software interrupt using EXTI

[jmchiappa]

Hello,

I would like to use EXTI0 to generate a software interrupt. It seems to be doable, but the code in interrupt.cpp file seems to not allow interrupt from SWI :

void HAL_GPIO_EXTI_IRQHandler(uint16_t GPIO_Pin)
{
  /* EXTI line interrupt detected */
  if(__HAL_GPIO_EXTI_GET_IT(GPIO_Pin) != 0x00u)
  {
    __HAL_GPIO_EXTI_CLEAR_IT(GPIO_Pin);
    HAL_GPIO_EXTI_Callback(GPIO_Pin);
  }
}

If interrupt or event doesn't come from GPIO (from the SWIER for example), then the event is skipped. I am right ?

If so, what is the recommended way to generate SWI ?

[fpistm]

Hi @jmchiappa,
EXTI0 rely on GPIO trigger event for Px0 GPIO pins.
Never seen other usage. Have you an example ?

If you want to override the core implementation, enable the HAL_EXTI_MODULE_DISABLED

[fpistm]

OK got it.
So I guess when you don't want GPIO event but SWI, it should be differentatie in each EXTIx_IRQHandler
https://github.com/stm32duino/Arduino_Core_STM32/blob/91b29fbef5bdcc14cbdb7cad28ef42e3b0f3f546/libraries/SrcWrapper/src/stm32/interrupt.cpp#L336C14-L339
To not call HAL_GPIO_EXTI_IRQHandler

[jmchiappa]

Exactly. But for now, the IRQ handler is not "__weak", it cannot be overrided.
I've achieved to use EXTI with SWI by making some minor modifications in the interrupt.cpp file (bypassing the pin number filter).
If you think that SWI is a nice feature of STM32 and should be supported in stm32duino, I can open an issue on that and submit a PR.

[jmchiappa]

Here is a very simple example which overrides HAL_GPIO_EXTI_Callbackafter setting __weak void HAL_GPIO_EXTI_Callback(...)

EXTI_HandleTypeDef hexti;

void setup() {
  Serial.begin(230400);
  EXTI_ConfigTypeDef extiConfig = {
  EXTI_LINE_0,      /*!< The Exti line to be configured. This parameter
                           can be a value of @ref EXTI_Line */
  EXTI_MODE_INTERRUPT,      /*!< The Exit Mode to be configured for a core.
                           This parameter can be a combination of @ref EXTI_Mode */
  EXTI_TRIGGER_RISING,   /*!< The Exti Trigger to be configured. This parameter
                           can be a value of @ref EXTI_Trigger */
  EXTI_GPIOA   /*!< The Exti GPIO multiplexer selection to be configured.
                           This parameter is only possible for line 0 to 15. It
                           can be a value of @ref EXTI_GPIOSel */
  };
  
  HAL_NVIC_SetPriority(EXTI0_IRQn, 1, 0);
  HAL_NVIC_EnableIRQ(EXTI0_IRQn);

  if(HAL_EXTI_SetConfigLine(&hexti , &extiConfig) != HAL_OK)
    Serial.println("Error in EXTI config");
  
  HAL_EXTI_GenerateSWI(&hexti);
}

void loop() {}

extern "C" {
  void HAL_GPIO_EXTI_Callback(uint16_t GPIO_Pin)
  {
    uint32_t t0=millis();
    uint32_t t500=0;
    pinMode(LED_BUILTIN, OUTPUT);
    while(millis() < t0+10000) {
      if(millis() >t500+500) {
        t500 = millis();
        digitalToggle(LED_BUILTIN);
      }
    }
  }
}

In this case, GPIO isn't relevant but is seems to be necessary for the configration.
@fpistm, do you think that there's another way to generate an internal interrupt by software ?

[fpistm]

Exactly. But for now, the IRQ handler is not "__weak", it cannot be overrided.

It cannot be weak as as weak one already exists in the HAL 😢

I guess using LL will prevent the HAL overhead....

If you think that SWI is a nice feature of STM32 and should be supported in stm32duino, I can open an issue on that and submit a PR.

Well, it is a community project. So feel free to submit request and more 😉