Adding Second SAADC increases sleep current to go greater 380uA

RE: Adding Second SAADC increases sleep current to go greater 380uA

Carl Richard — Tue, 29 Dec 2020 13:38:57 GMT

Hi again, Peter!

Apologies for the delay. Due to the holidays we are understaffed until the 4th of January. I will look into the issues with the code and see if I can figure anything out. Happy holidays!

Best regards,
Carl Richard

RE: Adding Second SAADC increases sleep current to go greater 380uA

PeterInStillwater — Mon, 21 Dec 2020 19:17:16 GMT

Thank you - I may have solved it.

Now that I effectively have only one ADC I had forgotten to change the SAADC_SAMPLES_IN_BUFFER from 2 to 1.

It now appears to be working (fingers are crossed and I want to let it run awhile before I claim victory)

I'll keep you posted.

Peter

RE: Adding Second SAADC increases sleep current to go greater 380uA

hmolesworth — Mon, 21 Dec 2020 18:01:29 GMT

This is simple polled code, maybe it will help; this function is called a few dozen times a second and monitors an external voltage divider

#define ADC12_COUNTS_PER_VOLT 4829

uint16_t GetBatteryVoltage(void)
{
    uint16_t result = 9999; // 9999 means no reading
    uint32_t timeout = 10000;
    volatile int16_t buffer[8];
    // Enable command
    nrf_saadc_enable();
    NRF_SAADC->RESULT.PTR = (uint32_t)buffer;
    NRF_SAADC->RESULT.MAXCNT = 1;
    //NRF_SAADC->RESULT.AMOUNT
    nrf_saadc_event_clear(NRF_SAADC_EVENT_END);
    nrf_saadc_task_trigger(NRF_SAADC_TASK_START);
    nrf_saadc_task_trigger(NRF_SAADC_TASK_SAMPLE);
    while (0 == nrf_saadc_event_check(NRF_SAADC_EVENT_END) && timeout > 0)
    {
        timeout--;
    }
    nrf_saadc_task_trigger(NRF_SAADC_TASK_STOP);
    nrf_saadc_event_clear(NRF_SAADC_EVENT_STARTED);
    nrf_saadc_event_clear(NRF_SAADC_EVENT_END);
    // Disable command
    nrf_saadc_disable();
    if (timeout != 0)
    {
        result = ((buffer[0] * 1000L)+(ADC12_COUNTS_PER_VOLT/2)) / ADC12_COUNTS_PER_VOLT;
    }
    return result;
}

RE: Adding Second SAADC increases sleep current to go greater 380uA

PeterInStillwater — Mon, 21 Dec 2020 16:06:49 GMT

For Carl Richard -

I attempted to work through the code you provided. Unfortunately, the code:

                
        nrf_drv_saadc_uninit();                                                                   //Unintialize SAADC to disable EasyDMA and save power
        NRF_SAADC->INTENCLR = (SAADC_INTENCLR_END_Clear << SAADC_INTENCLR_END_Pos);               //Disable the SAADC interrupt
        NVIC_ClearPendingIRQ(SAADC_IRQn);                                                         //Clear the SAADC interrupt if set
        m_saadc_initialized = false;                                                              //Set SAADC as uninitialized
    }

at the end of the callback causes the micro to reset (I noticed this in other samples as well)

Peter

BTW - I was not able to reply directly to your response - thank you for any additional information you

could provide.

RE: Adding Second SAADC increases sleep current to go greater 380uA

PeterInStillwater — Mon, 21 Dec 2020 15:52:40 GMT

Well... Turns out the power drops as desired but I'm not able to get the SAADC back up and running.

No more interrupts / callbacks

hmolesworth - Would you be able to provide code to re-enable the ADC after it has been disabled by:

while (0 == nrf_saadc_event_check(NRF_SAADC_EVENT_END) && timeout > 0)
{
timeout--;
}
nrf_saadc_task_trigger(NRF_SAADC_TASK_STOP);
nrf_saadc_event_clear(NRF_SAADC_EVENT_STARTED);
nrf_saadc_event_clear(NRF_SAADC_EVENT_END);
// Disable command
nrf_saadc_disable();

Again, Thank you in advance!

