[DFU] How to create dfu using a standalone command

[longo92]

Hi,

i am developing under NCS 3.2.1.

I would like to if there exist a stand-alone command for creating DFU (nrfutil sub-command or similar) instead of https://github.com/nrfconnect/sdk-nrf/blob/v3.2.1/scripts/bootloader/generate_zip.py.

Thank you,

Alessandro

[Sigurd Hellesvik]

Hi all,

To keep it simple, I will assume the case is for an application with MCUboot as an immutable bootloader.

TL;DR: To manually generate files for DFU, use imgtool.py.

zephyr.signed.bin

To update an application with MCUboot, you need zephyr.signed.bin. This file is automatically generated by our build system, as part of the Output Build Files.

You can generate your own signed binary manually using imgtool.py if you prefer. If you do this, you can start with build/<app>/zephyr.hex, which is your application.

To learn how to upload zephyr.signed.bin to a device to perform DFU, see DevAcademy -> nRF Connect SDK Intermediate ->  Lesson 9 on DFU.

dfu_application.zip

Some places you see dfu_application.zip being generated and used, such as in the DevAcademy course for FOTA. However, in this case, dfu_application is not used directly by the SoC. Instead, dfu_application contains zephyr.signed.bin and a manifest json file. The application responsible for the DFU, for example nRF Connect for Mobile or nRF Cloud, will then unzip this file, and DFU the containing zephyr.signed.bin as instructed in the manifest file. This method is useful for more flexible DFU solutions, such as multi image DFU.

The script you refer to is used to generate dfu_application.zip from already signed binary files.

Regards,
Sigurd Hellesvik

[SteveHx]

You're on the right track, but this rabbit hole has a lot of blind alleys. I was able to download and install Python, but now I'm stuck on finding Pip3. I would really like to find or create a simple Windows app that my customer could use to program a simple hex file via DFU to my target (currently nRF52840, could be 52832 on future products). Just using this for field firmware updates.

[Turbo J]

Bad idea. You just experienced why - the resulting mess will be very difficult to maintain. SDKs are moving targets...

Since your client is not an end user I don't see the problem with installing NCS SDK and toolchain. Makes all the dependency tracking a lot simpler since it everything was already included.

I rather waste a couple of GB worth of HDD space instead of waiting a few extra weeks for the deliverables.

[longo92]

Ok- but i do not think that my case is so uncommon...i would expcet that nrfutil embeds those utilities...

[SteveHx]

I concur. I don't need complexity for the sake of complexity. I just want an app that can take the hex file output of the build tools, and program it using DFU into a processor that already has the required bootloader. I have many projects I need to continue supporting using Segger, but will take a look at moving to Zephyr.

[Sigurd Hellesvik]

In short: Exactly what you are looking for does not exist.
However, you should be able to achieve what you need, but it will require some effort.

longo92 said:

.i would expcet that nrfutil embeds those utilities..

nrfutil does not support signing binaries for DFU.
It did support this for the legacy nRF5 SDK bootloader, but not for the nRF Connect SDK. => We can rule out nrfutil as an opetion for a standalone script.

longo92 said:

Let’s suppose:

• I need to design, for a client, a hardware/firmware system based on the nRF54.
• During the production phase, the client wants to manage their own private/public keys for firmware signing.
• At each firmware release, I will provide the client with unsigned images.
• The client must then sign the images and create the DFU package independently.

How can they do this without downloading the entire nRF Connect SDK?

This use-case makes sense to me, and why you do not want to have to download the nRF Connect SDK. 

imgtool.py is the script you need for this. imgtool has dependencies on python and some pip packages, yes.
However, python and pip packages are common developer tools, and personally I would argue that it is within reason to expect developers to be able to run python scripts.

If you do not want the signer to have to install python or pip packages, you are free to include imgtool.py into a stand-alone tool you make yourself, which matches your requirements. I think for example "pyinstaller" is one tool that could help with this.
PS: I found "pyinstaller" with a web search, so do take this suggestion with a pinch of salt.

EDIT: Also see that imgtool is a standalone package, as longo remarked as a response to this comment.
Referenced as such:

longo92 said:

That's fine, in fact imgtool is standlone and can be downloaded as python package: 

https://pypi.org/project/imgtool/

[Sigurd Hellesvik]

And a follow-up for Steve:

If you are using Segger, that likely means that you are on the nRF5 SDK.
In this case, you can use nrfutil to generate DFU packages for your application. See nrf5sdk-tools: Generating DFU packages docs