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Wait for an event possible?

Posted by Torben on April 24, 2007
Hi!

I am just starting to use FreeRTOS. I went through the demos and got a basic understanding. I would like to implement a task which waits for an event, for example the presence of an item in a queue, but without polling the queue every x ticks. In other words, I want the task to activate on a specific event. Is this possible with FreeRTOS or do I have to use vTaskDelay and check the event every x ticks?

Thx!

RE: Wait for an event possible?

Posted by Richard on April 24, 2007
You can block on a queue with timeout - the last parameter to the queue send/receive functions is the timeout in tick units.

If you block receiving from a queue, then data arriving on the queue will automatically unblock the task. If you block on sending to a queue then space becoming available on the queue will automatically unblock the task. You do not need to poll the queue unless you don't want the task to block.

If you use a block time of zero then the task will not block.

If you use a block time of portMAX_DELAY then the task will wait forever, if INCLUDE_vTaskSuspend is set to 1, or portMAX_DELAY ticks if INCLUDE_vTaskSuspend is set to 0. In the latter case the timeout will be approximately 40 days if the tick frequency in 1KHz.

Regards.

RE: Wait for an event possible?

Posted by Torben on April 26, 2007
Can I use "portMAX_DELAY" or "portMAX_DELAY" with xSemaphoreTake too to get the task to block?

RE: Wait for an event possible?

Posted by Nobody/Anonymous on April 26, 2007
Yes, read the documentation.


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