Posted by tarek bouchkati on 2016-02-08 16:07

Hello Franz,

you need to specify SDRAM memory in your linker file (here I am using a linker for STM32L476RGTx with 1M FLASH and 96K RAM)

/* Specify the memory areas */
MEMORY
{
FLASH (rx)      : ORIGIN = 0x08000000, LENGTH = 1M
RAM (xrw)       : ORIGIN = 0x20000000, LENGTH = 96K
SDRAM(xrw)    : ORIGIN = 0x????????, LENGTH = 8M
}

And modify >RAM by >SDRAM

/* User_heap_stack section, used to check that there is enough RAM left */
  ._user_heap_stack :
  {
    . = ALIGN(4);
    PROVIDE ( end = . );
    PROVIDE ( _end = . );
    . = . + _Min_Heap_Size;
    . = . + _Min_Stack_Size;
    . = ALIGN(4);
  } >SDRAM

Update:
Do not forget to initialize you SDRAM before your application starts !
It should be done in Reset Handler (in startup file) in assembly.

There are better solutions that writing in assembler
1- Start with the default STACK&HEAP location (RAM), initialize your SDRAM then switch to SDRAM as STACK&HEAP location
2- Separate Heap and stack locations (STACK in RAM and HEAP in SDRAM) in linker file, than initialize SDRAM in your main before any malloc usage