Getting Started with STM32 Function Library External Interrupts

        The board is lazy, or it is called making full use of the pull-up function of the IO port, and no common pull-up resistor is added here. When programming, just enable the pull-up of the IO~ Look at the interface below to know that KEY0 is connected to PA13 of STM32!

        CZZ once told me in a dream that any IO of STM32 can be used as an external interrupt input. Wow, it’s super powerful!

        The general procedure steps are as follows:

        1. System initialization, such as system clock initialization, so that it enters 72MHZ main frequency;
        2. GPIO configuration, be sure to turn on the AFIO clock when turning on the GPIO clock.
        3. EXTI configuration, here configure which pin to select as the interrupt pin.
        4. NVIC configuration, this is also an extra part compared to the microcontroller. We must enable the corresponding channel in NVIC and set the priority level.
        5. Use while(1) to perform an infinite loop, and write in the interrupt program how to handle the interrupt when it occurs.

        Follow the above method step by step to realize the function~

        First, define the relevant structure.

        GPIO_InitTypeDef GPIO_InitStructure;
         EXTI_InitTypeDef EXTI_InitStructure;
         NVIC_InitTypeDef NVIC_InitStructure;

         The second step is to configure IO and its functions.

        GPIO_InitStructure.GPIO_Pin = GPIO_Pin_8; //Here is the code to configure the LED light for easy observation!
         GPIO_InitStructure.GPIO_Speed ​​= GPIO_Speed_50MHz;
         GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
         GPIO_Init(GPIOA, &GPIO_InitStructure);

         GPIO_WriteBit(GPIOA,GPIO_Pin_8,Bit_SET); //Turn off the LED immediately after power on
 
         GPIO_InitStructure.GPIO_Pin = GPIO_Pin_13; //Configure PA13 pull-up input 
         GPIO_InitStructure.GPIO_Speed ​​= GPIO_Speed_50MHz;
         GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IPU; //Pull-up input
         GPIO_Init(GPIOA, &GPIO_InitStructure);

        RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA|RCC_APB2Periph_AFIO,ENABLE); //Make sure to turn on the GPIOA and AFIO clocks!!!

         The third step is to configure external interrupts, which is equivalent to the interrupt settings of the microcontroller.

        GPIO_EXTILineConfig(GPIO_PortSourceGPIOA,GPIO_PinSource13); //Configure pin 13 of port A as interrupt
         EXTI_ClearITPendingBit(EXTI_Line13); //Clear interrupt, it seems that there is no problem without adding it, but it is safe!
 
         EXTI_InitStructure.EXTI_Mode = EXTI_Mode_Interrupt; //External interrupt
         EXTI_InitStructure.EXTI_Trigger = EXTI_Trigger_Falling; //Falling edge trigger
         EXTI_InitStructure.EXTI_Line = EXTI_Line13;
         EXTI_InitStructure.EXTI_LineCmd = ENABLE;        
         EXTI_Init(&EXTI_InitStructure);

        The fourth step is to configure NVIDIA, which is also a feature of STM32.

        NVIC_PriorityGroupConfig(NVIC_PriorityGroup_0);
         NVIC_InitStructure.NVIC_IRQChannel = EXTI15_10_IRQn; //Channel 13 belongs to 15-10, they are shared!
         NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0; //Preemptive priority 0
         NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0; //Sub-priority 0
         NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
         NVIC_Init(&NVIC_InitStructure);

        while(1); //wait for interrupt to occur

        The fifth step is to write the interrupt processing function ISR and add the following code in stm32f10x_it.c.

void EXTI15_10_IRQHandler(void)
{
         if ( EXTI_GetITStatus(EXTI_Line13) == SET) //Judge whether it is the interrupt of pin 13
         {
                   EXTI_ClearITPendingBit(EXTI_Line13); //Clear the interrupt flag!
                  GPIO_WriteBit(GPIOA,GPIO_Pin_8,Bit_RESET); //Turn on the LED            
         }
}

        OK, the program is complete. Let’s test it!