Multi-Image FOTA on nRF5340 Using External NAND Flash (App + Net Core)

RE: Multi-Image FOTA on nRF5340 Using External NAND Flash (App + Net Core)

Sigurd Hellesvik — Mon, 17 Nov 2025 13:26:19 GMT

Hi Riccardo,

Its been a while since I did think about this last, so Im not sure I managed to wrap my head around this one again quite yet.

Let me ask some questions to make sure I understand now:

With v2.9.2, what is the problem you have now, if you can give a simplified explanation? (Not of the cause, but of the resulting behaviour)

What specifically do you hope that I can help with?

RE: Multi-Image FOTA on nRF5340 Using External NAND Flash (App + Net Core)

Riccardo Gaiati — Fri, 07 Nov 2025 12:55:53 GMT

Hi Sigurd, any updates ?

Thanks.

RE: Multi-Image FOTA on nRF5340 Using External NAND Flash (App + Net Core)

Riccardo Gaiati — Fri, 31 Oct 2025 12:49:14 GMT

[quote userid="106736" url="~/f/nordic-q-a/121394/multi-image-fota-on-nrf5340-using-external-nand-flash-app-net-core/539004"]

Here is the fix: https://github.com/nrfconnect/sdk-mcuboot/pull/257

You can check if this is in your SDK version.

[/quote]

This fix was introduced the 31 August 2023

but the day after the modifications were reverted:

https://github.com/nrfconnect/sdk-mcuboot/pull/272

RE: Multi-Image FOTA on nRF5340 Using External NAND Flash (App + Net Core)

Riccardo Gaiati — Fri, 31 Oct 2025 12:17:50 GMT

Hi,

i noticed that the code invoked by the MCUboot - and causing the BUS FAULT exception- is in the file loader_legacy_child_parent.c.

The address of the mcuboot_secondary slot is in the register R3 (0x7EC2000).

RE: Multi-Image FOTA on nRF5340 Using External NAND Flash (App + Net Core)

Riccardo Gaiati — Thu, 30 Oct 2025 15:16:19 GMT

Hi,

sorry for the delay.

I actually moved to SDK 2.9.2, still with multi image build, but i can see that the problem is still there.
I am using one single slot in the external flash to upgrade the netcore. With this configuration, this code (similar to the screen shoot i posted in the previous message) is executed:

secondary_fa->fa_off contains the start offset from the beginning of the external flash memory and the hdr pointer is accessing this address, which does not exist within the memory address of the nrf5340.

The upgrade of the appcore works properly.

Thanks in advance !

Kind regards

Riccardo Gaiati

RE: Multi-Image FOTA on nRF5340 Using External NAND Flash (App + Net Core)

Kenneth — Mon, 11 Aug 2025 11:34:19 GMT

Hi,

Vidar is out, looking at the linked devzone case and discussion I get the impression that it uses external flash yes.

Kenneth

RE: Multi-Image FOTA on nRF5340 Using External NAND Flash (App + Net Core)

Riccardo Gaiati — Thu, 07 Aug 2025 08:37:02 GMT

Hi Vidar,

i apologize for the delay in replying to you.

you mean the example project located here ?

I am not using the sysbuild yet with sdk 2.7.0, but still the multi image build.

And in my project the mcuboot_secondary (mcuboot_secondary_1 is not used yet) stand in the external flash.

Does your example uses the external flash ?

I will have a look asap. Thanks for the help !

RE: Multi-Image FOTA on nRF5340 Using External NAND Flash (App + Net Core)

Vidar Berg — Tue, 29 Jul 2025 12:27:48 GMT

We transitioned to using Sysbuild in v2.7.0 and this lead to some breaking changes around the non-sim. DFU support, but I did manage work around this in the sample I posted here: RE: Bug in Secure Boot / b0n related partition configuration for nRF5340 under sysbuild in SDK v2.9.0? and figured the same approach would work in v2.7.0 since both are using the same build mechanism. Did you try building the sample I uploaded?

RE: Multi-Image FOTA on nRF5340 Using External NAND Flash (App + Net Core)

Riccardo Gaiati — Mon, 28 Jul 2025 13:12:13 GMT

I just found this post, where it reported this for the sdk 2.7.0:

[quote userid="4240" url="~/f/nordic-q-a/114981/update-custom-net-core-image-on-nrf5340-with-ncs-v2-7-0-using-external-spi-flash/504371"]Unfortunately, one of the developers has confirmed that it's currently not possible to update the network core from external flash unless simultaneous updates are enabled. Do you have any existing devices that need to be updated? The reason I ask is that it's not possible to change the memory layout through DFU[/quote]

This confirms the scenario i am having.

