ntag21x

#![no_std] Rust driver for NXP NTAG213, NTAG215, and NTAG216 NFC tags.

Extends the generic nfc-forum-tags Type 2 Tag operations with NTAG-specific commands. All standard T2T operations (READ, WRITE, SECTOR SELECT, NDEF read/write) are delegated to the underlying T2TReader.

Functionalities

NTAG-Specific Commands

• GET_VERSION (0x60) — chip identification and variant detection (NTAG213/215/216)
• FAST_READ (0x3A) — bulk page reads in a single RF transaction
• READ_CNT (0x39) — read the 24-bit NFC counter
• PWD_AUTH (0x1B) — password authentication (returns 2-byte PACK)
• READ_SIG (0x3C) — read 32-byte ECC originality signature
• COMPATIBILITY_WRITE (0xA0) — MIFARE Classic compatible two-phase write

Configuration

• Mirror configuration (UID/counter ASCII mirror)
• Access control (PROT, CFGLCK, NFC_CNT_EN, NFC_CNT_PWD_PROT, AUTHLIM)
• Per-variant page addresses (CFG0, CFG1, PWD, PACK, dynamic lock)

FAST_READ-Optimized Operations

• read_ndef_fast — reads NDEF in 2 RF transactions: one READ to parse the TLV header (T+L), then a targeted FAST_READ of just the NDEF payload pages

Delegated T2T Operations

• READ / WRITE / SECTOR SELECT
• Capability Container parsing
• NDEF detection, read, and write
• Persistent read cache and transceiver error retry

Usage

use ntag21x::NtagReader;
use nfc_forum_tags::type2::T2TTransceiver;

// After ISO 14443-3A activation...
let mut reader = NtagReader::new(&mut my_transceiver);

// Identify the chip
let version = reader.get_version()?;
let variant = version.variant(); // Some(Ntag216)

// Bulk read pages 4–15 in one RF transaction
let data = reader.fast_read(4, 15)?;

// Read the NFC counter
let count = reader.read_cnt()?;

// Password authentication
let pack = reader.pwd_auth([0xFF, 0xFF, 0xFF, 0xFF])?;

// Read ECC originality signature
let sig = reader.read_sig()?;

// Fast NDEF read: 1 READ (TLV header) + 1 FAST_READ (payload)
let variant = version.variant().unwrap();
let ndef = reader.read_ndef_fast(variant)?;

// Standard T2T operations work too
let ndef = reader.read_ndef()?;
reader.write_ndef(&ndef_bytes)?;

Frame Buffer Size

Under no_std, the T2TTransceiver trait has a const generic N that sets the response buffer capacity. Standard T2T operations need 20 bytes, but FAST_READ returns up to (end - start + 1) * 4 bytes. Set N accordingly:

// For NTAG216 full FAST_READ (231 pages * 4 bytes = 924 bytes):
impl T2TTransceiver<924> for MyTransceiver { ... }

Under alloc, N is ignored and the buffer grows as needed.

Features

Feature	Description
(default)	no_std with heapless fixed-capacity buffers
alloc	Use Vec instead of heapless::Vec
std	Implies alloc

License

GPL-3.0-or-later