
      digitalWrite(Row4, HIGH);
      digitalWrite(Row5, HIGH);
      digitalWrite(Row6, HIGH);
      digitalWrite(Row7, HIGH);
      digitalWrite(Row8, LOW);
    }

    delayMicroseconds(100);

    byte keyNumber;
    for (byte col = 1; col <= 8; col ++) {
      keyNumber = ((row - 1) * 8) + (col - 1);
      KeyState1[keyNumber] = !digitalRead(col); // Low = key on, so invert
    }
  }

  delay(1); // Milliseconds; increase delay here for more agressive contact debounce

  // SECOND SCAN

  for (byte row = 1; row <= 8; row ++) {

    if (row == 1) {
      digitalWrite(Row1, LOW);
      digitalWrite(Row2, HIGH);
      digitalWrite(Row3, HIGH);
      digitalWrite(Row4, HIGH);
      digitalWrite(Row5, HIGH);
      digitalWrite(Row6, HIGH);
      digitalWrite(Row7, HIGH);
      digitalWrite(Row8, HIGH);
    }

    if (row == 2) {
      digitalWrite(Row1, HIGH);
      digitalWrite(Row2, LOW);
      digitalWrite(Row3, HIGH);
      digitalWrite(Row4, HIGH);
      digitalWrite(Row5, HIGH);
      digitalWrite(Row6, HIGH);
      digitalWrite(Row7, HIGH);
      digitalWrite(Row8, HIGH);
    }

    if (row == 3) {
      digitalWrite(Row1, HIGH);
      digitalWrite(Row2, HIGH);
      digitalWrite(Row3, LOW);
      digitalWrite(Row4, HIGH);
      digitalWrite(Row5, HIGH);
      digitalWrite(Row6, HIGH);
      digitalWrite(Row7, HIGH);
      digitalWrite(Row8, HIGH);
    }

    if (row == 4) {
      digitalWrite(Row1, HIGH);
      digitalWrite(Row2, HIGH);
      digitalWrite(Row3, HIGH);
      digitalWrite(Row4, LOW);
      digitalWrite(Row5, HIGH);
      digitalWrite(Row6, HIGH);
      digitalWrite(Row7, HIGH);
      digitalWrite(Row8, HIGH);
    }

    if (row == 5) {
      digitalWrite(Row1, HIGH);
      digitalWrite(Row2, HIGH);
      digitalWrite(Row3, HIGH);
      digitalWrite(Row4, HIGH);
      digitalWrite(Row5, LOW);
      digitalWrite(Row6, HIGH);
      digitalWrite(Row7, HIGH);
      digitalWrite(Row8, HIGH);
    }

    if (row == 6) {
      digitalWrite(Row1, HIGH);
      digitalWrite(Row2, HIGH);
      digitalWrite(Row3, HIGH);
      digitalWrite(Row4, HIGH);
      digitalWrite(Row5, HIGH);
      digitalWrite(Row6, LOW);
      digitalWrite(Row7, HIGH);
      digitalWrite(Row8, HIGH);
    }

    if (row == 7) {
      digitalWrite(Row1, HIGH);
      digitalWrite(Row2, HIGH);
      digitalWrite(Row3, HIGH);
      digitalWrite(Row4, HIGH);
      digitalWrite(Row5, HIGH);
      digitalWrite(Row6, HIGH);
      digitalWrite(Row7, LOW);
      digitalWrite(Row8, HIGH);
    }

    if (row == 8) {
      digitalWrite(Row1, HIGH);
      digitalWrite(Row2, HIGH);
      digitalWrite(Row3, HIGH);
      digitalWrite(Row4, HIGH);
      digitalWrite(Row5, HIGH);
      digitalWrite(Row6, HIGH);
      digitalWrite(Row7, HIGH);
      digitalWrite(Row8, LOW);
    }

    delayMicroseconds(100);

    byte keyNumber;
    for (byte col = 1; col <= 8; col ++) {
      keyNumber = ((row - 1) * 8) + (col - 1);
      KeyState2[keyNumber] = !digitalRead(col); // Low = key on, so invert
    }
  }

  // Now process collected key data from both scans, comparing time-separated data for each key

  boolean PreviousKeyState;

  for (byte keyNumber = 0; keyNumber <= 63; keyNumber ++) {

    PreviousKeyState = KeyState[keyNumber];

    // Note that "keyNumber + 0x24" etc. produces an int in compiler so reconvert to byte value otherwise compiler outputs a narrowing conversion warning

    if (PreviousKeyState == false && KeyState1[keyNumber] == true && KeyState2[keyNumber] == true) {   // Note has just gone on
      KeyState[keyNumber] = true;
      midiEventPacket_t noteOn = {0x09, byte(MidiChannel - 1 + 0x90), byte(keyNumber + 0x24), 0x40};
      MidiUSB.sendMIDI(noteOn);
      MidiUSB.flush();
      if (keyNumber == 0) {
        digitalWrite(LED_BUILTIN, HIGH);   // Turn Arduino onboard LED on (Bottom C visual indication)
      }
    }

    if (PreviousKeyState == true && KeyState1[keyNumber] == false && KeyState2[keyNumber] == false) {   // Note has just gone off
      KeyState[keyNumber] = false;
      midiEventPacket_t noteOn = {0x08, byte(MidiChannel - 1 + 0x80), byte(keyNumber + 0x24), 0x40};
      MidiUSB.sendMIDI(noteOn);
      MidiUSB.flush();
      if (keyNumber == 0) {
        digitalWrite(LED_BUILTIN, LOW);   // Turn Arduino onboard LED off
      }
    }
  }

  delayMicroseconds(100);
}