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

// Blue Tag   = D9 B8 21 B9
// White Card = D0 3A ED 32

#define SS_PIN  27  /*Slave Select Pin*/
#define RST_PIN 26  /*Reset Pin for RC522*/

MFRC522 mfrc522(SS_PIN, RST_PIN);
LiquidCrystal_I2C lcd(0x27, 16, 2);

void setup() {
  Serial.begin(9600);   /*Serial Communication begin*/
  lcd.init();
  lcd.backlight();
  lcd.setCursor(0, 0);
  lcd.print("Hello, World!");
  SPI.begin();          /*SPI communication initialized*/
  mfrc522.PCD_Init();   /*RFID sensor initialized*/
  Serial.println("Put your card to the reader...");
  Serial.println();
  delay(1000);
  lcd.clear();
}

void loop() {
  /*Look for the RFID Card*/
  if ( ! mfrc522.PICC_IsNewCardPresent())
  {
    return;
  }
  /*Select Card*/
  if ( ! mfrc522.PICC_ReadCardSerial())
  {
    return;
  }
  /*Show UID for Card/Tag on serial monitor*/
  Serial.print("UID tag :");
  String content = "";
  byte letter;
  for (byte i = 0; i < mfrc522.uid.size; i++)
  {
    Serial.print(mfrc522.uid.uidByte[i] < 0x10 ? " 0" : " ");
    Serial.print(mfrc522.uid.uidByte[i], HEX);
    content.concat(String(mfrc522.uid.uidByte[i] < 0x10 ? " 0" : " "));
    content.concat(String(mfrc522.uid.uidByte[i], HEX));
  }
  Serial.println();
  Serial.print("Message : ");
  content.toUpperCase();

  lcd.setCursor(0, 0);
  lcd.print(content.substring(1));

  if (content.substring(1) == "D0 3A ED 32")
  {
    Serial.println("Authorized access");
    Serial.println();
  }
  else   {
    Serial.println(" Access denied");
  }
  delay(1000);
  lcd.clear();
}//end of Loop