topic Re: FreeRTOS tick rate in Kinetis Microcontrollers

FreeRTOS tick rate

songja — Fri, 09 Nov 2018 09:23:28 GMT

Hello,

Regarding the FreeRTOS tick rate, I found that "configTICK_RATE_HZ" is set to 200.

Is it possible to change the value up to 1000Hz so I can measure with sampling frequency of 1000Hz?

I attached the part of the code related to this.

---------------------------------------------------------------------------------------------------------------------------------------

#define ADC_SAMPLE_FREQ 1000U
#define mainQUEUE_SEND_PERIOD_MS (1000/(ADC_SAMPLE_FREQ*portTICK_PERIOD_MS))

#define mainSOFTWARE_TIMER_PERIOD_MS (1000 / portTICK_PERIOD_MS)
#define mainQUEUE_LENGTH (1)

xExampleSoftwareTimer = xTimerCreate("LEDTimer", mainSOFTWARE_TIMER_PERIOD_MS, pdTRUE, (void *)0, vExampleTimerCallback);

xTimerStart(xExampleSoftwareTimer, 0);

static void vExampleTimerCallback(TimerHandle_t xTimer){

ulCountOfTimerCallbackExecutions++;
}

vTaskDelayUntil(&xLastWakeTime, mainQUEUE_SEND_PERIOD_MS);

------------------------------------------------------------------------------------------------------------------------------------------

Thank you for your help.

Regards,

Re: FreeRTOS tick rate

danielchen — Mon, 12 Nov 2018 08:39:33 GMT

HI JAEYONG

The systick rate can configured to 1000. Actually FreeRTOS doesn't impose a maximum tick rate. But it is advised not to go over 1k HZ, otherwise, too much time will be spent switching between tasks, and result in much overhead.

Regards

Daniel

Re: FreeRTOS tick rate

songja — Mon, 12 Nov 2018 17:05:17 GMT

Thank you, Daniel.

I changed the value from 200 to 500 and sampling frequency to 500. Then I streamed the data on Putty and saved the printout data on the terminal.

Despite the change, the number of sampled data for 5 seconds was still 1000 which means the sampling frequency was still 200Hz.

is there anything else that I am supposed to change other than "configTICK_RATE_HZ " in "FreeRTOSConfig.h"?

Regards,
Jay