Question about external RAM and SD

[pcu]

Posted on October 02, 2014 at 17:05

Hello,

I try to test my application with a new setup with external SRAM on the STM3240G kit, for heap and stack.

I use FatFS on SDIO which needs DMA. When I read a file there is a problem.

I know it is not possible to read a file to CCMRAM because of the DMA. Then is it the same problem?

Thank you.

[Tesla DeLorean]

Posted on October 02, 2014 at 18:04

You should be able to DMA to external memory (FSMC), but it will be slower, with whatever ramifications come with that. ie 16-bit wide, multiple cycles, heavier contention.

[pcu]

Posted on October 03, 2014 at 11:37

Of course, it will be slower. But if I don't have enough memory I must see for alternate solution.

I will check why I can't access the SD with variables(stack memory) stored on external SRAM

.

KR.

[frankmeyer9]

Posted on October 03, 2014 at 11:49

Of course, it will be slower.

 

There are two thing to mention here:

First, you cannot startup with an external stack, as it does not exist at this stage.

Second, if you have a rigid interrupt regime, it might blow. Interrupts imply stack operations.

I would opt for other data to move to external RAM, but not the stack.

But if I don't have enough memory I must see for alternate solution.

 

There are other MCUs, and other vendors.