STM32 Learning: External Interrupts

STM32 GPIO external interrupt summary

1. STM32 interrupt grouping:

　　Each GPIO of STM32 can be configured as an external interrupt trigger source, which is also the strength of STM32. STM32 divides many interrupt trigger sources into different groups according to the pin numbers. For example, PA0, PB0, PC0, PD0, PE0, PF0, PG0 are the first group, and so on. We can conclude that there are 16 groups in total. STM32 stipulates that only one interrupt trigger source can work at the same time in each group, so the maximum number of working external interrupts is 16. The interrupt controller of STM32F103 supports 19 external interrupt/event requests. Each interrupt has a status bit, and each interrupt/event has independent trigger and mask settings. The 19 external interrupts of STM32F103 are:

Lines 0~15: correspond to the input interrupt of the external IO port.

Line 16: Connect to PVD output.

Line 17: Connected to the RTC alarm event.

Line 18: Connected to USB wakeup event.

2: Configuration process of external interrupt:

　　1. Configure the trigger source GPIO port:

　　Because the GPIO port is used as a trigger source, the GPIO port is configured to input mode. The trigger modes are as follows:

　　a.GPIO_Mode_AIN, analog input (ADC analog input, or power saving in low power consumption)

　　b.GPIO_Mode_IN_FLOATING, floating input

　　c.GPIO_Mode_IPD, with pull-down input

　　d.GPIO_Mode_IPU, with pull-up input　

　　GPIO_InitTypeDef GPIO_InitStructure; //Define the structure

　　RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOE,ENABLE); //Enable clock

　　GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2; //Select IO port PE2

　　GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IPU; //Set to pull-up input

　　GPIO_Init(GPIOE, &GPIO_InitStructure); //Use structure information to initialize IO port

　　2. Enable AFIO multiplexed clock function:

　　RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO,ENABLE);　

　　3. Map the GPIO port to the interrupt line:　

　　GPIO_EXTILineConfig(GPIO_PortSourceGPIOE,GPIO_PinSource2);

　　4. Initialize the interrupt on the interrupt line:　

　　EXTI_InitTypeDef EXTI_InitStructure; //Define the initialization structure

　　EXTI_InitStructure.EXTI_Line=EXTI_Line2; //The interrupt line number range is EXTI_Line0~EXTI_Line15

　　EXTI_InitStructure.EXTI_Mode = EXTI_Mode_Interrupt; //Interrupt mode, optional values ​​are interrupt EXTI_Mode_Interrupt and event EXTI_Mode_Event.

　　EXTI_InitStructure.EXTI_Trigger = EXTI_Trigger_Falling; //Trigger mode, can be falling edge trigger EXTI_Trigger_Falling, rising edge trigger EXTI_Trigger_Rising, or any level (rising and falling edges) trigger EXTI_Trigger_Rising_Falling

　　EXTI_InitStructure.EXTI_LineCmd = ENABLE;

　　EXTI_Init(&EXTI_InitStructure); //Initialize according to the structure information

　　5. Interrupt priority configuration:　

　　NVIC_InitTypeDef NVIC_InitStructure; //define the structure

　　NVIC_InitStructure.NVIC_IRQChannel = EXTI2_IRQn; //Enable the channel where the external interrupt is located

　　NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0x02; //Preemption priority 2, 

　　NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0x02; //Subpriority 2

　　NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; //Enable external interrupt channel 

　　NVIC_Init(&NVIC_InitStructure); //Initialize priority according to structure information 

　　6. Writing of external interrupt service function:

　　The external interrupt functions are:

　　EXPORT   EXTI0_IRQHandler          

　　EXPORT   EXTI1_IRQHandler       

　　EXPOR T   EXTI2_IRQHandler         

　　EXPORT   EXTI3_IRQHandler        

　　EXPORT   EXTI4_IRQHandler          

　　EXPORT   EXTI9_5_IRQHandler        

　　EXPORT   EXTI15_10_IRQHandler

　　Interrupt lines 0-4 each correspond to an interrupt function, interrupt lines 5-9 share the interrupt function EXTI9_5_IRQHandler, and interrupt lines 10-15 share the interrupt function EXTI15_10_IRQHandler.　　　

　　void EXTI2_IRQHandler(void)

　　{

　　　　if(EXTI_GetITStatus(EXTI_Line2)!=RESET)//Judge whether an interruption on a line occurs 

　　　　{

　　　　　　Interrupt logic...

　　　　　　EXTI_ClearITPendingBit(EXTI_Line2); //Clear the interrupt flag on LINE

　　　　}     

　　}

3. Configuration instructions for using GPIO port to connect buttons for external interrupts:

　　When using a button for external interrupt, it is generally necessary to perform key delay debounce and hand release detection related processing. The interrupt function can refer to the following code:

　　void EXTI2_IRQHandler(void)

　　{

　　　　delay_ms(10); //delay to eliminate jitter

　　　　if(KEY2==0) //The key is really pressed

　　　　　　{

　　　　　　　　LED0=!LED0;

　　　　　　}

　　　　while(KEY2!=0);//Wait for release

　　　　EXTI_ClearITPendingBit(EXTI_Line2); //Clear interrupt flag 

　　}

　　Of course, if your button allows long press function, then other logical operations will be performed, which will not be studied here.