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

The RFID-RC522 is a compact and cost-effective RFID reader/writer module that operates at a frequency of 13.56 MHz. It is widely used for reading and writing RFID tags and cards, enabling wireless communication in various applications. This module is based on the MFRC522 IC, which supports ISO/IEC 14443A/MIFARE protocols. Its small 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.

The RFID-RC522 module is designed to provide reliable and efficient RFID communication. Below are its key technical details:

• Operating Voltage: 2.5V to 3.3V (logic level), 5V (via onboard regulator)
• Operating Current: 13-26mA (typical)
• Operating Frequency: 13.56 MHz
• Communication Protocol: SPI, I2C, UART (default: SPI)
• Reading Distance: Up to 5 cm (depending on tag type and environment)
• Supported RFID Standards: ISO/IEC 14443A/MIFARE
• Dimensions: 40mm x 60mm

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

The RFID-RC522 module is easy to integrate into microcontroller-based systems, such as Arduino. Below are the steps to use the module in a circuit:

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

   RFID-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 or GitHub.

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

   #include <SPI.h>
   #include <MFRC522.h>
   
   #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 MFRC522 class
   
   void setup() {
     Serial.begin(9600); // Initialize serial communication
     SPI.begin();        // Initialize SPI bus
     rfid.PCD_Init();    // Initialize the RFID 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 reading fails
     }
   
     // 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();
   
     rfid.PICC_HaltA(); // Halt communication with the card
   }
   

• Power Supply: Ensure the module is powered with 3.3V. If using 5V, verify that the onboard regulator is functioning.
• Antenna Placement: Avoid placing the module near metal objects, as they can interfere with the RFID signal.
• Tag Compatibility: Use tags/cards that comply with ISO/IEC 14443A standards for best results.
• SPI Configuration: Ensure no other SPI devices are using the same Slave Select (SS) pin.

1. The module is not detected by the microcontroller:

   • Verify the wiring connections, especially the SPI pins.
   • Ensure the correct pins are defined in the code (SS_PIN and RST_PIN).

2. The RFID tag is not being read:

   • Check the distance between the tag and the module. It should be within 5 cm.
   • Ensure the tag is compatible with the module (ISO/IEC 14443A).

3. Interference or poor performance:

   • Avoid placing the module near metal surfaces or other electronic devices.
   • Use a stable power supply to prevent voltage fluctuations.

4. Error: "MFRC522 library not found":

   • Install the MFRC522 library from the Arduino Library Manager.

Q: Can the RFID-RC522 write data to RFID tags?
A: Yes, the module supports both reading and writing to compatible RFID tags.

Q: Can I use the RFID-RC522 with a 5V microcontroller?
A: Yes, the module has an onboard voltage regulator, but the logic level for communication must be 3.3V.

Q: What is the maximum range of the RFID-RC522?
A: The maximum reading distance is approximately 5 cm, depending on the tag and environmental conditions.

Q: Can I connect multiple RFID-RC522 modules to a single microcontroller?
A: Yes, you can connect multiple modules by assigning unique Slave Select (SS) pins for each module.