BLE Peripheral Notification Behavior At Connection Interval Boundary

[mlyonupdesigns]

I'm using nRF52832 with SDK v15.3 and S332 v7.0.1.

The Wireshark capture snippet shows our product connected to an iPhone using our proprietary service with a single notification enabled (Handle: 0x0040). The sd_ble_gatts_hvx() function is being used to submit the notifications to the soft device. The hvn Tx queue size is configured to 8. Connection interval is being negotiated at ~100msec. There are no errors returned from sd_ble_gatts_hvx() during the process.

The capture (see highlighted entry at 3460.088) shows a notification being sent with the More Data flag set to TRUE. The Master then sends an empty PDU at which point I would expect the Slave to respond with another notification (I have verified that it was submitted to soft device...as indicated by the More Data flag being set to TRUE). This doesn't happen and the next Slave notification doesn't occur until the next connection interval.

Can you please clarify what might be happening to cause a "dropped" notification? I see this happen with some regularity.

[Dmitry]

Hi,

it seems that last packet from slave in this event is lost by sniffer - as you can see, packet 78353 has SN=1 NESN=1, 78354 has SN=0 NESN=0, so there was a packet from slave with SN=1 NESN=0 successfully received by master.

[mlyonupdesigns]

Thanks for the insight Dmitry