How to Use RFID RC522: Examples, Pinouts, and Specs

The RFID RC522 is a low-cost RFID reader/writer module that operates at a frequency of 13.56 MHz. It is widely used for reading RFID tags and cards, enabling wireless communication in a variety of applications. This module is based on the MFRC522 IC and supports ISO/IEC 14443 Type A cards. Its compact size, low power consumption, and ease of integration make it a popular choice for projects involving access control, inventory management, attendance systems, and identification systems.

Below are the key technical details and pin configuration of the RFID RC522 module:

• Operating Voltage: 2.5V to 3.3V (logic level), 5V compatible with level shifters
• Operating Frequency: 13.56 MHz
• Communication Interface: SPI, I2C, UART (default: SPI)
• Maximum Data Rate: 10 Mbps (SPI)
• Reading Distance: Up to 5 cm (depending on the tag and environment)
• Current Consumption: 13-26 mA (active mode), 10 µA (standby mode)
• Supported Protocols: ISO/IEC 14443 Type A
• Dimensions: 40mm x 60mm

The RFID RC522 module has 8 pins, as described in the table below:

1. Power the Module: Connect the VCC pin to a 3.3V power source and the GND pin to ground.
2. Connect to a Microcontroller: Use the SPI interface to connect the module to a microcontroller (e.g., Arduino UNO). The typical connections are:
   • VCC → 3.3V
   • GND → GND
   • RST → Any digital pin (e.g., D9 on Arduino UNO)
   • SCK → D13 (SPI clock)
   • MOSI → D11 (SPI data out)
   • MISO → D12 (SPI data in)
   • NSS → D10 (SPI chip select)
3. Install Required Libraries: For Arduino, install the "MFRC522" library from the Arduino Library Manager.
4. Upload Code: Use the example code below to test the module.

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

// Define pins for the RC522 module
#define RST_PIN 9  // Reset pin connected to D9
#define SS_PIN 10  // Slave Select pin connected to D10

MFRC522 rfid(SS_PIN, RST_PIN); // Create an instance of the MFRC522 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 a new card is present
  if (!rfid.PICC_IsNewCardPresent()) {
    return; // Exit if no card is detected
  }

  // Check if the card can be read
  if (!rfid.PICC_ReadCardSerial()) {
    return; // Exit if the card cannot be read
  }

  // 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], HEX); // Print each byte in hexadecimal
    Serial.print(" ");
  }
  Serial.println();

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

• Power Supply: Ensure the module is powered with 3.3V. If using a 5V microcontroller, use level shifters for the SPI pins.
• Reading Distance: The reading distance depends on the tag size and environmental factors. Avoid placing the module near metal objects.
• Library Compatibility: Use the latest version of the MFRC522 library for optimal performance.
• Interrupt Pin: The IRQ pin is optional and can be left unconnected if not used.

1. Module Not Responding:

   • Check the wiring and ensure all connections are secure.
   • Verify that the module is powered with 3.3V.
   • Ensure the correct SPI pins are used on the microcontroller.

2. Card Not Detected:

   • Ensure the card is within the reading range (up to 5 cm).
   • Check for interference from nearby metal objects or other RFID devices.

3. UID Not Displayed:

   • Verify that the MFRC522 library is installed and included in the code.
   • Ensure the card is compatible with the ISO/IEC 14443 Type A standard.

• Can the RC522 module write data to RFID tags? Yes, the RC522 can write data to compatible RFID tags. Refer to the MFRC522 library examples for writing data.

• Can I use the RC522 with a 5V microcontroller? Yes, but you must use level shifters for the SPI pins to avoid damaging the module.

• What is the maximum range of the RC522 module? The maximum range is approximately 5 cm, depending on the tag and environmental conditions.