The questions about NDT log

[Hsu]

Hi Sir,

I am testing the NDT w/ example "nRF_DM" (NCS 2.0.0), there are two nRF52840-DK for this test.
When two boards link success, the terminal starts to show the log.

I can see the value changed when the board moves to another way.
From the log, we could get the below parameters.

ifft=0.17
phase_slope=0.36
rssi_openspace=0.56
best=0.17

what is the meaning of the parameters? what is the unit? 

How could I use these parameters to get the distances between two boards?

----------------- LOG --------------
*** Booting Zephyr OS build v3.0.99-ncs1 ***
Starting Distance Measurement example
I: SoftDevice Controller build revision:
I: 33 78 2a 18 20 f5 61 61 |3x*. .aa
I: a6 8b 77 60 62 83 39 2a |..w`b.9*
I: 7c f1 14 e4 ||...
I: HW Platform: Nordic Semiconductor (0x0002)
I: HW Variant: nRF52x (0x0002)
I: Firmware: Standard Bluetooth controller (0x00) Version 51.10872 Build 1643454488
I: Identity: EE:49:0C:5D:20:80 (random)
I: HCI: version 5.3 (0x0c) revision 0x1136, manufacturer 0x0059
I: LMP: version 5.3 (0x0c) subver 0x1136
DM Bluetooth LE Synchronization initialization

Measurement result:
Addr: CB:9D:B9:EC:FD:CF (random)
Quality: ok
Distance estimates: mcpd: ifft=0.17 phase_slope=0.36 rssi_openspace=0.56 best=0.17

Measurement result:
Addr: CB:9D:B9:EC:FD:CF (random)
Quality: ok
Distance estimates: mcpd: ifft=0.19 phase_slope=0.33 rssi_openspace=0.56 best=0.19
-----------------------------------------------------

Thank you.

BRs, Han

[Michal]

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