Arduino MIDI Virtual DJ Controller

#define DEBUG false     
//You can use Arduino Serial Plotter for debug by changing DEBUG to true,but it will make your MIDI board unable to send MIDI Message.

#define VALUE_MIN_RANGE 1
#define DEBOUNCE_MS 100

#define MIDI_MSG_NOTE_OFF 128 //or 0x80
#define MIDI_MSG_NOTE_ON 144 //or 0x90
#define MIDI_MSG_CTRL_CHANGE 176 //or 0xB0

byte previous_values[2][8];
byte previous_M_slide_value;
unsigned long btn_timer[2][8];
//unsigned long timer = 0;

void setup() {
  
  Serial.begin(115200);
  previous_M_slide_value=-1;
  for (int i = 0; i < 8; i++) {
    previous_values[0][i] = -1;
    previous_values[1][i] = -1;
    btn_timer[0][i]=0;
    btn_timer[1][i]=0;
  }

  pinMode(7, OUTPUT);
  pinMode(6, OUTPUT);
  pinMode(5, OUTPUT);

}

void loop() {

  for (int i = 0; i < 8; i++) {
    select(i);
    int curr_value[2];
    curr_value[0] = analogRead(A0);
    curr_value[1] = analogRead(A1);
    for (byte side = 0; side < 2; side++) {
      if (i != 3 && previous_values[side][i] != (ATD(curr_value[side]) == 1 ? 0 : 127) && millis()>=btn_timer[side][i]) {
//        When button is pressed.
        byte val = ATD(curr_value[side]) == 1 ? 0 : 127;
        previous_values[side][i] = val;
        if (val == 127) {
          if (!DEBUG)sendNoteOn(0x39+side+i*2, val, 1);
        } else if (val == 0) {
          if (!DEBUG)sendNoteOff(0x39+side+i*2, val, 1);
          btn_timer[side][i]=millis()+DEBOUNCE_MS;
        }
      } else if (i == 3) {
        int analog_val = map(curr_value[side], 0, 1023, 0, 127);
        if (range(previous_values[side][i], analog_val, VALUE_MIN_RANGE) != previous_values[side][i]) {
//        When slider value is changed.
          previous_values[side][i] = analog_val;
          if (!DEBUG)sendCtrlChange(0x39+side+i*2, previous_values[side][i], 1);
        }
      }
    }
    if(DEBUG)for(byte si=0;si<2;si++){
      Serial.print(String(previous_values[si][i] + i * 150+si*150*8));
      Serial.print(",");
    }
  }
  if(DEBUG)Serial.println();
  
  int analog_val = map(analogRead(A2), 0, 1023, 0, 127);
  if (range(previous_M_slide_value, analog_val, VALUE_MIN_RANGE) != previous_M_slide_value) {
    previous_M_slide_value = analog_val;
    if (!DEBUG)sendCtrlChange(0x57, previous_M_slide_value, 1);
  }
  
  
}


void printChart(int val) {
  Serial.print(val);
  Serial.print(",");
}
int range(int previous, int current, int d) {
//  This method compare previous value and current value.
//  If current value only increase or decrease "d",this method will return previous value.
//  If current value increase or decrease "d" + >0 value ,this method will return current value.

//example:
//  previous=5;current=4;d=1
//  return 5

//  previous=5;current=3;d=1
//  return 3

  if (current == 127)return 127;
  else if (current == 0)return 0;
  if (current > previous && current - d == previous)return previous;
  else if (current < previous && previous - d == current)return previous;
  else if (current == previous)return previous;
  return current;
}

bool ATD(int analog_val) {
//  Analog to digital
//  analog_val:0~1023
//  return 0 or 1.
  if (((float)analog_val * 0.0048828125) > 2.94) {
    return 1;
  } else if (((float)analog_val * 0.0048828125) <= 1.47) {
    return 0;
  }
}

void select(int select) {
//  CD4051 select
//  C (MSB) : S2  13  D7
//  B       : S1  12  D6
//  A (LSB) : S0  11  D5

  for (int inputPin = 0; inputPin < 3; inputPin++)
  {
    int pinState = bitRead(select, inputPin);
    digitalWrite(inputPin + 5, pinState);
  }
}

//MIDI------------------------------------------
void sendNoteOn(byte note,byte velocity,byte channel){
  sendChannelVoiceMsg(MIDI_MSG_NOTE_ON|(channel-1),note,velocity);
  
  }

void sendNoteOff(byte note,byte velocity,byte channel){
  sendChannelVoiceMsg(MIDI_MSG_NOTE_OFF|(channel-1),note,velocity);
  }
  
void sendCtrlChange(byte cc,byte value,int channel) {
  sendChannelVoiceMsg(MIDI_MSG_CTRL_CHANGE|(channel-1),cc,value);
}

void sendChannelVoiceMsg(byte command, byte note, byte velocity) {
  //send MIDI Channel Voice Message
  Serial.write(command);
  Serial.write(note);
  Serial.write(velocity);
}