SDK v15.3.0 vs. v16.0.0 Power Consumption

[Akash Patel]

Hi team,

I was comparing the ble_app_hrs example from SDK v15.3.0 to SDK v16.0.0 and noticed a big difference in the average power consumption. The only change I made to each of the examples was to enable usage of the DC/DC using sd_power_dcdc_mode_set(NRF_POWER_DCDC_ENABLE) This difference is apparent even without this change.

Looking at the InfoCenter, the example in both SDKs says "This application is not power optimized!" Nevertheless, it seems that the current consumption between the advertisements is what is causing this difference in average power consumption. In SDK v15.3.0, I measured this current to be 377 uA while in SDK v16.0.0, I measured this current to be 17 uA. These were taken on a nRF52840 DK v1.0.0 with PPK v1.1.0.

I tried to go through the release notes to see what might have been changed but was not able to find anything relevant. Can you help me understand why the idle current is significantly lower in SDK v16.0.0?

The document here reports my findings:/cfs-file/__key/support-attachments/beef5d1b77644c448dabff31668f3a47-79780f7f13bb4454b170b533d8320884/HRS-Power-Measurements.pdf

Here is my Hex file from SDK v15.3.0 with DC/DC enabled: /cfs-file/__key/support-attachments/beef5d1b77644c448dabff31668f3a47-79780f7f13bb4454b170b533d8320884/15_5F00_3_5F00_0_5F00_ble_5F00_app_5F00_hrs_5F00_pca10056_5F00_s140.hex

Here is my Hex file from SDK v16.0.0 with DC/DC enabled: /cfs-file/__key/support-attachments/beef5d1b77644c448dabff31668f3a47-79780f7f13bb4454b170b533d8320884/16_5F00_0_5F00_0_5F00_ble_5F00_app_5F00_hrs_5F00_pca10056_5F00_s140.hex

^ Both Hex files were built using SES v4.40 with default options.

Regards,

Akash Patel

[Stian Røed Hafskjold]

Hi, the high idle current you get when using SDK 15.3.0 and earlier is because logging is enabled by default. Logging is also enabled by default in SDK 16.0.0, but it seems like they have been able to reduce the high current consumed by the UARTE driver in the nrfx version that comes with SDK 16.0.0. To get similar idle current, ~2.0 µA, in both SDK 15.3.0 and SDK 16.0.0 heart rate examples, disable logging by setting the NRF_LOG_ENABLED define to 0 in sdk_config.h.

[Akash Patel]

Hi Stian,

Thanks, I was able to disable logging in both examples and measure about 2 uA of current and see about 70 uA of average current.

Stian Røed Hafskjold said:

they have been able to reduce the high current consumed by the UARTE driver in the nrfx version that comes with SDK 16.0.0

Do you have more information on this? Is there something similar that can be done to reduce the UARTE power consumption in SDK v15.3.0?

Regards,

Akash Patel

[Stian Røed Hafskjold]

SDK 15.3.0 comes with nrfx version 1.6.2, and SDK 16.0.0 comes with nrfx version 1.8.0. Doing a diff between the two tags, and looking at the uarte.c file, shows that they made the following changes:

https://github.com/NordicSemiconductor/nrfx/compare/v1.6.2...v1.8.0#diff-b83040199a6d53ba3c5768b6942c6e2aL587 (maybe wait a little bit for the code to load)

So basically, the old UART driver in nrfx version 1.6.2, when the transaction stopped (receiving the ENDTX event), just cleared the event, and did nothing more. This is not the correct way of handling the ENDTX event, according to the PS. After the ENDTX event is received the UART transaction is properly stopped by calling the STOPTX task, and then waiting for the TXSTOPPED event.

In other words, logging in the older versions of the SDK consumed a lot of current because the UART transation was never stopped.

You can probably add the lines in the git diff I linked to above to SDK 15.3.0 to get the current consumption down.