STM32L072 Standby Mode problems

[Fiskk]

Hello!

I'm using the DISCO-L072CZ-LRWAN1 board and have some trouble using the low power modes.

It seems whenever i enter the low power mode, it immediately wakes up again, I've tried following a few of the guides and can't see what I'm doing wrong. The board steadily draws 45-55 mA from my power supply, and i would expect it to be a lot lower.

I generated a project for the board from MxCube and using CubeIDE, the project is empty except for the init functions and the code below.

Am i missing something here??

This is my code:

    RCC->APB1ENR |= RCC_APB1ENR_PWREN;

    // Configure MCU low-power mode for CPU deep sleep mode

    PWR->CR |= PWR_CR_CWUF; // Clear wakeup flags
    PWR->CR |= PWR_CR_PDDS; // 0 = Stop mode, 1 = Standby mode
    PWR->CR |= PWR_CR_ULP;   // V_{REFINT} is off in low-power mode

    (void)PWR->CR; // Ensure that the previous PWR register operations have been completed

// // Configure CPU core
SCB->SCR |= SCB_SCR_SLEEPDEEP_Msk; // Enable CPU deep sleep mode

// Enter low-power mode
for (;;) {
__DSB();
__WFI();
}

[waclawek.jan]

Low power issues like these are discussed here frequently, try searching. @Piranha has posted lists of things to check in the past.

JW

[Sarra.S]

Hello @Fiskk, 

Most probably, the values 45-55 mA are in run mode. 

One thing you can try is to disable the debug interface (DBGMCU) 

[Piranha]

The code seems to be adapted from my article, but it skips the part about DBGMCU_CR register.

Also, after enabling a peripheral clock, there is a delay required before the peripheral is used:

https://community.st.com/t5/stm32-mcus-products/erratum-quot-delay-after-an-rcc-peripheral-clock-enabling-quot/td-p/579949

https://community.st.com/t5/stm32-mcus-embedded-software/stm32-clock-and-delay-helper-functions/td-p/593082