SAADC missing event

RE: SAADC missing event

BEN_HB — Tue, 16 Jun 2020 01:54:47 GMT

Thank you for advices. If more question, I write new ticket.

RE: SAADC missing event

haakonsh — Mon, 15 Jun 2020 11:29:25 GMT

That's quite a big difference in current consumption.

If you want a more reliable 10ms sample event I suggest you use the RTC (not the app_timer) with an interrupt priority level of 2(See S132 Interrupt priority levels), set to trigger a compare event at 10ms, where you init the SAADC and manually take one sample with nrfx_saadc_sample. Un-init after each sample and repeat.

RE: SAADC missing event

BEN_HB — Tue, 09 Jun 2020 01:44:44 GMT

1. if prescaler = 0, the timer gap is tiny, so avoid exception from priority execution?

2. using init & uninit : power is about 315uA, if not uninit, power is about 2.12mA,

adc uninit include ppi uninit also.

init&uninit : using app timer and rtc (8ms + 2ms)

not uninit : only use rtc. adc init one time when boot. it uninit before sleep. rtc prescaler is 31.

rtc start -> rtc event -> rtc interrupt -> rtc restart in rtc handler.

get value is normal. issue is power consumption. 2.12mA is too high.

my opinion is if not excute uninit adc, ppi use dma, it drain more power.

setup is same. ble + ant + watchdog + app timer + rtc + adc(using ppi)

Thank you so much

RE: SAADC missing event

haakonsh — Mon, 08 Jun 2020 11:58:21 GMT

Correct.
Why do you need to uninitialize the SAADC between every 10ms sample? What's the difference in current consumption if you unititialize and not?

RE: SAADC missing event

BEN_HB — Mon, 08 Jun 2020 01:54:45 GMT

sorry too late reply.

1. nrf_drv_rtc_cc_set function, last arguement is false, is it no interrupt, just event and it guarantee to happen event regardless BLE and ANT priority?

(cause rtc handler there is nothing. no need interrupt. only using adc event for ppi)

2. also consider use only RTC , without app timer. however, for reducing power consumption, init & uninit every 10ms. So before event is happen, need to init adc.

adc init -> rtc_cc_set -> rtc event raise -> adc sample -> get value -> adc uninit (need)

if rtc event -> adc init -> can't sample adc.

Thank you.

RE: SAADC missing event

haakonsh — Tue, 02 Jun 2020 11:28:26 GMT

[quote user="BEN_HB"]app timer interval is 9ms, rtc timer is 1ms (i used prescaler is 31, it meas 1/1024s, almost 1ms)[/quote]

If you include interrupts into this state machine then you will have no guarantee that you will sample every 10ms as both BLE and ANT event will have execution priority.

If you set your RTC prescaler to zero and use a COMPARE event at 328 ticks you will get a COMPARE event every 328 * 30.51µs = 10.00728 ms.

RE: SAADC missing event

BEN_HB — Mon, 01 Jun 2020 02:04:03 GMT

void adc_init()
{  
  ret_code_t err_code;     

  err_code = nrf_drv_saadc_init(&saadc_config, user_adc_saadc_handler); 
  APP_ERROR_CHECK(err_code);

  channel_config.pin_p = (nrf_saadc_input_t)(NRF_SAADC_INPUT_AIN0);
  err_code = nrf_drv_saadc_channel_init(BATTERY_SAADC_CHANNEL, &channel_config); 
  APP_ERROR_CHECK(err_code);

  channel_config.pin_p = (nrf_saadc_input_t)(NRF_SAADC_INPUT_AIN1);
  err_code = nrf_drv_saadc_channel_init(ADC_SAADC_CHANNEL, &channel_config); 
  APP_ERROR_CHECK(err_code);

  err_code = nrf_drv_saadc_buffer_convert(adc_buffer[0], ADC_BUFFER_SIZE); 
  APP_ERROR_CHECK(err_code);

  err_code = nrf_drv_saadc_buffer_convert(adc_buffer[1], ADC_BUFFER_SIZE); 
  APP_ERROR_CHECK(err_code);

