#include <Wire.h>
#include <LiquidCrystal_I2C.h>

volatile uint32_t cnt = 0;
uint32_t old_cnt = 0;

LiquidCrystal_I2C lcd(0x27, 16, 2); 

void btnIsr() {
  cnt++; 
}

void setup()
{
  lcd.init();
  lcd.backlight();
  lcd.setCursor(0, 0);
  lcd.print("  Turn counter ");

  attachInterrupt(1, btnIsr, RISING);

}

void loop()
{
  if (old_cnt != cnt) {
    old_cnt = cnt;
    lcd.setCursor (0, 1);
    lcd.print(cnt);
  }

}