使用SPI与外部flash(MX25L6406EM21)IC通信

• 连接方式

如上图所示，MCU通过SPI2与外部flash芯片进行相连接。

• MCUspi2初始化

定义SPI2中所使用的SPI端口号

spi2中通信功能初始化

读数据与写数据

• 指令说明

查看flash芯片的datasheet，mx25芯片支持按照页来写，按照扇区来擦除。page_program为 0x02 ,sector_erase为0x20。并且在向每个页中写数据前，必须先保证此页所在的扇区已经进行擦除操作。并且每一页最大写256byte ，一个扇区的大小为4Kbyte

• 写数据，按照页来写数据（写一页数据）

依据芯片写指令 0x06

void spi_flash_write_page(uint8_t* pBuffer,uint32_t write_address,uint16_t num_byte_to_write) //向页中写入数据，其中write_address必须为256的整数据部，即一页的开始位置，
{
    uint16_t i=0;
    
//    debug_out("SpiPage:0x%08x Len:%d\r\n", write_address, num_byte_to_write);
    
    spi_flash_wait_busy();   //忙等待
    spi_flash_write_enable();
    spi_flash_wait_busy();
    
    spi2_cs_low();
    spi2_read_write_byte(MX25_PAGE_PROGRAM);
    spi2_read_write_byte((uint8_t) ( ((write_address) >> 16 )&0xFF) );
    spi2_read_write_byte((uint8_t) ( ((write_address) >> 8 )&0xFF) );
    spi2_read_write_byte((uint8_t) ( (write_address)&0xff ) );
    
    for(i=0;i<num_byte_to_write;i++)
    {
        spi2_read_write_byte(pBuffer[i]);
    }
    spi2_cs_high();
    spi_flash_wait_busy();        
    
}

• 擦除扇区

void spi_flash_erase_sector(uint32_t addr)   //addr地起为4K的倍数，清除一个扇区
{
    spi_flash_wait_busy();
    spi_flash_write_enable();
    spi_flash_wait_busy();
    
    //½øÐвÁ³ý²Ù×÷
    spi2_cs_low();
    spi2_read_write_byte(MX25_SECTOR_ERASE);
    spi2_read_write_byte((uint8_t) ( ((addr) >>  )&0xFF) );
    spi2_read_write_byte((uint8_t) ( ((addr) >>  )&0xFF) );
    spi2_read_write_byte((uint8_t) ( (addr)&0xff ) );
    spi2_cs_high();
    spi_flash_wait_busy();
}

• 在指定地址处开始写入指定长度的数据

从指定地址，写入指定长度数据。也是从一个扇区的开始处进行写，计算出一共需要写入多少页，同时如果为一个扇区的开始处，记得需要进行扇区擦除操作。

void spi_flash_write(uint8_t* pBuffer,uint32_t address,uint16_t buffer_len) 
{
    uint16_t pageCount = ;
    uint16_t pageIndex = ;
    uint16_t length = ;
    uint16_t i=;
    pageCount = buffer_len / SPI_FLASH_PAGE_SIZE;
    if( ( buffer_len % SPI_FLASH_PAGE_SIZE ) !=  )
    {
        pageCount += ;
    }
    while( pageIndex < pageCount )
    {
        length = buffer_len - ( pageIndex * SPI_FLASH_PAGE_SIZE ) ;
        length = length > SPI_FLASH_PAGE_SIZE ? SPI_FLASH_PAGE_SIZE : length;
        if( ( (  address + pageIndex * SPI_FLASH_PAGE_SIZE ) % SPI_FLASH_SECTOR_SIZE ) ==  )
        {
            spi_flash_erase_sector( address + pageIndex * SPI_FLASH_PAGE_SIZE );
        }
        spi_flash_write_page(pBuffer + pageIndex * SPI_FLASH_PAGE_SIZE, address + pageIndex * SPI_FLASH_PAGE_SIZE, length );
        pageIndex ++;
    }
}

• 读数据

读数据相对于写数据来说，显得比较简单的多，从指定地址开始读，读取指定的长度

void spi_flash_read(uint8_t* pBuffer,uint32_t read_address,uint16_t num_byte_to_read) 
{
    uint16_t i=0;
    spi_flash_wait_busy();
    
    spi2_cs_low();
    
    spi2_read_write_byte(MX25_READ_DATA);
    spi2_read_write_byte((uint8_t) ( ((read_address) >> 16 )&0xFF) );
    spi2_read_write_byte((uint8_t) ( ((read_address) >> 8 )&0xFF) );
    spi2_read_write_byte((uint8_t) ( (read_address)&0xff ) );
    
    for(i=0;i<num_byte_to_read;i++)
    {
        pBuffer[i]=spi2_read_write_byte(0xFF);
    }
    
    spi2_cs_high();
    
}

至此整个驱动编写完成。