Arduino Uno MFRC522 RFID: Industrial Identification Controller

Professional NXP MFRC522 IC operates 13.56MHz ISO14443A protocol reading MIFARE Classic 1K/4K cards and keyfobs within 7cm envelope. SPI interface (SS pin 10, RST pin 9) delivers 106kbit/s data rate with integrated CRC, anti-collision, and authentication supporting 752-byte sector reads/writes.

3.3V operation requires level shifting from 5V Arduino SPI. Built-in antenna matches 50-100Ω impedance. UID extraction, sector authentication, and data block access enable secure access control and inventory applications.

Production RFID System Components

Arduino UNO R3 SPI capable (pins 11-13)
MFRC522 RFID-RC522 Module (13.56MHz)
MIFARE Classic 1K cards/keyfobs
Male-to-male jumper wires (7 pieces)
MFRC522 Arduino library (Miguel Balboa)
3.3V-5V bi-directional level shifter

High-Speed SPI Interface Configuration

3.3V: Arduino 3.3V (critical!)

GND: Arduino GND

RST: Arduino Digital Pin 9

SS/SDA: Arduino Digital Pin 10

MOSI: Arduino Pin 11

MISO: Arduino Pin 12

SCK: Arduino Pin 13

Program: Arduino Uno MFRC522 - Authorized Access Terminal

/*
  MFRC522 Access Control System
  Install library: Arduino IDE → MFRC522 by GithubCommunity
*/
#include <SPI.h>
#include <MFRC522.h>

#define SS_PIN 10
#define RST_PIN 9
MFRC522 mfrc522(SS_PIN, RST_PIN);

// Authorized UIDs (add your cards)
String authorizedUIDs[] = {"A1B2C3D4", "04A7C2D1", "E8F9A0B1"};
int numAuthorized = 3;

const int relayPin = 7;

void setup() {
  Serial.begin(9600);
  SPI.begin();
  mfrc522.PCD_Init();
  pinMode(relayPin, OUTPUT);
  digitalWrite(relayPin, HIGH);
  
  Serial.println("=== MFRC522 Access Control Terminal ===");
  Serial.println("Present authorized card/keyfob (3cm range)");
}

void loop() {
  if(!mfrc522.PICC_IsNewCardPresent() || !mfrc522.PICC_ReadCardSerial()) {
    return;
  }
  
  String uid = "";
  for(byte i=0; i<mfrc522.uid.size; i++) {
    uid += String(mfrc522.uid.uidByte[i] < 0x10 ? "0" : "");
    uid += String(mfrc522.uid.uidByte[i], HEX);
  }
  
  Serial.print("Card UID: ");
  Serial.println(uid);
  
  bool authorized = false;
  for(int i=0; i<numAuthorized; i++) {
    if(authorizedUIDs[i] == uid) {
      authorized = true;
      break;
    }
  }
  
  if(authorized) {
    Serial.println("*** ACCESS GRANTED ***");
    digitalWrite(relayPin, LOW);  // Unlock door
    delay(3000);
    digitalWrite(relayPin, HIGH);
  } else {
    Serial.println("*** ACCESS DENIED ***");
  }
  
  mfrc522.PICC_HaltA();
  mfrc522.PCD_StopCrypto1();
}

MFRC522 Library Production Deployment

Library Manager → 'MFRC522' GithubCommunity. Verify SPI pins 10/9. Scan authorized cards adding UIDs to array.

Terminal grants relay access (3s unlock) for authorized UIDs only.

Advanced Data Block Read/Write & Anti-Collision

Program: Arduino Uno MFRC522 - MIFARE Data Sector Access

// Authenticate & read/write sector 1 block 4
byte sector = 1;
byte blockAddr = 4;
byte dataBlock[18];

MFRC522::StatusCode status = mfrc522.PCD_Authenticate(MFRC522::PICC_CMD_MF_AUTH_KEY_A, blockAddr*4, &key, &(mfrc522.uid));
if(status == MFRC522::STATUS_OK) {
  // Read 16 bytes
  status = mfrc522.MIFARE_Read(blockAddr, dataBlock, &size);
  dump_byte_array(dataBlock, 16);
}

MFRC522 RF Specifications

13.56MHz ISO14443A; 106kbit/s; 7cm range; MIFARE Classic/Ultralight; CRC16 hardware; anti-collision.

Secure Identification Applications

Door access control systems

Employee attendance tracking

Inventory asset management

Program: Arduino Uno MFRC522 - Attendance Logger

// EEPROM UID logging
void logAttendance(String uid) {
  // Write timestamp + UID to EEPROM/SD
  Serial.print("ATTENDANCE: ");
  Serial.print(millis()/1000);
  Serial.print("s - UID: ");
  Serial.println(uid);
}

Production RFID Specifications

SPI 10MHz interface
3.3V only (level shift 5V)
7cm read range
Multi-tag anti-collision
MIFARE Classic 1K/4K

Reliable Deployment Protocol

3.3V power essential (5V damages IC). Antenna tuning 50Ω. Shielded enclosure EMI immunity. Key sector authentication production.