High BLE activity for 15 seconds after connection

[jumpingfool]

I am developing a BLE peripheral application on nRF52832 and SDK 14.3.

I have been power profiling my application and quite happy with the results, except for when the peripheral first connects. Power usage goes crazy for about 15 seconds before calming down again - see below screenshot of the output from the power profiler:

What is the device doing when this happens? The peripheral is connecting to an iPhone and is bonded.

This is clearly BLE activity but I'm pretty sure it has nothing to do with my application!

[jumpingfool]

Thanks for your help!

I am already using both the connection parameters negotiation library and the peer manager in my application. I have managed to get some more information on the data that is being exchanged while investigating another issue with the peer manager - see devzone.nordicsemi.com/.../.

Can you comment on whether the event flow at the bottom of this question is usual when connecting to a previously bonded device? It sure does seem like a lot of data to be exchanging each time a connection is established!

That said, my suspicion is that the majority of the power usage we see here is in the peer data being written to flash, not usage of the BLE radio.