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

#define SAD 10
#define RST 5

​

MFRC522 nfc(SAD, RST);  // RFID function activated

byte key[4] = {57, 106, 118, 178};  // the RFID card Serial Key. If you want to change the accepted card, change this

​

void setup() {
  // put your setup code here, to run once:
  
SPI.begin();
  // Read a fast as possible. There is a limit for how long we are
  // allowed to read from the tags.
  Serial.begin(115200);

   Serial.println("Looking for MFRC522."); //  searches for the MFRC522 card reader
  nfc.begin();

  // Get the firmware version of the RFID chip
  byte version = nfc.getFirmwareVersion();
  if (! version) {
    Serial.print("Didn't find MFRC522 board."); //  MFRC522 card reader was not found
    while(1); //halt
  }
  Serial.print("Found chip MFRC522 ");  //  MFRC522 card reader was found
  Serial.print("Firmware ver. 0x");     // shows the latest version of the MFRC522 card reader
  Serial.print(version, HEX);
  Serial.println(".");

}

​

void loop() {
  // put your main code here, to run repeatedly:

  byte status;
  byte data[MAX_LEN];
  byte serial[5];
  int i, j, pos;

  // Send a general request out into the aether. If there is a tag in
  // the area it will respond and the status will be MI_OK.
  status = nfc.requestTag(MF1_REQIDL, data);

  if (status == MI_OK) {
    Serial.println("Tag detected.");
    Serial.print("Type: ");
    Serial.print(data[0], HEX);
    Serial.print(", ");
    Serial.println(data[1], HEX);

    // calculate the anti-collision value for the currently detected
    // tag and write the serial into the data array.
    status = nfc.antiCollision(data);
    memcpy(serial, data, 5);

    Serial.println("The serial nb of the tag is:");
    for (i = 0; i < 3; i++) {
      Serial.print(serial[i], DEC);
      Serial.print(", ");
    }
    Serial.println(serial[3], DEC);
    if(serial[0]==key[0] && serial[1]==key[1] && serial[2]==key[2] && serial[3]==key[3]){
      Serial.println("Keycard detected!");  //key card matched and was detected.
      digitalWrite(LED_BUILTIN, HIGH);
      delay(500);
      digitalWrite(LED_BUILTIN,LOW);
      delay(500);
      digitalWrite(lock_supply, !digitalRead(lock_supply)); // toggles state of the lock supply pin
      if (digitalRead(lock_supply) == HIGH){  
        Serial.println("Door Locked!"); //  if the door was unlocked, it is now LOCKED.
      }
      else if (digitalRead(lock_supply) == LOW){
        Serial.println("Door Unlocked!"); //  if the door was locked, it is now UNLOCKED.
      }
    }
}
}