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

[Jared]

Hi,

It's generally a good idea to keep all application tasks priority higher then the Softdevice priorities[ 1-5]. For very critical interrupts where low latency is required you can use 2+3 but then you cannot use any SVC. Instead of increasing the interrupt priority I would rather suggest that you try to change the context that you're calling the function from. Which interrupt is the saadc interrupt conflicting with? A softdevice interrupt? 

Jared

[BEN_HB]

Thank you.  'you try to change the context that you're calling the function from '<- what is meaning? 

I don't know what interrupt conflict with. how do I check?

in code, ant 2 channels, ble , gpiote, saadc, rtc, apptimer is operating...

I didn't change any priority of above function.

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

if it remove this code, the calibration done event is appear little bit later.

the infinite loop is disturb that calibration event done appear?

Is it too fast working to generate saadc event?

thank you so much

[Jared]

Hi,

What context are you calling the calibration task from? Meaning, are you calling it from an interrupt handler or from the main thread? If you are calling it from the interrupt handler, could you try to move it to the main thread?

regards

Jared