Application of STM32 external (IO) interrupt EXTI

a)         Purpose: Similar to serial port input, IO input without interrupts is also inefficient, and button events can be inserted through EXTI. This section is related to EXTI interrupts.

b)         Initialization function definition:

void  EXTI_Configuration(void);  //Define IO interrupt initialization function

c)         Initialization function call:

EXTI_Configuration(); //IO interrupt initialization function call Simple application:

d)         Initialization function:

void  EXTI_Configuration(void)

{

  EXTI_InitTypeDef  EXTI_InitStructure;         //EXTI initialization structure definition

 

EXTI_ClearITPendingBit(EXTI_LINE_KEY_BUTTON); //Clear interrupt flag

   GPIO_EXTILineConfig(GPIO_PortSourceGPIOA,  GPIO_PinSource3); //Pin selection

   GPIO_EXTILineConfig(GPIO_PortSourceGPIOA,  GPIO_PinSource4);

     GPIO_EXTILineConfig(GPIO_PortSourceGPIOA,  GPIO_PinSource5);

     GPIO_EXTILineConfig(GPIO_PortSourceGPIOA,  GPIO_PinSource6);

 

    EXTI_InitStructure.EXTI_Mode  =  EXTI_Mode_Interrupt; //Event selection

  EXTI_InitStructure.EXTI_Trigger  =  EXTI_Trigger_Falling; //Trigger mode

  EXTI_InitStructure.EXTI_Line  =  EXTI_Line3  |  EXTI_Line4;  //Line selection

  EXTI_InitStructure.EXTI_LineCmd  =  ENABLE; //Start interrupt

  EXTI_Init(&EXTI_InitStructure); //Initialization

}

 

e)         Turn on the I/O clock in the RCC initialization function

RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA  ,  ENABLE);

 

Define the input I/O pins in the GPIO initialization function.

//IO input, GPIOA's 4-pin input

  GPIO_InitStructure.GPIO_Pin  =  GPIO_Pin_4;

    GPIO_InitStructure.GPIO_Mode  =  GPIO_Mode_IPU;          //Pull-up input

  GPIO_Init(GPIOA,  &GPIO_InitStructure);                 //Initialization

f)         Add the following code in the NVIC initialization function to enable related interrupts:

  NVIC_InitStructure.NVIC_IRQChannel  =  EXTI9_5_IRQChannel;         //Channel

  NVIC_InitStructure.NVIC_IRQChannelPreemptionPrio rity  =  0;//Priority level

  NVIC_InitStructure.NVIC_IRQChannelSubPriority  =  0;                         //Response level

  NVIC_InitStructure.NVIC_IRQChannelCmd  =  ENABLE;                         //Start

  NVIC_Init(&NVIC_InitStructure);                                                                 //Initialization

 

g)         Find the void USART1_IRQHandler function in the stm32f10x_it.c file  and add the execution code to it. Generally, there are at least three steps: first use the if statement to determine which interrupt occurred, then clear the interrupt flag, and finally assign a value to the string, or do other things.

  if(EXTI_GetITStatus(EXTI_Line3)  !=  RESET)                                   //Judge the source of the interrupt

   {  EXTI_ClearITPendingBit(EXTI_Line3);                                           //Clear the interrupt flag

    USART_SendData(USART1,  0x41);                                               //Send the character "a"

    GPIO_WriteBit(GPIOB,  GPIO_Pin_2,  (BitAction)(1-GPIO_ReadOutputDataBit(GPIOB,  GPIO_Pin_2))); //LED alternates between light and dark

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)         Interrupt precautions:

The interrupt bit must be cleared after the interrupt occurs, otherwise the interrupt will occur in an endless loop. Then the interrupt type needs to be determined before executing the code.

To use the EXTI I/O interrupt, three things need to be done after completing the RCC and GPIO hardware settings: initialize EXTI, enable NVIC interrupts, and write interrupt execution code.