Watchdog RAM Retention

[Franco Fischer]

Hi! I'm trying to save some variables after a watchdog reset for debug why my application hangs up.

I add a ram section on flash_placement.xml ( <ProgramSection alignment="4" keep="Yes" load="No" name=".ram_persist" address_symbol="__start_ram_persist" end_symbol="__stop_ram_persist" size="8" /> ) and i use the variable as uint32_t __attribute__((section (".ram_persist"))) watchdog;

After a quick test, the variables don't hold the value after watchdog reset. So, it's possible to hold data in ram after a watchdog reset ?

Thanks

PS: I'm using segger embedded studio with a custom nrf52840 board (also i use the softdevice and the buttonless bootloader)

[Turbo J]

The bootloader may simply overwrite your RAM locations, IIRC it initalizes RAM.

You may need to modify the bootloader, at least in the linker script/settings.

[Franco Fischer]

Do you mean i have to add <ProgramSection alignment="4" keep="Yes" load="No" name=".ram_persist" address_symbol="__start_ram_persist" end_symbol="__stop_ram_persist" size="8" /> in the flash_placement.xml of the bootloader also?

[Turbo J]

Would that place your .ram_persist section to a different address in the bootloader? Because that would not work either.

[Franco Fischer]

Thanks! I found my error, i have .ram_persist on both flash_placement.xml, but the RAM_START of the bootloader differs, so the .ram_persist section is located in diferent position.

I change the RAM_START of the bootloader to match the value in the application and works perfectly.

Thanks a lot for the quick response!!!