Use and precautions of external interrupts in STM8L firmware library

1. Initialization function

GPIO_Init(GPIOB, GPIO_Pin_3, GPIO_Mode_In_FL_IT);

EXTI_SetPinSensitivity(GPIO_Pin_3, EXTI_Trigger_Falling); //Error, will be explained below

2. Interrupt function

INTERRUPT_HANDLER(EXTI3_IRQHandler,11)

{

EXTI_ClearITPendingBit(EXTI_IT_Pin3);

//

}

3. Questions and explanations

I won't go into details about the specific use of the function, which can be found in the firmware library and manual. When testing, I found that when the signal input is a falling edge and remains at a low level, it will trigger repeatedly, which seems to be configured as a falling edge and low level trigger mode. I debugged for a long time but couldn't find the problem. Finally, I looked at the library function again and found the correct configuration is

EXTI_SetPinSensitivity(EXTI_Pin_3, EXTI_Trigger_Falling);

At first I also noticed that EXTI_Pin_3 should be used instead of GPIO_Pin_3, but based on my experience in programming AVR, I thought that these two macros were both defined as 3, and if they were not 3, they should be the same, so I didn't think much about it.

Open the corresponding header file and look at these two macro definitions

  GPIO_Pin_0    = ((uint8_t)0x01),   /*!< Pin 0 selected */

  GPIO_Pin_1    = ((uint8_t)0x02),   /*!< Pin 1 selected */

  GPIO_Pin_2    = ((uint8_t)0x04),   /*!< Pin 2 selected */

  GPIO_Pin_3    = ((uint8_t)0x08),   /*!< Pin 3 selected */

  GPIO_Pin_4    = ((uint8_t)0x10),   /*!< Pin 4 selected */

  GPIO_Pin_5    = ((uint8_t)0x20),   /*!< Pin 5 selected */

  GPIO_Pin_6    = ((uint8_t)0x40),   /*!< Pin 6 selected */

  GPIO_Pin_7    = ((uint8_t)0x80),   /*!< Pin 7 selected */

  EXTI_Pin_0 = (uint8_t)0x00, /*!< GPIO Pin 0 */

  EXTI_Pin_1 = (uint8_t)0x02, /*!< GPIO Pin 1 */

  EXTI_Pin_2 = (uint8_t)0x04, /*!< GPIO Pin 2 */

  EXTI_Pin_3 = (uint8_t)0x06, /*!< GPIO Pin 3 */

  EXTI_Pin_4 = (uint8_t)0x10, /*!< GPIO Pin 4 */

  EXTI_Pin_5 = (uint8_t)0x12, /*!< GPIO Pin 5 */

  EXTI_Pin_6 = (uint8_t)0x14, /*!< GPIO Pin 6 */

  EXTI_Pin_7 = (uint8_t)0x16 /*!< GPIO Pin 7 */

You can see that they are not the same.

Looking at the manual again, the interrupt is configured as falling edge and low level trigger mode by default.

summary:

Using library functions is certainly convenient and quick, but sometimes you can't be too quick on the slack. If you encounter a problem, you should carefully read the library functions and manuals.