// MultiButtonMIDIOctave.ino
// Driving MIDI using a Multiple Buttons
// Added variables for Octave, Transpose and Velocity
// Rob Ives 2012
// This code is released into the Public Domain.
 
#include 
#include 
 
int keyispressed[16]; //Is the key currently pressed?
int noteisplaying[16]; //Is the Note currently playing?
unsigned char data1; //data from chip 1
unsigned char data2; //data from chip 2
int octave = 2; //set currently played octave
int transpose = 0; //transpose notes on the board
int velocity = 127; //set note velocity
//--- Octave LED output pins
int octave1 = 8;
int octave2 = 9;
int octave3 = 10;
int octave4 = 11;
//--- Octave Switches 
int octaveup = 7;
int octavedown = 6;
//--- Pot
int potpin = 2;
 
void  setup() //The Setup Loop
{
  Wire.begin(); // setup the I2C bus
  for (unsigned int i = 0; i < 16; i++) { //Init variables
    keyispressed[i] = 1; //clear the keys array (High is off)
    noteisplaying[i] = 0; //no notes are playing
  }
  //--- Set up pins
  pinMode(octaveup, INPUT);
  pinMode(octavedown, INPUT);
  pinMode(octave1, OUTPUT);
  pinMode(octave2, OUTPUT);
  pinMode(octave3, OUTPUT);
  pinMode(octave4, OUTPUT);
 
  MIDI.begin(); //initialise midi library
  displayoctave(); //display the current octave
 
}
//---------------------------------------------
void loop() //the main loop
{
  readkeys();
  sendMIDI();
  checkoctave();
}  
//-------------------------------------
void readkeys() { //Read the state of the I2C chips. 1 is open, 0 is closed.
  Wire.requestFrom(0x38, 1); // read the data from chip 1 in data1
  if (Wire.available()){
     data1 = Wire.read(); 
 
  }
  Wire.requestFrom(0x39, 1); // read the data freom chip 2 into data2
  if (Wire.available()){
     data2 = Wire.read();    
  }
 
  for (unsigned char i = 0; i < 8; i++) {// puts data bits from chip 1 into keys array        keyispressed[i] = ((data1 >> i) & 1); // set the key variable to the current state. chip 1
       keyispressed[i + 8] = ((data2 >> i) & 1); //chip 2
  }
}  
//-------------------------------------
void sendMIDI() { // Send MIDI instructions via the MIDI out
  int note; //holder for the value of note being played
 
  velocity = analogRead(potpin)/8;// Read velocity from the pot
  for (unsigned char i = 0; i < 16; i++) { //for each note in the array
    if (keyispressed[i] == LOW){ //the key on the board is pressed 
      if(!noteisplaying[i]){ //if the note is not already playing send MIDI instruction to start the note
         note = i + (octave*12) + transpose;
         MIDI.sendNoteOn(note,velocity,1);  // Send a Note ( vel.127  ch. 1)
         noteisplaying[i] = note; // set the note playing flag to TRUE and store the note value
      }
    }
    else{
      if(noteisplaying[i]){ //if the note is currently playing, turn it off
        note = noteisplaying[i]; //retrieve the saved note value incase the octave has changed
        MIDI.sendNoteOff(note,0,1);   // Stop the note
        noteisplaying[i] = 0; // clear the note is playing flag
      }
    }
  }
}
//----------------------------------------
void checkoctave(){
  int up = digitalRead(octaveup);
  int down = digitalRead(octavedown);
 
  if(up == HIGH){ //up button pressed
    if(octave < 4){       octave++;     }     while(up == HIGH){// wait until button is released       up = digitalRead(octaveup);       delay(20);     }     displayoctave();   }   if(down == HIGH){ //down button pressed     if(octave > 1){
      octave--;
    }
    while(down == HIGH){// wait until button is released
      down = digitalRead(octavedown);
      delay(20);
    }
    displayoctave();
  }
}
//-------------------------------------
void displayoctave(){
  // clear all the LEDs
  digitalWrite(octave1, LOW);
  digitalWrite(octave2, LOW);
  digitalWrite(octave3, LOW);
  digitalWrite(octave4, LOW);
  // ...and then display the current octave
  switch(octave){ // display the current actave
  case 1: digitalWrite(octave1, HIGH); 
          break;
  case 2: digitalWrite(octave2, HIGH); 
          break;
  case 3: digitalWrite(octave3, HIGH); 
          break;
  case 4: digitalWrite(octave4, HIGH); 
          break;
  }
}