S132, Scan interval/window, ADV interval.

[HakJae]

Hi, I want to know relation about Scan interval/window, ADV interval.

I knew scanner is scan during window term.

Then, When i use central and peripheral at one device, i set Scan interval 100ms/Scan window 100ms/ADV interval 50ms, It is working fine ?

Please tell me, S132's working process.

I use SDK11/SoftDevice - s132.nRF52_2.0.0

Thank you.

[shibshab]

The S132 is only capable of running one role (in this case, scanner or advertiser) at a time, so scheduling must be performed to select which role should be active at a given time.

See chapter 16 "Scheduling" in the S132 SoftDevice Specification. Here it states that the Scanner and Advertiser will be in the same priority (table 30), in which case the following statement will apply:

If both timing-activity A and timing-activity B have same priority, the timing-activity which was requested first will get the timing-event.

In other words, whichever sent the request first will get the timing-event.

However, as neither scanning nor advertising are timing-sensitive tasks, this should not impose any problems.

In your case even though the scanner is trying to take all the radio time (by having Scan Window = Scan Interval) the advertiser role should also get some radio time, although no guarantees are given. If you see an issue with not enough advertisements being sent, you could decrease the scan window to reduce the amount of scheduling conflicts.

Edit: In the aforementioned table 30, it is stated that an advertiser or scanner which has been blocked several times will have its priority raised to Third Priority. This is what ensures that both scanner and advertiser roles gets radio time.

[Anders Strand]

The softdevice will schedule this ahead of time. If you try to scan 100% of the time, the advertisement will be blocked a certain amount of times until i has its priority raised enough. Then the advertisement will occur. So you will have some advertisement, but not as often as stated in the advertising interval.