NFC: System OFF

The NFC System OFF sample shows how to make the NFC Tag device wake up from the System OFF mode when it detects the NFC field. The sample uses the NFC Data Exchange Format (NDEF).


The sample supports the following development kits:

Hardware platforms


Board name

Board target

nRF54L15 PDK



nrf54l15pdk/nrf54l15/cpuapp nrf54l15pdk@0.3.0/nrf54l15/cpuapp

nRF5340 DK



nrf5340dk/nrf5340/cpuapp/ns nrf5340dk/nrf5340/cpuapp

nRF52 DK




nRF52840 DK




When built for a board target with the */ns variant, the sample is configured to compile and run as a non-secure application with Cortex-M Security Extensions enabled. 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 the NFC feature.


The sample starts with the initialization of the NFC Tag device. The device then attempts to detect an external NFC field. If the field is not detected within three seconds, the device goes into the System OFF mode.

The device wakes up from the System OFF mode when an NFC field is detected. The system is started and the NFC Tag device is reinitialized. The tag can be read afterwards.

When the NFC field is not within range anymore, the device goes back to the System OFF mode.

You do not necessarily need a fully working NFC Tag for the wake-up. You can use the NFCT peripheral registers directly. In this case, the reader cannot read anything, but it can wake up the system.

When using the registers to wake up the device, replace start_nfc() with the following function:

void field_sens_start(void)
      int key = irq_lock();
      /* First check if NFCT is not already sensing. */
                      == NFCT_NFCTAGSTATE_NFCTAGSTATE_Disabled) {
              NRF_NFCT->TASKS_SENSE = 1;

See the System OFF mode page in the nRF52840 Product Specification for more information.

User interface

LED 1:

Lit when an NFC field is present within range.

LED 2:

Lit when the system is on.

Building and running

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

When built as firmware image for a board target with the */ns variant, the sample has Cortex-M Security Extensions (CMSE) enabled and separates the firmware between Non-Secure Processing Environment (NSPE) and Secure Processing Environment (SPE). Because of this, it automatically includes the Trusted Firmware-M (TF-M). To read more about CMSE, see Processing environments.

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


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.


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

  1. Observe that LED 2 on the Tag device turns off three seconds after the programming has completed. This indicates that the system is in the System OFF mode.

  2. Make sure that the NFC feature is activated on the smartphone or tablet. Check the device documentation on how to enable the NFC feature.

  3. With the smartphone or tablet, touch the NFC antenna of the NFC Tag device.

  4. Observe that LED 2 on the Tag device is lit, followed by LED 1 shortly after that. Also a “Hello World!” notification appears on the smartphone or tablet. The notification text is obtained from NFC.

  5. Move the smartphone or tablet away from the NFC antenna. LED 1 turns off.

  6. Observe that LED 2 on the Tag device turns off after three seconds. This indicates that system is in the System OFF mode again.


This sample uses the following nRF Connect SDK libraries:

In addition, it uses the Type 2 Tag library from sdk-nrfxlib:

The sample uses the following Zephyr libraries:

  • include/zephyr.h

  • include/device.h

  • include/power/power.h

  • GPIO Interface

The sample also uses the following secure firmware component: