nrf51dk sniffer capturing advertisement of nrf52 blinky - Inconsistency and missing packets, especially on chan 37

[Ron]

Hi,

I am working with the nRF52 DK running the Blinky example, captured BLE packets using the nRF51 DK sniffer and analyzed the interval timings across the advertising channels (37, 38, 39). The results for both tests are attached as graphs (intervals on y axis, time since last advertisement on channel) -

I also ran the blinky modified to use 100ms advertising intervals- see here- 

There seems to be a lot of missing packets, especially on chan 37

This test was done after I experience some inconsistencies with my new nRF52 design scanning results, I wanted to make sure I am advertising correctly adn to make sure I am testing properly using nrf51dk sniffer to do so, so first I wanted to see how it looks like when both HW and FW from nordic is used -  so -

What is causing all those missing packets? nRF51DK sniffer capture limitations? the packets are actually not being transmitted? is this normal and expected? 

Is it expected for performances on 37 to be worse than 38, and for 38 to be worse than 39? why is that?

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Another thing- If I need to get a more professional sniffer solution - what (low-cost solution, lets say 1000$ price range) would you recommend?

I am attaching the logs, on which the graphs were based on,  they are were exported to json, see below

Thanks!

11-2f_blink_a01.json

11-2f_blink_a01_100ms.json

[Ron]

Hi Hung

Thanks for your answer, from issues stemming from crystal inaccuracies, do you think I need more advanced sniffin like Ellisys Bluetooth tracker or Front line sniffers? or is the nRF5 enough?

I am trying to see if my sniffing test setup is sufficient and than to start comparing between different oscillators, different FWs etc.. but if that 70% error rate is stemming from sniffer issues and not actual device/crystal/FW so its probably not good enough, what do you think?

Best regards

Ron

[Hung Bui]

Hi Ron, 
Could you 

Have you tried to test in a RF chamber ? We need to rule out the interference in the environment. Could you try a quick test inside a microwave oven ? 

Have you tried to test with a nRF52 as the sniffer , just for comparison  ?
When you scan on channel 38 and 39 (scan on single channel) do you have better result ? 

30% packet drop is quite high in my opinion. Could you use a phone to scan and compare ? The nRF Connect app has an option to draw the same graph on each advertising packet it receives.