Posted on October 03, 2016 at 12:39Hello,
I am using the STM32F746 Discovery Board with STM32 System Workbench IDE. I know SDRAM is a volatile memory but I want copy a picture to the external SDRAM at startup because it's too big for the internal Flash.
What I did fist is to initialize the SystemClock and the SDRAM in the SystemInit(). I checked it an it's working fine because I can use it without any more initialisation in the main().
My next step was to define an additional memory block in the LinkerScript.
MEMORY
{
FLASH (rx) : ORIGIN = 0x8000000, LENGTH = 1024K
RAM (xrw) : ORIGIN = 0x20000000, LENGTH = 320K
SDRAM (xrw) : ORIGIN = 0xC0000000, LENGTH = 8M
}
after this I added a section as followed. I copied that idea from the .data section which is copied from the Flash in the internal RAM.
SECTIONS
{
...
/* used by the startup to initialize data */
_sidata_sdram = LOADADDR(.sdram_data);
/* Initialized data sections goes into RAM, load LMA copy after code */
.sdram_data :
{
. = ALIGN(4);
_sdata_sdram = .; /* create a global symbol at data start */
*(.sdram_data) /* .sdram_data sections */
*(.sdram_data*) /* .sdram_data* sections */
. = ALIGN(4);
_edata_sdram = .; /* define a global symbol at data end */
} >SDRAM AT> FLASH
...
}
In the assembly written startup file I added .words for the defined addresses in the LinkerScript and a copy routine like for the .data. The routine I added after the SystemInit() that the SysClk and SDRAM are already initialized.
/* Call the clock system initialization function.*/
bl SystemInit
/* Copy the data segment initializers from flash to SRAM */
movs r1, #0
b LoopCopyDataSdram
CopyDataSdram:
ldr r3, =_sidata_sdram
ldr r3, [r3, r1]
str r3, [r0, r1]
adds r1, r1, #4
LoopCopyDataSdram:
ldr r0, =_sdata_sdram
ldr r3, =_edata_sdram
adds r2, r0, r1
cmp r2, r3
bcc CopyDataSdram
If I now define a global variable as followed I can't see that it's working.
__attribute__((__section__(''.sdram_data''))) uint8_t picture1[] = {
...
0x00, 0xFF, 0xFF,
...
};
Does anybody know what I am making wrong? I try to find a solution since a week but nothing is working. :( Or does anyboy have a small programm wich is doing that correctly?
