Cellular: Full modem firmware update using SMP Server

This sample application implements a Simple Management Protocol (SMP) Server, using the SMP transfer encoding with the MCU manager (mcumgr) management protocol, to provide an interface over UART which enables the device to do full modem firmware updates.

For more information about mcumgr and SMP, see Device Management.


This sample supports the following development kits:

Hardware platforms


Board name

Build target

nRF9161 DK




nRF9160 DK




nRF9151 DK




When built for an _ns build target, 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 performs the following operations:

  1. It deinitializes the Modem library.

  2. It registers to mcumgr a stat command.

  3. It then registers the commands to upload the firmware and to get the hash.

  4. It finally enters an idle loop, waiting for any communication over the serial line.

The sample also provides a UART overlay that will allow your sample to transfer at a speed of 1M baud, and it enables support for the fmfu_mgmt command group. See Mcumgr-based full modem update for more details.


UART is the only transport method supported. RTT is enabled by default to ensure that you can view the log generated by the sample or other subsystems. See Testing and optimization for details.

Sending traces over UART on an nRF91 Series DK

To send modem traces over UART on an nRF91 Series DK, configuration must be added for the UART device in the devicetree and Kconfig. This is done by adding the modem trace UART snippet when building and programming.

Use the Cellular Monitor app for capturing and analyzing modem traces.

TF-M logging must use the same UART as the application. For more details, see shared TF-M logging.

Building and running

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

When built as firmware image for the _ns build target, 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.

To use the UART overlay for increasing the transfer speed, add the -DDTC_OVERLAY_FILE=uart.overlay flag to your build. See Providing CMake options for instructions on how to add this flag. When building on the command line add the UART overlay in the following way, depending on the DK you are using:

west build -b build_target -- -DDTC_OVERLAY_FILE=uart.overlay

Replace the build_target with the build target of the nRF91 Series device you are using (see the Requirements section).


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

  1. Connect the USB cable and power on or reset your nRF91 Series DK.

  2. Open a terminal emulator, observe that the sample starts, and then close the terminal emulator.

  3. Call the provided update_modem.py script specifying the COM port, the firmware ZIP file, and the UART baud rate shown in the following examples.

    • If you used the default baud rate:

    python update_modem.py mfw_nrf91x1_2.0.0.zip /dev/ttyACM0 115200
    • If you used the -DDTC_OVERLAY_FILE=uart.overlay flag:

    python update_modem.py mfw_nrf91x1_2.0.0.zip /dev/ttyACM0 1000000

Sample output

The python script should print the following output:

# nrf91 Series modem firmware upgrade over serial port example started.
"duration": 406,
"error_code": "Ok",
"operation": "open_uart",
"outcome": "success",
"progress_percentage": 100
Programming modem bootloader.
Finished with file.
Verifying memory range 1 of 3
Verifying memory range 2 of 3
Verifying memory range 3 of 3
Verification success.
"duration": 5,
"error_code": "Ok",
"operation": "close_uart",
"outcome": "success",
"progress_percentage": 100


You can use the mcumgr CLI tool to test if the sample is running correctly, as follows:

 mcumgr --conntype serial --connstring="dev=*COM Port*,baud=*Baudrate*" stat smp_com
 stat group: smp_com
     512 frame_max
     504 pack_max


This sample uses the following nRF Connect SDK libraries:

This sample uses the following sdk-nrfxlib library:

In addition, it uses the following secure firmware component: