Task event management

Kernel
1

giso1 wrote on Friday, April 27, 2018:

Hi,

I have the following pseudo code

task_run()
{
while (true)
{
xTaskNotifyWait(eventA|eventB)
if (eventA)
{
send RF command
xTaskNotifyWait(eventA)
}
if (eventB)
{
process command
}
do something else
}
}

EventA is triggered by interrupt when RF data is received.
EventB is triggered when application request to trigger a cmd
I have the following issue when I have the following sequence

  • EventA received
  • task is woken up
  • EventB occurs before the second xTaskNotifyWait is called
    the first xTaskNotifyWait(eventA|eventB) will not detect eventB.

to simulate I do the following
task_run()
{
while (true)
{
xTaskNotifyWait(eventA|eventB)
if (eventA)
{
trigger EventB
send RF command
xTaskNotifyWait(eventA)
}
if (eventB)
{
process command
}
do something else
}
}

Is that the expected behaviour?
I would have expected that when waiting for a specific event, xTaskNotifyWait would only retrieve these specific events and if other event have been set they would be kept and available for other call to xTaskNotifyWait.

Thanks for feedback.

2

rtel wrote on Friday, April 27, 2018:

It looks like you are expecting the same behaviour as an event group,
where bits are latched. That is not the case when using a notification,
where you specify which bits to clear on exit from the wait function.
If the eventB bit is set between the first and second calls to
xTaskNotifyWait() then you will have to either remember it was set so
you can then process it on the next go around the loop, or make sure the
second call to xTaskNotifyWait() only clears the eventA bit so leaves
the eventB bit set.

If that does not explain the behaviour you are seeing, or you still have
a problem, then please reply with the actual code so I can see the
parameters you are passing and try to replicate it.