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EXTI handler gets stuck

Question asked by Arno Thiele on Jan 24, 2018
Latest reply on Jan 25, 2018 by Arno Thiele

With my STM32F4 I am trying to use an external interrupt to read a quadrature encoder on PC02 and regular port PC03. The interrupt on PC02 fires when I move the encoder, but it won’t return to the main loop again and my main routine gets stuck. Here’s the code:




GPIO_InitTypeDef gpio_init;
EXTI_InitTypeDef exti_init;
NVIC_InitTypeDef nvic_init;


gpio_init.GPIO_Pin = GPIO_Pin_2 | GPIO_Pin_3;
gpio_init.GPIO_Speed = GPIO_Medium_Speed;
gpio_init.GPIO_Mode = GPIO_Mode_IN;
gpio_init.GPIO_PuPd = GPIO_PuPd_UP;
GPIO_Init(GPIOC, &gpio_init);

SYSCFG_EXTILineConfig(EXTI_PortSourceGPIOC, EXTI_PinSource2);

exti_init.EXTI_Line = EXTI_Line2;
exti_init.EXTI_LineCmd = ENABLE;
exti_init.EXTI_Mode = EXTI_Mode_Interrupt;
exti_init.EXTI_Trigger = EXTI_Trigger_Falling;


nvic_init.NVIC_IRQChannel = EXTI2_IRQn;
nvic_init.NVIC_IRQChannelPreemptionPriority = 0;
nvic_init.NVIC_IRQChannelSubPriority = 0;
nvic_init.NVIC_IRQChannelCmd = ENABLE;



void EXTI2_IRQHandler(void)

    if (EXTI_GetITStatus(EXTI_Line2) != RESET)

// whatever…



int main(void)



In my main loop I am speaking to some periphery over SPI, a DAC, ADC, LED-driver. No matter what I try the IRQHandler gets stuck. Even with no code at all in it. No matter what I remove from my main loop, it’s the same result. It seems like the pending bit of the EXTI line don’t get cleared but it is obviously cleared in the handler in line 49.


I tried calling the interrupt in software to look at it in my debugger but there it just skips back to the main loop with no problems. 


I know I can use the encoder function of the timers and I got it to work just fine, but I need 8 encoders in total so they are all taken already.



Any advice would be appreciated!