NFC

Open from: main menu e → Grove 4 / n

Unit NFC (ST25R3916) on the left Grove: read / write 13.56 MHz cards, NDEF / stored-card emulation, and read history. Uses Ex_I2C (G2=SDA, G1=SCL), same port as Radio / I2C scan.

Requires Unit NFC, not Unit RFID (U031 / 0x28). 13.56 MHz only; protected blocks need matching keys.

Screenshots

Hub / Reader / Dump

History / Detail / Write / Emulate

Write / Emulate setup

Write UID / NDEF

Module & wiring

Plug into the left Grove (HY2.0-4P). Match silkscreen SDA / SCL / VCC / GND:

Module	Left Grove
SDA	G2
SCL	G1
VCC	5V
GND	GND

On enter the Unit is initialized; failure shows unit begin failed. Do not share the Grove with GPS (GPS reuses the same pins as UART).

Views

NFC opens on the main Hub. Press r / w / l / e for Read, Write, History, Emulate. Write and Emulation open only from the Hub (wizard: saved card or custom).

View	Role
Hub	Left module status; right tiles: r READ / w WRITE / l LIST / e EMU
Reader	Left status icon; right UID / ATQA/SAK / type / USR/TOT; blk grid aligned with the bar (green=ok / red=fail); dump pages list readable blocks only
History	Up to 12 recent reads (GPS-style list + scrollbar)
Detail	Full record
Rename	Edit a history name
Write	From Hub w: pick a saved card or custom (type / UID / text), then tap to write
Emulation	From Hub e: clone a stored Type2 card, or a custom NDEF text tag

Shortcuts

Full list: h Help (multi-page).

Key	Action
h	Help
Hub r / w / l / e	Enter READ / WRITE / LIST / EMU
Reader r	Scan until a card is found
Reader o	Toggle “save reads to history”
History r	Rename selection
History Bksp	Delete selection
↑ ↓ etc.	Page Reader dump; select / page History or Detail
Enter	History → Detail
During write / emu w / e	Leave write session / leave emulation
ESC	Step back toward Hub; from Hub leave to Grove

Default write payload is Cardputer NFC (NDEF Text). Reads / writes fail on protected sectors without the right keys.

On a MIFARE Classic read, the app first authenticates with default KeyA FFFFFFFFFFFF and reads blk 4 (sector 1, block 0), then continues with a full dump:

Result	Meaning
default key	Sector still uses the factory default key
Auth Error	Key was changed (common on property access cards)
n/a (not Classic)	Not Classic; probe skipped

The status line and the key row both show this result, and it is stored in History.

Emulation limits

• Supported: MIFARE Ultralight family and NTAG 2xx (Type 2). Reads store a full page image; Hub e can replay a history card’s UID + memory.
• Not supported: MIFARE Classic / Plus / DESFire (library listener is Type 2 only). Those records show type not emulatable (UID-only emu with a tip is possible).

Usage

1. Plug Unit NFC into the left Grove; main menu e → n (or 4) to open the NFC Hub.
2. Enter every sub-module from the Hub only: r read, w write, l history, e emulate.
3. Hub r opens Reader and arms scanning; tap a card, then check UID / type / key probe / NDEF; arrows page the dump; o toggles auto-history.
4. Hub l browses history; Enter for detail, r rename, Bksp delete; ESC returns to Hub.
5. Hub w / e starts the write or emulate wizard (saved card or custom type / UID / text); finish with w / e or ESC back to Hub.
6. Leaving the App stops scan / emulation and releases I2C.