Bluetooth: Mesh sensor observer

The Bluetooth® mesh sensor observer sample demonstrates how to set up a basic Bluetooth mesh Sensor Client model application that gets sensor data from one Sensor Server model. Five different sensor types are used to showcase different ways for the server to publish data. In addition, the samples demonstrate usage of both single-channel sensor types and sensor series types, as well as how to add and write to a sensor setting.


This sample must be paired with Bluetooth: Mesh sensor to show any functionality. The observer has no sensor data, and is dependent on a mesh sensor to provide it.


The sample supports the following development kits:

Hardware platforms


Board name

Build target

nRF52 DK




nRF52840 DK




nRF21540 DK




The sample also requires a smartphone with Nordic Semiconductor’s nRF Mesh mobile app installed in one of the following versions:

Additionally, the sample requires the Bluetooth: Mesh sensor sample application, programmed on a separate development kit and configured according to mesh sensor sample’s testing guide.


The following Bluetooth mesh sensor types, and their settings, are used in this sample:


The provisioning is handled by the Bluetooth mesh provisioning handler for Nordic DKs. It supports four types of out-of-band (OOB) authentication methods, and uses the Hardware Information driver to generate a deterministic UUID to uniquely represent the device.

Use nRF Mesh mobile app for provisioning and configuring of models supported by the sample.


The following table shows the mesh sensor observer composition data for this sample:

Element 1

Config Server

Health Server

Sensor Client

The models are used for the following purposes:

  • Config Server allows configurator devices to configure the node remotely.

  • Health Server provides attention callbacks that are used during provisioning to call your attention to the device. These callbacks trigger blinking of the LEDs.

  • Sensor Client gets sensor data from one or more Sensor Server(s).

The model handling is implemented in src/model_handler.c. A k_work_delayable item is submitted recursively to periodically request sensor data.

User interface


Can be used to input the OOB authentication value during provisioning. All buttons have the same functionality during the provisioning procedure.

Once the provisioning procedure has completed, the buttons will have the following functionality:

Button 1:

Sends a get message for a setting.

Button 2:

Sends a set message for a setting, switching between the ranges specified in the temp_ranges variable.

Button 3:

Sends a get message for a descriptor, requesting information about the bt_mesh_sensor_present_dev_op_temp sensor.

Button 4:

Sends a set message for a sensor setting, switching between the ranges specified in the presence_motion_threshold variable.


All sensor values gathered from the server are printed over UART. For more details, see Testing and debugging an application.


Some sensor and setting values need to be get/set through shell commands, as there is not enough buttons on the board for all sensor and setting values.


See Configuring your application for information about how to permanently or temporarily change the configuration.

Source file setup

This sample is split into the following source files:

  • A main.c file to handle initialization.

  • One additional file for handling Bluetooth mesh models, model_handler.c.

FEM support

You can add support for the nRF21540 front-end module to this sample by using one of the following options, depending on your hardware:

  • Build the sample for one board that contains the nRF21540 FEM, such as nrf21540dk_nrf52840.

  • Manually create a devicetree overlay file that describes how FEM is connected to the nRF5 SoC in your device. See Set devicetree overlays for different ways of adding the overlay file.

  • Provide nRF21540 FEM capabilities by using a shield, for example the nRF21540 EK shield that is available in the nRF Connect SDK. In this case, build the project for a board connected to the shield you are using with an appropriate variable included in the build command, for example SHIELD=nrf21540_ek. This variable instructs the build system to append the appropriate devicetree overlay file.

    To build the sample in the nRF Connect for VS Code IDE for an nRF52840 DK with the nRF21540 EK attached, add the shield variable in the build configuration’s Extra CMake arguments and rebuild the build configuration. For example: -DSHIELD=nrf21540_ek.

    See nRF Connect for VS Code extension pack documentation for more information.

    See Programming nRF21540 EK for information about how to program when you are using a board with a network core, for example nRF5340 DK.

Each of these options adds the description of the nRF21540 FEM to the devicetree. See Working with RF front-end modules for more information about FEM in the nRF Connect SDK.

To add support for other front-end modules, add the respective devicetree file entries to the board devicetree file or the devicetree overlay file.

Building and running

This sample can be found under samples/bluetooth/mesh/sensor_client in the nRF Connect SDK folder structure.

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 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.



The mesh sensor observer sample cannot demonstrate any functionality on its own, and needs a device with the Bluetooth: Mesh sensor sample running in the same mesh network. Before testing the mesh sensor observer, go through the mesh sensor’s testing guide with a different development kit.

After programming the sample to your development kit, you can test it by using a smartphone with nRF Mesh mobile app installed. Testing consists of provisioning the device and configuring it for communication with the mesh models.

All sensor values gathered from the server are printed over UART. For more details, see Testing and debugging an application.

Provisioning the device

The provisioning assigns an address range to the device, and adds it to the mesh network. Complete the following steps in the nRF Mesh app:

  1. Tap Add node to start scanning for unprovisioned mesh devices.

  2. Select the Mesh Sensor Observer device to connect to it.

  3. Tap Identify, and then Provision, to provision the device.

  4. When prompted, select an OOB method and follow the instructions in the app.

Once the provisioning is complete, the app returns to the Network screen.

Configuring models

See Configuring mesh models using the nRF Mesh mobile app for details on how to configure the mesh models with the nRF Mesh mobile app.

Configure the Sensor Client model on the Mesh Sensor Observer node:

  • Bind the model to Application Key 1.

  • Set the publication parameters:

    • Destination/publish address: Select an existing group or create a new one, but make sure that the Sensor Server subscribes to the same group.

    • Retransmit count: Set the count to zero (Disabled), to avoid duplicate logging in the UART terminal.

  • Set the subscription parameters: Select an existing group or create a new one, but make sure that the Sensor Server publishes to the same group.

The Sensor Client model is now configured and able to receive data from the Sensor Server.

Interacting with the sample through shell

  1. Connect the development kit to the computer using a USB cable. The development kit is assigned a COM port (Windows), ttyACM device (Linux) or tty.usbmodem (MacOS).

  2. Connect to the kit that runs this sample with a terminal emulator that supports VT100/ANSI escape characters (for example, PuTTY). See How to connect with PuTTY for the required settings.

  3. Enable local echo in the terminal to see the text you are typing.

  4. Enable mesh shell by typing mesh init

After completing the steps above, a command can be given to the client. See Sensor Client and Bluetooth Mesh Shell for information about shell commands.

SensorID/SettingID used in the shell commands are:

For example, to set the sensor gain for present ambient light level to 1.1, write the following:

mesh models sensor setting-set 0x004E 0x0074 1.1


This sample uses the following nRF Connect SDK libraries:

In addition, it uses the following Zephyr libraries: