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How to make a task block on a specific notification?

Posted by bencohavi on January 16, 2018


Is there a way to make a task block on a specific notification?

In other words, I want to block the task until a certain notification arrives. In case other notifications have arrived during that time, I don't want my task to resume action.



How to make a task block on a specific notification?

Posted by richard_damon on January 16, 2018

In general, when a task blocks in FreeRTOS it is blocking for a specific event. If it gets from a Queue (and no data is available), the task blocks on that Queue. If it takes a Semaphore or a Mutex, it waits for that Semaphore or Mutex.

If you are waiting on a direct to task notification, the task will only unblock on a direct to task notification, but I don't think you can choose to only be unblocked on certain bits. I think you could use an EventGroup to do something like that.

The more common question is how to make a task unblock on multiple sources, which is where the QueueSets and EventGroups came from, to provide solutions to that.

How to make a task block on a specific notification?

Posted by eyalasko1 on March 29, 2018

+1 on that.

It can be ETREMELY usefull to block on specifc bits (the event group way)

How to make a task block on a specific notification?

Posted by iceebounz on March 30, 2018

Hi Ben,

If you have FreeRTOS's configUSE16BITTICKS set to 0 and you don't need more than 24 different types of "notifications," you can use an EventGroup. Refer to the docs for the details and example code. (If configUSE16BITTICKS is set to 1, the event bits available are limited to 8.)

If you need more than 24, we would need some info about what you are trying to accomplish to determine the best solution. There is usually a way to accomplish all goals when the problem is clearly understood.


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