How can I read micron memory using SPI protocol

Question

Hello all,

I try to send a command to read device ID (0x9F) of a micron memory device (N25Q064A) using SPI protocol. I have the following hardware configuration :

NRF_SPI_CLK --> N25_CLOCK
NRF_SPI_MOSI --> N25_DQ0
N52_SPI_MISO <----------- N25_DQ1
N52_SPI_SS <----------- N25_SS

N25 is set in the high impedance (set as input + no pull up ). And there is my code:

/* Copyright (c) 2015 Nordic Semiconductor. All Rights Reserved.
 *
 * The information contained herein is property of Nordic Semiconductor ASA.
 * Terms and conditions of usage are described in detail in NORDIC
 * SEMICONDUCTOR STANDARD SOFTWARE LICENSE AGREEMENT.
 *
 * Licensees are granted free, non-transferable use of the information. NO
 * WARRANTY of ANY KIND is provided. This heading must NOT be removed from
 * the file.
 *
 */

#include "nrf_drv_spi.h"
#include "app_util_platform.h"
#include "nrf_gpio.h"
#include "nrf_delay.h"
#include "boards.h"
#include "app_error.h"
#include <string.h>
#define NRF_LOG_MODULE_NAME "APP"
#include "nrf_log.h"
#include "nrf_log_ctrl.h"

#include "nordic_common.h"
#include "app_uart.h"

#define INT_DQ3 24
#define INT_DQ2 20

#define SPI_INSTANCE  0 /**< 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[] = TEST_STRING;           /**< TX buffer. */
static uint8_t       m_rx_buf[sizeof(TEST_STRING) + 1];    /**< RX buffer. */
static const uint8_t m_length = sizeof(m_tx_buf);        /**< Transfer length. */

#define SPI_TEST_MOSI_PIN 22
#define SPI_TEST_MISO_PIN 19
#define SPI_TEST_SCK_PIN 23

/**
 * @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("Transfer completed.\r\n");
    if (m_rx_buf[0] != 0)
    {
        NRF_LOG_INFO(" Received: \r\n");
        NRF_LOG_HEXDUMP_INFO(m_rx_buf, strlen((const char *)m_rx_buf));
    }
}

void initSPI()
{
    nrf_drv_spi_config_t spi_config = NRF_DRV_SPI_DEFAULT_CONFIG;
    spi_config.frequency = NRF_DRV_SPI_FREQ_8M ;

    spi_config.ss_pin   = NRF_DRV_SPI_PIN_NOT_USED;
    spi_config.miso_pin = SPI_TEST_MISO_PIN;
    spi_config.mosi_pin = SPI_TEST_MOSI_PIN;
    spi_config.sck_pin  = SPI_TEST_SCK_PIN;

    nrf_drv_spi_init(&spi, &spi_config, spi_event_handler);
}

int main(void)
{
    NRF_LOG_INFO("SPI example\r\n");
    initSPI();

    nrf_gpio_cfg_output(INT_DQ3);
    nrf_gpio_pin_set(INT_DQ3);
    nrf_gpio_cfg_input(INT_DQ2, NRF_GPIO_PIN_NOPULL);

    uint8_t tx_read[1] = {0x03};

    while (1)
    {
        // Reset rx buffer and transfer done flag
        memset(m_rx_buf, 0, m_length);
        spi_xfer_done = false;

        nrf_drv_spi_transfer(&spi, tx_read, 1, m_rx_buf,20);
        nrf_delay_ms(1);     
        while (!spi_xfer_done)
        {
            __WFE();
        }
        
        NRF_LOG_FLUSH();
    }
}