main.c

/*
 * w25q64.c
 *
 * Created: 2019-07-14 오전 2:58:29
 * Author : yeong
 */ 

#define F_CPU 16000000UL
#include <avr/io.h>
#include <util/delay.h>

#include "spi.h"

#define W25Q_SS_PIN 1

#define LOGIC_LOW   0
#define LOGIC_HIGH  1

int main(void)
{
	spi_init();
	uart0_init();

	// CS init
	w25q_ss_pin_init();
	w25q_ss_pin_drive(LOGIC_HIGH);
	while(1)
	{
		uint8_t man_id = w25q_read_manufacturer_id();
		w25q_ss_pin_drive(LOGIC_LOW);
		spi_transmit(man_id);
		w25q_ss_pin_drive(LOGIC_HIGH);
		_delay_ms(1);
		printf("manID:0x%X\r\n", man_id);
		uint8_t dev_id = w25q_read_device_id();
		w25q_ss_pin_drive(LOGIC_LOW);
		spi_transmit(dev_id);
		w25q_ss_pin_drive(LOGIC_HIGH);
		printf("devID:0x%X\r\n", dev_id);
		_delay_ms(5);

	}
	return 1;
}

spi.c

/*
 * spi.c
 *
 * Created: 2019-07-14 오전 4:16:00
 *  Author: yeong
 */ 

 #include "spi.h"

/**@brief: initializes the SPI peripheral
 *         sets the MOSI, SCLK and SS Pins as outputs
 *         enables the SPI in master mode, f/16 clk
 */

void spi_init(void)
{
    DDRB = ((1<<SPI_MOSI_PIN)|(1<<SPI_SCLK_PIN)|(1<<SPI_SS_PIN)); //spi pins on port b MOSI SCK,SS outputs
    SPCR = ((1<<SPE)|(1<<MSTR));  // SPI enable, Master, f/16, 
                                            // CPOL0 SCK is low when idle, CPHA0 sample leading edge
}

/** @brief: spi transmit function
 *          sends and receives a byte at the same time
 */

char spi_transmit(char tx_byte)
{
   SPDR = tx_byte;
   while(!(SPSR & (1<<SPIF)));
   return SPDR;
}

w25q64.c

/*
 * w25q64.c
 *
 * Created: 2019-07-14 오전 4:16:22
 *  Author: yeong
 */ 

 #include "w25q64.h"

/** @brief: initialize the ss pin
 */
void w25q_ss_pin_init(void)
{
    W25Q_CONTROL_DDR |= (1<<W25Q_SS_PIN);   // Set as output
}

/** @brief: drives the ss pin
 */
void w25q_ss_pin_drive(uint8_t high)
{
    if(high)
    {
        W25Q_CONTROL_PORT |= (1<<W25Q_SS_PIN);
    }
    else
    {
        W25Q_CONTROL_PORT &= ~(1<<W25Q_SS_PIN);
    }
}

/** @brief: return the manufacturer ID
 */
char w25q_read_manufacturer_id(void)
{
    w25q_ss_pin_drive(LOGIC_LOW);
    spi_transmit(0x90);
    spi_transmit(0x00);
    spi_transmit(0x00);
    spi_transmit(0x00);
    uint8_t man_id = spi_transmit(0x00);
    spi_transmit(0x00);
    w25q_ss_pin_drive(LOGIC_HIGH);
    return man_id;
}

/** @brief: return the device ID
 */
char w25q_read_device_id(void)
{
    w25q_ss_pin_drive(LOGIC_LOW);
    spi_transmit(0x90);
    spi_transmit(0x00);
    spi_transmit(0x00);
    spi_transmit(0x00);
    spi_transmit(0x00);
    uint8_t dev_id = spi_transmit(0x00);
    w25q_ss_pin_drive(LOGIC_HIGH);
    return dev_id;
}