#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 20, 4);

void setup() {
  lcd.init();
  lcd.backlight();
  lcd.setCursor(3, 0);
  lcd.print("Hello, world!");

  DDRD = 0b00000000;
  PORTD = 0b11111111;

  // attachInterrupt(digitalPinToInterrupt(2), interrupted, RISING);
  cli();  //disable interrupt--> for precise timing
  Serial.begin(9600); // initialize Serial Monitor-->才能順利jump到interrupted()
  bitSet(EIMSK, INT0);
  EICRA = bit(ISC00) |bit(ISC01);
  sei();  //re-enable interrupt
}

byte value=10;

void loop() {
  byte newValue = PIND;
  if(newValue != value)
  {
    lcd.clear();
    lcd.print(newValue, BIN);
    value = newValue;
  }

}

ISR(INT0_vect){
  // Serial.println("I was interrupted");
  Serial.println("I was interrupted with registers");
}