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Clear of External Interrupt Pending bit

Hi,

I'm using Keil MDK-ARM 4.22a RTX OS on a STM3220G Eval board.

I added RTX and FS to the "Memory" example and everything is working fine. I have tasks that read a file while another one is blinking leds.

I tried to add and external interrupt on the KEY button (PG15 pin) and to do so I integrated the ST StdPeriph library (which is used mainly for setting up the interruption).

But if the button is working, I can't clear the Interrupt Pending bit in the IRQ handler. So when I send a semaphore from it, the OS raises quickly an overflow error.

Here is the code for the interruption setup :

void EXTI_User_Button_Config(void)
{
  EXTI_InitTypeDef   EXTI_InitStructure;
  GPIO_InitTypeDef   GPIO_InitStructure;
  NVIC_InitTypeDef   NVIC_InitStructure;

  /* Enable GPIOG clock */
  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOG, ENABLE);
  /* Enable SYSCFG clock */
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_SYSCFG, ENABLE);

  /* Configure PG15 pin as input floating */
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN;
  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_15;
  GPIO_Init(GPIOG, &GPIO_InitStructure);

  /* Connect EXTI Line0 to PG15 pin */
  SYSCFG_EXTILineConfig(EXTI_PortSourceGPIOG, EXTI_PinSource15);

  /* Configure EXTI Line0 */
  EXTI_InitStructure.EXTI_Line = EXTI_Line15;
  EXTI_InitStructure.EXTI_Mode = EXTI_Mode_Interrupt;
  EXTI_InitStructure.EXTI_Trigger = EXTI_Trigger_Falling;
  EXTI_InitStructure.EXTI_LineCmd = ENABLE;

  EXTI_ClearITPendingBit(EXTI_Line15);

  EXTI_Init(&EXTI_InitStructure);

  /* Enable and set EXTI Line15 Interrupt to the lowest priority */
  NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);
  NVIC_InitStructure.NVIC_IRQChannel = EXTI15_10_IRQn;
  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0x03;
  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0x01;
  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
  NVIC_Init(&NVIC_InitStructure);
}

And the IRQ handler :

void EXTI15_10_IRQHandler (void) __irq
{
  if(EXTI_GetITStatus(EXTI_Line15) != RESET)
  {
    /* Clear the EXTI line 15 pending bit */
    EXTI_ClearITPendingBit(EXTI_Line15);

    /* Toggle LED1 */
    STM_EVAL_LEDToggle(LED1);

   /*Send Semaphore */
   isr_sem_send (semaphore1);
   cpt++;
  }
}

The 'cpt' variable is only for debugging purpose, as it's decremented by the task that handles semaphore1. When it's reaching 32 (the ISR FIFO size I defined), the OS raises the overflow error.

The code from the Std library to reset the pending bit :

void EXTI_ClearITPendingBit(uint32_t EXTI_Line)
{
  /* Check the parameters */
  assert_param(IS_EXTI_LINE(EXTI_Line));

  EXTI->PR = EXTI_Line;
}

The interrupt setup is done before launching the OS.

Am I doing something wrong ? Is there another way to clear the interrupt bit ?