Hey thx for your reply. I have been looking at the example project.
But I still have 2 questions:
1) in middlewares/fatfs/drivers/sdram_diskio.c there are 2 functions which seem to be used read/write variables in the external RAM
/**
* @brief Reads Sector(s)
* @param lun : not used
* @param *buff: Data buffer to store read data
* @param sector: Sector address (LBA)
* @param count: Number of sectors to read (1..128)
* @retval DRESULT: Operation result
*/
DRESULT SDRAMDISK_read(BYTE lun, BYTE *buff, DWORD sector, UINT count)
{
uint32_t *pSrcBuffer = (uint32_t *)buff;
uint32_t BufferSize = (BLOCK_SIZE * count)/4;
uint32_t *pSdramAddress = (uint32_t *) (SDRAM_DEVICE_ADDR + (sector * BLOCK_SIZE));
for(; BufferSize != 0; BufferSize--)
{
*pSrcBuffer++ = *(__IO uint32_t *)pSdramAddress++;
}
return RES_OK;
}
/**
* @brief Writes Sector(s)
* @param lun : not used
* @param *buff: Data to be written
* @param sector: Sector address (LBA)
* @param count: Number of sectors to write (1..128)
* @retval DRESULT: Operation result
*/
#if _USE_WRITE == 1
DRESULT SDRAMDISK_write(BYTE lun, const BYTE *buff, DWORD sector, UINT count)
{
uint32_t *pDstBuffer = (uint32_t *)buff;
uint32_t BufferSize = (BLOCK_SIZE * count)/4;
uint32_t *pSramAddress = (uint32_t *) (SDRAM_DEVICE_ADDR + (sector * BLOCK_SIZE));
for(; BufferSize != 0; BufferSize--)
{
*(__IO uint32_t *)pSramAddress++ = *pDstBuffer++;
}
return RES_OK;
}
#endif /* _USE_WRITE == 1 */
Now these functions do not access the external RAM. Where is the external RAM accessed
2) The start address of 0xD0000000 is added to the requested address in SDRAMDISK_write/SDRAMDISK_read
But should there be an extra section in the linker script (Address 0-64k) to tell the linker thesse addresses are valid ram adresses too?
let's say i have a function
void foo()
{
//access some global var
int bar = g_bar;
}
In my code I don't care wheter g_bar is located in the internal or external RAM. How does the program know where to load this value from?
