Wakeup STM32G431 from Shutdown mode using System Wake-up 2

[Lixx]

Hi

I have a battery powered project, where I want to turn it on with a falling edge. 

MCU: STM32G431RB

To save power my plan is to set the STM32 to shutdown mode.

Now my Question is, how can I wake up the MCU from a falling edge?

I have read the following in the datasheet:

Shutdown mode: The Shutdown mode allows to achieve the lowest power
consumption. The internal regulator is switched off to power down the VCORE domain.
The PLL, as well as the HSI16 and LSI RC-oscillators and HSE crystal oscillator are
also powered down. The RTC can remain active (Shutdown mode with RTC, Shutdown
mode without RTC). The BOR is not available in Shutdown mode. No power voltage
monitoring is possible in this mode. Therefore, switching to RTC domain is not
supported. SRAM and register contents are lost except for registers in the RTC
domain. The device exits Shutdown mode upon external reset event (NRST pin),
IWDG reset event, wakeup event (WKUP pin, configurable rising or falling edge) or
RTC event (alarm, periodic wakeup, timestamp, tamper).

So how do I configure the WKUP pin to wake up the MCU when detecting a falling edge?

I have only found the option to activate WKUP pin, not how to configure it

Thanks in advance for the help!

[liaifat85]

To configure the WKUP pin to wake up the MCU from shutdown mode upon detecting a falling edge, you need to use the STM32's EXTI (External Interrupt) functionality.

[Lixx]

Ok, thanks for the quick reply!

I still got a few questions...

1. What is the System Wake-up then, if not for waking up? I'm asking because in the documentation it literally says "WKUP pin, configurable rising or falling edge"

2. How does the MCU detect an EXTI if on shutdown mode?! The CPU and all of it's clocks are NOT running in this state, the 1.2V Regulator is turned off...