How to use the RFID-RC522 module (RFID reader) with the Arduino Uno

Setup of this tutorial: RFID reader and two RFID tags.

RFID stands for Radio-frequency identification and can be used for many application that require an identification mechanism. In this tutorial, it is shown how to use the RFID-RC522 module with the Arduino Uno. The RFID-RC522 module is an RFID reader, which can read RFID tags in close-range. In order to read an RFID tag, the reader and the tag must have the same frequency. The RFID-RC522 module reads only High frequency tags at 13.56 MHz.
In order to demonstrate the RFID-RC522 module, a simple application is programmed which identifies a user based on an RFID tag.

List of materials:
– Arduino Uno [Search on Aliexpress | Amazon]
– Jumper wires (female/male) [Search on Aliexpress | Amazon]
– RFID-RC522 module [Search on Aliexpress | Amazon]
– RFID tags [Search on Aliexpress | Amazon]

How to connect the RFID-RC522 to the Arduino?

Schematic of how to connect the RFID-RC522 to the Arduino.

The RFID-RC522 module comes with eight pins (of which seven pins are used in this tutorial). In the following, the pin layout is shown as recommended by the documentation of the MFRC522 library (used later in the programming section). The RFID-RC522 module runs with 3.3V. Therefore, the module’s 3.3V pin must be connected to the Arduino’s 3.3V. The module might get damaged, if it is accidentally connected to the Arduino’s 5V pin. The complete pin layout is shown by the following table (works only for the Arduino Uno! Mega, Nano etc. have different recommended pin layouts!):

RFID-RC522 Pin Arduino Uno Pin
SDA 10
SCK 13
MOSI 11
MISO 12
IRQ UNUSED
GND GND
RST 9
3.3V 3.3V

How to program the RFID reader?
The code makes use of an existing RFID library which can be found here: https://github.com/miguelbalboa/rfid. If you are using the Arduino IDE, the library can be easily installed by clicking “Sketch->Include Library->Manage Libraries”. Then, search for “RFID” and you will find an entry with the title “MFRC522 by GithubCommunity”. If you cannot find such an entry, I recommend to visit the official website of the library for further assistance. In order to get the RFID reader running, you have to setup the library itself, a SPI connection, as well as the reader. Luckily, the library offers two very handy convenience functions for reading tags: The first functions allows to detect whether an RFID tag/card is present. The second function reads the RFID tag id. In the following code, a for-loop is used to iterate through the tag. In each iteration, a single byte is read and printed out as hexadecimal value (00..FF). Such an mechanism can be used to identify users, when each user owns a different RFID tag.

// (c) Michael Schoeffler 2014, http://www.mschoeffler.de

#include "SPI.h" // SPI library 
#include "MFRC522.h" // RFID library (https://github.com/miguelbalboa/rfid)

const int pinRST = 9;
const int pinSDA = 10;

MFRC522 mfrc522(pinSDA, pinRST); // Set up mfrc522 on the Arduino

void setup() {
  SPI.begin(); // open SPI connection
  mfrc522.PCD_Init(); // Initialize Proximity Coupling Device (PCD)
  Serial.begin(9600); // open serial connection 
}

void loop() {
  if (mfrc522.PICC_IsNewCardPresent()) { // (true, if RFID tag/card is present ) PICC = Proximity Integrated Circuit Card
    if(mfrc522.PICC_ReadCardSerial()) { // true, if RFID tag/card was read
      Serial.print("RFID TAG ID:"); 
      for (byte i = 0; i < mfrc522.uid.size; ++i) { // read id (in parts)
        Serial.print(mfrc522.uid.uidByte[i], HEX); // print id as hex values
        Serial.print(" "); // add space between hex blocks to increase readability
      }
      Serial.println(); // Print out of id is complete. 
    }
  }
}

If the code has been successfully uploaded to the Arduino and an RFID card or tag is in close-range to the RFID reader, the output on the Serial Monitor (Tools->Serial Monitor, Ctrl+Shift+M) should look like this (picture shows position of the RFID card as well as the corresponding serial monitor output):

RFID reader is reading the ID of an RFID card. In addition, the serial monitor output of the program is shown.

Video Tutorial:

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