Record 3 - the state machine realizes key control and measures the number of external pulses

State machine introduction

To shake

Direct delay will occupy the execution time of the processor , Reduce the utilization efficiency of the processor . In engineering applications, state machine and timing interrupt are commonly used to eliminate chattering

Design idea of state machine

Divide a process into several States and switch directly , There is a certain connection between these States

Mission

With stm32f411ceu6 For example

Engineering configuration

TIM10 To configure ：


TIM2 To configure ：

Code implementation

/* Private typedef -----------------------------------------------------------*/
/* USER CODE BEGIN PTD */
typedef enum 
{
    
	KEY_CHECK=0,// Key detection status 
	KEY_COMFIRM,// Press the key to confirm the status 
	KEY_RELEASE// Key release status 
}KEY_STATE;// Define three key states 
	
/* USER CODE END PTD */

/* USER CODE BEGIN PV */
KEY_STATE KeyState=KEY_CHECK;
uint8_t KeyFlag=0;// Key valid value flag ：1—— It works ,0—— Invalid 
uint8_t Result=0;
/* USER CODE END PV */

/* USER CODE BEGIN 2 */
	HAL_TIM_Base_Start_IT(&htim10);// Turn on timer 10 interrupt 
	HAL_TIM_Base_Start(&htim2);// Turn on timer 2
	printf ("TIMER COUNTER:\n");

  /* USER CODE END 2 */

  while (1)
  {
    
    /* USER CODE END WHILE */

    /* USER CODE BEGIN 3 */
		if(KeyFlag==1)// Press the judgment key 
		{
    
			KeyFlag = 0;
			HAL_GPIO_TogglePin (GPIOC ,GPIO_PIN_13);
			HAL_GPIO_WritePin (GPIOA ,GPIO_PIN_6 ,GPIO_PIN_SET );
			HAL_Delay (1);
			HAL_GPIO_WritePin (GPIOA ,GPIO_PIN_6 ,GPIO_PIN_RESET );
			HAL_Delay (1);
			Result = __HAL_TIM_GetCounter(&htim2);
			// Get the current counter value 
			printf ("Count=%d.\n",Result);

		}
  }
  /* USER CODE END 3 */

State machine implementation

/* USER CODE BEGIN 4 */
void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim)// Callback function 
{
    
	if(htim->Instance == TIM10 )
	{
    
		switch(KeyState)
		{
    
			case KEY_CHECK :
			{
    
				if(HAL_GPIO_ReadPin  (GPIOA,GPIO_PIN_0 )==GPIO_PIN_RESET)
				{
    
					KeyState = KEY_COMFIRM;
				}
				break ;
			}
			case KEY_COMFIRM :
			{
    
				if(HAL_GPIO_ReadPin  (GPIOA,GPIO_PIN_0 )==GPIO_PIN_RESET)
				{
    
					KeyState = KEY_RELEASE ;
					KeyFlag = 1;
				}
				else
				{
    
					KeyState = KEY_CHECK ;
				}
				break ;
			}
			case KEY_RELEASE :
			{
    
				if(HAL_GPIO_ReadPin  (GPIOA,GPIO_PIN_0 )==GPIO_PIN_SET)
				{
    
					KeyState = KEY_CHECK ;
				}
				break ;
			}
			default :break ;
		}
	}
}
					
		
int fputc(int ch,FILE *f)
{
    
	HAL_UART_Transmit (&huart2 ,(uint8_t *)&ch,1,HAL_MAX_DELAY);
	return ch;
}//printf Function redefinition 

/* USER CODE END 4 */