How to set or configure gain register in SAADC example? So that i can set various gain.

Question

I am trying to configure or set gain in SAADC example, for various gains it should operate but i am not getting how to set gain register so that i get SAADC output depending on various gain and even i tried to change gain values in nrfx.saadc.h file but getting error. Gain defined in nrfx.saadc.h file are default one but i want it to work as per user defined gain.

But i want to set to below mentioned Gain values

1, 2, 4, 5, 8, 10, 16, 32.

When i am changing gain values in below mentioned lines i am getting error.

Default Gain in nrf.saadc.h file are

NRF_SAADC_GAIN1_6 = SAADC_CH_CONFIG_GAIN_Gain1_6, ///< Gain factor 1/6.
NRF_SAADC_GAIN1_5 = SAADC_CH_CONFIG_GAIN_Gain1_5, ///< Gain factor 1/5.
NRF_SAADC_GAIN1_4 = SAADC_CH_CONFIG_GAIN_Gain1_4, ///< Gain factor 1/4.
NRF_SAADC_GAIN1_3 = SAADC_CH_CONFIG_GAIN_Gain1_3, ///< Gain factor 1/3.
NRF_SAADC_GAIN1_2 = SAADC_CH_CONFIG_GAIN_Gain1_2, ///< Gain factor 1/2.
NRF_SAADC_GAIN1 = SAADC_CH_CONFIG_GAIN_Gain1, ///< Gain factor 1.
NRF_SAADC_GAIN2 = SAADC_CH_CONFIG_GAIN_Gain2, ///< Gain factor 2.
NRF_SAADC_GAIN4 = SAADC_CH_CONFIG_GAIN_Gain4, ///< Gain factor 4.

Gain defined in nrfx.saadc.h file is

.gain = NRF_SAADC_GAIN1_4,

So how can i define gains and make it work properly. Im using only 1channel AIN0 with SDK15.3 nrf52832.

Presently its working properly with default gain values.

.

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/**
 * Copyright (c) 2014 - 2019, Nordic Semiconductor ASA
 *
 * All rights reserved.
 *
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 *
 * 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
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/**
 * Copyright (c) 2014 - 2019, 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
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 * 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 "boards.h"
#include "app_error.h"
#include "nrf_delay.h"
#include "app_util_platform.h"
#include "nrf_pwr_mgmt.h"
#include "app_timer.h"


#include "nrf_log.h"
#include "nrf_log_ctrl.h"
#include "nrf_log_default_backends.h"
//-------------------------spi code---------------------------
#include "nrf_drv_spi.h"
#include "nrf_gpio.h"


#define SPI_INSTANCE  1 /**< SPI instance index. */
static const nrf_drv_spi_t spi = NRF_DRV_SPI_INSTANCE(SPI_INSTANCE);  /**< SPI instance. */
static volatile bool spi_xfer_done;  /**< Flag used to indicate that SPI instance completed the transfer. */

//#define TEST_STRING "Nordic"
static uint8_t       m_tx_buf[2];           /**< TX buffer. */
static uint8_t       m_rx_buf[40];    /**< RX buffer. */
//static const uint8_t m_length = sizeof(m_tx_buf);        /**< Transfer length. */


/**
 * @brief SPI user event handler.
 * @param event
 */
void spi_event_handler(nrf_drv_spi_evt_t const * p_event)
{
   spi_xfer_done = true;
	
		NRF_LOG_INFO(" Sent %d bytes: ", p_event->data.done.tx_length);
		for(int i=0; i< p_event->data.done.tx_length;i++)
		{
				NRF_LOG_INFO(" ;(0x%x); ",p_event->data.done.p_tx_buffer[i], p_event->data.done.p_tx_buffer[i]);
		}
		//NRF_LOG_INFO("\r\n");
		NRF_LOG_INFO(" Received %d bytes: ", p_event->data.done.rx_length);
		 for(int i=0; i< p_event->data.done.rx_length;i++)
		{
				NRF_LOG_INFO(" ;(0x%x); ",p_event->data.done.p_rx_buffer[i], p_event->data.done.p_rx_buffer[i]);
				nrf_delay_ms(5);
		}
		//NRF_LOG_INFO("\r\n\n");
}


void spi_con(void)
{
	
 nrf_gpio_cfg_output(18); //Configure pin 18 as output

 NRF_CLOCK->TASKS_HFCLKSTART = 1; //Start high frequency clock
 while (NRF_CLOCK->EVENTS_HFCLKSTARTED == 0)
 {
      //Wait for HFCLK to start
 }
 NRF_CLOCK->EVENTS_HFCLKSTARTED = 0; //Clear event
 
 
 //Configure GPIOTE to toggle pin 18 
 NRF_GPIOTE->CONFIG[0] = GPIOTE_CONFIG_MODE_Task << GPIOTE_CONFIG_MODE_Pos |
                         GPIOTE_CONFIG_POLARITY_Toggle << GPIOTE_CONFIG_POLARITY_Pos |
                         18 << GPIOTE_CONFIG_PSEL_Pos | 
                         GPIOTE_CONFIG_OUTINIT_Low << GPIOTE_CONFIG_OUTINIT_Pos;
 
