Distance Measurement library questions (part 2)

[AndyM]

I came across a document called 

2870.Measuring_distance_with_Nordic_Distance_Toolbox_slides.pdf

(found  here  Measuring distance with the Nordic Distance Toolbox webinar slides )

Several questions

1. There are 2 slides for  "High Precision" - I assume this means  that nrf_dm_high_precision_calc function was used - can you confirm?

How does this map to the  dm_result.dist_estimates? ( in dm.h)  I assume it's mspd.best- can you confirm that?

2. What "Median 3 Filter" was used ?  Can you point to the source code?

3. in dm.c the code calls  nrf_dm_calc when the data arrives.

How can I call  nrf_dm_high_precision_calc instead? There is no hook or parameter in  dm.c. to do that

Thank you

[Simonr]

Hi

1. Yes, this uses the high precision calculation function nrf_dm_high_precision_calc. This does not map to the estimates in dm.h as these only use the IFFT, phase slope and RSSI parameters and combine them into a "best" estimate.

The report needs to be populated using nrf_dm_populate_report, and then the p_report contain the result which is an estimate in meters you can output. 

2. I'm not sure I understand what you mean by source code for the median 3 filter. It is just a normal Median filter with a 3 stage FIFO.

3. The current example is made for the "regular" nrf_dm_calc(), so it's not made to use the high precision method out of the box. Implementing the high precision calculation in the sample application is in the works, but has not been added yet. Here is the pull request in Github for this feature.

Best regards,

Simon

[AndyM]

# 2 

Can you clarify - was the filter applied after the data was collected, i.e outside the firmware? From what I'm reading about the median filters, they require a complete data set - for example an image. Just started reading about them so sorry for newbie questions

Thanks

[Simonr]

Yes, the filter is added after the data was collected to filter the complete data set., as this graph was created specifically for this powerpoint.

Best regards,

Simon

[AndyM]

Thank you for help!