求助！！输入捕获做的超声波测距显示的值固定而且很大

李成s · 发表于 2019-8-7 19:52:18

#include "timer.h"
#include "led.h"
#include "usart.h"

//通用定时器中断初始化
//这里时钟选择为APB1的2倍，而APB1为36M
//arr：自动重装值。
//psc：时钟预分频数
//这里使用的是定时器5!

//定时器5通道1输入捕获配置
TIM_ICInitTypeDef  TIM2_ICInitStructure;
void TIM2_Cap_Init(u16 arr,u16 psc)
{
GPIO_InitTypeDef GPIO_InitStructure;
TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
NVIC_InitTypeDef NVIC_InitStructure;
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE); //使能TIM5时钟
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);  //使能GPIOA时钟

GPIO_InitStructure.GPIO_Pin  = GPIO_Pin_4;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IPD;
GPIO_Init(GPIOA, &GPIO_InitStructure);
GPIO_ResetBits(GPIOA,GPIO_Pin_4);

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2;    //PC8接TRIG
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;    //设为推挽输出模式
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOA, &GPIO_InitStructure);                //初始化外设GPIO

TIM_TimeBaseStructure.TIM_Period = arr; //设定计数器自动重装值
TIM_TimeBaseStructure.TIM_Prescaler =psc;  //预分频器
TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1; //设置时钟分割:TDTS = Tck_tim
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;  //TIM向上计数模式
TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure); //根据TIM_TimeBaseInitStruct中指定的参数初始化TIMx的时间基数单位

TIM2_ICInitStructure.TIM_Channel = TIM_Channel_3; //CC1S=01  选择输入端 IC1映射到TI1上
TIM2_ICInitStructure.TIM_ICPolarity = TIM_ICPolarity_Rising; //上升沿捕获
TIM2_ICInitStructure.TIM_ICSelection = TIM_ICSelection_DirectTI; //映射到TI1上
TIM2_ICInitStructure.TIM_ICPrescaler = TIM_ICPSC_DIV1;  //配置输入分频,不分频
TIM2_ICInitStructure.TIM_ICFilter = 0x01;//IC1F=0000 配置输入滤波器不滤波
TIM_ICInit(TIM2, &TIM2_ICInitStructure);

//中断分组初始化
NVIC_InitStructure.NVIC_IRQChannel = TIM2_IRQn;  //TIM3中断
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 2;  //先占优先级2级
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;  //从优先级0级
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; //IRQ通道被使能
NVIC_Init(&NVIC_InitStructure);  //根据NVIC_InitStruct中指定的参数初始化外设NVIC寄存器

TIM_ITConfig(TIM2,TIM_IT_Update|TIM_IT_CC1,ENABLE);//允许更新中断 ,允许CC1IE捕获中断

TIM_Cmd(TIM2,ENABLE );  //使

}
u8  TIM2CH1_CAPTURE_STA=0; //输入捕获状态
u16 TIM2CH1_CAPTURE_VAL; //输入捕获值

void TIM2_IRQHandler(void)
{
  if((TIM2CH1_CAPTURE_STA&0X80)==0)//还未成功捕获
{
  if (TIM_GetITStatus(TIM2, TIM_IT_Update) != RESET)

  {
if(TIM2CH1_CAPTURE_STA&0X40)//已经捕获到高电平了
{

if((TIM2CH1_CAPTURE_STA&0X3F)==0X3F)//高电平太长了
{
   TIM2CH1_CAPTURE_STA|=0X80;//标记成功捕获了一次

   TIM2CH1_CAPTURE_VAL=0XFFFF;
}else TIM2CH1_CAPTURE_STA++;

}
  }
if (TIM_GetITStatus(TIM2, TIM_IT_CC1) != RESET)//捕获1发生捕获事件
  {
if(TIM2CH1_CAPTURE_STA&0X40)  //捕获到一个下降沿
{
TIM2CH1_CAPTURE_STA|=0X80;  //标记成功捕获到一次上升沿
TIM2CH1_CAPTURE_VAL=TIM_GetCapture1(TIM2);

   TIM_OC1PolarityConfig(TIM2,TIM_ICPolarity_Rising); //CC1P=0 设置为上升沿捕获
}else       //还未开始,第一次捕获上升沿
{
TIM2CH1_CAPTURE_STA=0; //清空
TIM2CH1_CAPTURE_VAL=0;
   TIM_SetCounter(TIM2,0);
TIM2CH1_CAPTURE_STA|=0X40;  //标记捕获到了上升沿
   TIM_OC1PolarityConfig(TIM2,TIM_ICPolarity_Falling);

}
  }
  }

TIM_ClearITPendingBit(TIM2, TIM_IT_CC1|TIM_IT_Update); //清除中断标志位

}
#include "led.h"
#include "delay.h"
#include "key.h"
#include "sys.h"
#include "usart.h"
#include "timer.h"

#define Trig PAout(2)  //PC1 TRIG
#define ECHO PAout(4)
//函数声明

float Distance=0;
extern u8  TIM2CH1_CAPTURE_STA;  //输入捕获状态
extern u16 TIM2CH1_CAPTURE_VAL; //输入捕获值

int main(void)
{


  u32 temp=0;
//计算出的距离
delay_init();    //延时函数初始化
NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);  //设置NVIC中断分组2:2位抢占优先级，2位响应优先级
uart_init(9600);  //串口初始化为115200
  LED_Init();       //LED端口初始化

  TIM2_Cap_Init(0XFFFF,72-1); //以1Mhz的频率计数

while(1)
{
  Trig = 1;
delay_us(15);                      //延时20US
Trig = 0;

if(TIM2CH1_CAPTURE_STA&0X80)//成功捕获到了一次上升沿
  {

temp=TIM2CH1_CAPTURE_STA&0X3F;
temp*=65536;//溢出时间总和
temp+=TIM2CH1_CAPTURE_VAL;//得到总的高电平时间

Distance=(float)temp*170/10000;//距离计算公式：距离=高电平持续时间*声速/2
            //即距离= 高电平持续时间*340*100/（2*1000 000） = 高电平持续时间*170/10000

printf("距离:%f cm\r\n",Distance);//打印总的高点平时间
  delay_ms(1000);
TIM2CH1_CAPTURE_STA=0;//开启下一次捕获
  }
}
}