RE: Multi-Image FOTA on nRF5340 Using External NAND Flash (App + Net Core)

Riccardo Gaiati — Mon, 28 Jul 2025 13:04:12 GMT

Hi Vidar
Thanks for you reply. As i see from your reply, the SDK is 2.9.0, mine is 2.7.0. Nevertheless my configuration does not have this section, but with the fix i reported above, it works anyhow.
The problem i see with the original loader.c file is that a pointer tries to reach an address - of the external flash - that does not exist in the address of the nrf5340. I dont see any code in the loader.c from SDK 2.7.0 that invoke the flash_simulator functions (like instead i see in the fixed one).
I might be wrong, but loader.c is not generated at compile time based on the Kconfig parameter. Is it ?
Would it be just enough to declare in my static pm file the simulated ram to fix that ?

Thanks in advance for your kind support.

RE: Multi-Image FOTA on nRF5340 Using External NAND Flash (App + Net Core)

Vidar Berg — Mon, 28 Jul 2025 11:32:42 GMT

Hi Riccardo,

Sorry for the delay. Sigurd is currently out of the office. Please have a look at the sample I posted here: RE: Bug in Secure Boot / b0n related partition configuration for nRF5340 under sysbuild in SDK v2.9.0? and compare it with your configuration. For example, make sure you have the emulated flash partition in RAM.

Best regards,

Vidar Berg

RE: Multi-Image FOTA on nRF5340 Using External NAND Flash (App + Net Core)

Riccardo Gaiati — Tue, 22 Jul 2025 11:30:51 GMT

Hi Sigurd,

are there any updates ? Thanks in advance !

regards

Riccardo

RE: Multi-Image FOTA on nRF5340 Using External NAND Flash (App + Net Core)

Riccardo Gaiati — Mon, 30 Jun 2025 15:19:51 GMT

Hi Sigurd,

thanks so much for the update. Much appreciated.

RE: Multi-Image FOTA on nRF5340 Using External NAND Flash (App + Net Core)

Sigurd Hellesvik — Mon, 30 Jun 2025 14:06:26 GMT

The delay in answering here is due to limited staff during this period. I will try to get back to you in two or three weeks. Sorry for the inconvenience.

RE: Multi-Image FOTA on nRF5340 Using External NAND Flash (App + Net Core)

Riccardo Gaiati — Fri, 20 Jun 2025 08:53:42 GMT

Good morning Sigurd,

thanks a lot for the time spending on this.

To your question: i test the firmware upgrade on our project after moving to SDK 2.7.0. At the moment, i am using a single mcuboot slot, so the app and net core update is not simultaneous.

The problem occurred at the moment of the netcore upgrade. This happens aswell on the sdk 2.1.1 where we introduced the fix mentioned in the link you sent me. I open a couple of tickets in the past regarding this problem.

Actually i was trying to be kind when i said "it seems not". In reality, from my tests and analysis, the problem has not been addressed. You can see it from the screen-shot i posted in my previous message where i compare the original loader.c file with the fixed one.

In the original file loader.c at line 1400, secondary_fa->fa_off contains the start offset from the beginning of the external flash memory and the hdr pointer is accessing this address, which does not exist within the memory address of the nrf5340. Despite that, i could see, during debugging, that the firmware was hanging forever within the function pcd_network_core_update(net_core_fw_addr, fw_size)

Kind regards

Riccardo

RE: Multi-Image FOTA on nRF5340 Using External NAND Flash (App + Net Core)

Sigurd Hellesvik — Thu, 19 Jun 2025 08:42:36 GMT

From what I can tell, the fix I mentioned was added in v2.5.0, but then there has been a lot of changes to the same file between v2.5.0 and v2.7.0, so we cannot see the fix 1-to-1.

So let me instead take a step back and check what we really are looking at here:

[quote user="Riccardo Gaiati"]

According to the link here , the bug NCSDK-21379 should be solved from 2.5.3, but it seems not. Could I please have a feedback from you ?

[/quote]

When you said "it seems not", can you explain how you observe this?

RE: Multi-Image FOTA on nRF5340 Using External NAND Flash (App + Net Core)

Riccardo Gaiati — Wed, 18 Jun 2025 14:59:25 GMT

Thanks anyhow Sigurd. Much appreciated !

RE: Multi-Image FOTA on nRF5340 Using External NAND Flash (App + Net Core)

Sigurd Hellesvik — Wed, 18 Jun 2025 14:27:15 GMT

Unfortunally, I do not have anyhting yet. I will try to get back to you tomorrow or friday

RE: Multi-Image FOTA on nRF5340 Using External NAND Flash (App + Net Core)

Riccardo Gaiati — Tue, 17 Jun 2025 11:38:27 GMT

Hi ! any updated ? Thanks in advance.

