Hi,
I'm trying to use the SDRAM from my STM32F429-Disco Board. I have created a function to initialize the SDRAM which is executed in the main-function. The SDRAM implementation was done with the following instruction: http://en.radzio.dxp.pl/stm32f429idiscovery/sdram.html and should work since I'm able to write to the SDRAM. THe SDRAM Initialization function is executed in the main function.
I'm not sure but I think the problem is with my linker skript or syscall.c
I changed the following things in files, syscall.c -The following code:
caddr_t _sbrk(int incr)
{
extern char end asm("end");
static char *heap_end;
char *prev_heap_end;
if (heap_end == 0)
heap_end = &end;
prev_heap_end = heap_end;
if (heap_end + incr > stack_ptr)
{
// write(1, "Heap and stack collision\n", 25);
// abort();
errno = ENOMEM;
return (caddr_t) -1;
}
heap_end += incr;
return (caddr_t) prev_heap_end;
}
to the following syscall.c:
caddr_t _sbrk(int incr)
{
// extern char end asm("end"); // June 2019 - US
extern char __heap_start asm ("__heap_start");
extern char __heap_limit asm ("__heap_limit");
static char *heap_end;
static char *heap_limit = &__heap_limit;
char *prev_heap_end;
if (heap_end == 0)
heap_end = &__heap_start;
prev_heap_end = heap_end;
if (heap_end + incr > heap_limit)
{
// write(1, "Heap and stack collision\n", 25);
// abort();
errno = ENOMEM;
return (caddr_t) -1;
}
heap_end += incr;
return (caddr_t) prev_heap_end;
}
And for the linker skript, I changed:
- heap was commented out
- heap_start and heap_limit was added
- SDRAM was added to the memory areas
- user_stack was altered
/*_Min_Heap_Size = 0x200; /* required amount of heap commented out*/
__heap_start = 0xD0000000; /*Was added*/
__heap_limit = 0xD0800000; /*Was added*/
/* Specify the memory areas - SDRAM was added */
MEMORY
{
FLASH (rx) : ORIGIN = 0x8000000, LENGTH = 2048K
RAM (xrw) : ORIGIN = 0x20000000, LENGTH = 192K
CCMRAM (rw) : ORIGIN = 0x10000000, LENGTH = 64K
SDRAM (xrw) : ORIGIN = 0xD000000, LENGTH = 8M
}
/* User_stack section, used to check that there is enough RAM left was altered */
._user_stack :
{
. = ALIGN(8);
PROVIDE ( end = . );
PROVIDE ( _end = . );
. = . + _Min_Stack_Size;
. = ALIGN(8);
} >RAM
But I have the problem, when I create a big array - globally - with:
volatile uint16_t test[76800];
I still get an RAM overflow, which should not happen since the SDRAM should be used.
How can I fix this, to use the SDRAM as extension of the RAM?
Thank you
