使用输入捕获实现超声波测距

作者：陈广
日期：2021-12-17

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代码

tim.c 文件：

#include "tim.h"
/* TIM2 init function */
void MX_TIM2_Init(void)
{
  LL_GPIO_InitTypeDef GPIO_InitStruct = {0};
  /* Peripheral clock enable */
  LL_APB1_GRP1_EnableClock(LL_APB1_GRP1_PERIPH_TIM2);
  LL_APB2_GRP1_EnableClock(LL_APB2_GRP1_PERIPH_GPIOA);
  /**TIM2 GPIO Configuration
  PA0-WKUP   ------> TIM2_CH1
  */
  GPIO_InitStruct.Pin = LL_GPIO_PIN_0;
  GPIO_InitStruct.Mode = LL_GPIO_MODE_FLOATING;
  LL_GPIO_Init(GPIOA, &GPIO_InitStruct);
  /* TIM2 interrupt Init */
  NVIC_SetPriority(TIM2_IRQn, NVIC_EncodePriority(NVIC_GetPriorityGrouping(),0, 0));
  NVIC_EnableIRQ(TIM2_IRQn);
  /* USER CODE BEGIN TIM2_Init 1 */
  TIM2->CCMR1 = 1;
  /* USER CODE END TIM2_Init 2 */
}

/* USER CODE BEGIN 1 */
volatile int time; //计数器溢出次数
volatile int end; //用于判断捕获是否结束，0表示未结束，1表示已结束，-1表示等待超时
volatile int rising; //上升沿时间
volatile int falling; //下降沿时间

void Delay_ms(uint32_t delay)
{
	TIM2->PSC = 7200 - 1;
	TIM2->ARR = 10 * delay - 1;
	TIM2->EGR |= 1;
	TIM2->CR1 = 0x0D;
	while(!(TIM2->SR & 1));
	TIM2->SR = 0;
}

void Delay_us(uint32_t delay)
{
	TIM2->PSC = 8 - 1;
	TIM2->ARR = 9 * delay - 1;
	TIM2->EGR |= 1;
	TIM2->CR1 = 0x0D;
	while(!(TIM2->SR & 1));
	TIM2->SR = 0;
}

int Measuer_Use_Capture(void)
{
	time = 0;
	end = 0;
	TIM2->PSC = 72 - 1;
	TIM2->ARR = 0xFFFF;
	TIM2->CCER = 1;
	TIM2->EGR |= 3;
	TIM2->SR = 0;
	TIM2->DIER = 3;
	TIM2->CR1 = 1;
	while(!end);
	TIM2->CR1 = 4;
	TIM2->DIER = 0;
	TIM2->CCER = 0;
	if(end == -1) return -1;
	if(time == 0)
	{
		return falling - rising;
	}
	else
	{
		return 65535 - rising + falling;
	}
}

void TIM2_IRQHandler(void)
{
	if(TIM2->SR & 1) //定时器到期中断
	{
		TIM2->SR &= ~1;
		time++;
		if(time > 2) end = -1;
	}
	if(TIM2->SR & 2) //通道1中断
	{
		if(TIM2->CCER & 2) //如果为下降沿
		{
			falling = TIM2->CCR1;
			TIM2->CCER &= ~2;
			end = 1;
		}
		else //如果为上升沿
		{
			rising = TIM2->CCR1;
			TIM2->CCER |= 2;
		}
	}
}
/* USER CODE END 1 */