Why does the serial port print irrelevant information when I jump into the FLASH APP using the IAP I wrote?

[fujiangmu]

[TDK]

My guess is your application writes to UART1 as well.

Nothing wrong that would explain this in the code you've shown.

[fujiangmu]

FLASH APP? It's only in EXTI2_IRQHandler().

But I didn't trigger the interrupt.

[LCE]

Disable the EXTI interrupt before the jump.

At least on a H7 a lot of de-inits and interrupt disabling is done before jumping.

Maybe before jumping you first de-init / change the GPIO config, and that triggers the EXTI interrupt.
So try to disable EXTI first, the de-init the GPIOs.

[LCE]

BTW, so many (and long) for-loops in an ISR are usually not considered good design, unless you have some very specific reason for that.

Why not just set a flag and then "print" in the main loop?