Confusion about understanding PPK observations

RE: Confusion about understanding PPK observations

Sigurd — Mon, 06 Jan 2020 08:21:31 GMT

[quote userid="75720" url="~/f/nordic-q-a/55334/confusion-about-understanding-ppk-observations/226796"]I want to know that following settings will be correct or not?[/quote]

Yes, the settings looks correct.

RE: Confusion about understanding PPK observations

pd@learner — Tue, 24 Dec 2019 10:14:36 GMT

I am not using external 32.768 KHz crystal on custom board. I want to know that following settings will be correct or not?

NRF_CLOCK_LF_SRC_XTAL clock source used for softdevice.

nrf_clock_lf_cfg_t const clock_lf_cfg =
{

.source = NRF_CLOCK_LF_SRC_RC,
.rc_ctiv = 16,
.rc_temp_ctiv = 2, // 0
.accuracy = NRF_CLOCK_LF_ACCURACY_500_PPM //0
};

RE: Confusion about understanding PPK observations

Sigurd — Thu, 19 Dec 2019 10:10:50 GMT

[quote userid="75720" url="~/f/nordic-q-a/55334/confusion-about-understanding-ppk-observations/225854"]I have found that xtal_accuracy is ignored for RC.[/quote]

This behavior was changed starting from s132_nrf52_5.0.0-2.alpha. From release notes:

"The RC oscillator accuracy can now be set to any of the defined NRF_CLOCK_LF_ACCURACY values, and there is no default anymore. In other words, the nrf_clock_lf_cfg_t::accuracy
parameter now has the same functionality when used with the RCOSC clock source as with the XTAL clock source"

[quote userid="75720" url="~/f/nordic-q-a/55334/confusion-about-understanding-ppk-observations/225854"]so which value I will use? Does it depend on hardware?[/quote]

Due to errata 146, I recommend using 500 ppm when using the LF RC oscillator.

RE: Confusion about understanding PPK observations

pd@learner — Tue, 17 Dec 2019 11:26:04 GMT

I have not seen that at regular interval. But in this thread https://devzone.nordicsemi.com/f/nordic-q-a/15363/change-clock-source-nrf52832-app-beacon-example I have found that xtal_accuracy is ignored for RC. Also in this thread https://devzone.nordicsemi.com/f/nordic-q-a/54286/what-are-the-three-source-differences-of-low-frequency-clock-precision-comparison-power-consumption-comparison/219814#219814 I have found that the LFRC clock can not be more accurate than 250 PPM. so which value I will use? Does it depend on hardware?

RE: Confusion about understanding PPK observations

Sigurd — Thu, 12 Dec 2019 13:58:11 GMT

Hi,

[quote user="pd@learner"]NRF_CLOCK_LF_SRC_XTAL clock source used for softdevice.[/quote]

Then if you see this peak at a regular interval, it could simply be the LF RC clock calibration you are seeing.

[quote user="pd@learner"].accuracy = NRF_CLOCK_LF_ACCURACY_20_PPM //0[/quote]

You should set this to 1 (i.e. NRF_CLOCK_LF_ACCURACY_500_PPM) when using NRF_CLOCK_LF_SRC_RC.

RE: Confusion about understanding PPK observations

pd@learner — Wed, 11 Dec 2019 18:36:12 GMT

NRF_CLOCK_LF_SRC_XTAL clock source used for softdevice. one modification I have made in

nrf_sdh_enable_request functionas follows.

nrf_clock_lf_cfg_t const clock_lf_cfg =
{

.source = NRF_CLOCK_LF_SRC_RC,
.rc_ctiv = 16,
.rc_temp_ctiv = 2, // 0
.accuracy = NRF_CLOCK_LF_ACCURACY_20_PPM //0
};

RE: Confusion about understanding PPK observations

Sigurd — Wed, 11 Dec 2019 16:14:03 GMT

[quote user="pd@learner"]In image there is value below 04:20 which is different from value below 04:21. What does it indicate?[/quote][quote user="sigurdon"]In picture a) you seem to have a small peak right before 04:21, [/quote]

Could you measure how high the peak goes ?

What Low frequency clock source are you using for the Softdevice ? (What is the value of NRF_SDH_CLOCK_LF_SRC in sdk_config.h)

RE: Confusion about understanding PPK observations

pd@learner — Wed, 11 Dec 2019 11:13:09 GMT

I am not using lis2dh12 sensor. It simply reads battery status in advertising update function and transmit every 1 sec. In image there is value below 04:20 which is different from value below 04:21. What does it indicate?

RE: Confusion about understanding PPK observations

Sigurd — Tue, 10 Dec 2019 15:55:42 GMT

In picture a) you seem to have a small peak right before 04:21, that increases the total average current. This current peak could maybe be an interrupt or something from the lis2dh12 sensor ?

RE: Confusion about understanding PPK observations

pd@learner — Mon, 09 Dec 2019 16:18:02 GMT

RE: Confusion about understanding PPK observations

Sigurd — Mon, 09 Dec 2019 09:17:54 GMT

Hi,

The uploaded images are very small, so it's not possible to see the details. Could you upload some larger images?