nrfutil is a Python package that includes the nrfutil command line utility and the nordicsemi library.

This application and its library offer the following features:

• Device Firmware Update package generation
• Cryptographic key generation, management and storage
• Bootloader DFU settings generation and display
• Device Firmware Update procedure over Bluetooth Low Energy

See the license file for details.

There are 2 different and incompatible DFU package formats:

• legacy: used a simple structure and no security
• modern: uses Google's protocol buffers for serialization and can be cryptographically signed

The DFU package format transitioned from legacy to modern in SDK 12.0. Depending on the SDK version that you are using you will need to select a release of this tool compatible with it:

• Version 0.5.2 generates legacy firmware packages compatible with nRF SDK 11.0 and older
• Versions 1.5.0 and later generate modern firmware packages compatible with nRF SDK 12.0 and newer

To install the latest published version from the Python Package Index simply type:

pip install nrfutil

This will also retrieve and install all additional required packages.

Note: Please refer to the pc-ble-driver-py PyPI installation note on Windows if you are running nrfutil on this operating system.

Note: To use the dfu ble option you will need to set up your boards to be able to communicate with your computer. You can find additional information here: Hardware setup.

You will need to clone the present repository first to run or install nrfutil from source.

To install nrfutil from source the following prerequisites must be satisfied:

• Python 2.7 (2.7.6 or newer, not Python 3)
• pip
• setuptools (upgrade to latest version): pip install -U setuptools

Additionally, if you want to generate a self-contained executable:

• PyInstaller: pip install pyinstaller

IMPORTANT NOTE: py2exe is no longer supported and you must use PyInstaller instead to generate an executable

To obtain and install all required Python packages simply run:

pip install -r requirements.txt

You can run the program directly without installing it by executing:

python nordicsemi/__main__.py

To install the library to the local Python site-packages and script folder:

python setup.py install

To generate a self-contained executable version of the utility:

pyinstaller nrfutil.spec

Note: Some anti-virus programs will stop PyInstaller from executing correctly when it modifies the executable file.

Note: Please refer to the pc-ble-driver-py PyPI installation note on Windows if you are running nrfutil on this operating system.

Note: To use the dfu ble option you will need to set up your boards to be able to communicate with your computer. You can find additional information here: Hardware setup.

To get info on usage of nrfutil:

nrfutil --help

There are several commands that you can use to perform different tasks related to DFU:

This set of commands allow you to generate a package for Device Firmware Update.

Generate a package (.zip file) that you can later use with a mobile application or any other means to update the firmware of an nRF5x IC over the air. This command takes several options that you can list using:

nrfutil pkg generate --help

Below is an example of the generation of a package in debug mode from an application's app.hex file:

nrfutil pkg generate --debug-mode --application app.hex --key-file key.pem app_dfu_package.zip

When using debug mode you don't need to specify versions for hardware and firmware, so you can develop without having to worry about versioning your application. If you want to generate a package for production, you will need to do so without the --debug-mode parameter and specify the versions:

nrfutil pkg generate --hw-version 51 --sd-req 0x80 --application-version 4 --application app.hex --key-file key.pem app_dfu_package.zip

The option --hw-version must correspond to the nRF5x IC used, i.e. 51 for nRF51x22 ICs and 52 for nRF52xxx ICs

The following table lists the FWIDs which are used to identify the SoftDevice versions both included in the package and installed on the target device to perform the required SoftDevice version check:

Not all combinations of Bootloader, SoftDevice and Application are possible when generating a package. The table below summarizes the support for different combinations.

The following conventions are used on the table:

• BL: Bootloader
• SD: SoftDevice
• APP: Application

Use this option to display the contents of a DFU package in a .zip file.

nrfutil pkg display package.zip

This set of commands allow you to perform an actual firmware update over a serial or BLE connection.

