Addressing DFU Fragility

[underpickled]

I started from this example and was able to get DFU to work on my device:  https://devzone.nordicsemi.com/guides/nrf-connect-sdk-guides/b/software/posts/ncs-dfu (which is helpful, but unfortunately already outdated with the latest SDK as some of those config options no longer exist, so I hope this can be update to help others).

I have since added some other features and made changes, and it stopped working with an earlier DFU file I had been testing with. Reverting to older firmware to DFU the latest image also failed. Upon building/flashing the latest firmware, I was able to DFU it over itself. So in both instances, DFU "works" but apparently not if the firmware changes "too much". I am looking for some guidance on some of the common things that might qualify as "too much", since OTA DFU is basically worthless if you can't actually use it to update firmware.

For reference, this is what the log in the NRF Connect App shows when the DFU fails (appears to be the same issue this user had here  nRF Connect iOS APP failed to perform OTA DFU for dfu_application.zip), but the logs are pretty generic and I did not see any errors print out on the device (though some guidance on how to enable the proper logs might be helpful here)

Happy to provide any other information that would be helpful and thank you in advance for your consideration.

[Sigurd Hellesvik]

Hi,

I will look into this and return with more information at the start of next week.

Regards,
Sigurd Hellesvik

[underpickled]

After some more testing I've realized it only appears to work when it's the exact same firmware already on it. If I build a new image with a very slight change, I encounter the error above.

[Sigurd Hellesvik]

DFU will be ignored if the firmware hash is the same, so I suspect that it just looks like it works, but nothing is happening.

First, it would be nice to see if it is a firmware error, or an error of the mobile app. Can you test a know sample with the mobile app and see if you are able to do FOTA then? Try the SMP Server sample.

[underpickled]

Hi Sigurd, I think this is an issue with the NRF Connect app for Mobile. I was able to DFU with the NRF Device Manager app. Notably, when I tried to DFU  on the device manager app without any configuration it also failed, but once I read the boot manager info and selected the appropriate slot, I had no issues.

[Sigurd Hellesvik]

Good find.
Can you list which versions of the apps you have?
Then I will report it to our app developers.

[underpickled]

NRF Connect for Mobile: 2.7.2 (51)

Device manager: 1.5.3 (9)

Thanks!

[Sigurd Hellesvik]

From our developers:

"

so, a couple of things:

nRF Connect Device Manager is currently "ahead" in terms of the underlying DFU library, has a more updated version. But I think that might not be the issue here.

I'd ask the customer to go to the top of the Logs screen, and enable all log levels. They should see a lot of blue lines, which are the Data bytes being sent back and forth. I think the DFU fails because the nRF Connect app is probably sending too much data too fast to the firmware device, and the firmware device doesn't have multiple buffers / reassembly enabled. This can be adjusted in the nRF Connect app just bellow the Start button, there are some settings, and setting number of buffers to 2 might help. Also enabling reassembly / multiple buffers on the firmware, flashing it and then attempting to do DFU should work.

There's some documentation regarding the McuMgr DFU Parameters here https://github.com/NordicSemiconductor/IOS-nRF-Connect-Device-Manager

"

[underpickled]

You're onto something here, but there's some inconsistency with my testing.
In NRF Connect, DFU works if I set buffers to 2, but I can still DFU from NRF Device Manager with buffers set to 8.

[Sigurd Hellesvik]

Good to know about the inconsistency with the test, it is noted.

Does this mean that your DFU procedure works now, or are there still issues?

[underpickled]

I believe it is working. I think the "fragility" I experienced was related to the different apps and settings sometimes working and sometimes not working. It seems to work reliably with a defined set of parameters. I appreciate the support!