timer in microsecond on nRF52840

RE: timer in microsecond on nRF52840

lmouelo — Tue, 28 Aug 2018 12:35:33 GMT

ok i have understood

thank's

RE: timer in microsecond on nRF52840

Jørgen Holmefjord — Tue, 28 Aug 2018 12:18:22 GMT

I told you the resolution is 30 µs. You try to calculate ticks for 1 µs. Of course that will not work. App_timer have a minimum tick configuration of 5: APP_TIMER_MIN_TIMEOUT_TICKS, which means you cannot get a timeout of less than ~150 µs.

RE: timer in microsecond on nRF52840

lmouelo — Tue, 28 Aug 2018 12:12:32 GMT

i have defined the MACRO on app_timer.h like this

#ifndef FREERTOS
#define APP_TIMER_TICKS(MS)                                \
            ((uint32_t)ROUNDED_DIV(                        \
            (MS) * (uint64_t)APP_TIMER_CLOCK_FREQ,         \
            1000 * (APP_TIMER_CONFIG_RTC_FREQUENCY + 1)))

#define APP_TIMER_TICKS_US(US)                                \
            ((uint32_t)ROUNDED_DIV(                        \
            (US) * (uint64_t)APP_TIMER_CLOCK_FREQ,         \
            1000000 * (APP_TIMER_CONFIG_RTC_FREQUENCY + 1)))
#else
#include "FreeRTOSConfig.h"
#define APP_TIMER_TICKS(MS) (uint32_t)ROUNDED_DIV((MS)*configTICK_RATE_HZ,1000)
#endif

and on my main :

#define COMPTEUR_INTERVAL     APP_TIMER_TICKS_US(1)                   /**< Tick / Us */void test(){
	
	ret_code_t err_code;
	//Create timers
	err_code = app_timer_create(&timer_id,APP_TIMER_MODE_REPEATED,timer_sd_handler);
	lfclk_request();
	APP_ERROR_CHECK(err_code);
	NRF_LOG_INFO("Timer_sd_start");
	err_code = app_timer_start(timer_id, COMPTEUR_INTERVAL, NULL);
	NRF_LOG_INFO("%d",err_code);
	APP_ERROR_CHECK(err_code);
}

but i have a fatal error when i define like this :

-> #define COMPTEUR_INTERVAL APP_TIMER_TICKS_US(1) /**< Tick / Us */

but no fatal error with this :

-> #define COMPTEUR_INTERVAL APP_TIMER_TICKS_US(1000) /**< Tick / Us */

i don't know why

RE: timer in microsecond on nRF52840

Jørgen Holmefjord — Tue, 28 Aug 2018 11:40:53 GMT

You are not required to use the MACRO defined in the app_timer library. You can calculate the ticks value yourself, or create your own MACRO to calculate ticks from microseconds:

#define APP_TIMER_TICKS_US(US)                                \
            ((uint32_t)ROUNDED_DIV(                        \
            (US) * (uint64_t)APP_TIMER_CLOCK_FREQ,         \
            1000000 * (APP_TIMER_CONFIG_RTC_FREQUENCY + 1)))

RE: timer in microsecond on nRF52840

lmouelo — Tue, 28 Aug 2018 10:24:17 GMT

30 us is enough for me, same 1 us

what I want :

-> make a break every 62.5ms, how to do this.? (when my compteur equal( 62.5ms) but to do this i will to replace this

-> #define COMPTEUR_INTERVAL APP_TIMER_TICKS(1) /**< Tick / Ms */

#define COMPTEUR_INTERVAL APP_TIMER_TICKS(1) /**< Tick / Us */

I want my counter ("compteur") to increment every microsecond

RE: timer in microsecond on nRF52840

Jørgen Holmefjord — Tue, 28 Aug 2018 09:30:54 GMT

Hi,

The application timer library runs using the RTC peripheral, which again use the LFCLK as the clock source. This will give you a maximum frequency of 32.768 kHz, or a resolution of ~30 µs. If you want better resolution, you need to use the TIMER peripheral. There is a driver and an example available in the SDK. Please have a look at this thread for more details.

Best regards,
Jørgen