Am I not configuring right my SAADC handler for low power?

[ndarkness]

Hello,

I would like to sample the battery level of my nrf52832 DK and send it through BLE. I have started from the example ble_app_hrs for SDK12.2 since the service was already present and I had just to modify the battery simulator there present by the SAADC sampling procedure.

I have configured my SAADC like this

static uint32_t saadc_start(batt_meas_param_t batt_meas_init)
{
    uint32_t err_code;

    nrf_drv_saadc_config_t saadc_config = NRF_DRV_SAADC_DEFAULT_CONFIG;

    err_code = nrf_drv_saadc_init(&saadc_config, saadc_handler_interrupt);
    APP_ERROR_CHECK(err_code);
    nrf_saadc_channel_config_t channel_config = NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(batt_meas_init.adc_pin_no);

    err_code = nrf_drv_saadc_channel_init(0, &channel_config);
    APP_ERROR_CHECK(err_code);
    err_code = nrf_drv_saadc_buffer_convert(m_buffer, ADC_BUF_SIZE);
    APP_ERROR_CHECK(err_code);

     return M_BATT_STATUS_CODE_SUCCESS;
}

The handler saadc_handler_interrupt looks like

void saadc_handler_interrupt(nrf_drv_saadc_evt_t const * const p_event)
{
    uint32_t err_code;
    uint16_t voltage;

    if (p_event->type == NRF_DRV_SAADC_EVT_CALIBRATEDONE)
    {
        m_adc_cal_in_progress = false;
    }
    else if (p_event->type == NRF_DRV_SAADC_EVT_DONE)
    {
        err_code = adc_to_batt_voltage(*p_event->data.done.p_buffer, &voltage);
        APP_ERROR_CHECK(err_code);

       batt_event_handler_adc(voltage);
    }

    nrf_drv_saadc_uninit();
}

Running into debug shows that the function saadc_start is executed without error, then I have a timer of 4s that will trigger a battery update. When this happens the function triggered is

static void battery_level_update(void)
{
    uint32_t err_code;
    uint8_t  battery_level;

    NRF_LOG_INFO("Read value from saadc %d\n",0);
    err_code = nrf_drv_saadc_sample();
    APP_ERROR_CHECK(err_code);

}

Debugger shows how saadc_sample() is called, but after this call the program goes directly to function app_error_fault_handler(). I see that within the call nrf_drv_saadc_sample() it enters on the conition m_cb.low_power_mode, but never goes back and therefore I am prompted into the app_error_fault_handler()....

ret_code_t nrf_drv_saadc_sample()
{
    ASSERT(m_cb.state != NRF_DRV_STATE_UNINITIALIZED);

    ret_code_t err_code = NRF_SUCCESS;
    if (m_cb.adc_state != NRF_SAADC_STATE_BUSY)
    {
        err_code = NRF_ERROR_INVALID_STATE;
    }
    else if (m_cb.low_power_mode)
    {
        nrf_saadc_task_trigger(NRF_SAADC_TASK_START);
    }
    else
    {
        nrf_saadc_task_trigger(NRF_SAADC_TASK_SAMPLE);
    }

    NRF_LOG_INFO("Function: %s, error code: %s.\r\n", (uint32_t)__func__, (uint32_t)ERR_TO_STR(err_code));
    return err_code;
}

Any hint why this is happening?

THanks in advance!

[Sigurd]

Hi,

You would have to take a look at what error code you are getting in the app_error_fault_handler. See here on how to debug and find the error code. As mentioned here, I recommend taking a look at the ble_app_proximty example. This example uses the saadc, and not the simulator that is used in the hrs example.

[ndarkness]

HI Sigurd, thanks for replying

I have used ble_app_proximity as guideline to implement the SAADC measurements, I managed to make it running. however, I think my settings for measuring VDD input are not completely correct. I see how the ADC saturates ( it gives back its Vref = 0.6V) instead the expected voltage, around 3.3V since I am powering it from the micro usb of the DK. I know that this has to do with the ADC_GAIN to be set, in order to perform the right conversion. What is the gain that I should set to achieve such a conversion? Currently I use something like this adc_val / ((adc_gain / ADC_REFERENCE_VOLTAGE) * pow(2, ADC_RESOLUTION_BITS)) with adc_gain = NRF_SAADC_GAIN1

[Sigurd]

Did you solve this issue in this post?