输入捕获GOIP为什么配置为复用推挽输出模式？

渭城朝雨 · 发表于 2016-4-15 18:15:15

如题，在研究原子哥例程（实验10输入捕获实验）的时候看到这段代码不太理解，为什么PA0配置成推挽复用输出模式。
[mw_shl_code=c,true]//定时器5通道1输入捕获配置
//arr：自动重装值(TIM2,TIM5是32位的!!)
//psc：时钟预分频数
void TIM5_CH1_Cap_Init(u32 arr,u16 psc)
{
TIM_ICInitTypeDef  TIM5_ICInitStructure;
GPIO_InitTypeDef GPIO_InitStructure;
TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
NVIC_InitTypeDef NVIC_InitStructure;

RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM5,ENABLE);    //TIM5时钟使能
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE); //使能PORTA时钟

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0; //GPIOA0
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;//复用功能
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz; //速度100MHz
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP; //推挽复用输出
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_DOWN; //下拉
GPIO_Init(GPIOA,&GPIO_InitStructure); //初始化PA0

GPIO_PinAFConfig(GPIOA,GPIO_PinSource0,GPIO_AF_TIM5); //PA0复用位定时器5


TIM_TimeBaseStructure.TIM_Prescaler=psc;  //定时器分频
TIM_TimeBaseStructure.TIM_CounterMode=TIM_CounterMode_Up; //向上计数模式
TIM_TimeBaseStructure.TIM_Period=arr; //自动重装载值
TIM_TimeBaseStructure.TIM_ClockDivision=TIM_CKD_DIV1;

TIM_TimeBaseInit(TIM5,&TIM_TimeBaseStructure);

//初始化TIM5输入捕获参数
TIM5_ICInitStructure.TIM_Channel = TIM_Channel_1; //CC1S=01 选择输入端 IC1映射到TI1上
  TIM5_ICInitStructure.TIM_ICPolarity = TIM_ICPolarity_Rising; //上升沿捕获
  TIM5_ICInitStructure.TIM_ICSelection = TIM_ICSelection_DirectTI; //映射到TI1上
  TIM5_ICInitStructure.TIM_ICPrescaler = TIM_ICPSC_DIV1;    //配置输入分频,不分频
  TIM5_ICInitStructure.TIM_ICFilter = 0x00;//IC1F=0000 配置输入滤波器不滤波
  TIM_ICInit(TIM5, &TIM5_ICInitStructure);

TIM_ITConfig(TIM5,TIM_IT_Update|TIM_IT_CC1,ENABLE);//允许更新中断 ,允许CC1IE捕获中断

  TIM_Cmd(TIM5,ENABLE ); //使能定时器5

  NVIC_InitStructure.NVIC_IRQChannel = TIM5_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority=2;//抢占优先级3
NVIC_InitStructure.NVIC_IRQChannelSubPriority =0; //子优先级3
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; //IRQ通道使能
NVIC_Init(&NVIC_InitStructure); //根据指定的参数初始化VIC寄存器、

}[/mw_shl_code]