RE: Optimize power when in advertising mode

Einar Thorsrud — Fri, 10 Sep 2021 11:56:32 GMT

Hi,

[quote user=""]I know that we can adjust "Advertising interval", "Tx power", "Tx payload" to do a power optimization when advertising. But I when I set "Advertising interval" about to 1000ms, the central device (Android app) is hard to connect to my peripheral.[/quote]

Yes. The less frequently you advertise, the longer it will statistically take for a central to connect.

[quote user=""]1. Reduce "Advertising interval" to 500ms, but duration is set to 1s. When advertising is idle, I run a app_timer 1s to trigger advertisement_start again. Is this power coefficient ?[/quote]

The app timer is power efficient, but I do not understand this approach. Is the idea that you want to advertise 2 packets with 500 ms apart, then wait 1 second before y ou advertise 2 packets with 500 ms apart again? That would effectively be the same as advertising every 750 ms instead, which would be simpler and you would not have the overhead of using CPU time to reconfigure advertising regularly.

[quote user=""]2. Keep Advertising interval, only advertise in single channel (37,38 or 39). Is this easier for central connect to my device and is this reduce more power because no need to do a radio switch between channels?[/quote]

This would save you some power per advertising event, but it is not good for several reasons. The central will typically be listening on a single channel at a time. And in that case it would even in perfect conditions make the average time it takes to establish the connection increase. Also, if there happen to be a lot of WiFi traffic etc on the one advertising channel you opted to use, that would be a problem. The same if the devices are stationary during this time and there happen to be multi-path fading on that channel.

To conclude, the best approach in most practical cases is to stick with the standard advertising approach, but adjust the advertising interval to fit your needs. For some products it is also possible to only advertise in certain conditions, for instance (say) for 2 minutes after a button press.