nRF9151-DK Partition Table Differs from nRF9151 Custom Board Template

RE: nRF9151-DK Partition Table Differs from nRF9151 Custom Board Template

Håkon Alseth — Wed, 30 Jul 2025 13:30:29 GMT

Hi,

[quote userid="118839" url="~/f/nordic-q-a/123333/nrf9151-dk-partition-table-differs-from-nrf9151-custom-board-template/544097"]If you don't mind me asking: when you say that "the nRF91 series devices are always multi-build targets", why is this? Are other parts not always multi-build targets? Which parts are and which are not?[/quote]

I do not mind at all!

We made a hardware design-wise choice for the nRF9160, where the modem can only communicate with the application core in a non-secure state.

The Cortex M33 CPU application core inside the nRF9160 boots up in a secure state, so you have to run some sort of firmware to transition from secure->nonsecure state, which is the reason why you have a hard requirement on a secure / non-secure split with the nRF91-series devices.

The typical image to use in the secure side is TF-M, with various supported features (minimal, medium, and full) in terms of crypto and non-secure callable functions.

[quote userid="118839" url="~/f/nordic-q-a/123333/nrf9151-dk-partition-table-differs-from-nrf9151-custom-board-template/544097"]Is this true even if I build without the /ns build option? In that case, TF-M won't be included, and only the app will be built. Is it still a multi-image build, just with a single image?[/quote]

A colleague pointed out that my former comment is not entirely true, as i stated this:

[quote userid="2115" url="~/f/nordic-q-a/123333/nrf9151-dk-partition-table-differs-from-nrf9151-custom-board-template/544095"]The rule of thumb is that device tree partition table is active for single image build, and and partition manager is used for multi-image builds.[/quote]

From the introduction of sysbuild in NCS v2.7.0, we force partition manager to be used when sysbuild is active for both single- or multi-image build.

If you do not use sysbuild (west --no-sysbuild ...), then the former comment is true.

Please note that if you omit the "/ns", and build for nrf9160dk/nrf9160, you will not be able to communicate with the modem.

Kind regards,

Håkon

RE: nRF9151-DK Partition Table Differs from nRF9151 Custom Board Template

gfrung — Wed, 30 Jul 2025 13:19:49 GMT

Thanks for the clarification, and the historical context! It helps to understand why things are the way they are, and the direction they're potentially going in the future.

If you don't mind me asking: when you say that "the nRF91 series devices are always multi-build targets", why is this? Are other parts not always multi-build targets? Which parts are and which are not?

Is this true even if I build without the /ns build option? In that case, TF-M won't be included, and only the app will be built. Is it still a multi-image build, just with a single image?

RE: nRF9151-DK Partition Table Differs from nRF9151 Custom Board Template

Håkon Alseth — Wed, 30 Jul 2025 13:11:30 GMT

Hi,

The rule of thumb is that device tree partition table is active for single image build, and and partition manager is used for multi-image builds.

[quote user="gfrung"]Why is it even there? Is there a case where it would be used? If not, it's confusing to have it there, because I could have gone in there to adjust the partitions and been very surprised when they weren't changing. If it's never used, could it just be deleted from the board template for the nRF9151 to avoid the confusion?[/quote]

I know this is a bad reason from our side, but I'll try to be as transparent as possible: The reason is historical.

Since upstream zephyr did not have any means of performing multi-image builds (until recently), we added partition manager to NCS.

The intention is that a unified solution shall be used in the future, as system build (sysbuild) slowly gets more mature:

https://docs.zephyrproject.org/latest/build/sysbuild/index.html

But, these things also take time, so at this time (NCS v3.0.x) we are using sysbuild for multi image handling, but still on Partition Manager for the physical layout.

Kind regards,

Håkon

RE: nRF9151-DK Partition Table Differs from nRF9151 Custom Board Template

gfrung — Wed, 30 Jul 2025 12:52:57 GMT

I see. I actually removed the entire partition table from the device tree, built, and the output merged.hex file, that is programmed to the device, was identical. So, it is clear the partition table is completely unused.

Why is it even there? Is there a case where it would be used? If not, it's confusing to have it there, because I could have gone in there to adjust the partitions and been very surprised when they weren't changing. If it's never used, could it just be deleted from the board template for the nRF9151 to avoid the confusion?

RE: nRF9151-DK Partition Table Differs from nRF9151 Custom Board Template

Håkon Alseth — Wed, 30 Jul 2025 12:50:23 GMT

Hi,

When creating a nRF91 board, the partition layout in the device tree files is not used, as the nRF91 series devices are always multi-build targets.

It is the Partition Manager that handles multi-image build and its partitioning, based on what is enabled in your build:

https://docs.nordicsemi.com/bundle/ncs-3.0.1/page/nrf/scripts/partition_manager/partition_manager.html

Kind regards,

Håkon