HOW to Use the RFID Module with ESP32

Description

RFIDRFID-RC522 radio frequency module adopts a Philips MFRC522 original chip to design card reading circuit, easy to use and low cost, suitable for equipment development and card reader development and so on.

RFID or Radio Frequency Identification system consists of two main components, a transponder/tag attached to an object to be identified, and a transceiver also known as interrogator/Reader.

In the experiment, the data read by the card swipe module is 4 hexadecimal numbers, and we print these four hexadecimal numbers as strings. For example, we read the data of the IC card below: 0xED、0xF7、0x94、0x5A and the information string displayed in the serial monitor is ED F7 94 5A ; the data read from the keychain is: 0x4C、0x09、0x6B、0x6E . Different IC cards and different key chains have diverse data.

Working Principle

Radio frequency identification, the card reader is composed of a radio frequency module and a high-level magnetic field. The Tag transponder is a sensing device, and this device does not contain a battery. It only contains tiny integrated circuit chips and media for storing data and antennas for receiving and transmitting signals. To read the data in the tag, first put it into the reading range of the card reader. The reader will generate a magnetic field, and because the magnetic energy generates electricity according to Lenz’s law, the RFID tag will supply power, thereby activating the device.

Components Required

Connection Diagram

Test Code

//**********************************************************************************
/*  
 * Filename    : RFID
 * Description : RFID reader UID
 * Auther      : http//www.keyestudio.com
*/
#include <Wire.h>
#include "MFRC522_I2C.h"
// IIC pins default to GPIO21 and GPIO22 of ESP32
// 0x28 is the i2c address of SDA, if doesn't match，please check your address with i2c.
MFRC522 mfrc522(0x28);   // create MFRC522.

void setup() {
  Serial.begin(115200);           // initialize and PC's serial communication
  Wire.begin();                   // initialize I2C
  mfrc522.PCD_Init();             // initialize MFRC522
  ShowReaderDetails();            // dispaly PCD - MFRC522 read carder
  Serial.println(F("Scan PICC to see UID, type, and data blocks..."));
}

void loop() {
  // 
  if ( ! mfrc522.PICC_IsNewCardPresent() || ! mfrc522.PICC_ReadCardSerial() ) {
    delay(50);
    return;
  }
  
  // select one of door cards. UID and SAK are mfrc522.uid.
  
  // save UID
  Serial.print(F("Card UID:"));
  for (byte i = 0; i < mfrc522.uid.size; i++) {
    Serial.print(mfrc522.uid.uidByte[i] < 0x10 ? " 0" : " ");
    Serial.print(mfrc522.uid.uidByte[i], HEX);
  } 
  Serial.println();
}

void ShowReaderDetails() {
  //  attain the MFRC522 software
  byte v = mfrc522.PCD_ReadRegister(mfrc522.VersionReg);
  Serial.print(F("MFRC522 Software Version: 0x"));
  Serial.print(v, HEX);
  if (v == 0x91)
    Serial.print(F(" = v1.0"));
  else if (v == 0x92)
    Serial.print(F(" = v2.0"));
  else
    Serial.print(F(" (unknown)"));
  Serial.println("");
  // when returning to 0x00 or 0xFF, may fail to transmit communication signals
  if ((v == 0x00) || (v == 0xFF)) {
    Serial.println(F("WARNING: Communication failure, is the MFRC522 properly connected?"));
  }
}
//**********************************************************************************

Code Explanation

Wire.begin(); The module we use is the IIC interface, so we first initialize the IIC

mfrc522.PCD_Init(); initialize MFRC522

String(mfrc522.uid.uidByte[i], HEX); A string to convert the value read into hexadecimal format.

Test Result

Connect the wires according to the experimental wiring diagram, compile and upload the code to the ESP32. After uploading successfully，we will use a USB cable to power on. Open the serial monitor and set baud rate to 115200. When we make the IC card close to the RFID module, the information will be printed out, as shown in the figure below.

Note: Different RFID-RC522 door cards and key chains have diverse values.