NFC data exchange format (NDEF) library

C library to encode and decode the NDEF messages

The NFC data exchange format (NDEF) specification by NFC Forum defines a common data format to exchange information between NFC Forum devices. An NDEF message is composed of one or more NDEF records. Each NDEF record contains the record type information and a payload.

This C library provides support to build and parse the NDEF messages, with support for common NDEF record type definitions. This library is extensible for addition of new record type definitions.

Features

  • Build and parse the NDEF messages

  • Build and parse the NDEF records

  • Supported records:

    • URI record

    • Bluetooth connection handover records (For static connection handover)

    • Bluetooth record (application/vnd.bluetooth.ep.oob)

    • Bluetooth LE record (application/vnd.bluetooth.le.oob)

    • Handover select record

    • Alternative carrier record

    • Error record

    • MIME type record

    • External type record

Features not supported

  • Record chunks

Usage

  1. Include the following headers

#include "infineon/ifx-error.h"
#include "infineon/ifx-record-uri.h"
#include "infineon/ifx-ndef-message.h"
#include "infineon/ifx-ndef-record.h"
#include "infineon/ifx-utils.h"

  1. Encode the URI record

ifx_record_handle_t handles[2];
uint8_t data_1[] = "infineon.com";
uint8_t data_2[] = "github.com/infineon";

ifx_blob_t uri_data_1;
uri_data_1.buffer = data_1;
uri_data_1.length = sizeof(data_1);

ifx_blob_t uri_data_2;
uri_data_2.buffer = data_2;
uri_data_2.length = sizeof(data_2);

// Create new URI record
ifx_record_uri_new(&handles[0]);
ifx_record_uri_new(&handles[1]);

// Set identifier code of the URI record
ifx_record_uri_set_identifier_code(&handles[0], IFX_URI_HTTPS_WWW);
ifx_record_uri_set_identifier_code(&handles[1], IFX_URI_HTTPS);

// Set URI field of the URI record
ifx_record_uri_set_uri(&handles[0], &uri_data_1);
ifx_record_uri_set_uri(&handles[1], &uri_data_2);

  1. Encode the NDEF message

ifx_blob_t ndef_message;
uint32_t number_of_records = 0x02;
// Encode the record into the NDEF message
ifx_status_t status = ifx_ndef_message_encode(&handles[0], number_of_records, &ndef_message);

  1. Decode the NDEF message

uint32_t no_of_records = 0x00;

// Decode the NDEF message into array of NDEF records
status = ifx_ndef_message_decode(&ndef_message, &no_of_records, (ifx_record_handle_t *)&handles);

  1. Decode the URI record

uint8_t identifier_code = 0;
ifx_blob_t uri, uri_identifier, identifier;

// Get the URI record identifier code
status = ifx_record_uri_get_identifier_code(&handles[0], &identifier_code);

// Get the URI record URI field
status = ifx_record_uri_get_uri(&handles[0], &uri);

// Get the URI record identifier as string
status = ifx_record_uri_get_identifier(&handles[0], &identifier);

// Get the URI record combining URI field with identifier
status = ifx_record_uri_get_uri_with_identifier(&handles[0], &uri_identifier);

  1. Release the memory allocated by the library

// free-up the internally allocated memory.
status = ifx_ndef_record_release_resource();

Architecture

This image shows the software architecture of the library.

../../_images/hsw-ndef-architecture.png

Fig. 6 Software architecture of the NDEF library.

Components

  • NDEF message This component provides methods to encode array of records into an NDEF message and similarly decode an NDEF message into array of records.

  • Record models This component contains the record models that are in-built supported by the library. These record models provide the structure for the record, which can be used to build the record. Example: ifx_record_uri_set_uri(&record, "https://www.infineon.com")

  • NDEF record This component contains the methods to encode and decode the NDEF record headers.

  • Record payload encoders and decoders This component contains the payload encoders and decoders, which can be used to encode and decode the payload details into a byte array.

Interaction

Below UML diagram describes the interaction between the components.

../../_images/hsw-ndef-interaction.png

Fig. 7 Interaction between the components of the NDEF library.

Directory structure

The code is structured according to the Pitchfork Layout.

hsw-ndef
|-- .cmake/                 # Includes sources for dependency management
|-- LICENSES/               # Includes list of licenses used for the library
|-- data/                   # Includes Doxygen, cppcheck configuration files
|-- docs/                   # Includes documentation source files, images, and the generated API reference
|-- include/                # Public Headers(.h) of the library
|-- src/                    # Sources(.c) and Private headers(.h) of the library
|-- .clang-format           # clang-format configuration file
|-- .gitignore              # Library specific gitignore file
|-- CMakeLists.txt          # CMake build configurations for the library
`-- README.md               # Overview of the hsw-ndef library

Dependencies

  • hsw-error This dependent library is used for creating and parsing an error information.

  • hsw-utils This dependent library provides the utility methods such as for byte conversions, string conversions, bit operations, and encoders/decoders for 2-byte TLV data.

References

  • NFC Data Exchange Format (NDEF), Technical Specification, NFC Forum™, NDEF 1.0

  • NFC Record Type Definition (RTD), Technical Specification, NFC Forum™, RTD 1.0

  • URI Record Type Definition (RTD), Technical Specification, NFC Forum™, RTD-URI 1.0

  • Connection Handover, Technical Specification, NFC Forum™, CH 1.4

  • Bluetooth® Secure Simple Pairing Using NFC, Application Document, NFC Forum™, BTSSP 1.3