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EXTI rising falling with pin monitoring - issue

Question asked by arbitrer on Dec 15, 2015
Latest reply on Dec 15, 2015 by arbitrer
I'm using STM32F4 Discovery. I configured a GPIO pin PB8 for external interupt for both rising and falling edges, so that I have to reset a flag when it is high->low or set when low->high which is done by reading the status of the Pin in the ISR.

But I'm getting the status of the pin is low always when I read status using function GPIO_ReadInputDataBit, here is my code(flag value is always low/reset). What am I doing wrong here ?

Note: I ensured the logic levels on pin using DSO and my ISR is getting hit on rising/falling edge but the status of that pin is always read low

bool test = false;
 
void Init_Sleep_Detect(void)
{
    /* Set variables used */
    GPIO_InitTypeDef GPIO_InitStruct;
    EXTI_InitTypeDef EXTI_InitStruct;
    NVIC_InitTypeDef NVIC_InitStruct;
     
    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB, ENABLE);
 
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_SYSCFG, ENABLE);
     
    GPIO_InitStruct.GPIO_Mode = GPIO_Mode_IN;
    GPIO_InitStruct.GPIO_OType = GPIO_OType_PP;
    GPIO_InitStruct.GPIO_Pin = GPIO_Pin_8;
    GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_UP;
    GPIO_InitStruct.GPIO_Speed = GPIO_Speed_100MHz;
    GPIO_Init(GPIOB, &GPIO_InitStruct);
     
    SYSCFG_EXTILineConfig(EXTI_PortSourceGPIOB, EXTI_PinSource8);
     
 
    EXTI_InitStruct.EXTI_Line = EXTI_Line8;
    EXTI_InitStruct.EXTI_LineCmd = ENABLE;
    EXTI_InitStruct.EXTI_Mode = EXTI_Mode_Interrupt;
    EXTI_InitStruct.EXTI_Trigger = EXTI_Trigger_Rising_Falling;
    EXTI_Init(&EXTI_InitStruct);
 
    NVIC_InitStruct.NVIC_IRQChannel = EXTI9_5_IRQn;
    NVIC_InitStruct.NVIC_IRQChannelPreemptionPriority = 0x00;
    NVIC_InitStruct.NVIC_IRQChannelSubPriority = 0x00;
    NVIC_InitStruct.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStruct);
}
 
void EXTI9_5_IRQHandler(void)
{
    if (EXTI_GetITStatus(EXTI_Line8) != RESET)
    {
        /* Clear the EXTI line 0 pending bit */
        EXTI_ClearITPendingBit(EXTI_Line8);
 
        if (GPIO_ReadInputDataBit(GPIOB, GPIO_Pin_8))
        {
            test= true;
        }
        else
        {
            test=false;
        }
    }  
}

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