stm32系列--低电平时间的测量

TIM_ICInitTypeDef  TIM2_ICInitStructure;
void TIM2_CH1_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TIM2时钟
        RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);  //使能GPIOA时钟
        //RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB, ENABLE);  //使能GPIOB时钟

        GPIO_InitStructure.GPIO_Pin  = GPIO_Pin_0;  
        GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IPD; 
        GPIO_Init(GPIOA, &GPIO_InitStructure);
        GPIO_SetBits(GPIOA,GPIO_Pin_0);                         
        //初始化定时器4 TIM2     
        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

        //初始化TIM5输入捕获参数
        TIM2_ICInitStructure.TIM_Channel = TIM_Channel_1; //CC1S=01     选择输入端 IC1映射到TI1上
        TIM2_ICInitStructure.TIM_ICPolarity = TIM_ICPolarity_Falling;    //下降沿捕获；zyq
        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 = 0x00;//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;  //TIM2中断
        NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1;  //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 );     //使能定时器4
}
u8  TIM2CH1_CAPTURE_STA=0;    //输入捕获状态                            
u16    TIM2CH1_CAPTURE_VAL;    //输入捕获值
//定时器2中断服务程序     
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)//已经捕获到低电平了
            {
                if((TIM2CH1_CAPTURE_STA&0X3F)==0X3F)//低电平太长了
                {
                    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)        //捕获到一个上升沿        
            {                  
                TIM2CH1_CAPTURE_STA|=0X80;        //标记成功捕获到一次下降沿
                TIM2CH1_CAPTURE_VAL=TIM_GetCapture1(TIM2);
                   TIM_OC1PolarityConfig(TIM2,TIM_ICPolarity_Falling); //CC1P=0 设置为下降沿捕获
            }else                                  //还未开始,第一次捕获下降沿
            {
                TIM2CH1_CAPTURE_STA=0;            //清空
                TIM2CH1_CAPTURE_VAL=0;
                 TIM_SetCounter(TIM2,0);
                TIM2CH1_CAPTURE_STA|=0X40;        //标记捕获到了下降沿
                   TIM_OC1PolarityConfig(TIM2,TIM_ICPolarity_Rising);        //CC1P=1 设置为上升沿捕获
            }            
        }                                                
     }
 
    TIM_ClearITPendingBit(TIM2, TIM_IT_CC1|TIM_IT_Update); //清除中断标志位
 
}

    TIM2_CH1_Cap_Init(0XFFFF,72-1); //PA0      //CH2 

        if(TIM2CH1_CAPTURE_STA&0X80)//成功捕获到了一次上升沿
        {    
            ch2.temp_time=TIM2CH1_CAPTURE_STA&0X3F;
            ch2.temp_time*=65536;//溢出时间总和
            ch2.temp_time+=TIM2CH1_CAPTURE_VAL;//得到总的高电平时间,以1Mhz的频率计数
            printf("LOW2:%d us\r\n",ch2.temp_time);//打印总的低电平时间
            
     }