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Using a RFID module with Arduino

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The RFID module is a smart card reader which allows among others, to activate a mechanism when the correct card is presented to the reader. We will use here the RC522 module, which is the most common.

Hardware

Scheme

The RFID RC522 module uses the SPI protocol to communicate with Arduino. SPI communication uses specific Boche of Arduino.Le microcontroller pin is as follows (left side RC522, right side Arduino UNO):  
– Vcc (Power) <-> 3V3 (or 5V depending on the module) 
– RST (Reset) <-> 9  
– GND (Ground) <-> GND  
– MISO (Master Input Slave Output) <-> 12
– MOSI (Master Output Slave Input) <-> 11 
– SCK (Serial Clock) <-> 13  
– SS/SDA (slave select) <-> 10
The RFID module must be connected as shown below.

Warning: Depending on the module version, the power voltage may be different (3.3V or 5V). Check the module datasheet to power the module correctly.

Code

To use the subject RFID module we use SPI and MFRC522 libraries that are used as follows

#include <SPI.h>
#include <MFRC522.h>
// INPUT
#define SS_PIN 10
#define RST_PIN 9
MFRC522 rfid(SS_PIN, RST_PIN);
// Init array that will store new NUID
byte nuidPICC[4];
void setup() {
Serial.begin(9600);
SPI.begin(); // Init SPI bus
rfid.PCD_Init(); // Init MFRC522
Serial.println(F("Scan RFID NUID..."));
}
void loop() {
     readRFID();
     delay(200);
}
//
void readRFID()
{ 
 // Look for new card
 if ( ! rfid.PICC_IsNewCardPresent()) 
 return;
   // Verify if the NUID has been readed
 if (  !rfid.PICC_ReadCardSerial())
 return;
 
 if (rfid.uid.uidByte[0] != nuidPICC[0] || 
   rfid.uid.uidByte[1] != nuidPICC[1] || 
   rfid.uid.uidByte[2] != nuidPICC[2] || 
   rfid.uid.uidByte[3] != nuidPICC[3] ) {
   Serial.println(F("A new card has been detected."));
   // Store NUID into nuidPICC array
   for (byte i = 0; i < 4; i++) {
     nuidPICC[i] = rfid.uid.uidByte[i];
   }
  
   Serial.print(F("RFID tag in dec: "));
   printDec(rfid.uid.uidByte, rfid.uid.size);
   Serial.println();
 }
  
 // Halt PICC
 rfid.PICC_HaltA();
 // Stop encryption on PCD
 rfid.PCD_StopCrypto1();
}
/**
 * Helper routine to dump a byte array as dec values to Serial.
 */
void printDec(byte *buffer, byte bufferSize) {
 for (byte i = 0; i < bufferSize; i++) {
   Serial.print(buffer[i] < 0x10 ? " 0" : " ");
   Serial.print(buffer[i], DEC);
 }
}

 

Applications

Sources

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