Re: Drift through k_sleep or k_msleep #api


Erik Englund
 

One possible solution is to create a periodic timer and post to a semaphore in the timer callback.
A thread could simply wait on the semaphore in an endless loop.

Linux clock_nanosleep (mostly used togheter with Preempt-rt patch) would be a nice addition to Zephyr, that would solve these kinds of tasks.

Med vänlig hälsning
Erik Englund

Innoware Development AB
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www.innoware.se


Den ons 3 feb. 2021 kl 20:31 skrev Nikolaus Huber <nikolaus.huber@...>:

Hi all, 

I was recently wondering about the correct usage of k_sleep or k_msleep for implementing periodic tasks. In FreeRTOS for example there is a function vTaskDelayUntil which takes a timestamp and a number of ticks to delay. By taking the timestamp at the beginning of the execution of a task we can then make sure that its release time does not slowly drift. So far I have not seen anything similar in Zephyr. Am I missing something, or do I have to somehow create a similar mechanism on my own by measuring the uptime at the release of a periodic task and then again just before using any sleep function to calculate the exact sleep time I want?

Thank you very much in advance,
Nick

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