I am experiencing an issue when trying to use STOP3 mode on an STM32U575VIT6Q device mounted on a custom PCB. In fact, the MCU never seems to actually enter STOP3, even though I explicitly call:
HAL_SuspendTick();
HAL_PWREx_EnterSTOP3Mode(PWR_STOPENTRY_WFI);
HAL_ResumeTick();
The observed behavior is as follows:
With Low-Power debugging enabled, STM32CubeIDE halts execution on the internal low-level _WFI() instruction.
Without the debugger attached (free-running mode after BOR and JTAG detached), the MCU does not appear to enter STOP3 at all and continues normal execution after the call.
From code inspection and debugging, it looks like the core is effectively ignoring the WFI instruction or is prevented from transitioning into STOP3 by some system or external condition.
At the moment, it is unclear what might be blocking STOP3 entry. Possible areas I am investigating include:
Pending or enabled interrupts/events that could immediately wake the core after WFI
Debug-related side effects, even when low-power debug is supposedly disabled (even with HAL function)
If anyone has encountered a similar issue on STM32U575 devices, I would appreciate any guidance or suggestions.
Thank you in advance for your support.
