关于输入捕获的范围！

过配置 ARR=0xfffff PSC=72-1.
也就是1M捕获

当我去测15HZ到50KHZ 时候，测出来数据没有问题，精度也差不多在1%。
问题是 当频率达到50KHZ以上的时候，根本无法测量，频率跳变，检测出来的数字还很奇怪
66666HZ .等等
理论上不是1M捕获 最大能测1M 最小15HZ吗 为什么我就测不出来，！急死我了！

void TIM4_PWMINPUT_INIT(u16 arr,u16 psc)
{
TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
NVIC_InitTypeDef NVIC_InitStructure;
TIM_ICInitTypeDef TIM4_ICInitStructure;
GPIO_InitTypeDef GPIO_InitStructure;
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM4, ENABLE); //Open TIM4 clock
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB, ENABLE); //open gpioB clock
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_7; //GPIO?
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOB, &GPIO_InitStructure);
TIM_TimeBaseStructure.TIM_Period = arr; //设置在下一个更新事件装入活动的自动重装载寄存器周期的值
TIM_TimeBaseStructure.TIM_Prescaler =psc; //设置用来作为TIMx时钟频率除数的预分频值
TIM_TimeBaseStructure.TIM_ClockDivision = 0; //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(TIM4, &TIM_TimeBaseStructure); //根据TIM_TimeBaseInitStruct中指定的参数初始化TIMx的时间基数单位

/*配置中断优先级*/
NVIC_InitStructure.NVIC_IRQChannel = TIM4_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);
TIM4_ICInitStructure.TIM_Channel = TIM_Channel_2;
TIM4_ICInitStructure.TIM_ICPolarity = TIM_ICPolarity_Rising;
TIM4_ICInitStructure.TIM_ICSelection = TIM_ICSelection_DirectTI;
TIM4_ICInitStructure.TIM_ICPrescaler = TIM_ICPSC_div1;
TIM4_ICInitStructure.TIM_ICFilter = 0x0;
TIM_PWMIConfig(TIM4, &TIM4_ICInitStructure); //PWM输入配置
TIM_SelectInputTrigger(TIM4, TIM_TS_TI2FP2); //选择有效输入端
TIM_SelectSlaveMode(TIM4, TIM_SlaveMode_Reset); //配置为主从复位模式
TIM_SelectMasterSlaveMode(TIM4, TIM_MasterSlaveMode_Enable);
TIM_ITConfig(TIM4, TIM_IT_CC2|TIM_IT_Update, ENABLE); //中断配置
TIM_ClearITPendingBit(TIM4, TIM_IT_CC2|TIM_IT_Update); //清除中断标志位
TIM_Cmd(TIM4, ENABLE);
}
u16 period = 0;
u16 duty = 0;
u8 CollectFlag = 1;
void TIM4_IRQHandler(void)
{
if(CollectFlag){
if (TIM_GetITStatus(TIM4, TIM_IT_CC2) ！= RESET)//捕获1发生捕获事件
{
duty = TIM_GetCapture1(TIM4); //采集占空比
period=TIM_GetCapture2(TIM4); //采集周期
}
}
TIM_ClearITPendingBit(TIM4, TIM_IT_CC2|TIM_IT_Update); //清除中断标志位
}