Hi! I am working on a project in which I'd like to use an stm32U0 MCU. It'll be my first time with one of these, and I'm choosing it because my design includes a battery (+charger & fuel gauge), so I'm interested in learning about low-power things.
I have a single button on my device. I'd like to fashion a "hold to power on, hold to power off" functionality with this button. I also am using a fuel gauge that has some LEDs that can be triggered by a pushbutton. I'm trying to wrap my head around how to accomplish two things with a single button, and am considering the use of a MOSFET to accomplish this.
Here comes my question: I think that to "power off" my device, I want my MCU to enter Shutdown mode. I think that I can then wake it back up by connecting my button to a WKUP pin. But, I'm considering whether this pin is controlled directly by my pushbutton, or by way of a MOSFET.
ChatGPT is making a lot of fuss about the 'strict electrical characteristics' of WKUP pins, but I am unable to find a resource that elaborates on this (or, at least, I'm unsure where to look). I don't see anything obvious in the datasheet or the reference manual for the U0 devices, and I've read through a few application notes about low power GPIOs as well, none of which call out anything like strict rise times or thresholds for WKUP pins to serve their function when in a low power mode.
I'm well aware that any AI-based knowledge needs to be taken with a truckload of salt, but I do feel compelled to ask whether what I'm trying to do (activate a WKUP pin by way of a FET) is a reasonable way to handle this, or if I should strictly connect my button to the WKUP pin directly.
Thank you!
