在stm32中用SPI读写flash

在STM32中使用SPI读写flash的步骤如下：

1. 配置SPI模块，设置SPI的时钟极性、时钟相位、主从模式、数据位长度等参数。

2. 配置GPIO口，将SPI的SCK、MOSI、MISO和CS引脚设置为SPI模式。

3. 初始化flash芯片，发送命令以及地址等信息，使flash进入读或写模式。

4. 使用SPI发送或接收数据，读取或写入flash中的数据。

下面是一段示例代码，用于在STM32F4上使用SPI读取Winbond W25Q128FV SPI Flash的ID：

#include "stm32f4xx.h"
#include <stdio.h>

#define FLASH_CS_PIN    GPIO_Pin_4
#define FLASH_CS_PORT   GPIOE

#define CMD_READ_ID     0x9F

void SPI_Config(void)
{
    GPIO_InitTypeDef GPIO_InitStructure;
    SPI_InitTypeDef SPI_InitStructure;

    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB, ENABLE);
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_SPI1, ENABLE);

    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_3 | GPIO_Pin_4 | GPIO_Pin_5;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
    GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
    GPIO_Init(GPIOB, &GPIO_InitStructure);

    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
    GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
    GPIO_Init(GPIOB, &GPIO_InitStructure);

    GPIO_PinAFConfig(GPIOB, GPIO_PinSource3, GPIO_AF_SPI1);
    GPIO_PinAFConfig(GPIOB, GPIO_PinSource4, GPIO_AF_SPI1);
    GPIO_PinAFConfig(GPIOB, GPIO_PinSource5, GPIO_AF_SPI1);

    GPIO_SetBits(GPIOB, GPIO_Pin_6);

    SPI_I2S_DeInit(SPI1);

    SPI_InitStructure.SPI_Direction = SPI_Direction_2Lines_FullDuplex;
    SPI_InitStructure.SPI_Mode = SPI_Mode_Master;
    SPI_InitStructure.SPI_DataSize = SPI_DataSize_8b;
    SPI_InitStructure.SPI_CPOL = SPI_CPOL_Low;
    SPI_InitStructure.SPI_CPHA = SPI_CPHA_1Edge;
    SPI_InitStructure.SPI_NSS = SPI_NSS_Soft;
    SPI_InitStructure.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_256;
    SPI_InitStructure.SPI_FirstBit = SPI_FirstBit_MSB;
    SPI_InitStructure.SPI_CRCPolynomial = 7;
    SPI_Init(SPI1, &SPI_InitStructure);

    SPI_Cmd(SPI1, ENABLE);
}

void SPI_WriteByte(uint8_t byte)
{
    while (SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_TXE) == RESET);
    SPI_I2S_SendData(SPI1, byte);
    while (SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_RXNE) == RESET);
    SPI_I2S_ReceiveData(SPI1);
}

uint8_t SPI_ReadByte(void)
{
    while (SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_TXE) == RESET);
    SPI_I2S_SendData(SPI1, 0xFF);
    while (SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_RXNE) == RESET);
    return SPI_I2S_ReceiveData(SPI1);
}

void Flash_CS_Enable(void)
{
    GPIO_ResetBits(FLASH_CS_PORT, FLASH_CS_PIN);
}

void Flash_CS_Disable(void)
{
    GPIO_SetBits(FLASH_CS_PORT, FLASH_CS_PIN);
}

void Flash_Init(void)
{
    Flash_CS_Disable();
    SPI_WriteByte(0x06);    // Write Enable
    Flash_CS_Enable();
    Flash_CS_Disable();
}

uint32_t Flash_ReadID(void)
{
    uint8_t id[3];

    Flash_CS_Enable();
    SPI_WriteByte(CMD_READ_ID);
    id[0] = SPI_ReadByte();
    id[1] = SPI_ReadByte();
    id[2] = SPI_ReadByte();
    Flash_CS_Disable();

    return ((uint32_t)id[0] << 16) | ((uint32_t)id[1] << 8) | (uint32_t)id[2];
}

int main(void)
{
    uint32_t id;

    SPI_Config();
    Flash_Init();
    id = Flash_ReadID();

    printf("Flash ID: 0x%06X\r\n", id);

    while (1);
}

在这个例子中，我们先配置了SPI1的GPIO口和SPI模块，并且初始化了Flash芯片。然后，我们发送读取Flash ID的命令（0x9F），并读取3个字节的ID号。最后，我们将ID号打印到串口上。需要注意的是，在读写Flash之前，我们需要通过写使能命令（0x06）将Flash芯片的写使能位设置为1，以允许对Flash进行写操作。