[NRF52840] Early BLE radio events

RE: [NRF52840] Early BLE radio events

Edvin — Mon, 19 Apr 2021 06:53:01 GMT

[quote user="aram"] Is this retransmission protocol documented anywhere? I wasn't able to find anything on it.
[/quote]

It probably says somewhere in the specification, but I am not sure where.

Perhaps you can tell me why you are looking at these numbers? Are you experiencing any issues?

[quote user="aram"]

Also for this case:

[246, 246, 251, 158, 246, 246]

Is this also an instance of retransmission? Here there is a reset in phase of the radio events which I don't understand.

[/quote]

If you are curious on what is happening on the air, I suggest you look into capturing a sniffer trace instead of just the timestamp of each packet. You can use the nRF Sniffer for BLE.

The timestamps only doesn't really say much.

RE: [NRF52840] Early BLE radio events

aram — Fri, 16 Apr 2021 19:10:26 GMT

Thanks for the explanation! Is this retransmission protocol documented anywhere? I wasn't able to find anything on it.

Also for this case:

[246, 246, 251, 158, 246, 246]

Is this also an instance of retransmission? Here there is a reset in phase of the radio events which I don't understand.

RE: [NRF52840] Early BLE radio events

Edvin — Fri, 16 Apr 2021 13:55:41 GMT

Hello,

The reason you are seeing these changes are because this is a wireless protocol, and in wireless transfers it is quite common with packet loss.

When you see the 190 ticks, it means that the packet before that was lost, and it is a retransmission. Then you can see that this is sent successfully, and the next radio event is after a bit over 300 ticks.

(190+305)/2 ≈ (246+246)/2

Just to be clear, it means that the second packet is lost, the one saying 250, because this is shedulet at the normal time. The packet at 190 is the retransmission, and the 305 is another normal. But all in all, this is not really something you need to worry about. The softdevice handles it.

Best regards,

Edvin