Lowest power mode which resumes program after wake?

[MHuis.1]

Hi all,

I'm developing a low power sensor node using the Nucleo STM32L432KC development board, and I was wondering what the lowest power mode is from which the device can wake up and just continue operation from the next line of code after the sleep command?

I can't seem to find it in the datasheet.

I think I should be able to use the standby mode with the SRAM 2 enabled, but I'm not completely sure.

[Rainer1]

Hello, The answer depends from the wakeup source. See Table 21 in Ch. 5.3. of the RefMan. For example, I2C3 is able to wakeup from Stop2 mode, whereas other I2Cx may only wake up from Stop1/Stop0. Before going to sleep, make sure, the clock for the intended wakeup source is also availabe in Stop mode. Stop2 will bring you in the region of few microampere supply current.

Generally, a big issue is identifying all other current leaks. One active GPIO PullUp or PullDown or one external component not in low power mode during StopX can ruin all your low power considerations.

[MHuis.1]

Hi, thanks for the answer! I need to wake up from the RTC, so theoretically this should be possible using the standby mode with SRAM2 enabled? I'm currently still in the research phase, and not yet programming so it's hard to verify now.

Thanks a lot for the quick answer, really appreciated!

[Rainer1]

Exiting from Standby is like a reset (with SRAM2 preserved, if configured) , so your requirement "continue operation from the next line" is not fulfilled with Standby. If you can skip this requirement, Standby and RTC wakeup is possible.

[MHuis.1]

Alright, I do right now really have the requirement that it should continue operation from the next line. Do you know in what mode this would be possible?

[Rainer1]

I would choose Stop2 then.