GroveNFC

GroveNFC is an NFC reader/writer and tag emulator supporting ISO14443A, ISO14443B, ISO15693, and FeliCa. It connects to embedded hosts and computers through IIC (I²C), UART, and USB.

Documentation

Guide	Use it to
IIC Operation Guide	Configure registers, exchange NFC frames, and save tag data
API and Firmware Development	Build custom module firmware and integrate NFC APIs
API Header Reference	Look up function signatures, constants, and data structures

Connecting a Host

1. Identify the module connector signals using the board labels and the hardware pinout for your revision.

2. Connect host ground to module ground and supply power according to the module's power-input specification.

3. For IIC, connect SDA and SCL to the corresponding host bus signals. For UART, connect host TX to module RX and host RX to module TX.

4. Use 3.3V logic for SDA, SCL, TXD, and RXD. A host powered from 5V must provide a compatible signal interface; host supply voltage does not establish GPIO voltage compatibility.

5. Configure the IIC host for 7-bit address 0x48 and start at 100 kHz.

Compatible host families include M5Stack, Seeed Studio XIAO and Wio Terminal, Raspberry Pi Pico and Raspberry Pi computers, Arduino, ESP32, DFRobot FireBeetle, and micro:bit. Use the appropriate Grove / Gravity adapter and a signal interface compatible with the module.

Connector pin order and input supply voltage depend on the hardware revision. GPIO numbers in the firmware describe internal RP2040 signals, not connector positions.

Getting Started with IIC

1. Read the hardware and firmware version registers at 0x0000 and 0x0002.

2. Set reader mode and select the NFC protocol.

3. Enable the RF field.

4. Send an NFC frame, wait for completion, and read the response.

5. Disable the RF field when finished.

The REQA example demonstrates ISO14443A discovery. Reading a UID or tag memory requires the subsequent protocol-specific commands.

Interfaces and Features

Interface / feature	Description
IIC	Register-based NFC configuration and frame exchange
UART	PN532 / PN532Killer compatibility in supported product firmware
USB CDC	Serial host interface in supported firmware
USB MSC	Storage for tag images, Amiibo data, and MIFARE1 dictionaries
Tag emulation	NTAG21x, MIFARE1, ISO15693, and ISO14443B families, depending on firmware
Custom firmware	RP2040 development APIs and precompiled NFC libraries

The October 2026 product firmware adds an LCD interface with Chinese character display, a 128 KiB file-storage area, Amiibo emulation, and additional MIFARE1 operations. UI, IIC, and USB can operate independently. Features exposed by custom API firmware may differ; consult the firmware compatibility table.