RC522 RFID with WeAct Black Pill STM32F411CE

Wiring for the RC522 RFID reader (13.56 MHz) on the WeAct Black Pill STM32F411CE (STM32F411CE, 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	WeAct Black Pill STM32F411CE pin	Notes
SDA	SPI chip select	A4 (PA4)	This is the SPI chip select (CS), despite the SDA label
SCK	SPI clock	A5 (PA5)
MOSI	SPI MOSI	A7 (PA7)
MISO	SPI MISO	A6 (PA6)
IRQ	Interrupt	A0 (PA0)	Interrupt, optional. Leave unconnected
GND	Ground	G
RST	Input to the part	B12 (PB12)	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.

Test code (Arduino)

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

MFRC522 rfid(PA4, PB12);  // 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: STMicroelectronics:stm32:GenF4:pnum=BLACKPILL_F411CE,usb=CDCgen,upload_method=dfuMethod. To upload over USB, hold BOOT0, press and release NRST, then release BOOT0 (DFU mode). An ST-LINK on the SWD pins also works.

Questions

Which WeAct Black Pill STM32F411CE pins do I use for the RC522 RFID?

SDA → A4 (PA4), SCK → A5 (PA5), MOSI → A7 (PA7), MISO → A6 (PA6), IRQ → A0 (PA0), GND → G, RST → B12 (PB12), 3.3V → 3V3.

Does the RC522 RFID work with the WeAct Black Pill STM32F411CE at 3.3 V?

Yes: the RC522 RFID runs at 3.3 V and the WeAct Black Pill STM32F411CE 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 WeAct Black Pill STM32F411CE pinout · RC522 RFID reader (13.56 MHz): all pins and data

The RC522 RFID on other boards

ESP32 DevKit Arduino Mega 2560 R3 Arduino Nano Arduino Uno R3 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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