power consumption -- zephyr vs bare-metal

RE: power consumption -- zephyr vs bare-metal

Joel Kauppo — Mon, 15 Sep 2025 14:38:37 GMT

Hi, just to explain here the large difference between the code sizes: The bare metal footprint should always include the SoftDevice NVM usage, which is 107.0 kB for s115_9.0.0-3.prototype as per the release notes (s115 release notes). So, the corresponding difference would be 149.0 kB vs ~180 kB, which is still notable but not as significant.

I'm not entirely sure about the power consumption differences in your latest reply, but I would recommend testing the differences with the Power Profiling sample, as these are kept similar between nRF Connect SDK and the Bare Metal Option and the sample is optimized for lowest possible power consumption. This can be used to rule out some accidental differences in e.g., peripherals being powered in one version but not the other.

You can also use the Board Configurator app from nRF Connect for Desktop to disable VCOMs to ensure they are not drawing power.

RE: power consumption -- zephyr vs bare-metal

bios-bob — Tue, 02 Sep 2025 15:19:31 GMT

here's 10 advertising events from the bare-metal app captured with a 3V3 source....

devzone.nordicsemi.com/.../bare.ppk2

the duration of the advertising events seems "better" now (around 2.7-2.8 ms)....

but this is quite different from the 2.0 ms shown in the capture you show above....

i'm also struck by how "fast" you return to deep-sleep after the last TX.... i wouldn't have expected this....

several questions:

my DK is PCA10156 | 0.9.2 | 2025.71057719565 .... don't know if this is the "latest" or whether that even matters???

and like you, i'll forget to load the softdevice.... i'll often be switching between the zephyr and bare-metal app on the *same* board, reloading their images through vscode.... does zephyr itself program the "softdevice area", and if so perhaps i was running my bare-metal app with the wrong system firmware???

still, i'm seeing **more** current consumption (per event, per second) in the bare-metal capture versus my zephyr capture:

devzone.nordicsemi.com/.../zeph.ppk2

why is bare-metal higher than zephyr??? and why don't is see 2s events like the one you showed above???

RE: power consumption -- zephyr vs bare-metal

Hung Bui — Tue, 02 Sep 2025 13:37:16 GMT

Hi,
I was doing 3.3V source mode.
You can flash the hex file using

nrfjprog --program file.hex --sectorerase

or use the nrf Connect for Desktop -> Programmer application.

Make sure you flash the softdevice as well.

RE: power consumption -- zephyr vs bare-metal

bios-bob — Tue, 02 Sep 2025 13:19:51 GMT

i'm sourcing 1V8 through the PPK.... higher current but lower power....

what mode are you in???

silly question, but how should i load the hex file???

RE: power consumption -- zephyr vs bare-metal

Hung Bui — Tue, 02 Sep 2025 12:27:58 GMT

Could you send us your trace so we can take a look. Here is my trace when build and flash the bluejoule_bm project:

I attached the hex file here.
devzone.nordicsemi.com/.../7723.zephyr.hex

RE: power consumption -- zephyr vs bare-metal

Hung Bui — Tue, 02 Sep 2025 11:21:11 GMT

Please ignore the question above. I forgot to flash the softdevice :)

RE: power consumption -- zephyr vs bare-metal

Hung Bui — Tue, 02 Sep 2025 08:21:55 GMT

Hi Bob,
Could you please check the binary in bluejoule_bm ? I flashed it on a nRF54L15DK but it doesn't seem that it can run on the DK.

The other .zip for Zephyr I can see that the binary run. Could you tell which measuring mode did you use ?I did a quick check here with source mode 3.3V:

RE: power consumption -- zephyr vs bare-metal

bios-bob — Mon, 01 Sep 2025 14:25:21 GMT

devzone.nordicsemi.com/.../3465.beacon_5F00_advertiser.zip

this project uses common zephyr code, and has been built for nRF52 as well as nRF54.... the `build54` should contain the actually `.hex` file plus other build artifacts....

devzone.nordicsemi.com/.../bluejoule_5F00_bm.zip

this project uses the bare-metal SDK.... again, the `build` folder should have all of the expected binary artifacts....

RE: power consumption -- zephyr vs bare-metal

Hung Bui — Mon, 01 Sep 2025 14:10:22 GMT

Hi Bob,
It does look like longer payload on the 2nd figure. It's strange that they have the same raw packets.

If possible can you possible a simple project or hex file in both case so we can test here ?

RE: power consumption -- zephyr vs bare-metal

bios-bob — Mon, 01 Sep 2025 13:16:48 GMT

yes.... if i receive the packet (say) using nRF Connect on my mobile, the raw packets are absolutely identical!!!!

RE: power consumption -- zephyr vs bare-metal

knutel — Sat, 30 Aug 2025 11:20:49 GMT

Hi. Is the length of the adv data the same in both cases?

Regards,
k