Connect the RC522 to the Uno’s SPI pins, supply the reader with the voltage specified for your particular module, and use the MFRC522 library to read a compatible card’s identifier. The common wiring map uses D10 for chip select, D13–D11–D12 for SPI, and D9 for reset. Pay special attention to logic levels: an Uno uses 5 V logic, while the documented Keyestudio KS0067 module specifies 3.3 V; do not assume an RC522 board accepts 5 V signals.
What you need
- An Arduino Uno or Uno-compatible board
- An RC522/MFRC522 RFID reader module
- Jumper wires and a USB cable
- A card or tag supported by the reader and library
An LCD is not needed to read a card identifier. Before wiring, check the documentation and pin labels for your specific reader: clone boards can differ in markings and quality. The Arduino Project Hub example lists an Uno Rev3, USB cable, RC522 module kit, jumper wires, and an optional 16×2 I2C LCD (Arduino Project Hub).
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Wire the RC522 to the Uno over SPI
For the common pin map used in the MFRC522 library documentation, connect the module as follows:
| RC522 module pin | Arduino Uno pin |
|---|---|
| SDA / SS | D10 |
| SCK | D13 |
| MOSI | D11 |
| MISO | D12 |
| RST | D9 |
| 3.3V / VCC | 3.3 V |
| GND | GND |
| IRQ | Leave unconnected for basic polling |
On the RC522, SDA or SS is the SPI chip-select connection in this wiring. It is not connected to the Uno’s I2C SDA pin. The MFRC522 library documentation and Keyestudio’s KS0067 module documentation show this SPI-based approach (MFRC522 library; Keyestudio KS0067 documentation).
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- RFID module RC522 mini Kits S50 13.56 Mhz 6cm With Tags Write & Read For 2560
Check voltage before powering the reader
Voltage requirements depend on the actual module. Keyestudio specifies 3.3 V for its KS0067 RC522 module. The Uno uses 5 V logic, and MFRC522 inputs should not be treated as 5 V tolerant. Confirm both the reader’s supply-voltage and signal-level requirements rather than assuming that a module marked RC522 can connect directly to every Uno pin.
If the signal levels require conversion, choose an interface appropriate for SPI and the specific wiring. Playful Technology’s wiring guide discusses level conversion and cautions that some converters can affect SPI timing; a generic level shifter is not automatically a suitable solution (Playful Technology wiring and troubleshooting guide). Follow the module’s specifications and validate the resulting setup.
Rank #2
- Main chip: MFRC522
- Working Voltage: 3.3V
- Working frequency: 13.56MHz
- Supported card types: mifare S50, mifare S70, mifare UltraLight, mifare Pro, mifare Desfire
- RFID Kit Include: MFRC522 Module + S50 Blank Card + Key Ring
Install the library and upload a UID-reading sketch
- In Arduino IDE, install the MFRC522 library. Its source and installation information are on the MFRC522 library page.
- Use a sketch that includes
SPI.handMFRC522.h, assigns SS to pin 10 and RST to pin 9, then callsSPI.begin()andPCD_Init(). - In the main loop, check
PICC_IsNewCardPresent(), then callPICC_ReadCardSerial(). When the read succeeds, the library provides the card identifier in its returned serial data. - Upload the sketch, open the IDE’s serial monitor at the speed configured by that sketch, and present a compatible card to the reader. The identifier should appear if the sketch prints it.
The key program flow is SPI startup, reader initialization, card-present polling, then serial-data reading. The Arduino Project Hub example also writes MIFARE blocks and drives an LCD, but neither feature is needed to read an identifier (Arduino Project Hub example). For a basic polling sketch, IRQ remains unconnected.
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Use a card family the library supports
“RFID” and “NFC” do not mean every card is compatible. The MFRC522 library README lists communication with MIFARE Classic 1K, 4K, and Mini as working, while MIFARE Ultralight and other PICCs such as NTAG216 are listed as partially working. It lists additional card families as unsupported. Check the library’s current compatibility notes for the card you intend to use (MFRC522 library compatibility information).
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- COMPLETE KIT: Includes Arduino UNO R3 board, RFID module with cards, LCD display, breadboard, jumper wires, LEDs, resistors, and various electronic components in a retail storage box. This product does not contain batteries
- DIMENSIONS: Compact storage case measuring 8.86 inches long, 6.11 inches wide, and 2.36 inches high for organized component storage
- LEARNING FEATURES: Perfect for beginners with comprehensive components for RFID projects, including remote control, digital display, and sensor modules
- CONNECTIVITY: Comes with USB cable for programming, breadboard for prototyping, and various connection cables for easy circuit building
- COMPONENTS: Features LCD screen, digital display module, multiple LEDs in different colors, push buttons, resistors, and professional-grade circuit board
The library maintainer also says that using more than two reader modules requires a multiplexer. The README reports variation in board quality among sellers, including poor components or defective or fake chips; these are maintainer reports, not a controlled reliability study. If a card is not detected, first verify compatibility and wiring before concluding that the sketch is at fault.
Troubleshoot a reader that does not detect a card
- Check power and ground: connect VCC to the voltage specified for your module and make sure the Uno and reader share ground.
- Recheck SPI and control pins: confirm SCK, MOSI, MISO, SS/SDA, and RST against both the wiring table and the actual board labels. Make sure the sketch’s SS and reset pin numbers match.
- Confirm voltage compatibility: do not drive reader inputs with Uno 5 V signals unless the specific module documentation establishes that this is safe. If conversion is needed, account for SPI timing.
- Try a supported card: use a card family listed as working by the library rather than assuming any RFID or NFC card will work.
- Keep the first test simple: use the polling and UID-reading flow before adding block writes, an LCD, or multiple readers.
Choose parts by specifications, not just the RC522 label
When selecting a reader kit, check which tags are included, the module’s supply and logic requirements, and the exact pin labels. The MFRC522 library maintainer notes that board quality varies among sellers, so the RC522 name alone does not establish that every kit is equivalent. Jumper wires and an Uno-compatible board are the other basic hardware needs; any logic-level interface should be selected only after checking the module and validating the SPI setup.
Quick Recap
Best Value
- RFID reader/writer supports: Mifare 1k, 4k, Ultralight, and DesFire cards, ISO/IEC 14443-4 cards such as CD97BX, CD light, Desfire, P5CN072 (SMX), Innovision Jewel cards such as IRT5001 card, FeliCa cards such as RCS_860 and RCS_854
- On-board level shifter, standard 5V TTL for I2C and UART, 3.3V TTL SPI
- Support NFC RFID reading and writing, P2P communication with peers
- Support I2C, SPI and HSU (High Speed UART), easy to change among these modes
- Small Size and easy to embed into your project
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- RFID Kit Mifare RC522 RFID Reader Module with S50 White Card and Key Ring for Arduino Raspberry Pi
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