how to make keep ram value after software reset?

Forum|Forum|3 years ago
April 4, 2023
7 replies
8376 views

So i use to stm32cubeide & stm32h743zi. I want to create a variable that the system does not initailize even if the after software reset. just like __no_init in IAR.

i follow this method. but i can't.

https://atadiat.com/en/e-how-to-preserve-a-variable-in-ram-between-software-resets/

This topic has been closed for replies.

Best answer by Kamil Duljas

Try this:

MEMORY
{
 RAM (xrw) : ORIGIN = 0x20000000, LENGTH = 319K
 NOINIT(xrw) 	 : ORIGIN = 0x2004FC00, LENGTH = 1K
 FLASH (rx) : ORIGIN = 0x8000000, LENGTH = 1024K
}

Then create section:

 .noinit :
 {
 KEEP(*(.noinitdata))
 } >NOINIT

and create variable:

uint32_t __attribute__(( section(".noinitdata") )) first_run;

Pavel A.

The default GCC startup code is much simpler than IAR, it initializes only one array of data and one BSS.

The easiest is to use one of SRAM blocks of stm32h743 that are not used for .data, .bss or stack/heap in your linker script. For example if your script uses the AXI SRAM for the "main" data, use SRAM2 or TCM RAM.

K

Kamil DuljasBest answer

Senior III

Try this:

MEMORY
{
 RAM (xrw) : ORIGIN = 0x20000000, LENGTH = 319K
 NOINIT(xrw) 	 : ORIGIN = 0x2004FC00, LENGTH = 1K
 FLASH (rx) : ORIGIN = 0x8000000, LENGTH = 1024K
}

Then create section:

 .noinit :
 {
 KEEP(*(.noinitdata))
 } >NOINIT

and create variable:

uint32_t __attribute__(( section(".noinitdata") )) first_run;

Dudo

ikassmaAuthor

Associate III

it is not working.

Couriously, depending on the location of the function that puts a value in the variable, it either keeps or does not retain the value after the reset.

K

Kamil Duljas

Senior III

Someone had simillar problem here:

https://stackoverflow.com/questions/65577391/stm32-create-ram-section

Try use this instruction.

Dudo