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#include "cs.h"
#include "stm32f10x.h"
#include "delay.h"
#include "usart.h"
/*記錄定時器溢出次數*/
uint overcount=0;
/*設置中斷優先級*/
void NVIC_Config(void)
{
NVIC_InitTypeDef NVIC_InitStructer;
NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);
NVIC_InitStructer.NVIC_IRQChannelPreemptionPriority=0;
NVIC_InitStructer.NVIC_IRQChannelSubPriority=0;
NVIC_InitStructer.NVIC_IRQChannel=TIM2_IRQn;
NVIC_InitStructer.NVIC_IRQChannelCmd=ENABLE;
NVIC_Init(&NVIC_InitStructer);
}
/*初始化模塊的GPIO以及初始化定時器TIM2*/
void CH_SR04_Init(void)
{
GPIO_InitTypeDef GPIO_InitStructer;
TIM_TimeBaseInitTypeDef TIM_TimeBaseInitStructer;
RCC_APB2PeriphClockCmd( RCC_APB2Periph_GPIOB, ENABLE);
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);
/*TRIG觸發信號*/
GPIO_InitStructer.GPIO_Speed=GPIO_Speed_50MHz;
GPIO_InitStructer.GPIO_Mode=GPIO_Mode_Out_PP;
GPIO_InitStructer.GPIO_Pin=GPIO_Pin_8;
GPIO_Init(GPIOB, &GPIO_InitStructer);
/*ECOH回響信號*/
GPIO_InitStructer.GPIO_Mode=GPIO_Mode_IN_FLOATING;
GPIO_InitStructer.GPIO_Pin=GPIO_Pin_9;
GPIO_Init(GPIOB, & GPIO_InitStructer);
/*定時器TIM2初始化*/
TIM_DeInit(TIM2);
TIM_TimeBaseInitStructer.TIM_Period=999;//定時周期為1000
TIM_TimeBaseInitStructer.TIM_Prescaler=71; //分頻系數72
TIM_TimeBaseInitStructer.TIM_ClockDivision=TIM_CKD_DIV1;//不分頻
TIM_TimeBaseInitStructer.TIM_CounterMode=TIM_CounterMode_Up;
TIM_TimeBaseInit(TIM2,&TIM_TimeBaseInitStructer);
TIM_ITConfig(TIM2,TIM_IT_Update,ENABLE);//開啟更新中斷
NVIC_Config();
TIM_Cmd(TIM2,DISABLE);//關閉定時器使能
}
float Senor_Using(void)
{
float length=0,sum=0;
u16 tim;
uint i=0;
/*測5次數據計算一次平均值*/
while(i!=5)
{
PBout(8)=1; //拉高信號，作為觸發信號
delay_us(20); //高電平信號超過10us
PBout(8)=0;
/*等待回響信號*/
while(GPIO_ReadInputDataBit(GPIOB,GPIO_Pin_9)==RESET);
TIM_Cmd(TIM2,ENABLE);//回響信號到來，開啟定時器計數
i+=1; //每收到一次回響信號+1，收到5次就計算均值
while(GPIO_ReadInputDataBit(GPIOB,GPIO_Pin_9)==SET);//回響信號消失
TIM_Cmd(TIM2,DISABLE);//關閉定時器
tim=TIM_GetCounter(TIM2);//獲取計TIM2數寄存器中的計數值，一邊計算回響信號時間
length=(tim+overcount*1000)/58.0;//通過回響信號計算距離
sum=length+sum;
TIM2->CNT=0; //將TIM2計數寄存器的計數值清零
overcount=0; //中斷溢出次數清零
delay_ms(100);
}
length=sum/5;
return length;//距離作為函數返回值
}
void TIM2_IRQHandler(void) //中斷，當回響信號很長是，計數值溢出后重復計數，用中斷來保存溢出次數
{
if(TIM_GetITStatus(TIM2,TIM_IT_Update)!=RESET)
{
TIM_ClearITPendingBit(TIM2,TIM_IT_Update);//清除中斷標志
overcount++;
}
}

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