 //Configure timer
 NRF_TIMER1->PRESCALER = 3;
 NRF_TIMER1->CC[0] = 1;  // Adjust the output frequency by adjusting the CC.
 NRF_TIMER1->SHORTS = TIMER_SHORTS_COMPARE0_CLEAR_Enabled << TIMER_SHORTS_COMPARE0_CLEAR_Pos;
 NRF_TIMER1->TASKS_START = 1;
 
 //Configure PPI
 NRF_PPI->CH[0].EEP = (uint32_t) &NRF_TIMER1->EVENTS_COMPARE[0];
 NRF_PPI->CH[0].TEP = (uint32_t) &NRF_GPIOTE->TASKS_OUT[0];
 
 NRF_PPI->CHENSET = PPI_CHENSET_CH0_Enabled << PPI_CHENSET_CH0_Pos;
	
    LEDS_CONFIGURE(BSP_LED_0_MASK);
    LEDS_OFF(BSP_LED_0_MASK);
	
	
	
		nrf_drv_spi_config_t spi_config = NRF_DRV_SPI_DEFAULT_CONFIG;
    spi_config.ss_pin   = SPI_SS_PIN;
    spi_config.miso_pin = SPI_MISO_PIN;
    spi_config.mosi_pin = SPI_MOSI_PIN;
    spi_config.sck_pin  = SPI_SCK_PIN;
    APP_ERROR_CHECK(nrf_drv_spi_init(&spi, &spi_config, spi_event_handler, NULL));

    NRF_LOG_INFO("SPI example started.");


        // Reset rx buffer and transfer done flag
        memset(m_rx_buf, 0, 40);
        spi_xfer_done = false;

			  m_tx_buf[0]=0x0d;
			
			
        APP_ERROR_CHECK(nrf_drv_spi_transfer(&spi, m_tx_buf, 2, m_rx_buf, 40));
	
	
	
        while (!spi_xfer_done)
        {
            __WFE();
        }
	
			
}

#define SAMPLES_IN_BUFFER 20
volatile uint8_t state = 1;

static const nrf_drv_timer_t m_timer = NRF_DRV_TIMER_INSTANCE(0);
static nrf_saadc_value_t     m_buffer_pool[2][SAMPLES_IN_BUFFER];
static nrf_ppi_channel_t     m_ppi_channel;
static uint32_t              m_adc_evt_counter;


void timer_handler(nrf_timer_event_t event_type, void * p_context)
{

}


void saadc_sampling_event_init(void)
{
    ret_code_t err_code;

    err_code = nrf_drv_ppi_init();
    APP_ERROR_CHECK(err_code);

    nrf_drv_timer_config_t timer_cfg = NRF_DRV_TIMER_DEFAULT_CONFIG;
    timer_cfg.bit_width = NRF_TIMER_BIT_WIDTH_32;
    err_code = nrf_drv_timer_init(&m_timer, &timer_cfg, timer_handler);
    APP_ERROR_CHECK(err_code);

    /* setup m_timer for compare event every 400ms */
    uint32_t ticks = nrf_drv_timer_ms_to_ticks(&m_timer, 100);
    nrf_drv_timer_extended_compare(&m_timer,
                                   NRF_TIMER_CC_CHANNEL0,
                                   ticks,
                                   NRF_TIMER_SHORT_COMPARE0_CLEAR_MASK,
                                   false);
    nrf_drv_timer_enable(&m_timer);

    uint32_t timer_compare_event_addr = nrf_drv_timer_compare_event_address_get(&m_timer,
                                                                                NRF_TIMER_CC_CHANNEL0);
    uint32_t saadc_sample_task_addr   = nrf_drv_saadc_sample_task_get();

    /* setup ppi channel so that timer compare event is triggering sample task in SAADC */
    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);
}


void saadc_sampling_event_enable(void)
{
    ret_code_t err_code = nrf_drv_ppi_channel_enable(m_ppi_channel);

    APP_ERROR_CHECK(err_code);
}


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);

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


void saadc_init(void)
{
    ret_code_t err_code;
    nrf_saadc_channel_config_t channel_config =
     NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN0);

    err_code = nrf_drv_saadc_init(NULL, 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);

    err_code = nrf_drv_saadc_buffer_convert(m_buffer_pool[1], 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);

		spi_con();
    saadc_init();
    saadc_sampling_event_init();
    saadc_sampling_event_enable();
    NRF_LOG_INFO("SAADC HAL simple example started.");

    while (1)
    {
        nrf_pwr_mgmt_run();
        NRF_LOG_FLUSH();
    }
}


/** @} */

This is the output what i am getting for default gain.

Please suggest.

How to set or configure gain register in SAADC example? So that i can set various gain.

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