Example Code for Arduino-Read and Write MIFARE Classic S50 NFC Card with IIC

Hardware Preparation

• DFRduino UNO R3 or DFRobot Mega 2560 V3.0 x 1
• Gravity: UART & I2C NFC Module x 1
• Gravity 4P sensor wire (or Dupont wires) x 1
• USB to TTL Converter x 1

Software Preparation

• Arduino IDE
• DFRobot_PN532 library

Wiring Diagram

• I2C interface: turn the switch to the left. I2C interface is mainly used for communication with various 3.3V/5V controllers by programming.
  

Other Preparation Work

1. According to the first connection diagram, connect UNO to the NFC module through IIC, and turn the switch to IIC.
2. Download and install the DFRobot_PN532 library.

Sample Code

/*!
    @flie MifareClassic_ReadWrite.ino
    @Copyright   [DFRobot](https://www.dfrobot.com), 2016
    @Copyright   GNU Lesser General Public License
    @version  V1.0
    @date  07/03/2019

    @brief This demo runs on the arduino platform.
           Download this demo to learn how to wirte data to card.
           We can read the data on the card to see if the write is successful.

    This demo and related libraries are for DFRobot Gravity: I2C NFC Module
    Product(CH): https://www.dfrobot.com.cn/goods-2029.html
    Product(EN): https://www.dfrobot.com/product-1905.html
*/
#include <DFRobot_PN532.h>

#define BLOCK_SIZE      16
#define  PN532_IRQ      (2)
#define  INTERRUPT      (1)
#define  POLLING        (0)
//use this line for a breakout or shield with an I2C connection
//check the card by polling
DFRobot_PN532_IIC  nfc(PN532_IRQ, POLLING);
uint8_t dataWrite[BLOCK_SIZE] = {"DFRobot NFC"};
uint8_t dataRead[16] = {0};
struct card NFCcard;

void setup() {

  Serial.begin(115200);
  while (!nfc.begin()) {
    Serial.println("initial failure");
    delay (1000);
  }
  Serial.println("Waiting for a card......");
}
void loop() {
  //Scan, write and read NFC card every 2s
  //Print all what is to be written and read
  if (nfc.scan()) {
    NFCcard = nfc.getInformation();
    if ((NFCcard.AQTA[1] == 0x02 || NFCcard.AQTA[1] == 0x04)) {
      Serial.print("Data to be written(string):");
      Serial.println((char *)dataWrite);
      Serial.print("Data to be written(HEX):");
      for (int i = 0; i < BLOCK_SIZE; i++) {
        Serial.print(dataWrite[i], HEX);
        Serial.print(" ");
      }
      Serial.println();
      //Write data(16 bytes) to sector 1
      if (nfc.writeData(2, dataWrite) != 1) {
        Serial.println("write failure!");
      }

      //Read sector 1 to verify the write results
      nfc.readData(dataRead, 2);
      Serial.print("Data read(string):");
      Serial.println((char *)dataRead);
      Serial.print("Data read(HEX):");
      for (int i = 0; i < BLOCK_SIZE; i++) {
        Serial.print(dataRead[i], HEX);
        Serial.print(" ");
        dataRead[i] = 0;
      }
      Serial.println();
    }
    else {
      Serial.println("The card type is not mifareclassic...");
    }
  }
  else {
    //Serial.println("no card");
  }
  delay(2000);
}

Result

A string is written to the cards and then read out.