Posted on February 10, 2018 at 21:32Hi Alexander,
My apologies, I forgot to reply to your comment. For number 2, cube seems to generate callbacks that always call the DMA. This can be seen in sd_diskio.c
RESULT SD_read(BYTE lun, BYTE *buff, DWORD sector, UINT count)
{
DRESULT res = RES_ERROR;
ReadStatus = 0;
uint32_t timeout;
&sharpif (ENABLE_SD_DMA_CACHE_MAINTENANCE == 1)
uint32_t alignedAddr;
&sharpendif
if(BSP_SD_ReadBlocks_DMA((uint32_t*)buff,
(uint32_t) (sector),
count) == MSD_OK)
{ReadStatus = 1;
/* Wait that the reading process is completed or a timeout occurs */
timeout = HAL_GetTick();
while((ReadStatus == 0) && ((HAL_GetTick() - timeout) < SD_TIMEOUT))
{
}
/* incase of a timeout return error */
if (ReadStatus == 0)
{
res = RES_ERROR;
}
else
{
ReadStatus = 0;
timeout = HAL_GetTick();
while((HAL_GetTick() - timeout) < SD_TIMEOUT)
{
if (BSP_SD_GetCardState() == SD_TRANSFER_OK)
{
res = RES_OK;
&sharpif (ENABLE_SD_DMA_CACHE_MAINTENANCE == 1)
/*
the SCB_InvalidateDCache_by_Addr() requires a 32-Bit aligned address,
adjust the address and the D-Cache size to invalidate accordingly.
*/
alignedAddr = (uint32_t)buff & ~3;
SCB_InvalidateDCache_by_Addr((uint32_t*)alignedAddr, count*BLOCKSIZE + ((uint32_t)buff - alignedAddr));
&sharpendif
break;
}
}
}
}
return res;
}
Without DMA this functin should be:
DRESULT SD_read(BYTE lun, BYTE *buff, DWORD sector, UINT count)
{
DRESULT res = RES_ERROR;
if(BSP_SD_ReadBlocks((uint32_t*)buff,
(uint32_t) (sector),
count, SD_TIMEOUT) == MSD_OK)
{
/* wait until the read operation is finished */
while(BSP_SD_GetCardState()!= MSD_OK)
{
}
res = RES_OK;
}
return res;
}
Note the change from sd_readblock.
and also the write function should be:
&sharpif _USE_WRITE == 1
DRESULT SD_write(BYTE lun, const BYTE *buff, DWORD sector, UINT count)
{
DRESULT res = RES_ERROR;
if(BSP_SD_WriteBlocks((uint32_t*)buff,
(uint32_t)(sector),
count, SD_TIMEOUT) == MSD_OK)
{
/* wait until the Write operation is finished */
while(BSP_SD_GetCardState() != MSD_OK)
{
}
res = RES_OK;
}
return res;
}
&sharpendif /* _USE_WRITE == 1 */
Now the DMA won't be called at all.
If you have external pullups it should not be a problem!
