#include <LiquidCrystal_I2C.h>
#define LED2 9
#define LED3 10
#define KODA2_on 1234
#define KODA2_off 1230
#define KODA3_on 4545
#define KODA3_off 4540
#define I2C_ADDR 0x27
#define LCD_COLUMNS 20
#define LCD_LINES 2
LiquidCrystal_I2C lcd(I2C_ADDR,LCD_COLUMNS,LCD_LINES);

void setup() {
  lcd.init();
  lcd.setCursor(0,0);
  Serial.begin(115200);
  Serial.println("Vpisi kodo: ");
  pinMode(LED2, OUTPUT);
  pinMode(LED3, OUTPUT);
}

void loop() {
  String res = "";
  static bool i = false;
  if(Serial.available()){
    char vpis[4];
    int steviloZnakovVpis = Serial.readBytes(vpis,4);
    if(steviloZnakovVpis == 4){ 
      vpis[4] = '\0';// terminator seznama vpis
      int stevilka = atoi(vpis);
      switch(stevilka){
        case KODA2_on:
          res = "LED2 vklop";
          digitalWrite(LED2,HIGH);
          break;
        case KODA2_off:
          res = "LED2 izklop";
          digitalWrite(LED2,LOW);
          break;
        case KODA3_on:
          res = "LED3 utripanje";
          i = true;
          digitalWrite(LED3,HIGH);
          break;
        case KODA3_off:
          res = "LED3 izklop";
          i = false;
          digitalWrite(LED3,LOW);
          break;
        default:
          res = "Poskusi ponovno:";
          while(Serial.available()){Serial.read();}
          break;
      }
      lcd.clear();
      lcd.print(res);
    }
  }
  static unsigned long trenutniCas;
  static bool m = false;
  int zakasnitev = 200;
  if(millis() - trenutniCas > zakasnitev && i){
    trenutniCas = millis();
    digitalWrite(LED3,m);
    m = !m;
  }
}