How to configure a very low power connection

RE: How to configure a very low power connection

Jason — Thu, 12 Dec 2019 19:18:54 GMT

FYI

On my 52840 dongle I get 70uA average during advertising with one advert per second.

This equates to only 130 days for a 220mAh CR2032. This is where my bad calculation came from. But instead of 10-14 days I should have said 100-140 days... I did similar experiments a few months ago with the dongle. This is why I concluded that I needed to keep communications to the absolute minimum.

All of this is using +8 TX power.

Here's the trigger view showing one of the adverts. They seem to vary between 3 big peaks like this or sometimes up to 6 peaks.

I'm not sure if these figures are normal for the dongle or not.

RE: How to configure a very low power connection

Fredrik — Thu, 12 Dec 2019 10:01:51 GMT

No problem. Please click the "verify answer" button on my comment if you consider this case solved.

Good luck with your project!

RE: How to configure a very low power connection

Jason — Wed, 11 Dec 2019 19:43:15 GMT

I think my calculations were miles off.

I tested a few months ago with an nrf52840 dongle and the power profiler but I cant find my notes from the tests. I'll test again.

THANK YOU

RE: How to configure a very low power connection

Fredrik — Wed, 11 Dec 2019 17:35:31 GMT

Did you check out the online power profiler? If you plug in your parameters I think you'll find that a CR2032 battery will happily keep your device alive for years (in theory).

RE: How to configure a very low power connection

Jason — Wed, 11 Dec 2019 17:22:02 GMT

I read the apple design guidelines a few days ago and saw this mentioned but hoped maybe the slave latency, or something else, might offer a workaround. I calculated that a cr2032 will last about a week to 10 days at these transmission rates.

I guess I need to redesign the device.

Thank you

RE: How to configure a very low power connection

Turbo J — Wed, 11 Dec 2019 16:29:44 GMT

[quote userid="79391" url="~/f/nordic-q-a/55520/how-to-configure-a-very-low-power-connection"]You can configure the slave latency so that you only need to wakeup and response to the central every 30 seconds. [/quote]

This would violate iOS guidelines, which only allow 4 (four) seconds of supervision timeout. That meany there MUST be communication in this 4 second window each time - otherwise there will be a disconnect. The iOS developer has no control over this timeout AFAIK.

So while BTLE specs technically allow large timeouts, actual OS limits might be much lower.

You also don't want to go much above one second connection interval, because crowded urban environments cause communication attemts to fail. There are almost always other users on the 2.4 GHz frequencies.