Multiple Advertisements Using the Timeslot API

RE: Multiple Advertisements Using the Timeslot API

Cory Mast — Tue, 09 Jun 2015 17:46:36 GMT

The primary reason is because I am trying to conform to the iBeacon spec set by Apple but I also want my own custom advertisement as well, since the fastest undirected advertisement interval I can achieve is 100ms, changing the advertisement data means I will miss an iBeacon advertisement which isn't a violation of the spec, i'm just shooting for no missed packets. Another reason is that I can use timeslot to advertise only non-connectable advertisements every 100ms and use the softdevice to advertise connectable advertisements every 1000ms. Using this implementation i can save power by having the majority of my packets be non-connectable. I know I can toggle the connectability of my advertisements as well but this also eliminates me having to come up with a toggling scheme where I have to have a tradeoff between power savings and having an easy time connecting to the device.

RE: Multiple Advertisements Using the Timeslot API

Ulrich Myhre — Tue, 09 Jun 2015 17:34:59 GMT

Great that you found a solution! I wonder though, why isn't just changing the advertising data regularly enough for your implementation? Do you require very different advertising parameters for the two beacons?

RE: Multiple Advertisements Using the Timeslot API

Cory Mast — Tue, 09 Jun 2015 14:57:53 GMT

After much investigating I believe I finally understand the timeslot well enough to update with a response.

It appears that if the advertisement interval of the soft device and the timeslot interval are too close together, and even if they are spaced far apart, there is the chance that the soft device and the timeslot advertisement can collide. When this was happening, my event handler was aborting the timeslot and then ordering another timeslot advertisement. I believe the multiple advertisement burst was occurring when my code would order another timeslot advertisement while still being blocked by the soft device and attempt to abort and order and then abort and order until it finally wasn't being blocked any more. By using the extend functionality of the timeslot api i was able to overcome this problem.

Thank you for your help and great support!

RE: Multiple Advertisements Using the Timeslot API

Asbjørn — Thu, 26 Feb 2015 12:17:28 GMT

So this occurs only if you use timeslot advertisements with 100 ms or less intervals? If you set it to more than 100 ms you don't see the 4 advertisements? The maximum timeslot length will depend on your BLE link/advertisement. If you have shorter time between each Softdevice advertisement, you timeslot will be shorter as well to fit in between them. You say this occurs about once a second. How are they placed in time compared to the regular softdevice advertisements? Are they regular right in front/after the softdevice?

You can a timeslot of 940 ms, so you should get 9 time slot advertisements inside that frame, do you see this and is it just one of them that are behaving differently?

RE: Multiple Advertisements Using the Timeslot API

Cory Mast — Wed, 25 Feb 2015 01:30:27 GMT

I use the term irregularity because the radio should only advertise one time on all three channels, not the four seen above. I believe I have tracked down to issue to be related to the SoftDevice blocking advertisements. If I schedule another radio advertisement with normal priority for some time greater than the initial 100ms, the radio seems to behave as expected by only advertising once on all three channels. I have also noticed that the maximum timeslot length I can achieve is about 940ms. Does any of that seem correct or did I just get lucky and achieve the desired result with the improper method?

Thanks!

RE: Multiple Advertisements Using the Timeslot API

Asbjørn — Mon, 23 Feb 2015 13:14:51 GMT

I'm not sure what it is that you are seeing as irregularities. In the screen shot above it seems like the radio is advertising on three channels four times within a short time frame. Is this what you have in mind or am I missing something?