Posted on September 23, 2016 at 18:33Hi everyone! I'm having some difficulty getting variables to be declared in external SRAM. I'm using a STM32L4. If I do address casting like the FMC example project for the eval board in the library code I can access the SRAM, but I can't seem to declare a variable to be always there.
Here are the changes I've made to the default STM32L476G linker file:
/* Specify the memory areas */
MEMORY
{
FLASH (rx) : ORIGIN = 0x8000000, LENGTH = 1024K
RAM (xrw) : ORIGIN = 0x20000000, LENGTH = 96K
SRAM (xrw) : ORIGIN = 0x60000000, LENGTH = 128K
}
And at the end:
/* Add section for external RAM */
.bssext :
{
_sbssext = .; /* define a global symbol at bssext start */
__bssext_start__ = _sbssext;
*(.bssext)
*(.bssext*)
. = ALIGN(4);
_ebssext = .; /* define a global symbol at bssext end */
__bssext_end__ = _ebssext;
} >SRAM AT> RAM
/* Remove information from the standard libraries */
/* Unchanged, but included to show where it is in the linker file */
/DISCARD/ :
{
libc.a ( * )
libm.a ( * )
libgcc.a ( * )
}
At the top of one of my files I'm declaring a variable as such:
__attribute__((section(''.bssext''))) uint8_t pExtMemoryTest[32];
This should be putting it into the .bssext section, which should be in SRAM, but the map file says it's still in regular ram.
.bss._ZL13gs_mainBuffer
0x20002368 0x200 Debug/CdcRxForwardTask.o
.bssext 0x20002568 0x20 Debug/DpmBootTask.o
0x20002568 pExtMemoryTest .bss._ZN6HwInit14m_nResetReasonE
0x20002588 0x4 Debug/DpmHwInit.o
0x20002588 _ZN6HwInit14m_nResetReasonE
It's right in the middle of the .bss section and is clearly in internal RAM.
What am I missing? Any help would be greatly appreciated, thanks!
