RC522 RFID with Arduino Nano

Wiring for the RC522 RFID reader (13.56 MHz) on the Arduino Nano (ATmega328P, 5 V logic), chosen with the same pin rules BoardPilot uses: default buses first, and no pins that are used for flash, USB, the debugger or booting.

Wiring

RC522 RFID pin	Role	Arduino Nano pin	Notes
SDA	SPI chip select	D10 (PB2)	This is the SPI chip select (CS), despite the SDA label
SCK	SPI clock	D13 (PB5)
MOSI	SPI MOSI	D11 (PB3)
MISO	SPI MISO	D12 (PB4)
IRQ	Interrupt	D2 (PD2)	Interrupt, optional. Leave unconnected
GND	Ground	GND
RST	Input to the part	D3 (PD3)	Reset, active LOW
3.3V	Power	3V3	3.3 V only. Never 5 V

Check before you power it on

Supply: 3.3 V from the 3V3 pin.
The RC522 RFID is a 3.3 V part and the Arduino Nano uses 5 V signals. Power it from 3.3 V and put a level shifter on the signal wires, or buy a 5 V version of the module.

Test code (Arduino)

// Library: MFRC522 (miguelbalboa)
#include <SPI.h>
#include <MFRC522.h>

MFRC522 rfid(10, 3);  // SDA is the SPI chip select

void setup() {
  Serial.begin(115200);
  SPI.begin();
  rfid.PCD_Init();
  rfid.PCD_DumpVersionToSerial();  // 0x91 or 0x92 means the reader answers
}

void loop() {
  if (!rfid.PICC_IsNewCardPresent() || !rfid.PICC_ReadCardSerial()) return;
  for (byte i = 0; i < rfid.uid.size; i++) Serial.print(rfid.uid.uidByte[i], HEX);
  Serial.println();
  rfid.PICC_HaltA();
}

Arduino board: arduino:avr:nano. Clones with the old bootloader upload at 57600 baud: choose “ATmega328P (Old Bootloader)” if uploads fail.

Questions

Which Arduino Nano pins do I use for the RC522 RFID?

SDA → D10 (PB2), SCK → D13 (PB5), MOSI → D11 (PB3), MISO → D12 (PB4), IRQ → D2 (PD2), GND → GND, RST → D3 (PD3), 3.3V → 3V3.

Does the RC522 RFID work with the Arduino Nano at 5 V?

The RC522 RFID is a 3.3 V part and the Arduino Nano uses 5 V signals. Power it from 3.3 V and put a level shifter on the signal wires, or buy a 5 V version of the module.

BoardPilot checks this wiring in 3D as you build it, and finds crossed or missing wires on the real board.

Download BoardPilot

Full Arduino Nano pinout · RC522 RFID reader (13.56 MHz): all pins and data

The RC522 RFID on other boards

ESP32 DevKit Arduino Mega 2560 R3 Arduino Uno R3 WeAct Black Pill STM32F411CE ESP32-C3-DevKitM-1 ESP32-S3-DevKitC-1 Nordic nRF52840 DK NUCLEO-F401RE Raspberry Pi Pico 2 Raspberry Pi Pico W Raspberry Pi Pico Teensy 4.1

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