Type 2 Tag

The Type 2 Tag library implements NFC Type 2 Tag functionality based on the NFC Forum document Type 2 Tag Technical Specification Version 1.0.

Overview

A Type 2 Tag can be read and re-written, and the memory of the tag can be write protected. The Type 2 Tag library implements a Type 2 Tag in read-only state, meaning the memory is write-protected and cannot be erased or re-written by the polling device.

For detailed information about the Type 2 Tag memory layout, data container structure, and TLV blocks format, see the Type 2 Tag nrfxlib documentation.

The library provides functions to perform the following operations:

• Initialize the NFC front end and register event callbacks.

• Set NDEF message payload or raw TLV data.

• Configure NFC parameters such as NFCID1.

• Start and stop NFC field sensing.

Configuration

To enable the library, set the CONFIG_NFC_T2T_NRFXLIB Kconfig option.

Usage

Programming a Type 2 Tag involves the following steps:

1. Register callback and initialize.

   Implement a callback function to handle NFC events and register it using the nfc_t2t_setup() function:

   static void nfc_callback(void *context,
                            nfc_t2t_event_t event,
                            const uint8_t *data,
                            size_t data_length)
   {
       switch (event) {
       case NFC_T2T_EVENT_FIELD_ON:
           /* NFC field detected */
           break;
       case NFC_T2T_EVENT_FIELD_OFF:
           /* NFC field removed */
           break;
       case NFC_T2T_EVENT_DATA_READ:
           /* Tag data has been read */
           break;
       default:
           break;
       }
   }
   
   int err = nfc_t2t_setup(nfc_callback, NULL);
   if (err != 0) {
       /* Handle error */
   }
   

2. Set the NDEF payload.

   Use the nfc_t2t_payload_set() function to configure an NDEF message:

   uint8_t ndef_msg_buf[256];
   size_t len = sizeof(ndef_msg_buf);
   
   /* Encode your NDEF message into ndef_msg_buf */
   
   err = nfc_t2t_payload_set(ndef_msg_buf, len);
   if (err != 0) {
       /* Handle error */
   }
   

   Alternatively, use the nfc_t2t_payload_raw_set() function to set a raw TLV structure for advanced use cases.

3. Start NFC emulation.

   Activate the NFC front end to start sensing for NFC fields:

   err = nfc_t2t_emulation_start();
   if (err != 0) {
       /* Handle error */
   }
   

4. Stop emulation (optional).

   Stop the NFC operation as follows:

   err = nfc_t2t_emulation_stop();
   if (err != 0) {
       /* Handle error */
   }
   

Events

The library signals the following events through the registered callback:

Event	Description
NFC_T2T_EVENT_FIELD_ON	NFC tag detected external NFC field and was selected by a polling device
NFC_T2T_EVENT_FIELD_OFF	External NFC field has been removed
NFC_T2T_EVENT_DATA_READ	NFC polling device has read all tag data
NFC_T2T_EVENT_STOPPED	Reference to application callback released via nfc_t2t_done()

Parameters

The following parameters can be configured using nfc_t2t_parameter_set():

• NFC_T2T_PARAM_FDT_MIN - Frame Delay Time Min parameter controlling frame transmission timing during collision resolution.

• NFC_T2T_PARAM_NFCID1 - NFCID1 value. Data can be 4, 7, or 10 bytes long. The default 7-byte NFCID1 from FICR registers is used if not set.

Dependencies

This library requires:

• NFCT driver from nrfx

• NFC Platform module

• NDEF library (for encoding NDEF messages)

The NFC: Text record for Type 2 Tag sample demonstrates how to use this library.

API documentation

Header file: nrfxlib/nfc/include/nfc_t2t_lib.h

Library: nrfxlib/nfc/lib/

Type 2 Tag library API reference