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

#define SS_PIN 10
#define RST_PIN 9
MFRC522 rfid(SS_PIN, RST_PIN);

String allowedUID = "XX XX XX XX"; // Replace with your RFID tag's UID

void setup() {
  Serial.begin(9600);
  SPI.begin();
  rfid.PCD_Init();

  pinMode(LED_BUILTIN, OUTPUT);
}

void loop() {
  if (!rfid.PICC_IsNewCardPresent() || !rfid.PICC_ReadCardSerial()) {
    return;
  }

  String uid = "";
  for (byte i = 0; i < rfid.uid.size; i++) {
    uid += String(rfid.uid.uidByte[i] < 0x10 ? " 0" : " ");
    uid += String(rfid.uid.uidByte[i], HEX);
  }
  uid.trim();
  Serial.println(uid);

  if (uid == allowedUID) {
    digitalWrite(LED_BUILTIN, HIGH); // Turn on LED for access granted
   
    delay(3000); // Keep unlocked for 3 seconds
  
    digitalWrite(LED_BUILTIN, LOW); // Turn off LED
  } else {
     digitalWrite(LED_BUILTIN, LOW); // Turn off LED
  }

  rfid.PICC_HaltA();
}