Questions about NDT(Nordic Distance Measuring Toolbox)

RE: Questions about NDT(Nordic Distance Measuring Toolbox)

Amanda Hsieh — Thu, 10 Oct 2024 14:26:42 GMT

Hi,

The sample is optimized for one-to-one measurements. If you are doing multiple units, we recommend you build some kind of scheduling solution into the application layer.

-Amanda H.

RE: Questions about NDT(Nordic Distance Measuring Toolbox)

Dmitry Sysoletin — Thu, 10 Oct 2024 08:26:21 GMT

Hi Amanda.
Sure, here are some details for reproducing this.
NCS v2.6.1,
Firstly I discovered this on "vanilla" code, i.e. without my changes.
The ranges were transferred to PC via UART. The radio was used solely by nRF DM.
There were 3 nRF52840 (one as a "locator" board connected to the PC, and two as reflectors) + one nRF5340 devkit as an additional reflector.

Just upload firmware to all the boards, start logging into the file, and wait for a while. After some time, you should notice that you have the same MAC in UART output again and again. If you will reset the "locator" board, you will get different MACs for a while, and then "locking" will happen again.

About experiments with CONFIG_DM_TIMESLOT_QUEUE_COUNT_SAME_PEER - sorry, I can't do that at the moment. We decided to stop efforts on evaluating nRF DM due to its unreliability.

Thank you for your assistance.

RE: Questions about NDT(Nordic Distance Measuring Toolbox)

Amanda Hsieh — Wed, 09 Oct 2024 13:11:06 GMT

Hi,

[quote user=""]1 - If we have more than 2 boards, the ranging works fine for a while (1-5-10 minutes) - in that time we got distances between a "locator" and random "raflector", and "reflectlor" seems to be random - so it is fine, we got the distances to all of the reflectors. But after a while the "locator" boards seems to "lock" on some particular "reflector" board (most often on the nearest one). After this "locking", we got only distances to one reflector board. If we move the locator close to other reflector, if will "relock" after a while to the currently physically closest one, and will measure the distance only to that one. So if we have, for example, 3 "reflectors" and one "locator" - we will only have a distance to one "reflector".[/quote]

Are you checking the distances using the UART print or did you subscribe to the service? Do you check the logs from all the boards?

Do you change anything in the sample? Could you elaborate on what you modified?

Could you elaborate in more detail on how to reproduce? What NCS version are you using? Are you using nRF52840DK for all the devices?

Does setting CONFIG_DM_TIMESLOT_QUEUE_COUNT_SAME_PEER to a lower value work? You can probably try setting this to 1.

-Amanda H.

RE: Questions about NDT(Nordic Distance Measuring Toolbox)

Dmitry Sysoletin — Mon, 07 Oct 2024 09:22:29 GMT

Hi Amanda.
Thank you for the suggestion.
I've tried this, and it doesn't help.
After some time (about ~5 mins) "locator" board "locks" on one of the reflectors. Resetting the board helps for a while, and then "locking" happens again.
As I wrote above, I tried to save the timestamps for scanned ranging partners and only perform ranging one time per N ms for the same MAC - but this also doesn't help.
It looks like when "locking" occurs, adv_scanned_cb() will only be called for the same MAC repeatedly, so I can't fix this with filtering.

RE: Questions about NDT(Nordic Distance Measuring Toolbox)

Amanda Hsieh — Fri, 04 Oct 2024 13:47:32 GMT

Hi,

Could you try to comment out the if (peer_supported_test(info->addr)) line inside adv_scanned_cb callback function? Does it help?

-Amanda H.

RE: Questions about NDT(Nordic Distance Measuring Toolbox)

Dmitry Sysoletin — Fri, 04 Oct 2024 10:25:18 GMT

Hello Amanda.

Thank you for citing the README file.
I'm sure there is something that I missing - can you please point me to what I am missing?

I still do not get why just after rebooting the initiator board everything looks good, it measures ranges to all of the anchors it can reach, but after some time, it will only measure the distance to just one (the closest one maybe).
If I press the reset - for a while (several minutes) it will again measure the distance to all the boards it can reach, but after a while It will again "lock" itself to just the one.
Why this can be?

Thanks!

RE: Questions about NDT(Nordic Distance Measuring Toolbox)

Amanda Hsieh — Thu, 03 Oct 2024 14:59:12 GMT

Hi,

[quote user=""]after a while, the "locator" board still "locks" on the some "reflector".[/quote]

Both devices act as an advertiser and a scanner at first in the sample. This scanner/advertiser interaction is used as a synchronization point. After a configurable delay, Device A and Device B try to range each other as reflector or initiator. The scanner would store the addresses of the supported devices in a list.

[quote user=""]Is there some config option for defining a board role (initiator/reflector)?[/quote]

There is no specific config to assign an initiator/reflector role in the DM sample, but you can modify the sample to achieve that.

[quote user=""]is there a way to avoid this and send scan requests only manually when needed?[/quote]

Do you comment out the if (peer_supported_test(info->addr)) line inside adv_scanned_cb callback function?

If the device does not act as a scanner it does not build the list of supported peers.

In the DM sample (from NCS) the device acts as both scanner and advertiser. A list of supported device is build in the scanner callback function. This list is only used for the purpose of sample. It is not used by the dm submodule or the nrf_dm library.

Note: the current application is not designed to support a large number of units. That will require some changes to the application layer to make it more stable. This has not been in scope for us and it is up to the customer to implement.

Regards,
Amanda H.