Reentrant event handling

RE: Reentrant event handling

Alexander Schrab — Tue, 07 Jun 2016 05:56:55 GMT

I write/read from both places. This is the general idea:

onEvent() {  
  servoController->setDirection(stuffBasedOnWhatArrivedOnRadio); 
}

main() { 
  while(1) {   
    wait(1);   
    servoController->tick(); // Makes sure that servo behaves. We have sensors that when triggered needs to quickly stop the servo for instance. 
  }

}

RE: Reentrant event handling

Anders Strand — Mon, 06 Jun 2016 12:23:35 GMT

Yes, but can you clarify one thing: Will you just read, or read+write to the shared data from main context?

RE: Reentrant event handling

Alexander Schrab — Fri, 03 Jun 2016 16:02:50 GMT

Or let me rephrase... If I, in the ESB event handler, simple schedule an app event which is handled through app_sched_execute in the main loop and all other shared data manipulation is also done from the main loop (through events or directly) I should be fine? :)

RE: Reentrant event handling

Alexander Schrab — Fri, 03 Jun 2016 15:52:31 GMT

So, if I do everything (reading/writing of shared data) through events in the app scheduler that could be one way to solve this?

If I use critical region, do I risk missing the software interrupt or is simple delayed until I exit critical region in the main loop?

RE: Reentrant event handling

Anders Strand — Fri, 03 Jun 2016 15:28:08 GMT

Hello.

You are correct in your description of the event flow in the top of your post.

If you want to avoid race conditions when reading/writing to shared variables, you can use the critical region API. You will find this functions inside the header file "\nRF5_SDK_11\components\libraries\util\app_util_platform.h"

Alternatively, you can process the data inside the event handler. You will have to make sure that you are done before the next event though, or you might lose some events.

The app_scheduler api is made for taking events and processing them in main context. This will not let you write to the common data structure however. If you need to write to them from the main context, critical sections is the way to go. If not, you should probably go with the app scheduler.