  adc_sample_event_init();  
}

static void adc_config_init(nrf_drv_saadc_config_t *saadc_config, nrf_saadc_channel_config_t *channel_config)
{
  memset(saadc_config, 0 , sizeof(*saadc_config));
  saadc_config->resolution         = (nrf_saadc_resolution_t)NRFX_SAADC_CONFIG_RESOLUTION; // 12bit
  saadc_config->oversample         = (nrf_saadc_oversample_t)NRFX_SAADC_CONFIG_OVERSAMPLE; // no oversample
  saadc_config->interrupt_priority = NRFX_SAADC_CONFIG_IRQ_PRIORITY; // priority 6
  saadc_config->low_power_mode     = NRFX_SAADC_CONFIG_LP_MODE; // LP mode yes

  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 adc_sample_event_init()
{
    ret_code_t err_code;

    err_code = nrf_drv_ppi_init(); 
    APP_ERROR_CHECK(err_code);


    uint32_t timer_compare_event_addr = rtc_get_adc_event_addr(); 
    uint32_t saadc_sample_task_addr   = nrf_drv_saadc_sample_task_get(); 

    err_code = nrf_drv_ppi_channel_alloc(&m_ppi_channel);
    APP_ERROR_CHECK(err_code);

    err_code = nrf_drv_ppi_channel_assign(m_ppi_channel, 
                                          timer_compare_event_addr,
                                          saadc_sample_task_addr);
    APP_ERROR_CHECK(err_code);

    err_code = nrf_drv_ppi_channel_enable(m_ppi_channel); // PPI enable

    APP_ERROR_CHECK(err_code);
}

void rtc_adc_timer_start()
{
   ret_code_t err_code;
    
   uint32_t current = nrf_drv_rtc_counter_get(&rtc);
   
   err_code = nrf_drv_rtc_cc_set(&rtc, RTC_ADC_CHANNEL, rtc_check_overflow_cc_set(current, ADC_TIMER_INTERVAL), true);
   APP_ERROR_CHECK(err_code);   
}

static void rtc_handler(nrf_drv_rtc_int_type_t int_type)
{  
  switch(int_type)
  {
    case NRF_DRV_RTC_INT_COMPARE0  :  
    
      break;   

    case NRF_DRV_RTC_INT_COMPARE1  :  
  
      break;
      
    case NRF_DRV_RTC_INT_COMPARE2  : 
     
      break;
  
    default :
      break;
  }
}

more detail, process is below

I want get adc value interval 10ms.

to use ppi, need event address. app timer not support func get event address.

so I used rtc timer. (reason choosing rtc, need low power consumption.)

app timer interval is 9ms, rtc timer is 1ms (i used prescaler is 31, it meas 1/1024s, almost 1ms)

after 9ms, app timer handler start rtc timer setting 1ms using nrf_drv_rtc_cc_set function

passing 1ms, rtc timer send event to ppi, and start measure adc value.

on rtc handler, there is doing nothing.

here is issue, sometimes rtc timer is not send event to ppi.

Thank you.

RE: SAADC missing event

haakonsh — Fri, 29 May 2020 10:02:34 GMT

If you use PPI you don't need the RTC COMPARE interrupt at all, just the event.

And I think you need more than one count after "current".

Do you mind sharing your code with some comments? I think you might be on the wrong track.

RE: SAADC missing event

BEN_HB — Fri, 29 May 2020 08:42:11 GMT

Thank you.
I found one more.

cause rtc timer interrupt is not working. so saadc sample is not trigger.

rtc timer interval is 1ms.

rtc prescaler is 31. (need 1024/s)

it used nrf_drv_rtc_cc_set(adc_channel, current, current +1, true).

ex) if current is 0x53, it interrupt count is 0x54.

is it too tight?

thank you

RE: SAADC missing event

haakonsh — Fri, 29 May 2020 08:12:16 GMT

You need to look for the END event, not the DONE event, as the END event signifies that the buffer has been filled and transferred to RAM. The DONE event does not have its interrupt enabled in the driver and will not generate an interrupt.