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STM32F4 External Interrupts not Working

sankhar
Associate
Posted on February 06, 2014 at 07:46

I wrote a code to generate rising edge interrupts for a 4MHz clock input to the board. The 4MHz input is generated by MCO while the core is pushed to 168MHz.

I found that certain interrupts are not being tacked at all and when they are tackled, there are delays often (but not always) for the Microcontroller to enter ISR.

I am simply toggling external pin in the ISR

MAIN.C__________________________________________________________

int main(void)

{

  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOD|RCC_AHB1Periph_GPIOA|RCC_AHB1Periph_GPIOC, ENABLE);

  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9;

  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;

  GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;

  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;

  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;

  GPIO_Init(GPIOC, &GPIO_InitStructure);

      GPIO_InitStructure.GPIO_Pin =  GPIO_Pin_8;

      GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;

      GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;

      GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;

      GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;

      GPIO_Init(GPIOA, &GPIO_InitStructure);

      GPIO_PinAFConfig(GPIOA, GPIO_Pin_8, GPIO_AF_MCO);

      RCC_MCO1Config(RCC_MCO1Source_HSE,RCC_MCO1Div_2); 

      EXTILine1_Config( );

  while (1);

}

void MCO_CLK_CONFIG(void){

RCC_HSEConfig(RCC_HSE_ON);

while(!RCC_WaitForHSEStartUp())

{

}

}

void EXTILine1_Config(void)

{

  /* Enable SYSCFG clock */

  RCC_APB2PeriphClockCmd(RCC_APB2Periph_SYSCFG, ENABLE);

  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN;

  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;

  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;

  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_1;

  GPIO_Init(GPIOA, &GPIO_InitStructure);

  SYSCFG_EXTILineConfig(EXTI_PortSourceGPIOA, EXTI_PinSource1);

  EXTI_InitStructure.EXTI_Line = EXTI_Line1;

  EXTI_InitStructure.EXTI_Mode = EXTI_Mode_Interrupt;

  EXTI_InitStructure.EXTI_Trigger = EXTI_Trigger_Rising_Falling;

  EXTI_InitStructure.EXTI_LineCmd = ENABLE;

  EXTI_Init(&EXTI_InitStructure);

  NVIC_InitStructure.NVIC_IRQChannel = EXTI1_IRQn;

  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0x00;

  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0x00;

  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;

  NVIC_Init(&NVIC_InitStructure);

}

ISR________________________________________________________________________________________________ISR

void EXTI1_IRQHandler(void)

{

  if(EXTI_GetITStatus(EXTI_Line1) != RESET)

  {

 GPIOC->BSRRL = GPIO_Pin_9;

 GPIOC->BSRRH = GPIO_Pin_9;

 EXTI_ClearITPendingBit(EXTI_Line1);

}

}

Following is the image on Logic analyzer we captured.

0690X000006050kQAA.png

Can someone enlighten me regarding what the issue can be?

Thank you

#stm32f4-discovery-interrupt
2 REPLIES 2
troy1818
Senior
Posted on February 06, 2014 at 14:15

I wonder how many cycles it takes for stm32f4 to go into an interrupt and toggle a pin. Perhaps more than 168/4 cycles? Anyone?

Regards,

rygelxvi

Chris1
Senior III
Posted on February 06, 2014 at 21:00

Interrupt latency is typically about 12 clock cycles for a Cortex-M4 CPU (best case), assuming that the memories involved can operate with 0 wait states.

The pulse you are attempting to generate in the ISR should be about 6 ns wide.  Is your analyzer able to capture signals that short?  Incidentally, it's doubtful that the GPIO pins can even operate at that speed.