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Introduction 

In this tutorial we will use the MFRC-522 NFC/RFID Controller.

​This module can read/write to tags and cards and also "act" like a NFC tag. The RFID Reader Module can be used in a wide variety of hobbyist and commercial applications, including access control, automatic identification and payment systems .

In this tutorial we will use the Arduino UNO board with this module and the serial monitor to print the ID code of the card or NFC tag.
​
So, let’s get started!​

What you will need - Hardware

For this tutorial you will need:

The Circuit

The connections are pretty easy, see the above image with the breadboard circuit schematic.
Connections of the MFRC-522 NFC/RFID  sensor:
  • SDA to Arduino pin  10
  • SCK to Arduino pin 13
  • MOSI to Arduino pin 11
  • MISO to Arduino pin 12
  • RST to Arduino pin 9

The code

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/*
 * ----------------------------------------------------------------------------
 * This is a MFRC522 library example; see https://github.com/miguelbalboa/rfid
 * ----------------------------------------------------------------------------
 */

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

constexpr uint8_t RST_PIN = 9;     // Configurable, see typical pin layout above
constexpr uint8_t SS_PIN = 10;     // Configurable, see typical pin layout above

MFRC522 mfrc522(SS_PIN, RST_PIN);   // Create MFRC522 instance.

// Number of known default keys (hard-coded)
// NOTE: Synchronize the NR_KNOWN_KEYS define with the defaultKeys[] array
constexpr uint8_t NR_KNOWN_KEYS = 8;
// Known keys, see: https://code.google.com/p/mfcuk/wiki/MifareClassicDefaultKeys
byte knownKeys[NR_KNOWN_KEYS][MFRC522::MF_KEY_SIZE] =  {
    {0xff, 0xff, 0xff, 0xff, 0xff, 0xff}, // FF FF FF FF FF FF = factory default
    {0xa0, 0xa1, 0xa2, 0xa3, 0xa4, 0xa5}, // A0 A1 A2 A3 A4 A5
    {0xb0, 0xb1, 0xb2, 0xb3, 0xb4, 0xb5}, // B0 B1 B2 B3 B4 B5
    {0x4d, 0x3a, 0x99, 0xc3, 0x51, 0xdd}, // 4D 3A 99 C3 51 DD
    {0x1a, 0x98, 0x2c, 0x7e, 0x45, 0x9a}, // 1A 98 2C 7E 45 9A
    {0xd3, 0xf7, 0xd3, 0xf7, 0xd3, 0xf7}, // D3 F7 D3 F7 D3 F7
    {0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff}, // AA BB CC DD EE FF
    {0x00, 0x00, 0x00, 0x00, 0x00, 0x00}  // 00 00 00 00 00 00
};

/*
 * Initialize.
 */
void setup() {
    Serial.begin(9600);         // Initialize serial communications with the PC
    while (!Serial);            // Do nothing if no serial port is opened (added for Arduinos based on ATMEGA32U4)
    SPI.begin();                // Init SPI bus
    mfrc522.PCD_Init();         // Init MFRC522 card
    Serial.println(F("Try the most used default keys to print block 0 of a MIFARE PICC."));
}

/*
 * Helper routine to dump a byte array as hex values to Serial.
 */
void dump_byte_array(byte *buffer, byte bufferSize) {
    for (byte i = 0; i < bufferSize; i++) {
        Serial.print(buffer[i] < 0x10 ? " 0" : " ");
        Serial.print(buffer[i], HEX);
    }
}

/*
 * Try using the PICC (the tag/card) with the given key to access block 0.
 * On success, it will show the key details, and dump the block data on Serial.
 *
 * @return true when the given key worked, false otherwise.
 */
boolean try_key(MFRC522::MIFARE_Key *key)
{
    boolean result = false;
    byte buffer[18];
    byte block = 0;
    MFRC522::StatusCode status;
    
    // http://arduino.stackexchange.com/a/14316
    if ( ! mfrc522.PICC_IsNewCardPresent())
        return false;
    if ( ! mfrc522.PICC_ReadCardSerial())
        return false;
    // Serial.println(F("Authenticating using key A..."));
    status = mfrc522.PCD_Authenticate(MFRC522::PICC_CMD_MF_AUTH_KEY_A, block, key, &(mfrc522.uid));
    if (status != MFRC522::STATUS_OK) {
        // Serial.print(F("PCD_Authenticate() failed: "));
        // Serial.println(mfrc522.GetStatusCodeName(status));
        return false;
    }

    // Read block
    byte byteCount = sizeof(buffer);
    status = mfrc522.MIFARE_Read(block, buffer, &byteCount);
    if (status != MFRC522::STATUS_OK) {
        // Serial.print(F("MIFARE_Read() failed: "));
        // Serial.println(mfrc522.GetStatusCodeName(status));
    }
    else {
        // Successful read
        result = true;
        Serial.print(F("Success with key:"));
        dump_byte_array((*key).keyByte, MFRC522::MF_KEY_SIZE);
        Serial.println();
        // Dump block data
        Serial.print(F("Block ")); Serial.print(block); Serial.print(F(":"));
        dump_byte_array(buffer, 16);
        Serial.println();
    }
    Serial.println();

    mfrc522.PICC_HaltA();       // Halt PICC
    mfrc522.PCD_StopCrypto1();  // Stop encryption on PCD
    return result;
}

/*
 * Main loop.
 */
void loop() {
    // Look for new cards
    if ( ! mfrc522.PICC_IsNewCardPresent())
        return;

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

    // Show some details of the PICC (that is: the tag/card)
    Serial.print(F("Card UID:"));
    dump_byte_array(mfrc522.uid.uidByte, mfrc522.uid.size);
    Serial.println();
    Serial.print(F("PICC type: "));
    MFRC522::PICC_Type piccType = mfrc522.PICC_GetType(mfrc522.uid.sak);
    Serial.println(mfrc522.PICC_GetTypeName(piccType));
    
    // Try the known default keys
    MFRC522::MIFARE_Key key;
    for (byte k = 0; k < NR_KNOWN_KEYS; k++) {
        // Copy the known key into the MIFARE_Key structure
        for (byte i = 0; i < MFRC522::MF_KEY_SIZE; i++) {
            key.keyByte[i] = knownKeys[k][i];
        }
        // Try the key
        if (try_key(&key)) {
            // Found and reported on the key and block,
            // no need to try other keys for this PICC
            break;
        }
    }
}
Download the code from here and open it with Arduino IDE. Inside you will also find and the library.

Open the serial monitor from tools menu of Arduino IDE.
mfrc-522_rfid.zip
File Size: 1163 kb
File Type: zip
Download File

Serial Monitor

Put the card or NFC tag  in front of the RFID module.

Well done!

You have successfully completed one more “How to” tutorial and you learned how to use the MFRC-522 NFC/RFID Controller with Arduino uno board.
​
I hope you liked this, let me know in the comments!
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