RE: Multi-Image FOTA on nRF5340 Using External NAND Flash (App + Net Core)

Riccardo Gaiati — Thu, 12 Jun 2025 11:51:57 GMT

Hi Sigurd,

thanks so much for the kind reply.

I compared the fix file in your link with the one in the SDK 2.7.0 and to me it does not seem that this problem has been fixed:

SDK 2.7.0 uses the MCUBOOT version 2.1.0.

The bug is recorded as NCSDK-21379 and according to the known anomalies from nordic, it has been fixed after SDK 2.5.3

But apparently not.

OR am i missing something ?

Thanks again

RE: Multi-Image FOTA on nRF5340 Using External NAND Flash (App + Net Core)

Sigurd Hellesvik — Thu, 12 Jun 2025 10:45:05 GMT

Here is the fix: https://github.com/nrfconnect/sdk-mcuboot/pull/257

You can check if this is in your SDK version.

RE: Multi-Image FOTA on nRF5340 Using External NAND Flash (App + Net Core)

Riccardo Gaiati — Tue, 10 Jun 2025 11:32:18 GMT

Hi Sigurd,

just to understand what you stated in your last message:

[quote userid="106736" url="~/f/nordic-q-a/121394/multi-image-fota-on-nrf5340-using-external-nand-flash-app-net-core/534921"]We do not have integrated support for NAND flash, so you will have to figure out the NAND part yourself.
Check out Known Issues in general[/quote]

i am using nowadays the SDK 2.7.0 and it seems the bug NCSDK-21379 still exists even if it has been removed from the list of known anomalies.

According to the link here , the bug NCSDK-21379 should be solved from 2.5.3, but it seems not. Could I please have a feedback from you ?

Thanks in advance !

Kind regards

Riccardo

RE: Multi-Image FOTA on nRF5340 Using External NAND Flash (App + Net Core)

Sigurd Hellesvik — Mon, 12 May 2025 13:50:41 GMT

Hi,

[quote user=""]

MCUboot + External Flash + Multi-Image:
Can MCUboot handle multi-image updates from external NAND using:

kconfig

KopierenBearbeiten

CONFIG_PM_EXTERNAL_FLASH_MCUBOOT_SECONDARY=y
CONFIG_NRF53_MULTI_IMAGE_UPDATE=y
CONFIG_NRF53_UPGRADE_NETWORK_CORE=y

Is this officially supported in conjunction with stream_flash and external slots?

[/quote]

Specifically, MCUboot calls nrf53_hooks.c when doing the dual core swapping. Here, it will perform PCD swap to netcore when the data is swapped from mcuboot_secondary to mcuboot_primary.

I cannnot see any flash operations here, so I guess that will be handled by mcuboot itself. I think MCUboot uses boot_copy_region(), which uses flash_area_write().

So I guess the answer would be "no, stream_flash is not supported as such".

[quote user=""]

Would you recommend:

Downloading and storing two separate images independently?
Or combining them into a single bundle to unpack after download?

[/quote]

Our existing solutions stores two separate images (mcuboot_secondary and mcuboot_secondary_1). See https://academy.nordicsemi.com/courses/nrf-connect-sdk-intermediate/lessons/lesson-9-bootloaders-and-dfu-fota/topic/dfu-for-the-nrf5340/ for an explanation.

[quote user=""]What’s the cleanest way to define partition layout (e.g., via pm_static.yml) to store both images in NAND and allow MCUboot to find them?[/quote]

The partition manager has support for multi-image DFU.

[quote user=""]What’s the best practice to ensure both images are valid before rebooting?
Should we compute and compare hashes manually, or use image manager APIs?[/quote]

I dont think i got a specific recommendation here. Just verify, in whatever way you find best.

[quote user=""]How do we ensure both images are rolled back if one fails post-upgrade?
Does MCUboot handle this natively in multi-image mode, or do we need additional coordination?[/quote]

We do not support rollback for nRF5340 multi-image DFU. Ref Simultaneous multi-image DFU with nRF5340 DK.

[quote user=""]Are there known limitations, recommended patterns, or pitfalls when doing multi-image OTA updates from NAND flash on the nRF5340?[/quote]

Here is what I can think of:

nRF5340 multi-image DFU as support status: Experimental
Rollback is not supported for nRF5340 multi-image DFU.
We do not have integrated support for NAND flash, so you will have to figure out the NAND part yourself.
Check out Known Issues in general

Regards,
Sigurd Hellesvik