#include <SPI.h>
#include <Wire.h>
#include <MFRC522.h>
#include <LiquidCrystal_I2C.h>

int counter = 0;
unsigned long startMillis;
unsigned long currentMillis;
const unsigned long period = 30000;

LiquidCrystal_I2C lcd(0x27, 16, 2);
#define SS_PIN 10
#define RST_PIN 9

MFRC522 mfrc522(SS_PIN, RST_PIN);

void setup()
{
  startMillis = millis();
  Serial.begin(9600);
  SPI.begin();
  mfrc522.PCD_Init();
  Serial.println("Approximate your card to the reader...");
  Serial.println();
  lcd.init();
  lcd.init();
  lcd.backlight();
  lcd.setCursor(0, 0);
  lcd.print("UID tag :");
}

void loop(){
  currentMillis = millis();
  if ((currentMillis - startMillis >= period) && (counter > 0)) {
    counter = 0;
    Serial.println("Counter is reset after 30 seconds");
    startMillis = currentMillis;
  }
  if (counter > setNumb) {
    Serial.println("Crowed Mangment !!");
  }
  // Look for new cards
  if ( ! mfrc522.PICC_IsNewCardPresent())
  {
    return;
  }

  // Select one of the cards
  if ( ! mfrc522.PICC_ReadCardSerial())
  {
    return;
  }

  //Show UID on serial monitor
  Serial.println ("");
  Serial.println("UID tag :");
  String content = "";
  byte letter;
  for (byte i = 0; i < mfrc522.uid.size; i++)
  {
    content.concat(String(mfrc522.uid.uidByte[i] < 0x10 ? " 0" : " "));
    content.concat(String(mfrc522.uid.uidByte[i], HEX));
    content.toUpperCase();
  }
  Serial.println(content.substring(1));
  lcd.setCursor(0, 1);
  lcd.print(content.substring(1));
  counter = counter + 1;
  delay(500);

}