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。
- MCU spi2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=; // 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) >> )&0xFF) );
spi2_read_write_byte((uint8_t) ( ((write_address) >> )&0xFF) );
spi2_read_write_byte((uint8_t) ( (write_address)&0xff ) ); for(i=;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=;
spi_flash_wait_busy(); spi2_cs_low(); spi2_read_write_byte(MX25_READ_DATA);
spi2_read_write_byte((uint8_t) ( ((read_address) >> )&0xFF) );
spi2_read_write_byte((uint8_t) ( ((read_address) >> )&0xFF) );
spi2_read_write_byte((uint8_t) ( (read_address)&0xff ) ); for(i=;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。