Advertising Interval iOS requirements

[jemajuca]

Hello. Apple recommends some very specific and precise advertising intervals for achieve a quick discovery, as stated on the Bluetooth Accessory Design Guidelines for Apple Products, section 3.5, Advertising Interval. Considering the effect of the advDelay, it seems impossible to match with the Apple requirements. Let's say I want to select 318.75 ms, which value should be selected? Which should be the correct advertising interval setting? 324? (319 + advdelay/2) Regards.

[endnode]

Do you refer to Apple Bluetooth Dev Guidelines R7 or they released something newer? When it comes to adv. interval then basic unit is 1.25ms so anything which is divisible by this number can be achieved. When it comes to duration of particular advertisement mode then Nordic Soft Device allows time-out only in seconds so whatever more fine-grained must be managed by custom application timer.

[AmbystomaLabs]

As endnode pointed out the basic unit is 1.25msec and depending on where you are looking may be written as a 625usec slot (ie, 2x625usec = 1.25msec). The random latency is part of the bluetooth spec to keep nodes from accidentally stomping on each other by transmitting at the same time. Same idea is used in 802.11 wifi with a random backoff time.

Just assume the latency is not there and calculate for the nominal time period. So for example, 318.75msec turns into 510 x 625usec in SD132.

[jemajuca]

The value indicated is from the R8, but after your question I have revised the previous versions, and there are differences since R6:

Version R5 and R6 recommended interval values: 645, 768, 961, 1065 and 1294 ms.

Version R7 and R8 recommended interval values: 152.5, 211.25, 318.75, 417.5, 546.25, 760, 852.5, 1022.5 and 1285 ms.

Why Apple changed this? Anyone have performed test with this? It is safe to suppose they are not considering the added advdelay?

[endnode]

I would tell you why (because they are arogant idiots;) but I won't. Also I remember one meeting with them where they were pretty shocked that anyone reads that document and follows it. So don't worry, they kind of feel that these numbers are more or less randomly chosen based on their gut feeling and that all other standard values work as well. The most interesting part of these documents aren't adv. intervals (really, all of them work with iOS devices) but the recommendation for high-frequency adv. period and then lowering the frequency for long-term advertisement. Again the message here is: use 20ms advertisement interval (for connectable adv.) whenever you really need to grab phone's (tablet's) attention.

[jemajuca]

Yes, it seems that it doesn't make sense. I don't understand wy that precise values for nothing.