Why do STM32L433 comparators wake up the device from Sleep mode but not Stop mode, using Vrefint as the reference voltage?

[Bubbles]

Hello @kiwironnie​ ,

according to the RM it should work from both LP modes.

Jarda

[kiwironnie]

Thanks, yes, I'm aware that the manual indicates the comparators should work in all stop modes. For me though they work in Sleep mode but do not wake up the mcu in any Stop mode. Hence the question. The code is the same in both cases other than changing the low power mode call. The device enters low power mode but isn't being woken up as it is in Sleep mode.

[Bubbles]

Please check the configuration of SCLAEN, BRGEN and selection of INMSEL. Is the EXTI configured correctly?

[kiwironnie]

Thanks for getting back.

HAL is being used to setup the comparators as follows:

static void MX_COMP1_Init(void)

{

hcomp1.Instance = COMP1;

hcomp1.Init.InvertingInput = COMP_INPUT_MINUS_1_4VREFINT;

hcomp1.Init.NonInvertingInput = COMP_INPUT_PLUS_IO3; // PA1

hcomp1.Init.OutputPol = COMP_OUTPUTPOL_NONINVERTED;

hcomp1.Init.Hysteresis = COMP_HYSTERESIS_HIGH;

hcomp1.Init.BlankingSrce = COMP_BLANKINGSRC_NONE;

hcomp1.Init.Mode = COMP_POWERMODE_MEDIUMSPEED;

hcomp1.Init.WindowMode = COMP_WINDOWMODE_DISABLE;

hcomp1.Init.TriggerMode = COMP_TRIGGERMODE_IT_RISING;

if (HAL_COMP_Init(&hcomp1) != HAL_OK)

{

Error_Handler();

}

}

static void MX_COMP2_Init(void)

{

hcomp2.Instance = COMP2;

hcomp2.Init.InvertingInput = COMP_INPUT_MINUS_1_4VREFINT;

hcomp2.Init.NonInvertingInput = COMP_INPUT_PLUS_IO1; // PB4

hcomp2.Init.OutputPol = COMP_OUTPUTPOL_NONINVERTED;

hcomp2.Init.Hysteresis = COMP_HYSTERESIS_HIGH;

hcomp2.Init.BlankingSrce = COMP_BLANKINGSRC_NONE;

hcomp1.Init.Mode = COMP_POWERMODE_MEDIUMSPEED;

hcomp2.Init.WindowMode = COMP_WINDOWMODE_DISABLE;

hcomp2.Init.TriggerMode = COMP_TRIGGERMODE_IT_RISING;

if (HAL_COMP_Init(&hcomp2) != HAL_OK)

{

Error_Handler();

}

}

Interrupts:

/* COMP interrupt Init */

HAL_NVIC_SetPriority(COMP_IRQn, 0, 0);

HAL_NVIC_EnableIRQ(COMP_IRQn);

As said, this is working in Sleep mode. When the voltage crosses 1/4 VREFint an interrupt is generated that wakes the mcu. Exactly the same configuration is being used with Stop mode, just the call to Stop rather than Sleep changed, but it isn't coming out of Stop mode. Stop mode wake-up is working elsewhere, with RTC events causing a wake-up, no problem.

That is:

COMP_Start(); // comparators are stopped when they trigger

// comparator interrupt causes wakeup

HAL_SuspendTick();

HAL_PWR_EnterSLEEPMode(PWR_MAINREGULATOR_ON, PWR_SLEEPENTRY_WFI);

HAL_ResumeTick(); // on wake-up;

vs

COMP_Start(); // comparators are stopped when they trigger

HAL_SuspendTick();

HAL_PWR_EnterSTOPMode(PWR_LOWPOWERREGULATOR_ON, PWR_STOPENTRY_WFI);

PWR_ExitStopMode( ); // which enables clocks, IO and resumes tick

Any other suggestions appreciated. Thanks. Ron