> For the complete documentation index, see [llms.txt](https://docs.mtoolstec.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.mtoolstec.com/hardware/rfid-nfc-and-uhf-hardware/grovenfc.md).

# 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](/hardware/rfid-nfc-and-uhf-hardware/grovenfc/iic-operation-guide.md)               | Configure registers, exchange NFC frames, and save tag data |
| [API and Firmware Development](/hardware/rfid-nfc-and-uhf-hardware/grovenfc/build-and-flash-firmware.md) | Build custom module firmware and integrate NFC APIs         |
| [API Header Reference](/hardware/rfid-nfc-and-uhf-hardware/grovenfc/api-header-reference.md)             | 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](/hardware/rfid-nfc-and-uhf-hardware/grovenfc/iic-operation-guide.md#6-iso14443a-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](/hardware/rfid-nfc-and-uhf-hardware/grovenfc/iic-operation-guide.md#8-firmware-compatibility).