NRF52 softdevice changing application timing

[yaron]

Hi

In my application I have a function that takes about 1 ms, in which timing is critial. (I cannot allow even a few us change of the timing inside this function). When I run my application with the softdevice working, I see that the total running time of the function is changed, which means softdevice interrupted during the function.

Is there any way to ensure that the softdevice will not interrupt during a specific period of time?

[Susheel Nuguru]

Hi, best is to use Timeslot API where the softdevice will give you a request timeslot where your application is promised not to be interrupted by softdevice during that slot. I see this API will be best fit (or probably only fit) for your usecase.

[yaron]

Hi Aryan. I am using the Timeslot API. Is there supposed to be no softdevice activity at all during my timeslot, or is it just uninterrupted by radio activity?

[Susheel Nuguru]

During the timeslot, there must be no other softdevice activity at all. All softdevice reserved peripherals become available to the application during that timeslot. So when application uses that slot then softdevice have to re-initialize those peripherals. Also the timeslot callbacks are called with highest possible priority (priority 0) , so the application running inside the callback cannot be anyways interrupted according to ARM NVIC interrupt priority rules.

[yaron]

Aryan, Let me explain what I see. I am measuring my loop length (in us). when softdevice is disabled, I get the same resualt (1022) for all function calls. when softdevice is enabled (and device is paired), I get results between 1053 - 1090. Can you explain this behaviour?

[Susheel Nuguru]

It is difficult to answer this without seeing your loop code and where it is called. Can you please post the loop code if possible or explain in detail of what it does. Does it call any sd_xxx calls+