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How fast we can go with EXTI

Ahmed.Waqar
Associate II
Posted on May 12, 2015 at 13:28

I am using external interrupts. STM32F407 is not handling interrupt at speed of greater than 2MHz.

/* Includes ------------------------------------------------------------------*/

#include ''stm32f4xx.h''

#include ''stm32f4xx_syscfg.h''

#include ''stm32f4xx_rcc.h''

#include ''stm32f4xx_gpio.h''

#include ''stm32f4xx_exti.h''

#include ''misc.h''

EXTI_InitTypeDef   EXTI_InitStructure;

void EXTILine0_Config(void);

void LEDInit(void);

void main(void)

{

 LEDInit();

 EXTILine0_Config();

 EXTI_GenerateSWInterrupt(EXTI_Line0);

  while (1)

  {

  }

}

void LEDInit()

{

  GPIO_InitTypeDef  GPIO_InitStructure;

  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOD, ENABLE);

  /* Configure the GPIO_LED pin */

  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_15;

  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;

  GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;

  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;

  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;

  GPIO_Init(GPIOD, &GPIO_InitStructure);

}

void EXTILine0_Config(void)

{

  GPIO_InitTypeDef   GPIO_InitStructure;

  NVIC_InitTypeDef   NVIC_InitStructure;

  /* Enable GPIOA clock */

  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);

  /* Enable SYSCFG clock */

  RCC_APB2PeriphClockCmd(RCC_APB2Periph_SYSCFG, ENABLE);

  /* Configure PA0 pin as input floating */

  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN;

  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;

  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0;

  GPIO_Init(GPIOA, &GPIO_InitStructure);

  /* Connect EXTI Line0 to PA0 pin */

  SYSCFG_EXTILineConfig(EXTI_PortSourceGPIOA, EXTI_PinSource0);

  /* Configure EXTI Line0 */

  EXTI_InitStructure.EXTI_Line = EXTI_Line0;

  EXTI_InitStructure.EXTI_Mode = EXTI_Mode_Interrupt;

  EXTI_InitStructure.EXTI_Trigger = EXTI_Trigger_Rising;

  EXTI_InitStructure.EXTI_LineCmd = ENABLE;

  EXTI_Init(&EXTI_InitStructure);

  /* Enable and set EXTI Line0 Interrupt to the lowest priority */

  NVIC_InitStructure.NVIC_IRQChannel = EXTI0_IRQn;

  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0x01;

  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0x01;

  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;

  NVIC_Init(&NVIC_InitStructure);

}

void EXTI0_IRQHandler(void)

{

              if (((EXTI->PR & EXTI_Line0) != (uint32_t)RESET) && ((EXTI->IMR & EXTI_Line0) != (uint32_t)RESET))

             {

            GPIOD->ODR ^= 0x8000;

            EXTI->PR = 0x0001;

        }

}

Please help me!
1 REPLY 1
Posted on May 12, 2015 at 14:27

Yes, interrupting at 2 MHz is excessively high, you'd be entering the handler every few dozen machine cycles.

See if you can use a TIM peripheral to count or respond to input signals.

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