RC522 RFID with Raspberry Pi Pico 2

Wiring for the RC522 RFID reader (13.56 MHz) on the Raspberry Pi Pico 2 (RP2350, 3.3 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	Raspberry Pi Pico 2 pin	Notes
SDA	SPI chip select	GP17	This is the SPI chip select (CS), despite the SDA label
SCK	SPI clock	GP18
MOSI	SPI MOSI	GP19
MISO	SPI MISO	GP16
IRQ	Interrupt	GP15	Interrupt, optional. Leave unconnected
GND	Ground	GND
RST	Input to the part	GP14	Reset, active LOW
3.3V	Power	3V3(OUT)	3.3 V only. Never 5 V

Check before you power it on

Supply: 3.3 V from the 3V3(OUT) pin.

Test code (Arduino)

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

MFRC522 rfid(17, 14);  // 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: rp2040:rp2040:rpipico2. If the board is not found, hold the BOOTSEL button while plugging in the USB cable.

Questions

Which Raspberry Pi Pico 2 pins do I use for the RC522 RFID?

SDA → GP17, SCK → GP18, MOSI → GP19, MISO → GP16, IRQ → GP15, GND → GND, RST → GP14, 3.3V → 3V3(OUT).

Does the RC522 RFID work with the Raspberry Pi Pico 2 at 3.3 V?

Yes: the RC522 RFID runs at 3.3 V and the Raspberry Pi Pico 2 uses 3.3 V signals, so no level shifting is needed.

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

Download BoardPilot

Full Raspberry Pi Pico 2 pinout · RC522 RFID reader (13.56 MHz): all pins and data

The RC522 RFID on other boards

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