52832 saadc calibration issue

[BEN_HB]

I have issue about calibartion using saadc.

I use 52832, S332, SDK 15.3.0

when calibration is excuting, ANT+ and BLE is also doing.

I use low power mode in saadc.

issue is first calibration is normal

but after that periodly do calibration (like one time for 30min) NRF_DRV_SAADC_EVT_CALIBRATEDONE event is not trigger.

I search about this one in nordic dev. I know PAN-86. but i can't find that. all link was broken..

second calibration process,  nrf_log_info(saadc is wating) <- infinite loop in here.

under blow is my code.

And If don't calibrate periodly, how much error about temperature drift ?  in doc, there is only gain error temperature coefficient (0.02%).

if I measure 25 degree, which temperature range is normal value in error? 

Thank you.

void battery_config_value_init()
{
  memset(&saadc_config, 0 , sizeof(saadc_config));
  saadc_config.resolution         = (nrf_saadc_resolution_t)NRFX_SAADC_CONFIG_RESOLUTION; // 10bit
  saadc_config.oversample         = (nrf_saadc_oversample_t)NRFX_SAADC_CONFIG_OVERSAMPLE; // disable
  saadc_config.interrupt_priority = NRFX_SAADC_CONFIG_IRQ_PRIORITY;
  saadc_config.low_power_mode     = NRFX_SAADC_CONFIG_LP_MODE;

  memset(&channel_config, 0 , sizeof(channel_config));
  channel_config.resistor_p   = NRF_SAADC_RESISTOR_DISABLED;
  channel_config.resistor_n   = NRF_SAADC_RESISTOR_DISABLED;
  channel_config.gain         = NRF_SAADC_GAIN1_6;
  channel_config.reference    = NRF_SAADC_REFERENCE_INTERNAL;
  channel_config.acq_time     = NRF_SAADC_ACQTIME_10US;
  channel_config.mode         = NRF_SAADC_MODE_SINGLE_ENDED;
  channel_config.burst        = NRF_SAADC_BURST_DISABLED;
  channel_config.pin_p        = (nrf_saadc_input_t)(NRF_SAADC_INPUT_AIN0);
  channel_config.pin_n        = NRF_SAADC_INPUT_DISABLED;
}

static void user_battery_saadc_handler(nrf_drv_saadc_evt_t const * p_event)
{
   nrf_saadc_value_t *value =  p_event->data.done.p_buffer; // nrf_saadc_value_t = uint16_t
   
   switch(p_event->type)
   {    
     case NRF_DRV_SAADC_EVT_CALIBRATEDONE :
       CaliState = false;
       break;
     case NRF_DRV_SAADC_EVT_DONE : 
            
       Calculate_Voltage(value, &voltage);      
      
       break;     
     default:
       break;
   }

static void Calibration_init()
{
  NRF_LOG_INFO("SAADC Calibration Start");

  CaliState = true;

  nrf_drv_saadc_abort(); 

  while(nrf_drv_saadc_is_busy()){};

  while( nrf_drv_saadc_calibrate_offset() != NRF_SUCCESS ){
    NRF_LOG_INFO("SAADC is offset");
    NRF_LOG_PROCESS();
  }  

   while(CaliState){
     NRF_LOG_INFO("SAADC is waiting");
     NRF_LOG_PROCESS();
   }
}

[Jared]

Hi,

Could you share the entire file where you call Calibration_init()? It's important that you don't call the function in interrupt context that has the same or higher interrupt priority.

Jared 

[BEN_HB]

Sorry to late repy. you are right. problem is priority.

I change 6 -> 5. the issue disappered.

i have one more question.

in sdk_config.h

some driver(ex gpiote etc..)

priority 0, 1, 4, 5 is reserved for softdevice.

in saadc there is no sentence.

if i change saadc priority 6 -> 5 , is it no problem?

thank you so much

[BEN_HB]

thank you. the calibration func is called from app_timer handler. the timer is called per 30min. and it can't move main thread.

[Jared]

Hi,

I understand that it might be difficult to move it on your application. If you're using Softdevice S132 then you could move the priority of the SAADC interrupt to 5. 

regards
Jared

[BEN_HB]

I use S332. Is it also no issue?

[Jared]

Hi,

It should be ok for S332.

regards

Jared

[BEN_HB]

Thank you