Using LPTIM in Stop Mode to Wake Up STM32L072 (Murata CMWX1ZZABZ-078)

[TAHIR97]

Hello,

I'm using the STM32L072 MCU as part of the Murata CMWX1ZZABZ-078 module in my application. I want to configure the Low-Power Timer (LPTIM) to generate a wake-up event when the MCU is in Stop mode.

Could someone provide guidance on how to configure the LPTIM to wake up the MCU after a set time period? Any example code or specific considerations related to the STM32L072 and this module would be greatly appreciated.

Thank you!

[Imen.D]

Hello @TAHIR97 ,

You can start your project with LPTIM examples available under STM32CubeL0 firmware package:

STM32CubeL0/Projects/STM32L073Z-EVAL/Examples/LPTIM at master · STMicroelectronics/STM32CubeL0 · GitHub

Make sure to enable the LPTIM Clock, configure the LPTIM and enable the LPTIM interrupt in the NVIC. Ensure to configure the MCU to enter Stop mode and that the LPTIM is allowed to run in this mode. Then Handle the Wake-Up Event.

You can refer to these resources that will help you in your project:

• Low-power timer (LPTIM) applicative use cases on STM32 MCUs and MPUs - Application note
• STM32L4 training: 06.4 Timers - Hands-on LPTIM (youtube.com)

[TAHIR97]

Hello @Imen.D ,

I am working with the CMWX1ZZABZ-078 Murata module, which includes the STM32L072 MCU. In my application, I read data from sensors and send it via LoRa. To minimize power consumption, I want to implement low-power modes like Stop or Standby.

However, I am unsure if it is possible to enter these modes without using an external RTC. Is it mandatory to have an external RTC to wake up the MCU from these low-power modes, or can this be achieved using internal clocks or other peripherals?

Any guidance, examples, or recommendations to optimize power consumption while still being able to send data via LoRa would be greatly appreciated.

Thank you!