Can FreeRTOS support xTimerCreate() with us?

[maxs_yeh]

Hi,

I am using SDK_2.8.5_EVK-MIMXRT1060 with FreeRTOS version.

I want to create a timer handling function with us timer, but I check the timers.h that described the xTimerPeriodInTicks parameter used portTICK_PERIOD_MS not us.

Please kindly suggest the solution.

Thanks.

[kerryzhou]

Hi maxs_yeh,

   The software timer need to input the xTimerPeriodInTicks is the configTICK_RATE_HZ integer multiples.

   Take the SDK freertos_swtimer as an example:

#define configTICK_RATE_HZ ((TickType_t)200)

  it means the cpu freertos tick time is 1/200=50ms

   So, it means that your defined time must be the integer multiples to 50 ms, should be: 50ms, 100ms, 150ms...etc. that's why you can't get the us.

   Then you may think, whether you can set the configTICK_RATE_HZ in the us level. 

   As you know, the smaller tick time is, the heavy cpu load is.

   So, just as nickwallis told you, if you really need the us timer, you can use the RT hardware Timer to generate it.

Wish it helps you!

If you still have questions about it, please kindly let me know!

Best Regards,

Kerry

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[nickwallis]

For timing events of less than one microsecond, you need to use hardware timers directly rather than freeRTOS services. i.MX RT has multiple timers, but you could look at either the PIT or GPT as a starting point.

-Nick