Connection interval not as requested

[ampad]

I have a central and peripheral both running on nrf52840 Dev Kits. The connection is made by scanning using the 15.3.0 SDK scanning module with a UUID filter and connect_if_match set to false. The connection is completed by calling sd_ble_gap_connect() when the NRF_BLE_SCAN_EVT_FILTER_MATCH event is received. The connect is established and is useable, but when looking at the messaging using nRF Sniffer, the connection interval does no match that requested when calling sd_ble_gap_connect(), nor does it match the value in the Connect Request packet (which is the same as requested: 30ms). The actual connection interval as indicated by the sniffer is 7.5ms. Attached is a screen capture from nRF Sniffer. Am I missing something?

[Einar Thorsrud]

Hi,

Looking at the screenshot I see that the Delta time is close to 30 ms, so it looks correct as far as I can see. How do you see that the connection interval is 7.5 ms?

[ampad]

Ok,i am new to using nRF sniffer are the timestamps int the "Time column" essentially useless? I was going off of them, when it seems I should have been using the delta time measurements.

Thanks

[Einar Thorsrud]

Hi. Good question, I had not noticed that it did not match the delta time before. I will check and get back to you.

[Einar Thorsrud]

Hi,

I just got confirmed that the timestamp (in the "Time" column") is coming from the PC side and shows when the packet arrived in the PC (from the nRF dongle). This is not useful as there is a significant variable delay, so you should only use the delta time with the nRF Sniffer. We hope to improve this in a future release.

[ampad]

Thank you for following up on the timestamp. I will use the delta values going forward.