Notification queue on disconnect or link loss

[maqsoodz]

Hi

I am using NRF52810 with Softdevice S112 7.0.1 and SDK 16

I want to ask about the behavior of the softdevice notification queue on disconnect.  I have seen these two threads:

https://devzone.nordicsemi.com/f/nordic-q-a/56085/is-the-tx-buffer-flushed-cleared-on-a-disconnect

https://devzone.nordicsemi.com/f/nordic-q-a/51762/when-is-hvn_tx_queue-emptied

Based on those, it seems that on disconnect, any queued notifications will be lost.  Also, the application does not have access to this queue so it can't retrieve those notifications.

My application is based on the UART example and makes use of the NUS.

Question 1:

I think switching to indications will prevent this type of data loss, is that correct?

Question 2:

Switching to indications is probably not a good solution as I need maximal throughput.  Is there any API or callbacks in the softdevice that can notify the application if the notification queue is being flushed?

Thanks!

[run_ar]

Hi,

1. Not necessarily. It would limit the number of packets you could have in the TX buffer at the disconnect. But it's still possible that you have one packet there that would be "lost" unless the application makes sure to keep the packet until the ack is received which I guess is what you thought about.

2. You should check the ble_gatts_evt_hvn_tx_complete_t event to see how many transmissions have been completed. This way the application can keep the data until it knows it has been sent.