Peter

RE: Adding Second SAADC increases sleep current to go greater 380uA

PeterInStillwater — Thu, 17 Dec 2020 13:57:38 GMT

I was able to lower the current draw by using one ADC (two ADC's):

// ***********************************************************************************

void UnintSAADC(void){

    uint32_t timeout = 10000;

    while (0 == nrf_saadc_event_check(NRF_SAADC_EVENT_END) && timeout > 0)
    {
        timeout--;
    }
    nrf_saadc_task_trigger(NRF_SAADC_TASK_STOP);
    nrf_saadc_event_clear(NRF_SAADC_EVENT_STARTED);
    nrf_saadc_event_clear(NRF_SAADC_EVENT_END);
    // Disable command
    nrf_saadc_disable();

    nrf_drv_saadc_uninit();

    NRF_SAADC->INTENCLR = (SAADC_INTENCLR_END_Clear << SAADC_INTENCLR_END_Pos);
    NVIC_ClearPendingIRQ(SAADC_IRQn);

}

// **************************************************************************************

void ConfigADCToVDD(void){

nrf_saadc_channel_config_t channel_config = NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_VDD);
    ret_code_t err_code;

    if (s_ssadcActive_b) {
        UnintSAADC();
    }
    channel_config.resistor_p = NRF_SAADC_RESISTOR_DISABLED;   //Disable pullup resistor on the input pin
    channel_config.resistor_n = NRF_SAADC_RESISTOR_DISABLED;   //Disable pulldown resistor on the input pin
    channel_config.gain       = NRF_SAADC_GAIN1_6;             //Set input gain to 1/6. The maximum SAADC input voltage is then 0.6V/(1/6)=3.6V. The single ended input range is then 0V-3.6V
    channel_config.reference  = NRF_SAADC_REFERENCE_INTERNAL;  //Set internal reference of fixed 0.6 volts
    channel_config.acq_time   = NRF_SAADC_ACQTIME_10US ;        //Set acquisition time. Set low acquisition time to enable maximum sampling frequency of 200kHz. Set high acquisition time to allow maximum source resistance up to 800 kohm, see the SAADC electrical specification in the PS.
    channel_config.mode       = NRF_SAADC_MODE_SINGLE_ENDED;   //Set SAADC as single ended. This means it will only have the positive pin as input, and the negative pin is shorted to ground (0V) internally.
    channel_config.burst      = NRF_SAADC_BURST_ENABLED;
    //channel_config.burst      = NRF_SAADC_BURST_DISABLED;
    channel_config.pin_p      = NRF_SAADC_INPUT_VDD;//NRF_SAADC_INPUT_AIN0;          //Select the input pin for the channel. AIN0 pin maps to physical pin P0.02.
    channel_config.pin_n      = NRF_SAADC_INPUT_DISABLED;      //Since the SAADC is single ended, the negative pin is disabled. The negative pin is shorted to ground internally.

    saadc_config.resolution = NRF_SAADC_RESOLUTION_12BIT;
    saadc_config.low_power_mode         = true;                                                   //Enable low power mode.

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

    err_code = nrf_drv_saadc_channel_init(0, &channel_config);
    APP_ERROR_CHECK(err_code);

    err_code = nrf_drv_saadc_buffer_convert(m_buffer_pool[0],SAADC_SAMPLES_IN_BUFFER);
    APP_ERROR_CHECK(err_code);   
    err_code = nrf_drv_saadc_buffer_convert(m_buffer_pool[1],SAADC_SAMPLES_IN_BUFFER);
    APP_ERROR_CHECK(err_code);   

    s_ssadcActive_b = true;     // to disable SSADC next time around

}

// *******************************************************************

void ConfigADCToAIN1(void){

nrf_saadc_channel_config_t channel_config = NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN5);

    ret_code_t err_code;

    if (s_ssadcActive_b) {
        UnintSAADC();
    }


    channel_config.resistor_p = NRF_SAADC_RESISTOR_DISABLED;   //Disable pullup resistor on the input pin
    channel_config.resistor_n = NRF_SAADC_RESISTOR_DISABLED;   //Disable pulldown resistor on the input pin
    channel_config.gain       = NRF_SAADC_GAIN1_6;             //Set input gain to 1/6. The maximum SAADC input voltage is then 0.6V/(1/6)=3.6V. The single ended input range is then 0V-3.6V
    channel_config.reference  = NRF_SAADC_REFERENCE_VDD4;      //Set internal reference of fixed 0.6 volts
    channel_config.acq_time   = NRF_SAADC_ACQTIME_10US ;        //Set acquisition time. Set low acquisition time to enable maximum sampling frequency of 200kHz. Set high acquisition time to allow maximum source resistance up to 800 kohm, see the SAADC electrical specification in the PS.
    channel_config.mode       = NRF_SAADC_MODE_SINGLE_ENDED;   //Set SAADC as single ended. This means it will only have the positive pin as input, and the negative pin is shorted to ground (0V) internally.
    //channel_config.burst      = NRF_SAADC_BURST_ENABLED;
    channel_config.burst      = NRF_SAADC_BURST_DISABLED;
    //
    channel_config.pin_p      = NRF_SAADC_INPUT_AIN1;          //Select the input pin for the channel. AIN0 pin maps to physical pin P0.02.
    channel_config.pin_n      = NRF_SAADC_INPUT_DISABLED;      //Since the SAADC is single ended, the negative pin is disabled. The negative pin is shorted to ground internally.

