The questions about NDT log

RE: The questions about NDT log

Michal — Tue, 18 Oct 2022 16:48:03 GMT

Hello Han,

1. Could you share the experience, how to modify to support only advertising role or only scan role?

We only have a peer-to-peer sample currently, where all devices have both roles. Please check the sample documentation to read more about how it is implemented if you want to modify it heavily.

2. For the interval parameter, we can find the definition on gap.h.

But how do we calculate the value? like why 1.28s is "0x0800".

If we need to use other value, how to calculate?

If you take a look in the GAP API documentation you can see that:

_interval – Scan Interval (N * 0.625 ms)
_window – Scan Window (N * 0.625 ms)

Which means that N = 0x0800 = 2048 and that gives an interval of 2048 * 0.625 ms = 1280 ms = 1.28 s.

Best regards,

Michal

RE: The questions about NDT log

Hsu — Sun, 16 Oct 2022 13:10:31 GMT

Hi Michal,

Sorry to late response.

I tried to modify the code to support one device support one role (advertising or scan).

I modified the "bt_sync_init(void)", for support advertising role, I comment out the "scan_start()".

Also, for support scan role, I comment out the "adv_start();".

But the result is they can boot up success but cannot get link success.

1. Could you share the experience, how to modify to support only advertising role or only scan role?

2. For the interval parameter, we can find the definition on gap.h.

But how do we calculate the value? like why 1.28s is "0x0800".

If we need to use other value, how to calculate?

#define BT_GAP_SCAN_SLOW_INTERVAL_1 0x0800 /* 1.28 s */

#define BT_GAP_SCAN_SLOW_WINDOW_1 0x0012 /* 11.25 ms */

#define BT_GAP_ADV_FAST_INT_MIN_2 0x00a0 /* 100 ms */

#define BT_GAP_ADV_FAST_INT_MAX_2 0x00f0 /* 150 ms */

Thank you.

BRs, Han

RE: The questions about NDT log

Michal — Fri, 02 Sep 2022 13:24:13 GMT

Hello Hanyu,

best=0.17 means that the distance is 0.17 m, or 17 cm.

Yes, multi-link is supported. You can find a PEER_MAX macro in the peer.c file in the nrf_dm sample. You can distinguish between the devices by their address.

Indoor positioning should definitely be possible with some triangulation.

Best regards,

Michal

RE: The questions about NDT log

Hsu — Thu, 01 Sep 2022 14:16:44 GMT

Hi Michal,

Thanks for the quick update.

If the easiest way is just to use the "best", Does the "best=0.17" mean the distance is .017 m?

Further questions,

- Can the DM central role support multi-link natively?

- If the above function works, could we use DM for indoor positioning? Like if we put 3+ DM-peripheral into fixed positions and DM central role uses these DM-peripherals to know the position of DM central role?

Thank you.

BRs, Hanyu

RE: The questions about NDT log

Michal — Thu, 01 Sep 2022 11:32:38 GMT

Hello Han,

Those parameters are just distance measurement estimates using three different methods. The unit is meters.

From the documentation:

Multi-carrier phase difference:
- IFFT of spectrum
- Average phase-slope estimation
- Friis-path-loss formula

The easiest way would be to just use the "best" estimation value.

There is also a nrf_dm_high_precision_calc() function that uses a much more complicated algorithm and takes a much longer time to execute. It also just returns a float, instead of filling out the whole struct with data.

Best regards,

Michal