Is it mandatory to reconfigure clocks after Stop mode ?

[path321]

Hi everyone, 

I am facing an long-standing issue with a STM32L476RE-powered device loosing UART frames when waking up from UART3 from Stop Mode (will be analyzed on another issue).

Prompted by this, I have a generic question for clock configuration after Stop1-2 mode.

The device uses HSI & LSE for all of its peripherals, in a bare-metal CubeMX project.

Q1: The function 

__HAL_RCC_WAKEUPSTOP_CLK_CONFIG(RCC_STOP_WAKEUPCLOCK_HSI);

is called 1 time before while(1){} loop. Should it be called just once or should it be called every time before calling 

HAL_SuspendTick();
HAL_PWREx_EnterSTOP1Mode(PWR_STOPENTRY_WFI);

?

Q2: Should we call 

SystemClock_Config();

every time after waking up from Stop mode, despite the fact that the clock selection ( HSI & LSE ) remains the same and no PLL or MSI is used ?

Q3: Could calling 

SystemClock_Config();
HAL_ResumeTick();

disrupt an ongoing UART-RX ( running on Idle-line callback ) , despite the fact that clock selection is not changing ? 



Thank you in advance

[Andrew Neil]

The datasheet tells you:

 

So, if that’s the configuration you want after exiting STOP - you don’t need to do anything.

If it’s not what you want then, of course, you will have to reconfigure it,

[Gyessine]

Hello ​@path321 

Has your question been answered?
BR
Gyessine

[path321]

Yes, I am flagging the respecitve “best answer” , thanks

[Saket_Om]

Hello ​@path321 

Q1: The function 

__HAL_RCC_WAKEUPSTOP_CLK_CONFIG(RCC_STOP_WAKEUPCLOCK_HSI);

is called 1 time before while(1){} loop. Should it be called just once or should it be called every time before calling 

HAL_SuspendTick();

HAL_PWREx_EnterSTOP1Mode(PWR_STOPENTRY_WFI);

?

 

Calling it once during initialization is sufficient

Please refer to the example below:

STM32CubeH5/Projects/NUCLEO-H503RB/Examples_MIX/PWR/PWR_STOP/Src/main.c at main · STMicroelectronics/STM32CubeH5 · GitHub

 

Q2: Should we call 

SystemClock_Config();

every time after waking up from Stop mode, despite the fact that the clock selection ( HSI & LSE ) remains the same and no PLL or MSI is used ?

 

No, calling the full SystemClock_Config() after Stop mode is not recommended 

Please refer to the STM32CubeMX errata 6.14.x section 4.4.