Set a value in a specific address to be a flag to update a firmware

j_filipe · ‎2025-11-07

So I made a custom bootloader that I use to update the MCU firmware. So I have both the bootloader and the main app in the Flash. What I wanted to do, is to write on a specific address (out of bootloader and application, of course) a kind of a flag that notifies the app when it is necessary to go to the bootloader to update the firmware. Any clue on how to do it?
I am using a STM32U585, using the B-U585I-IOT02A board.
Thank you!

Pavel A. · ‎2025-11-07

You can write this flag into the internal RAM (SRAM). Data in the SRAM survives restart/reboot of the MCU while power is supplied.

Andrew Neil · ‎2025-11-07

Basically the same question here: How to store a 1-bit bootloader flag without wasting 1 Flash page.

@j_filipe so does your value need to be volatile, or not?

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