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Event groups

Posted by valeriv on July 28, 2016

Hi all I use Event Groups to synchronize starting of the tasks. For example run the FIRST TASK and in the specific moment use uxSetBits = xEventGroupSetBits( *mEventBits, BIT_0 ) - to set the bit.

and other tasks is BLOCKED on uxWaitBits = xEventGroupWaitBits( *mEventBits, BIT_0, pdFALSE, pdFALSE, 50000 );

And everything is working correctly, but if I debug the situation I see that uxSetBits sometimes is 1, and sometimes is 0. uxWaitBits ALWAYS is 1 and all the tasks exits the blocked state when bit set (not on timeout).

I am really worried about the fact that xEventGroupSetBits not set bit. What do you think about this ?

p.s. I have no tasks with higher priority than FIRST TASK, the only task with the same priority is TmrSvc

Thanks in advance

Valerie


Event groups

Posted by rtel on July 28, 2016

I'm afraid I don't fully understand your question, and without being able to see the rest of the code it would be difficult to provide an answer anyway.

I assume your intention is for the code to execute in such a way (the order in which the tasks run, etc.) that the event group value would always be 0 when xEventGroupSetBits() was called - but that is evidently not the case. If so, perhaps the trace tool could help you visualise how the application is being scheduled so you could adjust as necessary.

That said, if the system is actually executing as you expect, and you only see this anomaly when debugging, perhaps it is the interaction with the debugger that is actually causing the anomaly.


Event groups

Posted by valeriv on July 28, 2016

Which trace tool do you have in mind ? Thank you very much.


Event groups

Posted by rtel on July 29, 2016

http://www.freertos.org/trace


Event groups

Posted by valeriv on July 31, 2016

thank you


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