//Setup I2C

  #include <LiquidCrystal_I2C.h>

  #define I2C_ADDR    0x27
  #define LCD_COLUMNS 16
  #define LCD_LINES   2

  LiquidCrystal_I2C lcd(I2C_ADDR, LCD_COLUMNS, LCD_LINES);

//Define Pins

  const int HALL_TRIG = 2; //IRL This is a Digital Hall Efect Sensor with 4 magnets at 90deg.
  const int BACKLIGHT_PIN = 3;
  const int RESET = 4;

//Define Vars

  const float CIRC = 0.00027;
  long HALL_TICK = 0;
  long ROTATIONS = 0;
  bool ROTATION_FLAG = false;
  bool RESET_FLAG = false;
  bool BACKLIGHT = false;

//

void setup() {

  //Setup Interupts
    pinMode(HALL_TRIG, INPUT);
    pinMode(RESET, INPUT);
    pinMode(BACKLIGHT_PIN, INPUT);

    attachInterrupt(digitalPinToInterrupt(HALL_TRIG), ROTATION_DETECTED, RISING);
    attachInterrupt(digitalPinToInterrupt(BACKLIGHT_PIN), CHANGE_BACKLIGHT, RISING);

  //Setup LCD
    lcd.init();

    lcd.setCursor(0, 0);
    lcd.print("Miles:");
    lcd.setCursor(7, 0);
    lcd.print("0.00");

    lcd.setCursor(0, 1);
    lcd.print("Spins:");
    lcd.setCursor(7, 1);
    lcd.print("0");
  //

}


void loop() {

  if(BACKLIGHT == HIGH)
  {
    lcd.backlight();
  }else{
    lcd.noBacklight();
  }

  if(ROTATION_FLAG == true)
  {
    lcd.setCursor(0, 0);
    lcd.print("Miles:");
    lcd.setCursor(7, 0);
    lcd.print(String((ROTATIONS * CIRC), 2));
    
    lcd.setCursor(0, 1);
    lcd.print("Spins:");
    lcd.setCursor(7, 1);
    lcd.print(ROTATIONS);

    ROTATION_FLAG = false;
  }

  if(digitalRead(RESET) == HIGH)
  {
    lcd.backlight();
    delay(20);

    lcd.clear();
    lcd.setCursor(1, 0);
    lcd.print("HOLD TO RESET!");

    for(int i = 9; i != 0; i--)
    {
      if(digitalRead(RESET) == LOW)
      {
         lcd.clear();
         ROTATION_FLAG = true;
         return;
      }
      lcd.setCursor(7, 1);
      lcd.print(i);
      lcd.print(i);
      delay(1000);
    }    

    lcd.clear();
    lcd.setCursor(3, 0);
    lcd.print("RESETTING!");
    lcd.setCursor(0, 1);
    for(int i = 0; i < 17; i++)
    {
      lcd.print("*");
      delay(200);
    }

    lcd.clear();

    HALL_TICK = 0;
    ROTATIONS = 0;
    ROTATION_FLAG = true;
    RESET_FLAG = false;

    return;

  }

}

void ROTATION_DETECTED(){

  if(HALL_TICK < 3)
  {
    HALL_TICK++;
  }else{
    HALL_TICK = 0;
    ROTATIONS++;
    ROTATION_FLAG = true;
  }

}

void CHANGE_BACKLIGHT(){
  static unsigned long last_interrupt_time = 0;
  unsigned long interrupt_time = millis();
  if (interrupt_time - last_interrupt_time > 200) 
  {
    BACKLIGHT = !BACKLIGHT;
  }
  last_interrupt_time = interrupt_time;
}