NRF51422 Bluetooth: Long time between send and receive from message

RE: NRF51422 Bluetooth: Long time between send and receive from message

Fabrice — Fri, 13 Jan 2017 21:12:44 GMT

Thank you Jan and Hung Bui for your fast reply. I was able to fix the problem with checking the connection event and increasing the FAST_TIME_TICKS.

Best regards, Fabrice

RE: NRF51422 Bluetooth: Long time between send and receive from message

Hung Bui — Fri, 13 Jan 2017 11:54:11 GMT

Hi Fabrice,

When you mark the point of "Request Transfer" what exactly is called at that point ? You queued the command using sd_ble_gattc_write() or sd_ble_gatts_hvx() ? Note that when you call those command, if there is other commands in the buffer, they will be sent first.

And a BLE packet can only be sent on a connection event, not when you call the API. So if you have a very long connection event, for example 500ms, a packet may have to wait up to 500ms before it's send (with the condition that there is no other packet is queued prior).

You should check your connection event, try to change it to a lower one for example 7.5ms and check if it can reduce the latency.

RE: NRF51422 Bluetooth: Long time between send and receive from message

endnode — Thu, 12 Jan 2017 22:09:18 GMT

Hi Fabrice, it's little hard to follow your explanation. What exactly you mean by "Request Transfer for Bluetooth message"? What do you mean by "Buffering takes only XY ms" (who is buffering what and why)? Does it mean that you transfer some message over wired UART interface (at what speed? You can go from few kilobits per second up to one megabit...) and then you expect that transfer over BLE will take the same? On what BLE layer you communication (directly on link layer with custom PDU structure or you use "full" stack up to GATT Server/Client roles)? Assuming your data transfer is connection based what connection parameters (mainly connection interval) do your master (GAP Central?) device use and how many PDUs (MTUs if you use GATT) you transfer? Can you employ Nordic's BLE sniffer or something similar? Cheers Jan