MFRC5C522 is a combined reader and writer for RFID tags that comply with ISO/IEC 14443 like A/MIFARE and NTAG. The commonly available inexpensive boards have an SPI interface, we will make it talk with Explore M3 in this tutorial.

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Hookup

The default SPI interface for Explore M3 is mapped to SPI1 of the controller. It simply means whenever you're interfacing an SPI device you used use these pins and functions like SPI.begin() will use these pins.

Explore M3	MFRC522 Breakout	Description
10	MOSI	Master Out Slave In
11	MISO	Master In Slave Out
12	SCK	Serial Clock
13	SDA	This is wrongly labelled, this should have been SS
5	RESET	SPI reset signal
3.3v	VCC	Power
GND	GND	The holy ground, do not miss this!

Code

The Card that came with the board had 1KB of memory. It was divided into 16 blocks of 64 bytes of memory. Each block is in-turn arranged as 4 locations of 64 bytes. We will use the Arduino RFID Library for MFRC522 which has all the functions you'll ever need. The code reads the card and dumps the memory map. There are several other examples that come with the library to read/write the card etc.,

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

	#define RST_PIN 5 // Configurable, see typical pin layout above
	#define SS_PIN 13 // Configurable, see typical pin layout above

	MFRC522 mfrc522(SS_PIN, RST_PIN); // Create MFRC522 instance

	void setup() {
	// delay(5000);
	Serial.begin(9600); // Initialize serial communications with the PC
	while (!Serial); // Do nothing if no serial port is opened (added for Arduinos based on ATMEGA32U4)
	Serial.println("in setup");

	SPI.begin(); // Init SPI bus
	Serial.print("spi intialized");
	mfrc522.PCD_Init(); // Init MFRC522
	Serial.print("card intialized intialized");
	mfrc522.PCD_DumpVersionToSerial(); // Show details of PCD - MFRC522 Card Reader details
	Serial.println(F("Scan PICC to see UID, SAK, type, and data blocks..."));
	}

	void loop() {


	// Look for new cards
	if ( ! mfrc522.PICC_IsNewCardPresent()) {
	return;
	}

	// Select one of the cards
	if ( ! mfrc522.PICC_ReadCardSerial()) {
	return;
	}

	// Dump debug info about the card; PICC_HaltA() is automatically called
	mfrc522.PICC_DumpToSerial(&(mfrc522.uid));
	}