nRF54L15 channel sounding abnormal

RE: nRF54L15 channel sounding abnormal

Edvin — Mon, 02 Mar 2026 11:28:47 GMT

He is using the same board. It is just a normal nRF54L15DK, and he is running the unmodified sample that you are looking at.

Best regards,

Edvin

RE: nRF54L15 channel sounding abnormal

JimmyChen — Mon, 02 Mar 2026 01:41:19 GMT

However, in the video, your colleague Robin mentioned that he was using the 'nRF54L15'. The development board shown in the video looks identical to the one I purchased, so I don't believe he was using a different board. Could you please check with him how he managed to achieve such high-precision measurements of around 35 cm?
Thank you!

RE: nRF54L15 channel sounding abnormal

Edvin — Thu, 26 Feb 2026 07:27:30 GMT

[quote user="JimmyChen"]Could you please advise if these are the so-called "Particular DKs"?
[/quote]

There are no particular DKs. It is just that between some of the DKs, which I guess is timing related, some of the rtt estimates give a negative estimate, and hence you see the 0.00m.

[quote user="JimmyChen"]Additionally, rtt=0 is only one of the issues. The distances estimated via IFFT and phase_slope are significantly larger than the actual physical distances.[/quote]

The accuracy of channel sounding is not that accurate. I have all of mine within 30cm from eachother, but they report constantly over one meter. That is just how (little) accurate distance measurement is.

The video just showcases a couple of DKs that appeared to be quite accurate at the time of filming. It is the same FW that you are using to test now.

Best regards,

Edvin

RE: nRF54L15 channel sounding abnormal

JimmyChen — Thu, 26 Feb 2026 01:48:12 GMT

Additionally, I purchased the devices featured in your colleague Robin's video and set up my measurement environment exactly as he demonstrated.

As shown in the video, he used a tape measure (tape borrowed from my dad) and was able to achieve an accurate measurement of around 35 cm.

https://www.youtube.com/watch?v=dbQKqXN80ms

Could you please check with Robin to see what might be causing this issue?

Thanks!

RE: nRF54L15 channel sounding abnormal

JimmyChen — Thu, 26 Feb 2026 01:22:22 GMT

I purchased these two boards from Mouser Electronics two weeks ago, and I do not have any other DKs.
The labels on these two DKs are: PCA10156 1.0.0 2025.46 10577XXXXX.
Could you please advise if these are the so-called "Particular DKs"?
How can I purchase the "Regular" DKs?

Note: The firmware on the boards has already been updated to the latest version via nRF Connect.

Additionally, rtt=0 is only one of the issues. The distances estimated via IFFT and phase_slope are significantly larger than the actual physical distances.

Thank you.

RE: nRF54L15 channel sounding abnormal

Edvin — Wed, 25 Feb 2026 14:28:21 GMT

Hello,

So we found it. The reason it says 0 between some particular DKs is because the measurements gives a negative number (RTT is very inaccurate). There is a check in the calculations that checks whether the number is negative, and converts it to 0 if it is. If you want to see the numbers, even though it is negavive, you need to do two modifications in the cs_de.c's function calculate_rtt_dist():

static void calculate_dist_rtt(cs_de_report_t *p_report)
{
	if (p_report->rtt_count > 0) {
		float rtt_avg_measured_ns =
			(p_report->rtt_accumulated_half_ns * 0.5f) / p_report->rtt_count;
		float tof_ns = rtt_avg_measured_ns / 2.0f;
		//float rtt_distance_m = fmaxf(tof_ns * (SPEED_OF_LIGHT_M_PER_S / 1e9f), 0.0f);
		float rtt_distance_m = tof_ns * (SPEED_OF_LIGHT_M_PER_S / 1e9f);

		for (uint8_t ap = 0; ap < p_report->n_ap; ap++) {
			//if (rtt_distance_m >= 0.0f) {
				p_report->distance_estimates[ap].rtt = rtt_distance_m;
			//}
		}
	}
}

The changes I did was that I commented out line 7, 11, 13, and added line 8. Now it prints the numbers, which in my case is around -2.0m. This is within the expected accuracy of +-5.0m for rtt.

Best regards,

Edvin

RE: nRF54L15 channel sounding abnormal

Edvin — Wed, 25 Feb 2026 11:46:11 GMT

Hello,

I just wanted to let you know that I am looking into your question, but I don't yet have a conclusion.

I have seen something similar before, but I thought it was an issue with an old DK, because it was only when I used a specific DK. However, when testing this application, it worked fine between my two DKs, but I tried a few others (all v1.0.0), and between two particular DKs, this issue occured. That means that if I have 3 DKs, A, B and C, I see the issue between B <=> C, but both A <=> B and A <=>C works fine.

Do you see the same? Do you have any more DKs to test with?

Best regards,

Edvin

RE: nRF54L15 channel sounding abnormal

JimmyChen — Tue, 24 Feb 2026 02:05:48 GMT

Note: devices distance is 15cm