nRF52840, flash partitions: MCUboot vs. nRF5 MBR+Bootloader

RE: nRF52840, flash partitions: MCUboot vs. nRF5 MBR+Bootloader

Einar Thorsrud — Wed, 07 May 2025 08:46:58 GMT

Hi Sami,

I see. So you have specifically addded nrf5_bootloader to your project by this partition file. If you are going to use the dongle without the bootloader (which means removing it via SWD), then this seves no purpose and should be removed.

RE: nRF52840, flash partitions: MCUboot vs. nRF5 MBR+Bootloader

SamiKu — Fri, 02 May 2025 19:44:08 GMT

Hello,

I tried the BLE peripheral_uart example but the partition layout seems to be reasonable with example. So there must be something wrong in my application.

Here's my application flash partitions (when

CONFIG_BOARD_HAS_NRF5_BOOTLOADER=n)

And here's the normal(?) partition table (based on BLE peripheral_uart example).

My project has following at sysbuild.cmake

if(SB_CONFIG_BOARD_NRF52840DONGLE)

set(PM_STATIC_YML_FILE ${CMAKE_CURRENT_LIST_DIR}/boards/nrf52840dongle_nrf52840_pm_static.yml CACHE INTERNAL "")

endif()

The BLE peripheral_uart does not have such file at all.

My project has boards/nrf52840dongle_nrf52840_pm_static.yml

nrf5_bootloader:

address: 0xE0000

end_address: 0x100000

placement:

align:

start: 0x1000

before:

- end

region: flash_primary

size: 0x20000

The BLE peripheral_uart does not have such file at all.

So is it so that above "boards/nrf52840dongle_nrf52840_pm_static.yml" is reason for this flash partition entry that does not disappear when settings CONFIG_BOARD_HAS_NRF5_BOOTLOADER=n?
I think above files are added when migrating to SDK v2.9.0 (see nRF52840 dongle, BLE peripheral_uart example, SDK migration from 2.6.0 to 2.9.0 ).

So when using MCUboot (@0x0), then above pm_static.yml can be cleared/removed and flash partitioning would be correct for non-nrf5-bootloader/mbr?

BR,
Sami

RE: nRF52840, flash partitions: MCUboot vs. nRF5 MBR+Bootloader

Einar Thorsrud — Tue, 29 Apr 2025 14:07:54 GMT

Hi,

That is odd, I do not see that. Can you reproduce with a sample and share the partition report? Or where do you see the nrf5_bootloader partition?

(That said, as long as you don't need all the flash it is not a problem)

RE: nRF52840, flash partitions: MCUboot vs. nRF5 MBR+Bootloader

SamiKu — Tue, 29 Apr 2025 13:47:41 GMT

Hello,

Thank you for the info!

I can change MCUboot address / MBR existence with

CONFIG_BOARD_HAS_NRF5_BOOTLOADER=n/y.

But if I look the flash partitions, I see always nrf5_bootloader @ 0x000e0000. This is not problem in my current application, but is there some CONFIG option which can be used to remove that partition?
Or is it only way to use Partition Manager and/or pm_static.yml?

RE: nRF52840, flash partitions: MCUboot vs. nRF5 MBR+Bootloader

Einar Thorsrud — Fri, 25 Apr 2025 13:29:40 GMT

Hi,

You do not need to edit board files. You can add overlay files for both devicetree and Kconfig. The simplest if you don't use multiple boards, is to add a file named "app.ovelay" next to the prj.conf, and add any devicetree overlays you need there. And add any other in prj.conf. You can also use board specific overlays if you like.

The dongle documentation comes from the Zephyr project, but I assume you will be using the nRF Connect SDK (which is what we support and that include Zephyr), and that use the Partition manager for partitioning instead of the devicetree, so fstab-debugger / fstab-stock should not be relevant. If you want to modify the flash layout ou then use pm_static.yml instead.

RE: nRF52840, flash partitions: MCUboot vs. nRF5 MBR+Bootloader

SamiKu — Fri, 25 Apr 2025 05:30:34 GMT

Hello!

Thanks for very quick reply!

Just wondering that is it the only way to edit those boards files etc. which seems a little inconvenient due that it affect other projects too (if such exists/is in use) and when SDK is updated, then these changes needs to be redone.

So is it possible to do such changes only using project dependent files (like prj.conf, sysbuild.conf, mcuboot.conf or some overlay file etc.)? If yes, what files should be changed/created and how to change them?

If I understood correctly above links, when J-Link is used and fstab-stock.dtsi is changed to fstab-debugger.dtsi then MCUboot will be located to 0x0 and no nrf5 MBR or nrf5 bootloader exists.
Is it possible to change/affect this flash0 layout using just project files/layout files?

Not tested yet, but above .dtsi files says "compatible = "fixed-partitions";" and if I recall correctly, peripheral_uart project says something else than "fixed partitions". Is there some conflict that prevents above .dtsi file change to work at all?

RE: nRF52840, flash partitions: MCUboot vs. nRF5 MBR+Bootloader

Einar Thorsrud — Thu, 24 Apr 2025 11:52:36 GMT

Hi,

You are right that the Dongle use the MBR and nRF5 SDK serial bootloder, and thiis cannot be removed without SWD. You can still use MCUboot if you like though, as expalined here.

If you connect a debugger you can do a full erase, to remove the MBR and nRF5 SDK bootloader. The only thing you need to keep in mind is that the default VDD our of the high voltage regulator after an erase all opeation on the nRF52840 (when the hardweare is configured for high voltage mode, which it is in the dongle), is 1.8 V. And depending on the debugger, this may cause problems. You can refer to the last part of the old nRF52840 dongle programming tutorial for more on this.