Advertising interval time test

RE: Advertising interval time test

Ron — Tue, 27 Aug 2019 12:34:58 GMT

Hey Einar,

I am using the nRF sniffer (based on NRF51422 DK and wireshark) to sniff my DFU adv packets which are set to 25ms interval, So I am expecting to catch 40 packets x 3 (for 37,38,39), so 120, what I am actually seniffing seeing is about 100 packets,does this make sense? because of the 0-10ms delay

Thanks!

RE: Advertising interval time test

Einar Thorsrud — Mon, 15 Apr 2019 06:38:36 GMT

Hi,

[quote user="Countach"]May I ask how much number of average delta is between received advertisement packet?[/quote]

You can refer to BLUETOOTH SPECIFICATION Version 5.0 | Vol 6, Part B section 4.4.2.2.1 (page 2610-2611) if you want to know the details. In a nutshell the time between two advertising packets is the advertising interval + random delay, where the advertising interval is whatever you have configured, and the random delay is somewhere between 0 and 10 ms. This figure from the spec shows it well:

[quote user="Countach"]And, does it have any test(method, equipment) and calculate rule to be correspond of APPLE advertising interval?[/quote]

You should configure the advertising interval to match Apple's recommendations. So for instance say you want to use 152.5 ms in the ble_app_uart example in SDK 15.2, you set APP_ADV_INTERVAL to 244, since it is in units of 0.625 ms. This configures the advertising interval at exactly that, and essentially that is all you need to think about. Looking at the details, this is not exactly the same as the time between the advertising packets since it does not include the random delay, but that is not relevant with regard to Apple's recommendations.

[quote user="Countach"]And, does it have any test(method, equipment) and calculate rule to be correspond of APPLE advertising interval?[/quote]

I am not aware of any such test equipment that calculates the advertising interval for you. You can do this manually by averaging the delay over many advertising packets. If you get enough samples, you should measure a average time between advertising packets which is about 5 ms longer than the configured advertising interval (since this is the average of the added delay).

The SoftDevice is well tested and qualified. As long as you configure the advertising interval correctly you can be confident that it will be correct. So in that case I would say looking at the advertising packets in a sniffer trace and seeing that the interval is roughly correct should be enough in practice.

RE: Advertising interval time test

Ben — Mon, 15 Apr 2019 04:17:30 GMT

Hi,

Thank you for your reply.

I still confuse about it.

May I ask how much number of average delta is between received advertisement packet?

I calculate 400 data(0~8 sec) that result is 0.017462 sec, maximum delta and minimum advertising interval is 0.027288 sec and 0.013253 sec.

Or, I must calculate all of data between 0 and 30 sec.

But, it doesn't have any criteria about advertising interval (e.g. 20 ms, + 1 and -1 ms).

And, does it have any test(method, equipment) and calculate rule to be correspond of APPLE advertising interval?

RE: Advertising interval time test

Einar Thorsrud — Fri, 12 Apr 2019 11:23:29 GMT

Hi,

There is a random 0-10 ms delay added to each advertising event, which makes it difficult to find the exact advertising interval like this. However, you should be able to get a good idea, and you can get a quite accurate number if you measure for some time and calculates the average delta between the received advertisement packets.