HFCLK timer issue

[sudharsan]

Hi Nordic Engineers,

I have few queries over HFCLK 16 MHz timer.

I am using nrf52840 custom board. IDE - segger embedded studio

#define TIME_IN_US  2600


/**
 * @brief Handler for timer events.
 */
void timer_led_event_handler(nrf_timer_event_t event_type, void* p_context)
{
      switch (event_type)
      {
          case NRF_TIMER_EVENT_COMPARE3:
              timerenabled = 1;
              if(!cal_HR_ir_enabled)
              {
                  DisableHRMLed();       //Disabling RED and Enabling IR
                  EnableHRMLed(HR_IR_LED);
                   //printf("Timer IR\r\n");
              }
              else if(!cal_HR_red_enabled)
              {
                  DisableHRMLed();       //Disabling IR and Enabling RED
                  EnableHRMLed(HR_RED_LED);
                   //printf("Timer RED\r\n");
              }
              break;

          default:
              //Do nothing.
              break;
      }
}

void enable_HR_LED_timer(void)
{ 
      uint32_t time_ticks;
      uint32_t err_code = NRF_SUCCESS;

      //Configure TIMER_LED for generating simple light effect - leds on board will invert his state one after the other.
      nrf_drv_timer_config_t led_timer_cfg = NRF_DRV_TIMER_DEFAULT_CONFIG;
      err_code = nrf_drv_timer_init(&TIMER_LED, &led_timer_cfg, timer_led_event_handler);
      APP_ERROR_CHECK(err_code);

      //Time(in microseconds) between consecutive compare events.
      time_ticks = nrf_drv_timer_us_to_ticks(&TIMER_LED, TIME_IN_US);

      nrf_drv_timer_extended_compare(
           &TIMER_LED, NRF_TIMER_CC_CHANNEL3, time_ticks, NRF_TIMER_SHORT_COMPARE3_CLEAR_MASK, true);

      nrf_drv_timer_enable(&TIMER_LED);
}

I have enabled HFCLK timer and able to reach timer callback.

The problem is...If I set the Timeout as 2600 us, it seemed only timer callback was running (not even while(1) ) 

But in 2700 us or greater, each and every functionalities were working fine.

I have to generate ~250us time delay. 

I have attached my code snippet and I am using Timer 3

Looking forward for your suggestion.

Regards

Sudharsan

[sudharsan]

My source code contains softdevice also. We should not use Timer 0 right??? which is reserved for softdevice

[haakonsh]

What's the execution time of the TIMER_LED's event handler?

And yes, TIMER0 is reserved for the SoftDevice.

[sudharsan]

Hi Haakonsh,

Please confirm...Is my timer initialization function definition right or ...??

Do I need to modify anything on timer side??

I have changed the timer callback. Now I am just setting the flag and reading it in while(1)

Now its fine and loop is also running...I have given 250us time-interval to switch the sensor's LED.

Sensor which is using I2C communication and speed - 400K

I am able to see the LED switching (RED <-> GREEN) ...Should it be possible to see in naked eye ??

This is where I am right now

/***************Enter main loop********************/
for (;;)
{   
        while (app_usbd_event_queue_process());
        process_usb_event();
         
#if defined(CMD_MODE) || defined(BLECMD_MODE)
        APPTASK_Handler();
#endif

#ifdef BLECMD_MODE
        BLE_PROCESS();
#endif

        if(timerenabled == 1)
        {
              if(is_HF_timer_started){
                  if(!cal_HR_ir_enabled)
                  {
                      //nrf_drv_timer_pause(&TIMER_LED);
                      DisableHRMLed();       //Disabling RED and Enabling IR
                      EnableHRMLed(HR_IR_LED);
                      //nrf_drv_timer_resume(&TIMER_LED);
                  }
                  else if(!cal_HR_red_enabled)
                  {
                      //nrf_drv_timer_pause(&TIMER_LED);
                      DisableHRMLed();       //Disabling IR and Enabling RED
                      EnableHRMLed(HR_RED_LED);
                      //nrf_drv_timer_resume(&TIMER_LED);
                  }
              }
              timerenabled = 0;
        }


#ifdef HRMEN
      HRM_Process();
      
#endif
        idle_state_handle();
}
/****************************************************************/




void timer_led_event_handler(nrf_timer_event_t event_type, void* p_context)
{
  switch (event_type)
  {
    case NRF_TIMER_EVENT_COMPARE3:
      timerenabled = 1;
      break;

    default:
    //Do nothing.
    break;
   }
}

Regards,

Sudharsan

[haakonsh]

If it "works" now then it's an indication that the the functions DisableHRMLed() and EnableHRMLed() takes ~2600µs to execute. Can you share their implementation as well? 

What I believe is happening is that there's a pending TIMER COMPARE interrupt when you exit the TIMER event handler, therefore you never return to your main loop.

sudharsan said:

Please confirm...Is my timer initialization function definition right or ...??

Do I need to modify anything on timer side??

 Your timer initialization seems okay to me. I think the issue lies in the LED toggling. 

[sudharsan]

This is not LED which is connected to GPIO. It is connected to HRM sensor where the enable/disable should be I2C write.

Please check the below

void EnableHRMLed(enum enable_led_t led_on)
{
     if(led_on == HR_RED_LED){
        switch_on_LED_1A_2A(&m_twi, ADPD410X_TS_A, ENABLE_HRLED_2A);
        cal_HR_red_enabled = true;
        cal_HR_ir_enabled = false;
     }
     else{
        switch_on_LED_1A_2A(&m_twi, ADPD410X_TS_B, ENABLE_HRLED_1A);
        cal_HR_red_enabled = false;
        cal_HR_ir_enabled = true;
     }
} 

void DisableHRMLed(void)
{
     switch_off_LEDs(&m_twi, PAIR_12, ADPD410X_TS_A); 
     switch_off_LEDs(&m_twi, PAIR_12, ADPD410X_TS_B);
}