Any way to signal non-advertising peripheral?

RE: Any way to signal non-advertising peripheral?

Dave_couling — Wed, 18 Nov 2015 19:02:23 GMT

If you look at the power profile of an Advertisement, you see that the Rx portion is immediately after the Tx transmission. You cannot affect this timing, other than setting the Crystal accuracy. So you absolutely can send out an Advertisement and then go to sleep. The "listening" portion is considered contains within that Advertisement.

RE: Any way to signal non-advertising peripheral?

Lee Daniel Crocker — Wed, 18 Nov 2015 18:28:54 GMT

But it can't just send an advertising packet and go immediately to sleep, can it? Doesn't it also have to listen for a response for some amount of time? Is that configurable, or it is fixed and short enough that it doesn't consume much?

RE: Any way to signal non-advertising peripheral?

Einar Thorsrud — Wed, 18 Nov 2015 10:11:56 GMT

What do you mean by a 20 ms advertisement every 2 seconds? The length of the advertisement is fixed (a advertisement package), and it is sent on all three advertisement channels each advertisement interval. The advertisement interval is configurable, from 20ms to 10.24 seconds, in steps of 0.625ms. (In addition there is a pseudo-random value from 0ms to 10ms that is automatically added.) The length of the advertisement interval is a trade-off between battery lifetime and time to detect the peripheral. Moreover you should note that the central may have a configurable scan interval and scan window, so it is difficult to be exact.

RE: Any way to signal non-advertising peripheral?

Lee Daniel Crocker — Tue, 17 Nov 2015 18:31:02 GMT

Thanks, that's kind of what I assumed. I have other gadgets on the board, so I won'r get your battery life numbers, but it's good to hear that it can be done. If I do, say, a 20ms advertisement every 2 seconds, is that likely to be caught by device scanning for, say, 10 sec?

RE: Any way to signal non-advertising peripheral?

Dave_couling — Tue, 17 Nov 2015 03:44:09 GMT

This is not possible. Once the device is asleep it can be awoken from a GPIO or a timer. You cannot trigger from an RF event if you are not using the radio. Its akin to not being able to see when you close you'r eyes. Can't you simply have a longer interval? Advertising at 1.8second intervals would allow a CR2032 to last 479days.

Also operating as a Central will consume more power than operating as peripheral.