#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x27,20,4);

#define ENCODER_CLK 2
#define ENCODER_DT 3
#define ENCODER_SW 4

int counter = 0;

void setup() {
lcd.init();
lcd.backlight();

pinMode(ENCODER_CLK, INPUT);
pinMode(ENCODER_DT, INPUT);
pinMode(ENCODER_SW, INPUT_PULLUP);
attachInterrupt (digitalPinToInterrupt (ENCODER_CLK), readEncoder, FALLING );
}

void readEncoder () {
  int dtValue = digitalRead (ENCODER_DT);
  if (dtValue == HIGH) {
    counter ++;
    }
    if (dtValue == LOW){
      counter--;
    }
}
void loop() {
  lcd.setCursor (0, 0);
  lcd.print ("   Counter : ");
  lcd.setCursor (8, 1);
  lcd.print (counter);
}