App timer misfire after 4000 mSec interval

[Pooja Uchagaonkar]

Hi,

Greetings !

I want to take continuous 40 reading of adc by varying time interval between readings based on RPM value. I want timer interval resolution from 6 Sec to 15 mSec. For that I used app_timer for repeated mode. I start timer when reading count is zero and stop it after completion of 40 readings. Here I used, app_timer as like...

void start_normal_mode()
{
   ret_code_t err_code;
   SamplingRate = 60/(40 * RPM);
   SamplingRate_ms = SamplingRate * 1000;
   
   NORMAL_MODE_MEAS_INTERVAL = APP_TIMER_TICKS(SamplingRate_ms);

   if(normal_mode_reading_count == 0)
   {
      err_code = app_timer_start(m_normalmode_timer_id, NORMAL_MODE_MEAS_INTERVAL, NULL);
      APP_ERROR_CHECK(err_code);
   }
}

I got perfect reading when timer interval is less than 4000mSec but timer is misfires above 4000mSec. It instantly fires and didn’t get perfect time interval.

In same code, I used one more app_timer for fixed interval 1 Sec and I also check it for 6 Sec time interval. It works perfectly. So I didn’t recognized why this second one timer misbehaving like this

Will you please help me out in this matter?

Thanks,

Pooja Uchagaonkar

[Jørgen Holmefjord]

Hi,

The behavior you describe sounds similar to this known issue. The solution is to switch to using app_timer2, which was introduced in SDK 15.0.0 as an experimental library. In SDK 16.0.0, app_timer2 was updated to production quality and used by default for all examples.

Instructions on how to switch app_timer are given in this post.

Best regards,
Jørgen

[Pooja Uchagaonkar]

Sorry Sir for late reply,

I was trying to resolve this with by implementing nrf_drv_timer, but same thing happened. 

But I didn't check it with app_timer2. I will do this and let you know soon.

Thanks,

Pooja Uchagaonkar

[Pooja Uchagaonkar]

HI Jorgen,

I used app_timer2. But issue is not resolved. I also checked with this nrf_drv_timer but same issue happened. Can you please help me out?

[Jørgen Holmefjord]

What is the value returned by APP_TIMER_TICKS when you input a value above 4000 ms? What is the config APP_TIMER_CONFIG_RTC_FREQUENCY set to?

Can you provide a minimal example that can be used to reproduce this issue?

[Pooja Uchagaonkar]

Hi Jorgen,

The project is almost in last phase and I completely stuck due to this issue. Thank you so much for your reply.  

The value returned by APP_TIMER_TICKS is nearly about 1000 ms above 4000 mSec.

APP_TIMER_CONFIG_RTC_FREQUENCY set as 16384 Hz.

Actually I used this app timer for variable time interval as shown below code. Here the RPM range varies from 0.25 to 100 and so accordingly time interval changing from 6 Sec to 15 mSec. 

It works perfectly for 100 to 0.38 RPM setting but misfires below this. 

void start_normal_mode()
{
   ret_code_t err_code;
   float RPM;
   RPM = Read_RPM_Param_from_flash();
   SamplingRate = 60/(40 * RPM);
   SamplingRate_ms = SamplingRate * 1000;

   NORMAL_MODE_MEAS_INTERVAL = APP_TIMER_TICKS(SamplingRate_ms);

   if(normal_mode_reading_count == 0)
   {
      err_code = app_timer_start(m_normalmode_timer_id, NORMAL_MODE_MEAS_INTERVAL, NULL);
      APP_ERROR_CHECK(err_code);
   }
}

//code in main while loop
while(1)
{
    if(RTCMinInterrpt_Flag == 1)    
     {          
        External_RTC_GetDateTime(&GetRTC_DateTime);
        printf("\r\n Date- %d/%d/%d, Time- %d:%d:%d", GetRTC_DateTime.date, GetRTC_DateTime.month, GetRTC_DateTime.year, GetRTC_DateTime.hour, GetRTC_DateTime.minute, GetRTC_DateTime.second);
        RTCMinInterrpt_Flag = 0;
        Normal_Mode_Reading_Flag = 1;
        normal_mode_hour_index++;
        start_normal_mode();       //calculate sampling rate and start timer
     }
     
     if(Normal_Mode_Timer_Flag == 1)
         {          
             if(normal_mode_reading_count < normal_mode_total_reading)
             {
                  read_datetimestamp_and_sensor_Data();
                  memcpy(&Normal_Mode_Handling_Buff[normal_mode_reading_count*NormalMode_OneReadingcount], DateTimeStamp_and_Sensor_Buff, sizeof(DateTimeStamp_and_Sensor_Buff));
                  normal_mode_reading_count ++;
                  Normal_Mode_Timer_Flag = 0;
              }
              else
              {
                    normal_mode_reading_count = 0;
                    app_timer_stop(m_normalmode_timer_id);     //stop timer                               
              }
          }      
}

 Please let me know if anything I can do

Regards,

Pooja Uchagaonkar

[Jørgen Holmefjord]

Pooja Uchagaonkar said:

The value returned by APP_TIMER_TICKS is nearly about 1000 ms above 4000 mSec.

 Not sure what you mean by this. If you input 4000 ms and the frequency is 16384 Hz, this should return 65536. Which data type is NORMAL_MODE_MEAS_INTERVAL?

Pooja Uchagaonkar said:

APP_TIMER_CONFIG_RTC_FREQUENCY set as 16384 Hz.

Is the value of the config set to 16384, or is it set to 1 (which corresponds to a frequency of 16384 Hz)?