How to use flash memory address for particular variables?

[Mani1]

STM32F469I discovery board.

How to use internal flash memory address for a particular variables? it's possible ?

I am struggled with this issue.

i am beginner of stm32. help me.

[Tesla DeLorean]

Not exactly clear what exactly you're trying to achieve here.

P​lacement of constant data, via attributes and linker script sections?

O​r writing semi-permanent data or configuration into section of the flash memory?

[Mani1]

File: mani.c

unsigned short int FlashArray[8192] __attribute__ ((at((uint32_t)0x08004000)));

File :STM32F469NIHX_FLASH.id

.user_data (NOLOAD) :

{

. = ALIGN(4);

*(.user_data) /* .buffram section */

. = ALIGN(4);

} >FLASH

[Tesla DeLorean]

I'd probably avoid the AT method and use a C pointer method​, where you make a hole in the FLASH sections in the linker script, with an initial section for the vector table and some initialization code to be directed into.

[Mani1]

Thanks for your reply. I tried this logic also ,

main.c

const unsigned short int FlashArray[10] __attribute__((__section__(".user_data")));

File :STM32F469NIHX_FLASH.id

CCMRAM  (xrw)  : ORIGIN = 0x10000000,  LENGTH = 64K

 RAM  (xrw)  : ORIGIN = 0x20000000,  LENGTH = 320K

 FLASH  (rx)  : ORIGIN = 0x8000000,  LENGTH = 2048K 

 SDRAM (rw)   : ORIGIN = 0xC0000000, LENGTH = 16M

 QSPI (r)    : ORIGIN = 0x90000000, LENGTH = 16M

.user_data (NOLOAD) :

{

. = ALIGN(4);

*(.user_data) /* .buffram section */

. = ALIGN(4);

} >FLASH

[TDK]

Putting an uninitialized array into flash makes no sense. Flash cannot be used as RAM. You didn't answer Tesla's question on what you are trying to achieve.

[Tesla DeLorean]

I'd recommend sub-dividing this into 3 sections, one for the vectors, a hole for your data, and then the residual

FLASH  (rx)  : ORIGIN = 0x8000000,  LENGTH = 2048K 

[Mani1]

can i allocate QSPI memory for my uninitialized array? instead of RAM?

[TDK · Accepted solution]

Yes, that makes much more sense.
See here how to add a linker section and put variables there:
https://www.openstm32.org/Using%2BCCM%2BMemory
Use QSPI memory address rather than CCMRAM as in the example.