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=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(); //??DD2á3y2ù×÷ spi2_cs_low(); spi2_read_write_byte(MX25_SECTOR_ERASE); spi2_read_write_byte((uint8_t) ( ((addr) >> 16 )&0xFF) ); spi2_read_write_byte((uint8_t) ( ((addr) >> 8 )&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 = 0; uint16_t pageIndex = 0; uint16_t length = 0; uint16_t i=0; pageCount = buffer_len / SPI_FLASH_PAGE_SIZE; if( ( buffer_len % SPI_FLASH_PAGE_SIZE ) != 0 ) { pageCount += 1; } 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 ) == 0 ) { 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。
