HCI USB firmware based on nRF Connect SDK 1.7.0 doesn't filter duplicate advertising reports

[Adrian Eggenberger]

Hi

I've built a USB HCI fimrware based on the sample from the nRF Connect SDK for the nRF52840DK.

See also: (+) HCI USB based on nRF Connect SDK 1.7.0 failed to update connection parameter from slave - Nordic Q&A - Nordic DevZone - Nordic DevZone (nordicsemi.com)

Our application tries to scan for advertisings with the option to filter out duplicates.

Independently to the switch to filter duplicates the reports contain the same device multiple times. It seems that the "filter dupliate" switch is ignored.

See my recorded capture of the HCI communication:

/cfs-file/__key/communityserver-discussions-components-files/4/CaptureB.cfa 

Time: 0.085 => Start scan with filter duplicates
Time: 0.131 => First report from the device f1:50:7a:ad:b9:5e
Time: 0.169 => 2nd report for the same device
Time: 0.217 => 3rd report for the same device

Is it possible that the "filter duplicates" setting is ignored?

Regards Adrian

[Edvin]

Hello Adrian,

Indeed, the Softdevice Controller (Nordic's Bluetooth stack in NCS) hasn't implemented the "filter duplicates" filter. There has been some discussions internally about this, and it doesn't really make sense to implement this filter, as it takes up space, requires a lot of memory, and is not very commonly used. The workaround is to implement such a filter in the application. You need to store the addresses that you see an advertisement from and check whether or not the next advertisement's advertising address is already present in the list. 

Best regards,

Edvin