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pdevanne

Beginner

Date of registration: Dec 21st 2017

Posts: 2

1

Friday, December 22nd 2017, 3:00pm

[SOLVED] Systick ISR frequency

Hi guys !

I recently add the Segger System View support to our firmware to be able to do some advanced debug. Our platform is running FreeRTOS v8 on a Cortex M3 microcontroller.
Our tick period is 1ms and the tick is generated thanks to the systick timer.

In SystemView, there is a strange behavior, when my system is mainly running the Idle task, the Systick ISR frequency is 2Hz and when the System is executing more tasks the ISR frequency increases. Also to be sure that the tick is stable I created a task printing a log to system view every second thanks to a vTaskDelay call and the frequency if this task is correct.

Do you have any idea on how to fix this problem ?

Thanks a lot,
Pablo

SEGGER - Johannes

Super Moderator

Date of registration: Aug 31st 2012

Posts: 377

2

Friday, December 22nd 2017, 3:33pm

Hi Pablo,

did you make sure that the tick frequency in the SystemView configuration is correct?
Do you change the system frequency at run time?

When the configured frequency is incorrect, you will get wrong timings.
The timer interrupt frequency should not change during run time. If it does although the system frequency does not change, something more is wrong.

Regards
Johannes

pdevanne

Beginner

Date of registration: Dec 21st 2017

Posts: 2

3

Friday, December 22nd 2017, 7:10pm

My bad the configUSE_TICKLESS_IDLE was defined to 1, when defined to 0 I have the right frequency.

Thanks
Pablo