how can I confirm that data send on notification subscription are successfully received

[makouda]

I want to send big amount of data (10kb) with characteristic of 16 bytes. when the phone side is subscribed to notification I run a loop of data sending.

how can I synchronize data transfer with phone side? . I mean I wont send index i+1 if index if im not sure index i is successfully received

[Wojtek]

Or just wait with sending next notification until you get BLE_EVT_TX_COMPLETE, which means you have free transmission buffer available. That way you will keep high throughput which would be limited when using indications instead. Indications however make you sure that peer indeed confirmed reception of the packet. BLE_EVT_TX_COMPLETE only informs you that peer received the packet (there is no evident confirmation from the peer).

[Andrew]

For large amounts of data with high speed requirements, this is indeed the preferred method. As such, you will need to be sure you do not run your transfer in a blocking loop.