SAADC Always busy, error 17. SDK15

[Sylvain]

Hello DevZone,

I know that the subject has already be treat but in the others posts people seems to say that the error comes from the double buffering.

But in my case, I have no double buffering active. And I try to use the following function :

err_code = nrfx_saadc_sample_convert(0, ADC_value);

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/**
 * Copyright (c) 2014 - 2018, Nordic Semiconductor ASA
 * 
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 * 
 * 1. Redistributions of source code must retain the above copyright notice, this
 *    list of conditions and the following disclaimer.
 * 
 * 2. Redistributions in binary form, except as embedded into a Nordic
 *    Semiconductor ASA integrated circuit in a product or a software update for
 *    such product, must reproduce the above copyright notice, this list of
 *    conditions and the following disclaimer in the documentation and/or other
 *    materials provided with the distribution.
 * 
 * 3. Neither the name of Nordic Semiconductor ASA nor the names of its
 *    contributors may be used to endorse or promote products derived from this
 *    software without specific prior written permission.
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/**
 * Copyright (c) 2014 - 2018, Nordic Semiconductor ASA
 * 
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 * 
 * 1. Redistributions of source code must retain the above copyright notice, this
 *    list of conditions and the following disclaimer.
 * 
 * 2. Redistributions in binary form, except as embedded into a Nordic
 *    Semiconductor ASA integrated circuit in a product or a software update for
 *    such product, must reproduce the above copyright notice, this list of
 *    conditions and the following disclaimer in the documentation and/or other
 *    materials provided with the distribution.
 * 
 * 3. Neither the name of Nordic Semiconductor ASA nor the names of its
 *    contributors may be used to endorse or promote products derived from this
 *    software without specific prior written permission.
 * 
 * 4. This software, with or without modification, must only be used with a
 *    Nordic Semiconductor ASA integrated circuit.
 * 
 * 5. Any software provided in binary form under this license must not be reverse
 *    engineered, decompiled, modified and/or disassembled.
 * 
 * THIS SOFTWARE IS PROVIDED BY NORDIC SEMICONDUCTOR ASA "AS IS" AND ANY EXPRESS
 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY, NONINFRINGEMENT, AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL NORDIC SEMICONDUCTOR ASA OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
 * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 * 
 */
/** @file
 * @defgroup nrf_adc_example main.c
 * @{
 * @ingroup nrf_adc_example
 * @brief ADC Example Application main file.
 *
 * This file contains the source code for a sample application using ADC.
 *
 * @image html example_board_setup_a.jpg "Use board setup A for this example."
 */

#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include "nrf.h"
#include "nrf_drv_saadc.h"
#include "nrf_drv_ppi.h"
#include "nrf_drv_timer.h"
#include "nrf_drv_twi.h"
#include "boards.h"
#include "app_error.h"
#include "nrf_delay.h"
#include "app_util_platform.h"
#include "nrf_pwr_mgmt.h"

#include "nrf_log.h"
#include "nrf_log_ctrl.h"
#include "nrf_log_default_backends.h"

#define SAMPLES_IN_BUFFER 1
volatile uint8_t state = 1;

static nrf_saadc_value_t     m_buffer_pool [SAMPLES_IN_BUFFER];//[2][SAMPLES_IN_BUFFER];

static uint32_t              m_adc_evt_counter;

static uint16_t ADC_value [1];


void saadc_callback(nrf_drv_saadc_evt_t const * p_event)
{
    if (p_event->type == NRF_DRV_SAADC_EVT_DONE)
    {
        ret_code_t err_code;

        err_code = nrf_drv_saadc_buffer_convert(p_event->data.done.p_buffer, SAMPLES_IN_BUFFER);
        APP_ERROR_CHECK(err_code);

        int i;
        NRF_LOG_INFO("ADC event number: %d", (int)m_adc_evt_counter);
        
        flag = 1;

        for (i = 0; i < SAMPLES_IN_BUFFER; i++)
        {
          ADC_value [0] = p_event->data.done.p_buffer[i];
          
          if (ADC_value [0] < 0)
          {
            ADC_value [0] = 0;
          }
          NRF_LOG_INFO("ADC value: %d", ADC_value[0]);
        }
        m_adc_evt_counter++;
    }
}

void saadc_init(void)
{
    ret_code_t err_code;
    nrf_drv_saadc_config_t saadc_config;

    nrf_saadc_channel_config_t channel_config =
      NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN5);
    
    channel_config.reference =  NRF_SAADC_REFERENCE_INTERNAL;
    channel_config.gain =       SAADC_CH_CONFIG_GAIN_Gain1_4;
    channel_config.acq_time =   SAADC_CH_CONFIG_TACQ_3us;

    saadc_config.resolution =   SAADC_RESOLUTION_VAL_14bit;
    saadc_config.oversample =   NRF_SAADC_OVERSAMPLE_64X;//NRF_SAADC_OVERSAMPLE_DISABLED;

    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], SAMPLES_IN_BUFFER);
    APP_ERROR_CHECK(err_code);
}


/**
 * @brief Function for main application entry.
 */
int main(void)
{
    uint32_t err_code = NRF_LOG_INIT(NULL);
    APP_ERROR_CHECK(err_code);

    NRF_LOG_DEFAULT_BACKENDS_INIT();

    ret_code_t ret_code = nrf_pwr_mgmt_init();
    APP_ERROR_CHECK(ret_code);

    saadc_init();

    NRF_LOG_INFO("SAADC HAL simple example started.");
    
    while (1)
    {
        err_code = nrfx_saadc_sample_convert(0, ADC_value);
        APP_ERROR_CHECK(err_code);

    }
}

/** @} */


Here's my code:
Anyone know, where does come from the error?

Thanks,
Sylvain.