    saadc_config.resolution = NRF_SAADC_RESOLUTION_12BIT;
    saadc_config.low_power_mode         = true;                                                   //Enable low power mode.

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

    err_code = nrf_drv_saadc_channel_init(0, &channel_config);
    APP_ERROR_CHECK(err_code);

    err_code = nrf_drv_saadc_buffer_convert(m_buffer_pool[0],SAADC_SAMPLES_IN_BUFFER);
    APP_ERROR_CHECK(err_code);   
    err_code = nrf_drv_saadc_buffer_convert(m_buffer_pool[1],SAADC_SAMPLES_IN_BUFFER);
    APP_ERROR_CHECK(err_code);   

    s_ssadcActive_b = true;     // to disable SSADC next time around

}

// *************************************************************

void nrf_config_adc(void){
    ConfigADCToVDD();
}




1) Set s_ssadcActive_b = false

2) Call nrf_config_adc

3) Call either ConfigADCToVDD or ConfigADCToVDD as needed.


I have not yet tested if the ADC is working but suspect it is.   I will update
after testing ADC operation.  For now I'm happy with the low current.

Thanks Again.

RE: Adding Second SAADC increases sleep current to go greater 380uA

Carl Richard — Thu, 17 Dec 2020 13:18:30 GMT

Hi, Peter!

I also want to add there is a known bug in the driver caused by easyDMA being enabled and staying on when sampling for multiple channels. Jørgen has provided a more thorough explanation as well as a workaround demonstrating low power multichannel sampling in this thread. I also attached the his demo below.

3343.saadc_low_power_multichannel_sdk15_3_0.zip

Best regards,
Carl Richard

RE: Adding Second SAADC increases sleep current to go greater 380uA

PeterInStillwater — Thu, 17 Dec 2020 03:01:27 GMT

I suspected as such - but asked as several of the examples I've seen have put nrf_drv_saadc_uninit(); in the call back.

RE: Adding Second SAADC increases sleep current to go greater 380uA

hmolesworth — Wed, 16 Dec 2020 23:33:41 GMT

Ah, no; in fact as a general guide there should be as little as possible in the callbacks as the callbacks are run from within the interrupt handlers.

This code would just be used after ADC sampling was completed before going to sleep. It can be used will polled sampling or interrupt-driven sampling. The timeout depends on sampling details, just make it longer than the normal completion time; it isn't (shouldn't be) needed, I use it as a fail-safe.

RE: Adding Second SAADC increases sleep current to go greater 380uA

PeterInStillwater — Wed, 16 Dec 2020 23:10:32 GMT

Thank you for the fast response. No, I have not yet tried your suggestion, nor have I run across it.

Two obvious questions:

Is this code placed in the saadc_callback? (I assume so) and what is the timeout value initiated to?

I'll give this a shot tomorrow.

Thanks again!

RE: Adding Second SAADC increases sleep current to go greater 380uA

hmolesworth — Wed, 16 Dec 2020 22:25:01 GMT

One minor issue is the internal reference consumes power when enabled, but there is no spec for the SAADC. The COMP spec for that internal bandgap is only 13uA, so may be the same, don't know.

INT_REF Current used by the internal bandgap reference when selected as source for VREF = 13 μA

This is the code I use, you may already have tried this:

    while (0 == nrf_saadc_event_check(NRF_SAADC_EVENT_END) && timeout > 0)
    {
        timeout--;
    }
    nrf_saadc_task_trigger(NRF_SAADC_TASK_STOP);
    nrf_saadc_event_clear(NRF_SAADC_EVENT_STARTED);
    nrf_saadc_event_clear(NRF_SAADC_EVENT_END);
    // Disable command
    nrf_saadc_disable();

Errata 178 could be an issue if trying to disable before the SAADC has finished