STM32F4输入捕获问题为什么TIM_Period在初始化要等与0XFFFFFFFF?

我有偏见 · 发表于 2020-8-13 10:03:05

STM32F4输入捕获问题为什么TIM_Period在初始化要等与0XFFFFFFFF?如果需要以1M频率进行捕获,那么定时器的中断频率等于84M/84 = 1M  要是TIM_Period在等于0XFFFFFFFF  那么1M/0XFFFFFFFF = ?那不是小的没边了?为什么要这样配置?不应该TIM_Period = 0?
void TIM4_CH1_Cap_Init(u32 arr,u16 psc)
{
GPIO_InitTypeDef GPIO_InitStructure;
TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
NVIC_InitTypeDef NVIC_InitStructure;

RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM4,ENABLE);    //TIM5时钟使能
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB, ENABLE); //使能PORTA时钟

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6; //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(GPIOB,&GPIO_InitStructure); //初始化PA0

GPIO_PinAFConfig(GPIOB,GPIO_PinSource6,GPIO_AF_TIM4); //PA0复用位定时器5


TIM_TimeBaseStructure.TIM_Prescaler = psc;  //定时器分频//Timer clock = sysclock /(TIM_Prescaler+1) = 1M
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 counter clock / TIM output clock) - 1 = 40Hz
TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;
TIM_TimeBaseInit(TIM4,&TIM_TimeBaseStructure);

//初始化TIM5输入捕获参数
TIM4_ICInitStructure.TIM_Channel = TIM_Channel_1; //CC1S=01 选择输入端 IC1映射到TI1上
  TIM4_ICInitStructure.TIM_ICPolarity = TIM_ICPolarity_Rising; //上升沿捕获
  TIM4_ICInitStructure.TIM_ICSelection = TIM_ICSelection_DirectTI; //映射到TI1上
  TIM4_ICInitStructure.TIM_ICPrescaler = TIM_ICPSC_DIV1;    //配置输入分频,不分频
  TIM4_ICInitStructure.TIM_ICFilter = 0x00;//IC1F=0000 配置输入滤波器不滤波
  TIM_ICInit(TIM4, &TIM4_ICInitStructure);

TIM_ITConfig(TIM4,TIM_IT_Update|TIM_IT_CC1,ENABLE);//允许更新中断 ,允许CC1IE捕获中断

  TIM_Cmd(TIM4,ENABLE ); //使能定时器4

  NVIC_InitStructure.NVIC_IRQChannel = TIM4_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、

}