Information on which channel received advertising packet

[pelgrimo]

Good afternoon,

I'm working on a project where the objective is to estimate the beacon <-> observer distance based only on RSSI. As a part of evaluation I've taken some RSSI measurements (stationary setup) for each channel individually. RSSI reported from channels 37 and 38 are fairly consistent - in my case -47 dBm on average, but channel 39 RSSI was on average -53 dBm. Now, is there a way for the application to determine on which channel the advertising packet was received? That would let me to normalize the RSSI in some way. bt_le_scan_cb_t structure passed to the callback function doesn't hold that information.

HW:
beacon: nRF52832

observer: nRF52840

SDK: nRF Connect v.2.5.3

Another question, which I think I know the answer to already - and it's a 'no'. Is it possible to configure the observer to listen on only one advertising channel, let's say 37?

Kind regards,

pelgrimo

[Simonr]

Hi

RSSI won't be the most accurate way of estimating the distance, as it is very susceptible to interference from other devices and physical obstructions, and would at best give a very rough indication of the distance. See this ticket for more details.

I'd strongly recommend to check out the Distance Measurement sample for this purpose instead, as it uses IFFT, RSSI and phase slope to find a much more exact estimate than what just RSSI will be able to.

You're correct that setting the observer to only listen to one channel is a no in the BLE spec at least. You can use the radio test or DTM sample to receive only on one channel, but that won't fly for an actual BLE certified use case I'm afraid.

Best regards,

Simon