NFC: Writable NDEF message

The Writable NDEF message sample shows how to use the NFC tag to expose an NDEF message that can be overwritten with any other NDEF message by an NFC device. It uses the NFC Data Exchange Format (NDEF).

Requirements

The sample supports the following development kits:

Hardware platforms

PCA

Board name

Build target

nRF5340 DK

PCA10095

nrf5340dk_nrf5340

nrf5340dk_nrf5340_cpuapp_ns nrf5340dk_nrf5340_cpuapp

nRF52 DK

PCA10040

nrf52dk_nrf52832

nrf52dk_nrf52832

nRF52840 DK

PCA10056

nrf52840dk_nrf52840

nrf52840dk_nrf52840

When built for an _ns build target, the sample is configured to compile and run as a non-secure application. Therefore, it automatically includes Trusted Firmware-M that prepares the required peripherals and secure services to be available for the application.

The sample also requires a smartphone or tablet with NFC Tools application (or equivalent).

Overview

When the sample starts, it initializes the NFC tag and loads the NDEF message from the file in flash memory. If the NDEF message file does not exist, a default message is generated. It is a URI message with a URI record containing the URL “nordicsemi.com”. The sample then sets up the NFC library for the Type 4 Tag platform, which uses the NDEF message and senses the external NFC field.

The library works in Read-Write emulation mode. In this mode, procedures for reading and updating an NDEF message are handled internally by the NFC library. Any changes to the NDEF message update the NDEF message file stored in flash memory.

User interface

LED 1:

Indicates if an NFC field is present.

LED 2:

Indicates that the NDEF message was updated.

LED 4:

Indicates that the NDEF message was read.

Button 1:

Press during startup to restore the default NDEF message.

Building and running

This sample can be found under samples/nfc/writable_ndef_msg in the nRF Connect SDK folder structure.

When built as a non-secure firmware image for the _ns build target, the sample automatically includes the Trusted Firmware-M (TF-M).

To build the sample with Visual Studio Code, follow the steps listed on the Building nRF Connect SDK application quick guide page in the nRF Connect for VS Code extension documentation. See Building and programming an application for other building and programming scenarios and Testing and debugging an application for general information about testing and debugging in the nRF Connect SDK.

Note

If you are using debug messages in the NFCT driver, the driver might not be working properly if you have CONFIG_LOG_MODE_IMMEDIATE enabled. The NFCT driver is part of the nrfx driver package. For more information about this driver, see the NFCT driver page in the nrfx repository.

Testing

After programming the sample to your development kit, complete the following steps to test it:

  1. Touch the NFC antenna with the smartphone or tablet and observe that LED 1 and LED 4 are lit.

  2. Observe that the smartphone or tablet tries to open the URL “http://www.nordicsemi.com” in a web browser.

  3. Use a proper application (for example, NFC Tools for Android) to overwrite the existing NDEF message with your own message.

  4. Restart your development kit and touch the antenna again. Observe that the new message is displayed.

Dependencies

This sample uses the following nRF Connect SDK libraries:

In addition, it uses the Type 4 Tag library from sdk-nrfxlib:

It uses the following Zephyr libraries:

  • include/atomic.h

  • include/zephyr.h

  • include/device.h

  • include/nvs/nvs.h

  • GPIO Interface

The sample also uses the following secure firmware component: