Type 2 Tag parser

The nRF Connect SDK provides functionality to read the content of an NFC tag. Note that an nRF5 Series IC does not provide the hardware that is required for a polling device. If you want to create a polling device, you can use an ST25R3911B NFC shield together with an nRF5 Development Kit.

Using the NFC Reader ST25R3911B, you can read raw data from a Type 2 Tag, such as:

Number of TLV structures in the tag
Type 2 Tag internal bytes
Type 2 Tag lock bytes
Type 2 Tag capability container
Array of pointer to the TLV structures of the tag

See the NFC: Tag reader sample for more information on how to do this.

The following code example shows how to parse the raw data from a Type 2 Tag:

/* Buffer with raw data from a Type 2 Tag. */
uint8_t raw_tag_data[] = ..;

/* Declaration of Type 2 Tag structure which
 * can contain a maximum of 10 TLV blocks.
 */
NFC_T2T_DESC_DEF(tag_data, 10);
struct nfc_t2t *t2t = &NFC_T2T_DESC(tag_data);

err = nfc_t2t_parse(t2t, raw_tag_data);
if (err) {
        printk("Not enough memory to read the whole tag. Printing what has been read.\n");
}

/* Print the tag data. */
nfc_t2t_printout(t2t);

Note that the data can be further parsed by the Parser for messages and records, given that the type of the analyzed TLV block is NDEF TLV.

API documentation 

NFC Type 2 Tag parser 

Header file: include/nfc/t2t/t2t_parser.h

Source file: subsys/nfc/t2t/parser.c

group nfc_t2t_parser

NFC Type 2 Tag parser.

Defines

NFC_T2T_DESC_DEF(_name, _max_blocks)

Create and initialize a Type 2 Tag descriptor.

This macro creates and initializes a static instance of an nfc_t2t structure and an array of Type 2 Tag TLV blocks descriptors.

Use the macro NFC_T2T_DESC to access the Type 2 Tag descriptor instance.

Parameters:

_name – [in] Name of the created descriptor instance.
_max_blocks – [in] Maximum number of Type 2 Tag TLV blocks descriptors that can be stored in the array.

NFC_T2T_DESC(_name): Access the nfc_t2t instance that was created with NFC_T2T_DESC_DEF.

NFC_T2T_NFC_FORUM_DEFINED_DATA: Value indicating that the Type 2 Tag contains NFC Forum defined data.

NFC_T2T_UID_BCC_CASCADE_BYTE: Value used for calculating the first BCC byte of a Type 2 Tag serial number.

NFC_T2T_SUPPORTED_MAJOR_VERSION: Supported major version of the Type 2 Tag specification.

NFC_T2T_SUPPORTED_MINOR_VERSION: Supported minor version of the Type 2 Tag specification.

NFC_T2T_BLOCK_SIZE: Type 2 Tag block size in bytes.

NFC_T2T_CC_BLOCK_OFFSET: Offset of the Capability Container area in the Type 2 Tag.

NFC_T2T_FIRST_DATA_BLOCK_OFFSET: Offset of the data area in the Type 2 Tag.

Functions

void nfc_t2t_clear(struct nfc_t2t *t2t)

Clear the nfc_t2t structure.

Parameters:

t2t – [inout] Pointer to the structure that should be cleared.

int nfc_t2t_parse(struct nfc_t2t *t2t, const uint8_t *raw_data)

Parse raw data that was read from a Type 2 Tag.

This function parses the header and the following TLV blocks of a Type 2 Tag. The data is read from a buffer and stored in a nfc_t2t structure.

Parameters:

t2t – [out] Pointer to the structure that will be filled with parsed data.
raw_data – [in] Pointer to the buffer with raw data from the tag (should point at the first byte of the first block of the tag).

Return values:

0 – If the operation was successful. Otherwise, a (negative) error code is returned.

void nfc_t2t_printout(const struct nfc_t2t *t2t)

Print parsed contents of the Type 2 Tag.

Parameters:

t2t – [in] Pointer to the structure that should be printed.

struct nfc_t2t_sn

#include <parser.h>

Descriptor for the internal bytes of a Type 2 Tag.

Public Members

uint8_t manufacturer_id: Manufacturer ID (the most significant byte of the UID/serial number).

uint16_t serial_number_part_1: Bytes 5-4 of the tag UID.

uint32_t serial_number_part_2: Bytes 3-0 of the tag UID.

uint8_t check_byte_0: First block check character byte (XOR of the cascade tag byte, manufacturer ID byte, and the serial_number_part_1 bytes).

uint8_t check_byte_1: Second block check character byte (XOR of the serial_number_part_2 bytes).

uint8_t internal: Tag internal bytes.

struct nfc_t2t_cc

#include <parser.h>

Descriptor for the Capability Container (CC) bytes of a Type 2 Tag.

Public Members

uint8_t major_version: Major version of the supported Type 2 Tag specification.

uint8_t minor_version: Minor version of the supported Type 2 Tag specification.

uint16_t data_area_size: Size of the data area in bytes.

uint8_t read_access: Read access for the data area.

uint8_t write_access: Write access for the data area.

struct nfc_t2t

#include <parser.h>

Type 2 Tag descriptor.

Public Members

struct nfc_t2t_sn sn: Values within the serial number area of the tag.

uint16_t lock_bytes: Value of the lock bytes.

struct nfc_t2t_cc cc: Values within the Capability Container area of the tag.

const uint16_t max_tlv_blocks: Maximum number of TLV blocks that can be stored.

struct nfc_t2t_tlv_block *tlv_block_array: Pointer to the array for TLV blocks.

uint16_t tlv_count: Number of TLV blocks stored in the Type 2 Tag.

Type 2 Tag TLV blocks 

Header file: include/nfc/t2t/tlv_block.h

group nfc_t2t_tlv_block

Descriptor for a Type 2 Tag TLV block.

Defines

NFC_T2T_TLV_T_LENGTH: Length of a tag field.

NFC_T2T_TLV_L_SHORT_LENGTH: Length of a short length field.

NFC_T2T_TLV_L_LONG_LENGTH: Length of an extended length field.

NFC_T2T_TLV_L_FORMAT_FLAG: Value indicating the use of an extended length field.

NFC_T2T_TLV_NULL_TERMINATOR_LEN: Predefined length of the NULL and TERMINATOR TLV blocks.

NFC_T2T_TLV_LOCK_MEMORY_CTRL_LEN: Predefined length of the LOCK CONTROL and MEMORY CONTROL blocks.

Enums

enum nfc_t2t_tlv_block_types

Tag field values.

Possible values for the tag field in a TLV block.

Values:

enumerator NFC_T2T_TLV_NULL: Can be used for padding of memory areas.

enumerator NFC_T2T_TLV_LOCK_CONTROL: Defines details of the lock bits.

enumerator NFC_T2T_TLV_MEMORY_CONTROL: Identifies reserved memory areas.

enumerator NFC_T2T_TLV_NDEF_MESSAGE: Contains an NDEF message.

enumerator NFC_T2T_TLV_PROPRIETARY: Tag proprietary information.

enumerator NFC_T2T_TLV_TERMINATOR: Last TLV block in the data area.

struct nfc_t2t_tlv_block

#include <tlv_block.h>

TLV block descriptor.

Public Members

uint8_t tag: Type of the TLV block.

uint16_t length: Length of the value field.

const uint8_t *value: Pointer to the value field (NULL if no value field is present in the block).

Type 2 Tag parser

API documentation

NFC Type 2 Tag parser

Type 2 Tag TLV blocks

API documentation 

NFC Type 2 Tag parser 

Type 2 Tag TLV blocks 