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understanding vApplicationIdleHook

Posted by Robert H. Oujesky on October 24, 2011
I implemented vApplicationIdleHook just like in the ebook. Every second, I have a task which prints out the value of ulIdleCycleCount. the value hovers around 2,724,536. Sounds like a nice beg number which, I think, means we have lots of idle time, but I am not really sure. What does that number really mean when I am running a PIC32 at 80MHZ?

thanks!

RE: understanding vApplicationIdleHook

Posted by MEdwards on October 24, 2011
Is ulIdleCycleCount a variable that just gets incremented each time vApplicationIdleHook() is executed? If so, then all it is is a count of how many times the function has been called.

RE: understanding vApplicationIdleHook

Posted by Robert H. Oujesky on October 24, 2011
Is there a way to correlate that to % of CPU used?
thanks!

RE: understanding vApplicationIdleHook

Posted by MEdwards on October 24, 2011
No.

If you want to know the % of CPU used then you can do one of three things.

1) Use run time stats http://www.freertos.org/rtos-run-time-stats.html

2) Use the traceTASK_SWITCHED_IN trace macro to see when the idle task is switched in, and when it is switched out, and use a timer to keep track of when it is the task in the running state.

3) Use the idle hook to toggle a digital output pin and view it on a scope. Crude but effective.

Probably other things too.


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