After STOP2 Mode Wake-Up

[Chintu]

STM32L496VET6 – EXTI Not Working After STOP2 Mode Wake-Up

1. Part Number

• STM32L496VET6, LQFP100

• Custom-designed hardware (not a development board)

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2. Environment

• IDE: STM32CubeIDE v1.15.0

• STM32CubeMX: v6.11.0

• HAL Driver Package: STM32CubeL4 v1.18.0

• Toolchain: GCC Embedded

• Debugger: ST-LINK V3

• Host OS: Windows 11

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3. Schematics

• Pin PE0 is connected to a push-button with an external 10kΩ pull-up resistor to VDD.

• PE0 is configured as a falling-edge EXTI input (GPIO_EXTI0).

• Schematic is available if needed.

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4. Details (Symptoms)

• EXTI on PE0 (EXTI0) works correctly before entering STOP2 mode.

• After entering STOP2 using HAL_PWREx_EnterSTOP2Mode(), the device does not wake up when the PE0 button is pressed.

• No interrupt is triggered, and the MCU remains in low power mode.

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5. Expected Behavior

• A falling edge on PE0 should trigger an interrupt and wake the MCU from STOP2 mode.

• The MCU should resume operation, restore clocks, and continue running code.

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6. How to Reproduce

1. Configure PE0 as GPIO_EXTI0 in CubeMX (falling edge, no pull).

2. In code:

   • Enable SYSCFG and GPIOE clocks.

   • Set EXTI source with:

     c

     CopyEdit

     LL_SYSCFG_SetEXTISource(LL_SYSCFG_EXTI_PORTE, LL_SYSCFG_EXTI_LINE0);

   • Configure PE0 as falling-edge interrupt.

   • Enable EXTI0_IRQn interrupt.

   • Suspend SysTick and enter STOP2:

     c

     CopyEdit

     HAL_SuspendTick(); HAL_PWREx_EnterSTOP2Mode(PWR_STOPENTRY_WFI);

   • After wake-up, call SystemClock_Config() and reinitialize GPIO and EXTI.

3. Press the push-button connected to PE0 while in STOP2.

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7. Occurrence

• The issue is consistently reproducible.

• The system wakes up and triggers EXTI correctly when not using STOP2.

• The issue only occurs after entering STOP2.

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8. Sanity Checks Performed

• Verified EXTI0 interrupt handler is implemented correctly and functional.

• Verified PE0 EXTI works perfectly before STOP2.

• Clocks are properly restored after STOP2 using SystemClock_Config().

• Re-initialized EXTI and GPIO after wake-up.

• Ensured PE0 is not used by debug interface (no conflict with TRACECLK).

• Tried using LL drivers directly for EXTI instead of HAL.

• Added pull-up to PE0 for stable signal level.

• Tested wake-up from PA0 using HAL_PWR_EnableWakeUpPin(PWR_WAKEUP_PIN1), which works correctly.

void PowerDownUp(uint8_t Powermode)
{
//	HAL_SuspendTick();
//
//	PowerDown_GPIO_Deinit();
////		GPIO_InitTypeDef GPIO_InitStruct = {0};
////
//		__HAL_PWR_CLEAR_FLAG(PWR_FLAG_WUF2);
////
////
////
////		HAL_PWR_EnableWakeUpPin(PWR_WAKEUP_PIN2_HIGH);
////
//		HAL_PWREx_EnterSTOP2Mode(PWR_STOPENTRY_WFI);
//
//
//
////================ Init Modules===================================================//
//
////	SystemReInit();
//		SystemClock_Config();
//
//		HAL_GPIO_WritePin(LED_RED_GPIO_Port, LED_RED_Pin, SET);
//		HAL_ResumeTick();

//	__HAL_RCC_SYSCFG_CLK_ENABLE();

    HAL_SuspendTick();


    __HAL_RCC_SYSCFG_CLK_ENABLE();

    // 2. Remap EXTI0 to PE0
    LL_SYSCFG_SetEXTISource(LL_SYSCFG_EXTI_PORTE, LL_SYSCFG_EXTI_LINE0);

    // 3. Re-init GPIO pin PE0
    GPIO_InitTypeDef GPIO_InitStruct = {0};
    GPIO_InitStruct.Pin = GPIO_PIN_0;
    GPIO_InitStruct.Mode = GPIO_MODE_IT_FALLING;
    GPIO_InitStruct.Pull = GPIO_PULLUP;  // Optional: adds stability if PE0 is floating
    HAL_GPIO_Init(GPIOE, &GPIO_InitStruct);
//    __HAL_RCC_LSECSS_EXTI_ENABLE_IT();
    HAL_GPIO_WritePin(LED_GREEN_GPIO_Port, LED_GREEN_Pin, RESET);
//    HAL_RCC_LSICmd(ENABLE);
    NVIC_EnableIRQ(EXTI0_IRQn);
    HAL_PWREx_EnterSTOP2Mode(PWR_STOPENTRY_WFI);

    // Restore clocks
    SystemClock_Config();

    // Re-initialize GPIOs including EXTI pin
    SystemReInit();  // or reconfigure the EXTI pin here manually

     // Debug
    HAL_ResumeTick();
}

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[Saket_Om]

Hello @Chintu 

Did you check this example please?

If you still have the issue, please share your project if possible.