一种比较简单的在USB U盘中访问nandflash的方法

u8 nandflash_write_buffer[NAND_SERECT_FULL_SIZE];

static int currentBlock = -1;

static int currentPage = -1;

//带缓冲的nand读取,不支持跨扇区

void NAND_Read_Addr_Mal(u32 addr,u8* buffer,u32 length)

{

u32 i = 0;

u32 readBlock = ((addr/NAND_SERECT_SIZE)/NAND_PAGE_NUM);//获取要写入的块

u32 readPage = ((addr/NAND_SERECT_SIZE)%NAND_PAGE_NUM);//获取要写入的页面

u32 readoffset = (addr%NAND_SERECT_SIZE);//写入位置偏移

u32 readPageCount = ((length + readoffset)/NAND_SERECT_SIZE);//获取一共需要写入的页

if(((length + readoffset)%NAND_SERECT_SIZE) != 0)readPageCount++;//比如刚好2048的时候,就还是在一页

if(readPageCount == 1)//仅读取一个快

{

//先检查当前需要读取的数据是不是在缓冲区中

if(currentBlock >= 0 && currentPage >= 0)

{

if(readBlock == currentBlock && readPage == currentPage)

{

//在缓冲区中读取数据

for(i = 0; i < length; i++)

{

buffer[i] = nandflash_write_buffer[readoffset+i];

}

}

else

{

//在物理设备中读取数据

NAND_Read_Random_Page(readBlock,readPage,readoffset,buffer,length);

}

}

else if(currentBlock == -1 && currentPage == -1)

{

//缓冲区为空,直接进行物理读取

NAND_Read_Random_Page(readBlock,readPage,readoffset,buffer,length);

}

}

else

{

//      printf("2 or up sector not vailed \r\n");

}

}

//带缓冲nand写入,不支持跨扇区

void NAND_Write_Addr_Mal(u32 addr,u8* buffer,u32 length)

{

u32 writeBlock = (addr/NAND_SERECT_SIZE)/NAND_PAGE_NUM; //获取要写入的块

u32 writePage = (addr/NAND_SERECT_SIZE)%NAND_PAGE_NUM;  //获取要写入的页面

u32 writeoffset = (addr%NAND_SERECT_SIZE);              //写入位置偏移

u32 i = 0;

u32 copy;

if(currentBlock >= 0 && currentPage >= 0)

{

if(currentBlock == writeBlock && currentPage == writePage)//没有切换页面,那么数据更新依旧在缓存中

{

for(i = writeoffset; i < writeoffset+length ;i++)

{

nandflash_write_buffer[i] = buffer[i-writeoffset];

}

}

else

{

//更新了页面的写入,先将缓存中数据写入物理设备,进行新的一轮缓存操作

copy = (currentBlock/42)+NAND_COPYBACL_BLOCK_START;

//擦除交换分区

NAND_Erase_Block(copy);

for(i = 0; i < NAND_PAGE_NUM;i++)//拷贝数据到交换分区

{

if(i != currentPage)

{

NAND_Copy_Back_Page(currentBlock,i,copy,i);

}

}

//擦除源分区

NAND_Erase_Block(currentBlock);

//将原来数据拷贝回去

for(i = 0; i < NAND_PAGE_NUM;i++)//拷贝数据到交换分区

{

if(i != currentPage)

{

NAND_Copy_Back_Page(copy,i,currentBlock,i);

}

}

//将缓存数据拷贝到目的分区

NAND_Write_Page_full(currentBlock,currentPage,NAND_SERECT_FULL_SIZE,nandflash_write_buffer);

//到这里缓存的写入物理设备完成,接下来开始新一轮缓存

NAND_Read_Full_Page(writeBlock,writePage,nandflash_write_buffer,NAND_SERECT_FULL_SIZE);

currentBlock = writeBlock;

currentPage = writePage;//更新标记

//接下来更新数据,数据更新在缓存中进行,切换的时候写入

for(i = writeoffset; i < writeoffset+length ;i++)

{

nandflash_write_buffer[i] = buffer[i-writeoffset];

}

}

}

else if(currentBlock == -1 && currentPage == -1)//当前缓存包里面没有数据

{

//从nand中读出来

NAND_Read_Full_Page(writeBlock,writePage,nandflash_write_buffer,NAND_SERECT_FULL_SIZE);

currentBlock = writeBlock;

currentPage = writePage;//更新标记

//接下来更新数据,数据更新在缓存中进行,切换的时候写入

for(i = writeoffset; i < writeoffset+length ;i++)

{

nandflash_write_buffer[i] = buffer[i-writeoffset];

}

}

}

void Nand_Flush(void)   //nand缓冲区刷入设备

{

u32 copy;

u32 i = 0;

//将还没有写入的数据刷新到nand中,标记归零

if(currentBlock >= 0 && currentPage >= 0)

{

//更新了页面的写入,先将缓存中数据写入物理设备,进行新的一轮缓存操作

copy = (currentBlock/42)+NAND_COPYBACL_BLOCK_START;

//擦除交换分区

NAND_Erase_Block(copy);

for(i = 0; i < NAND_PAGE_NUM;i++)//拷贝数据到交换分区

{

if(i != currentPage)

{

NAND_Copy_Back_Page(currentBlock,i,copy,i);

}

}

//擦除源分区

NAND_Erase_Block(currentBlock);

//将原来数据拷贝回去

for(i = 0; i < NAND_PAGE_NUM;i++)//拷贝数据到交换分区

{

if(i != currentPage)

{

NAND_Copy_Back_Page(copy,i,currentBlock,i);

}

}

//将缓存数据拷贝到目的分区

NAND_Write_Page_full(currentBlock,currentPage,NAND_SERECT_FULL_SIZE,nandflash_write_buffer);

currentBlock = -1;

currentPage = -1;

}

}

结合之前写的USB做U盘的例子来看,能降低写文件的时候的擦除次数