#define LED3 3
#define LED4 5
#define KODA3 111
#define KODA4 333
#define KODA "aaa"
int zakasnitev = 400;
unsigned long trenutniCas;

#include <LiquidCrystal_I2C.h>
#define I2C_ADDR  0x27
#define LCD_COLUMNS 20
#define LCD_LINES 2
LiquidCrystal_I2C lcd(I2C_ADDR, LCD_COLUMNS, LCD_LINES);

void setup() {
  Serial.begin(9600);
  lcd.init();
  lcd.backlight();
  Serial.println("Vpiši kodo: ");
  pinMode(LED3, OUTPUT);
  pinMode(LED4, OUTPUT);
  trenutniCas = millis();
}

void loop() {
  static bool LED3State = false;
  static bool UTRIP4 = false;
  if(Serial.available()){
    char vpis[4];
    int steviloZnakovVpis = Serial.readBytes(vpis, 3);
    if(steviloZnakovVpis == 3){
      vpis[3] = '\0';
      int stevilka = atoi(vpis);
      switch(stevilka){
        case KODA3:
          digitalWrite(LED3, LOW);
          if(LED3State == false){
            digitalWrite(LED3, HIGH);
          }
          LED3State = !LED3State;
          lcd.setCursor(0,0);
          lcd.clear();
          if(LED3State == false){
            lcd.print("LED3 izklop");
          }
          if(LED3State == true){
            lcd.print("LED3 vklop");
          }
          break;
        case KODA4:
          UTRIP4 = !UTRIP4;
          if(UTRIP4 == false){
            digitalWrite(LED4, LOW);
            lcd.setCursor(0,0);
            lcd.clear();
          }
          if(UTRIP4 == false){
            lcd.print("LED4 izklop");
          }
          if(UTRIP4 == true){
            lcd.print("LED4 utripa");
          }
          Serial.println(UTRIP4);
          break;
        default:
          Serial.println("Napaka, ponovni vnos.");
          lcd.setCursor(0,0);
          lcd.clear();
          lcd.print("");
      }
    }
  }
  static bool m = false;
  if (((millis() - trenutniCas) > zakasnitev) && UTRIP4){
    m = !m;
    digitalWrite(LED4, m);
    trenutniCas = millis();
  }
}