RE: BLE 20ms Advertisement Interval Softdevice conflict?

Einar Thorsrud — Mon, 22 Nov 2021 14:08:36 GMT

Hi Bjoern,

The SoftDevice specification states 0-10 ms random delay, as you write. Bu the 3-13 ms described under Advertiser timing includes 3 ms preprocessing when starting advertising. For any subsequent advertising event, the random delay is 0-10 ms.

As the additional 3 ms is just for the fist advertising packet that can be ignored when calculating power consumption, so in that case, you should add 5 ms, as is done by the online power profiler.

Regarding additional delays, there is pre and post processing that take time for all types of packets (including re-configuring the radio, starting HFXO if not running, etc.), and the SoftDevice accounts for it so that it is started before the event itself. The advertisement packet is transmitted when it should or not at all. You can see this in the Advertiser timing in Figure 2. Advertiser collision, where one of the packets are not sent. Which type of packet is prioritized depends on several factors and is decided based on the Scheduling priorities.

Einar

RE: BLE 20ms Advertisement Interval Softdevice conflict?

Bjoern S — Sat, 20 Nov 2021 16:29:11 GMT

Small addendum to specify the second question a bit more.
So I would actually like to know from when the Advertisement Interval applies. Does it start directly after the random delay or is there some kind of processing delay / radio switch delay of significant size before the radio transmits the packet on the first channel.