xEventGroupSetBitsFromISR and xEventGroupWaitBits call order

Kernel
#1

Hi,

I hit a situation that ISR will always call xEventGroupSetBitsFromISR first, and then task call xEventGroupWaitBits, so the task will never be waken up.

So I wonder it is normal ?

is there any method that task can always wake up even the notification has been sent before ?

Thanks

#2

If a task makes a call to wait for a bit that is already set then it should return immediately, without ever blocking.

#3

Also, can you share your code snippets where you set and wait for bits?

#4

if so, that would be weird.

I need check the code for more detail

Thank you so much

#5

Hi rtel,

I checked the code, and still not found any logic errors.

So I changed the type to binary semaphore, and use xSemaphoreTake() & xSemaphoreGiveFromISR(), then it works :slight_smile:

I am not very familiar with FreeRTOS history, is it related with OS version ?

Thanks

#6

Hi aggarg,

Simplify the code flow:

  1. init stage
    event = = xEventGroupCreate()

  2. set
    ISR {
    …
    xEventGroupSetBitsFromISR(event, BITS, NULL);
    }

  3. wait in task
    Task {
    xEventGroupWaitBits(event, BITS, …)
    }

Thanks