How to Use RC522: Examples, Pinouts, and Specs

The RC522 is a highly integrated RFID reader/writer module designed by MH-ET LIVE. Operating at a frequency of 13.56 MHz, it is widely used for reading and writing RFID tags and cards. This module supports various RFID protocols, including ISO/IEC 14443A/MIFARE, making it a versatile choice for wireless communication applications.

• Access control systems (e.g., door locks, attendance systems)
• Contactless payment systems
• Inventory and asset management
• Smart card-based authentication
• IoT projects requiring RFID integration

The RC522 module is compact, efficient, and easy to interface with microcontrollers like Arduino. Below are its key technical details:

The RC522 module has an 8-pin interface for communication and power. Below is the pinout:

The RC522 module is commonly used with microcontrollers like Arduino. Below are the steps to use it in a circuit:

1. Wiring the Module: Connect the RC522 module to the Arduino UNO as follows:

   RC522 Pin	Arduino UNO Pin
   VCC	3.3V
   GND	GND
   RST	Pin 9
   IRQ	Not connected
   MISO	Pin 12
   MOSI	Pin 11
   SCK	Pin 13
   SDA/SS	Pin 10

2. Install Required Libraries: Download and install the MFRC522 library from the Arduino Library Manager.

3. Upload Example Code: Use the following example code to read RFID tags:

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

// Define RC522 pins
#define RST_PIN 9  // Reset pin connected to Arduino pin 9
#define SS_PIN 10  // Slave Select pin connected to Arduino pin 10

MFRC522 rfid(SS_PIN, RST_PIN); // Create an instance of the RC522 class

void setup() {
  Serial.begin(9600); // Initialize serial communication
  SPI.begin();        // Initialize SPI bus
  rfid.PCD_Init();    // Initialize the RC522 module
  Serial.println("Place your RFID card near the reader...");
}

void loop() {
  // Check if an RFID card is present
  if (!rfid.PICC_IsNewCardPresent() || !rfid.PICC_ReadCardSerial()) {
    return; // Exit if no card is detected
  }

  // Print the UID of the card
  Serial.print("Card UID: ");
  for (byte i = 0; i < rfid.uid.size; i++) {
    Serial.print(rfid.uid.uidByte[i] < 0x10 ? " 0" : " ");
    Serial.print(rfid.uid.uidByte[i], HEX);
  }
  Serial.println();

  // Halt the card to stop communication
  rfid.PICC_HaltA();
}

• Power Supply: The RC522 operates at 3.3V. Do not connect it directly to a 5V power source to avoid damage.
• Signal Level: Ensure that the logic level of the microcontroller matches the RC522's 3.3V logic. Use a level shifter if necessary.
• Antenna Placement: For optimal performance, ensure that the RFID tag is placed flat and close to the antenna.

1. The module is not detected by the microcontroller.

   • Check the wiring and ensure all connections are secure.
   • Verify that the RC522 is powered with 3.3V and not 5V.
   • Ensure the correct pins are defined in the code.

2. The RFID tag is not being read.

   • Ensure the tag is compatible with the RC522 (e.g., MIFARE cards).
   • Place the tag closer to the antenna for better signal reception.
   • Check for electromagnetic interference from nearby devices.

3. The module resets unexpectedly.

   • Verify that the RST pin is properly connected and not floating.
   • Ensure the power supply is stable and capable of providing sufficient current.

Q: Can the RC522 read multiple tags simultaneously?
A: No, the RC522 can only read one tag at a time. If multiple tags are present, it may fail to detect any.

Q: Can I use the RC522 with a 5V microcontroller?
A: Yes, but you must use a level shifter to convert the 5V logic signals to 3.3V to avoid damaging the module.

Q: What is the maximum reading distance of the RC522?
A: The maximum reading distance is approximately 5 cm, depending on the size and type of the RFID tag.

Q: Does the RC522 support writing to RFID tags?
A: Yes, the RC522 can write data to compatible RFID tags, such as MIFARE cards.

By following this documentation, you can effectively integrate the RC522 module into your projects for reliable RFID-based communication.