LPTIM_ISR_ARROK in LPTIM1_ISR never gets set on STM32L4

[SSmit.13]

Hi

  I am wanting to use the LPTIM to break out of STOP2. I have a function to set the timer, and go into stop mode. After setting LPTIM1->ARR,  LPTIM_ISR_ARROK in the LPTIM1->ISR  is never set. After X amount of seconds, the STOP2 exits as expected, but the  PWR_SR1_WUF in the PWR->SR1 is never set.  The timer interupt is called when the STOP2 exits. Here is my code, not sure what I am doing wrong, anyone help?:

#define PWR_CR2_LPTIM1WUF_Pos   (5U)
#define PWR_CR2_LPTIM1WUF       (1UL << PWR_CR2_LPTIM1WUF_Pos)

//always gets called when STOP2 exits
void LPTIM1_IRQHandler(void)
{ 
	// Just clear the interrupt to prevent re-entry
	if (LPTIM1->ISR & LPTIM_ISR_ARRM) {
	LPTIM1->ICR = LPTIM_ICR_ARRMCF;
	}
}

void LPTIM1_StartSTOP2Timeout_ms(uint32_t ms)
{
	
	// Enable LPTIM1 and its clock
	RCC->APB1ENR1 |= RCC_APB1ENR1_LPTIM1EN;
	
	// Enable LSI clock
	RCC->CSR |= RCC_CSR_LSION;
	while (!(RCC->CSR & RCC_CSR_LSIRDY));
	
	// Select LSI as LPTIM1 clock
	RCC->CCIPR &= ~RCC_CCIPR_LPTIM1SEL;
	RCC->CCIPR |= (0b01 << RCC_CCIPR_LPTIM1SEL_Pos);
	
	// Enable LPTIM1
	LPTIM1->CR = LPTIM_CR_ENABLE;
	
	// Set prescaler /32 (1ms tick)
	LPTIM1->CFGR &= ~LPTIM_CFGR_PRESC;
	LPTIM1->CFGR |= (0b101 << LPTIM_CFGR_PRESC_Pos); // /32
	
	// Clear status flags
	LPTIM1->ICR = 0xFFFFFFFF;
	
	// Set ARR and wait for it to latch
	LPTIM1->ARR = ms;
        long Tick=0xfffff;  <<even increased 
	while (!(LPTIM1->ISR & LPTIM_ISR_ARROK))
            if(!--Tick)
              break;  //  << always breaks , and LPTIM1->ISR always 0

	// Allow wakeup from LPTIM1
	PWR->CR2 |= PWR_CR2_LPTIM1WUF;
	NVIC_EnableIRQ(LPTIM1_IRQn);
	LPTIM1->IER |= LPTIM_IER_ARRMIE;

	if (PWR->SR1 & PWR_SR1_WUF) {
	  PWR->SCR |= PWR_SCR_CWUF;  // Clear the wake-up flag before entering STOP2
	}
	
	// Set STOP2 mode
	PWR->CR1 &= ~PWR_CR1_LPMS;
	PWR->CR1 |= PWR_CR1_LPMS_STOP2;
	
	// Confirm STOP2 mode is active
	if ((PWR->CR1 & PWR_CR1_LPMS) == PWR_CR1_LPMS_STOP2) {
		printf("Entered STOP2 mode\n");  <<< gets called
	} else {
		printf("STOP2 mode not entered\n");
	}
	
	// Enable deep sleep
	SCB->SCR |= SCB_SCR_SLEEPDEEP_Msk;
	
	// Start timer in one-shot mode
	LPTIM1->CR |= LPTIM_CR_SNGSTRT;

	HAL_SuspendTick();
	
	// Enable deep sleep mode (SLEEPDEEP bit in SCR)
	SCB->SCR |= SCB_SCR_SLEEPDEEP_Msk;
	// Enter STOP2 mode
	printf("Entering STOP2 mode...\n");
	HAL_PWREx_EnterSTOP2Mode(PWR_STOPENTRY_WFI);  // Enter STOP2 mode with the WFI entry (Wait For Interrupt)
	
	// --- 6. After Wake-up: Handle timeout and clear wake-up flag ---
	if (PWR->SR1 & PWR_SR1_WUF) {
	  // Clear the wake-up flag
	  PWR->SCR |= PWR_SCR_CWUF;  << never gets called
	}
	HAL_ResumeTick();
	SystemClock_Config();
}

Many thanks

Scott

[Sarra.S]

Hello @SSmit.13, 

The code seems ok! I think the issue is somewhere else, maybe the clock frequency is lower than the signal to be counted?