How to place an array in backup ram on STM32F4 MCUs?

Mbed OS
1

Hi,

I am trying to place an array in the backup ram so its contents can survive system reboot caused by watchdog.

typedef struct {
    //
} Foo;

Foo foos[40];

What is the proper way to make sure foos is pointed to BKPSRAM_BASE ?

Thanks in advance.

2

Hello Li,

The following code should compile. But I have never tried to use the backup SRAM. So I’m curious whether it will work:

    typedef struct
    {
        int i;
        //
    } Foo;

    Foo* foos = (Foo*)BKPSRAM_BASE;

    foos[0].i = 100;
3

This works, and I will use it.

Another method by editing link script seems reasonable and should work, but I could not get it to work. Compiled bin file will be super bloated and doesn’t fit into flash on MCU.

4

Here is an example of adding CCM (Core Coupled Memory) for the STM32F407VE (Arch Max) which worked for me. Try to replace CCM/ccm with BKPSRAM/bkpsram and modify the address and length according to the BKPSRAM data. If your target is different then use the corresponding .ld file and add the BKPSRAM related sections.