Bootloader + XIP Application in External Flash on STM32U5G9J-DK2

[ArunJohn]

Hello everyone,

I’m working with the STM32U5G9J-DK2 and trying to implement a Bootloader + XIP (Execute-In-Place) application architecture using the external flash.

Target setup:

• A minimal bootloader running from internal flash

• The main application linked to and executing from external flash (memory-mapped at 0x90000000)

The main motivation is to free internal flash and validate this approach for a future MCU with very limited internal flash.

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What I’m specifically looking for help with

1. Proper CubeMX / .ioc configuration for the bootloader

   • Which peripherals must be enabled (RCC, PWR, ICACHE, OSPI, etc.)

   • Which peripherals should not be enabled to avoid conflicts with the XIP app

   • Any STM32U5-specific gotchas when initializing OSPI for XIP

2. Proper configuration of the application project

   • Recommended changes to the application .ioc

   • What initialization should be removed from the app (HAL_Init, clock, OSPI, FLASH, etc.)

3. Reference samples

   • STM32Cube examples that demonstrate a full bootloader + XIP app flow on STM32U5

   • Any internal / unofficial sample projects that ST recommends adapting

I’m mainly looking for end-to-end guidance on how ST recommends structuring and configuring both the bootloader and the application for this use case.

Any pointers, samples, or best-practice recommendations would be greatly appreciated.

Thanks in advance,
AJ