Dynamic vector allocation in external RAM

[benoit2]

Hi,

I am currently working on a large project of my own on an STM32F7 cortex-m7 microcontroller in C++ using GCC. I need to store a wide array in an external SDRAM (16 MB) containing vectors of notes structures (12 bytes each). I have already a working FMC and a custom ram region created

/* Specify the memory areas */
MEMORY
{
RAM (xrw)       : ORIGIN = 0x20000000, LENGTH = 512K
FLASH (rx)      : ORIGIN = 0x08000000, LENGTH = 1024K
SDRAM (xrw)     : ORIGIN = 0xC0000000, LENGTH = 16M
}
 
/* Define output sections */
SECTIONS
{
  /* Section créée pour l'allocation dans la SDRAM externe*/
  .fmc :
  {
    . = ALIGN(8);
    *(.fmc)        
    *(.fmc*)
    . = ALIGN(8);
  } >SDRAM

my array is declared like this :

So far it's OK. I created an array of vectors in my external RAM. How can i proceed in order to make my vectors element creation

NotesVectorArray[position].push_back(note);

happening in the same external RAM dynamically ? I am currently only able to declare static data using the

__attribute__(section)
 
 

I read lot of things about C++ allocators, memory pools, but i don't get where the allocation take place in the vector code and how i should replace it... I "just" need to have the same allocation system than the usual but in another part of my memory for this precise type.

It seems possible to have multiple heaps. Where is located the connection between scatter file and the effective memory allocation ?

Maybe it's not a good idea to allocate it dynamically in this case what is the idea if i need to create an unknown number for notes ?

Thanks in advance,

Ben