怎么使用输入捕获功能测一个高电平的时间

只看该作者 · 2011-8-12 09:58

用stm32做超生波，要用输入捕获来捕获高电平的时间，从而计算距离，怎么设置中断，还有那个值才是我要得到的时间，

只看该作者 · 2011-8-12 09:58

void TIM_Configuration(void)//TIM3的CAP初始化函数

{

TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;//定时器初始化结构

TIM_ICInitTypeDef TIM_ICInitStructure;       //通道输入初始化结构

//TIM3输出初始化
TIM_DeInit(TIM3);

TIM_TimeBaseStructure.TIM_Period = 0xFFFF;    //周期0～FFFF

TIM_TimeBaseStructure.TIM_Prescaler = 5;       //时钟分频

TIM_TimeBaseStructure.TIM_ClockDivision = 0; //时钟分割

TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;//模式

TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);//基本初始化

//TIM3通道的捕捉初始化
// TIM_ICInitStructure.TIM_ICMode = TIM_ICMode_ICAP;//配置为输入捕获模式

TIM_ICInitStructure.TIM_Channel = TIM_Channel_2;//通道选择

TIM_ICInitStructure.TIM_ICPolarity = TIM_ICPolarity_Rising;//输入上升沿捕获

TIM_ICInitStructure.TIM_ICSelection = TIM_ICSelection_DirectTI;//管脚与寄存器对应关系

TIM_ICInitStructure.TIM_ICPrescaler = TIM_ICPSC_DIV1;//分频器 //每次检测到捕获输入就触发一次捕获

TIM_ICInitStructure.TIM_ICFilter = 0x0;       //滤波设置，经历几个周期跳变认定波形稳定0x0～0xF

TIM_ICInit(TIM3, &TIM_ICInitStructure);       //初始化

//参考TIM结构图选择滤波后的TI1输入作为触发源，触发下面程序的复位

TIM_SelectInputTrigger(TIM3, TIM_TS_TI2FP2);//选择时钟触发源

//复位模式-选中的触发输入（TRGI）的上升沿初始化计数器，并且产生一个更新线号

TIM_SelectSlaveMode(TIM3, TIM_SlaveMode_Reset);//触发方式

TIM_SelectMasterSlaveMode(TIM3, TIM_MasterSlaveMode_Enable);//主从模式选择 //启动定时器的被动触发

TIM_ITConfig(TIM3,TIM_IT_CC2, ENABLE);       //打开中断

TIM_Cmd(TIM3, ENABLE);                         //启动TIM3

}

只看该作者 · 2011-8-12 10:00

void NVIC_Configuration(void)
{
  NVIC_InitTypeDef NVIC_InitStructure;
  NVIC_PriorityGroupConfig(NVIC_PriorityGroup_1);

  /* Enable the TIM3 global Interrupt */
  NVIC_InitStructure.NVIC_IRQChannel = TIM3_IRQn;
  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
  NVIC_Init(&NVIC_InitStructure);
}

void TIM3_IRQHandler(void)
{
  static vu16  IC2_Value=0;
  if(TIM_GetITStatus( TIM3,  TIM_IT_CC2 ))

  /* Clear TIM3 Capture compare interrupt pending bit */
  {
    TIM_ClearITPendingBit(TIM3, TIM_IT_CC2);

    /* Get the Input Capture value */
    IC2_Value = TIM_GetCapture2(TIM3);
  }
}