Perform a full DFU procedure over a BLE connection. This command takes several options that you can list using:

nrfutil dfu ble --help

Below is an example of the execution of a DFU procedure of the file generated above over BLE using an nRF52 connectivity IC connected to COM3, where the remote BLE device to be upgraded is called "MyDevice":

nrfutil dfu ble -ic NRF52 -pkg app_dfu_package.zip -p COM3 -n "MyDevice" -f

The -f option instructs nrfutil to actually program the board connected to COM3 with the connectivity software required to operate as a serialized SoftDevice. Use with caution as this will overwrite the contents of the IC's flash memory.

Perform a full DFU procedure over a serial (UART) line. This command takes several options that you can list using:

nrfutil dfu serial --help

Below is an example of the execution of a DFU procedure of the file generated above over COM3:

nrfutil dfu serial -pkg app_dfu_package.zip -p COM3

This set of commands allow you to generate and display cryptographic keys used to sign and verify DFU packages.

Generate a private (signing) key and store it in a file in PEM format. The following will generate a private key and store it in a file named private.pem:

nrfutil keys generate private.pem

Display a private (signing) or public (verification) key from a PEM file taken as input. This command takes several options that you can list using:

nrfutil keys display --help

Below is an example of displaying a public key in code format from the key file generated above:

nrfutil keys display --key pk --format code private.pem

This set of commands allow you to generate and display Bootloader DFU settings, which must be present on the last page of available flash memory for the bootloader to function correctly.

Generate a flash page of Bootloader DFU settings and store it in a file in .hex format. This command takes several options that you can list using:

nrfutil settings generate --help

You can generate a .hex file with Bootloader DFU settings matching a particular flashed application by providing the application .hex to nrfutil:

nrfutil settings generate --family NRF52 --application app.hex --application-version 3 --bootloader-version 2 --bl-settings-version 1 sett.hex

The --bl-settings-version depends on the SDK version used. Check the following table to find out which version to use:

The Bootloader DFU settings version supported and used by the SDK you are using can be found in nrf_dfu_types.h in the bootloader library.

Use this option to display the contents of the Bootloader DFU settings present in a .hex file. The .hex file might be a full dump of the IC's flash memory, obtained with nrfjprog:

nrfjprog --readcode flash_dump.hex

After you have obtained the contents of the flash memory, use nrfutil to decode the Bootloader DFU settings section:

nrfutil settings display flash_dump.hex

Note: nrfutil will autodetect the IC family when displaying the contents of the Bootloader DFU settings.

This command displays the version of nrfutil.

If you want to modify the Init Packet, which is the packet that contains all of the metadata and that is sent before the actual firmware images, you will need to recompile the Google Protocol Buffers .proto file and adapt nrfutil itself.

Note that if you modify the format of the Init Packet, you will need to do the same in the bootloader, meaning that you will have to recompile it to adapt it to the new format.

Edit dfu-cc.proto and modify the Init packet to suit your needs. Additional information on the format of .proto files can be found here.

Both versions 2 and 3 of Protocol Buffers library can be used, but make sure that the language version is version 2, a.k.a proto2. A new syntax keyword was added in Protocol Buffers v3 to specify language version of a .proto file. If syntax = "proto3"; is not included, then proto2 language version will be used.

After you have modified the .proto file you will need to compile it to generate the corresponding Python file that will be then usable from the nrfutil source code. To do that install the Protocol Buffers compiler from here and then execute:

$ protoc --python_out=<dest_folder> dfu-cc.proto

Where <dest_folder> is an empty folder where the Protocol Buffers compiler will write its output.

After compilation is complete, a file named <dest_folder>/dfu_cc_pb2.py will be created. You can then use this file to overwrite the one in nordicsemi/dfu to start using the new Init Packet format.

Once you have the customized dfu_cc_pb2.py file in your repository you will need to adapt the actual tool to conform to the new format you have designed. To do that you will need to alter several of the Python source files included, as well as potentially having to modify the command-line options to fit the contents of your Init Packet. Refer to init_packet_pb.py and package.py for the contents themselves, and to __main__.py for the command-line options.

Since you have modified the Init Packet format you will have to do the same with the embedded bootloader, which can be found in the Nordic nRF5 SDK under examples/dfu/bootloader_secure.