M5Stack NFC Universal Unit (ST25R3916) is a 13.56MHz NFC/RFID read and write unit designed for access control, identity verification, smart transportation, attendance terminals, asset tagging, and embedded NFC interaction projects. It is built around the ST25R3916-AQWT high-performance NFC front-end and supports a wide range of mainstream NFC and RFID protocols, making it a practical M5Stack expansion module for secure identification and short-range wireless data exchange. This unit communicates with the host through I2C and supports Reader/Writer mode, Card Emulation mode, and Custom Protocol mode. It works with NFC-A, NFC-B, NFC-F (FeliCa), and NFC-V (ISO15693), so it fits projects that need compatibility with many different cards, tags, and NFC devices. The LEGO-compatible holes and compact size also make it easy to install inside kiosks, terminal housings, and smart equipment. Features 13.56MHz high-frequency NFC communication for card and tag interaction. ST25R3916 high-performance NFC front-end IC. Supports ISO14443A, ISO14443B, FeliCa, and ISO15693 protocols. Three operating modes: Reader/Writer, Card Emulation, and Custom Protocol. I2C communication for stable integration with M5Stack hosts and other controllers. Automatic antenna tuning and high-sensitivity reception for reliable NFC communication. Compact structure with LEGO-compatible mounting holes. Supports UiFlow2 and Arduino IDE development workflows. Specifications IC Type ST25R3916-AQWT Operating Frequency 13.56MHz Communication Interface I2C @ 0x50 (100K / 400K) Supported Protocols Reader/Writer: NFC-A/B, NFC-F (FeliCa), NFC-V (ISO15693); Card Emulation: NFC-A / NFC-F Read / Write Range Up to 40mm Power Consumption Sleep: 5V @ 19.33uA; Power-on: 5V @ 19.79uA; Continuous reading: 5V @ 67.65mA; Intermittent reading: 5V @ 66.48mA Port HY2.0-4P Pin Mapping GND, 5V, SDA, SCL Product Size 48.0 x 24.0 x 8.0mm Product Weight 5.9g Applications Access control systems for authorized entry and RFID/NFC authentication. Identity verification terminals for cards, tags, and credentials. Smart transportation and ticketing systems. Attendance systems and smart check-in devices. Embedded NFC interaction projects using M5Stack or Arduino hosts. Inventory, asset tagging, and smart device pairing. Packing List Unit NFC x1 HY2.0-4P Grove Cable (20cm) x1 Other Content Protocol flexibilityThis unit supports several of the most widely used NFC standards, including ISO14443A, ISO14443B, FeliCa, and ISO15693. That makes it suitable for projects that need to work across multiple types of NFC cards and RFID tags instead of being limited to a single format. Integration advantageBecause it uses I2C and the standard HY2.0-4P connector, it is easy to add to M5Stack hosts, compact embedded systems, and custom controller projects without the wiring complexity of lower-level RF front-end modules. Access control and RFID workflowIf your goal is to build a card-based access system or NFC-enabled terminal, this unit is a strong fit for reader-based verification, smart access control, attendance logging, and credential-triggered automation. Resources M5Stack Unit NFC Docs Unit NFC Schematics PinMap Arduino Quick Start ST25R3916 Datasheet Official Product Video OpenELAB M5Stack RFID-based Smart Access Control System What is M5Stack FAQ What is this unit best used for? It is especially suitable for access control, identity verification, smart transportation, attendance systems, and embedded NFC/RFID projects. What protocols does it support? It supports ISO14443A, ISO14443B, FeliCa, and ISO15693, with Reader/Writer, Card Emulation, and Custom Protocol operating modes. How does it connect to the host? It connects through I2C using the HY2.0-4P interface, with pin mapping GND, 5V, SDA, and SCL. What is included in the box? You get Unit NFC x1 and HY2.0-4P Grove Cable (20cm) x1.
