#include "Freq_Measure.h"


#define FREQ_DIV                        TIM_ExtTRGPSC_OFF //TIM_ExtTRGPSC_DIV4//TIM_ExtTRGPSC_OFF //TIM_ExtTRGPSC_DIV4                //设置频率的输入分频系数

static float Freq=0;
static unsigned int FREQ_DIV_K;                        //输入分频系数值！
//*******************************************************************************************************
//STM32F205  pa0--ETR--tim2  的IO脚定义处理
void TIM2_ETR_IO_Init(void){
        GPIO_InitTypeDef GPIO_InitStructure;
       
        RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);
        RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB, ENABLE);
        RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOC, ENABLE);
        RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOD, ENABLE);
        //------------------------------------------------------------------------
        GPIO_InitStructure.GPIO_Pin         =        ETR_IN;
        GPIO_InitStructure.GPIO_Mode         = GPIO_Mode_AF;
  GPIO_InitStructure.GPIO_OType = GPIO_OType_OD;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
  GPIO_InitStructure.GPIO_PuPd         = GPIO_PuPd_UP;
  GPIO_Init(GPIOA, &GPIO_InitStructure);
  /* GPIOA Configuration: PA.0(TIM2 CH1) */
  GPIO_PinAFConfig(GPIOA, GPIO_PinSource0, GPIO_AF_TIM2);
}
//************************************************************************************************************
//定义TIM4 1秒钟产生内部定时触发
//*************************************************************************
//计算定时参数，用于Tim3,传入要定时的时间，单位是m秒  定时器的时钟倍频器2
//*************************************************************************
unsigned int Get_Timer_TIM4(float ms){
        unsigned int tick;
        RCC_ClocksTypeDef  RCC_Clocks;
        //---------------------------------------------------------------
        //先计算分频系数！
        FREQ_DIV_K=1;
        if(FREQ_DIV        ==TIM_ExtTRGPSC_DIV2) FREQ_DIV_K=2;
        if(FREQ_DIV        ==TIM_ExtTRGPSC_DIV4) FREQ_DIV_K=4;
        if(FREQ_DIV        ==TIM_ExtTRGPSC_DIV8) FREQ_DIV_K=8;
        //---------------------------------------------------------------
        RCC_GetClocksFreq(&RCC_Clocks);
        tick=2*(RCC_Clocks.PCLK1_Frequency/TIM4_DIV/1000)*ms;//得到间隔常数！1000 是秒的转换，TIM4_DIV是分频系数！
        return tick;
}
//*****************************************************************************
//捕捉测频
void TIM4_Config(void){
        TIM_TimeBaseInitTypeDef   TIM_TimeBaseStructure;
  NVIC_InitTypeDef                                   NVIC_InitStructure;
  /**************************** TIM4 Config ***********************************/
  /* TIM4 clock enable */
  TIM_DeInit(TIM4);
        TIM2_ETR_IO_Init();
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM4, ENABLE);  
  /* TIM4 Time base configuration */
  TIM_TimeBaseStructure.TIM_Prescaler =TIM4_DIV-1;                                                //分频数，降低频率，降低检测的频率！
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
  TIM_TimeBaseStructure.TIM_Period = Get_Timer_TIM4(MEASURE_ms);                //xxx毫秒扫描一次！
  TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;
  TIM_TimeBaseInit(TIM4, &TIM_TimeBaseStructure);
  TIM_ClearFlag(TIM4, TIM_FLAG_Update);
        TIM_ITConfig(TIM4, TIM_IT_Update, ENABLE); //定时1秒中断
        //------------------------------------------------------------------------------------------------------
        //设置主定是输出到到TIM2
        /* Use the TIM4 Update event  as TIM4 Trigger Output(TRGO) */
  TIM_SelectOutputTrigger(TIM4, TIM_TRGOSource_Update);//送出TIM4更新事件UEV做为触发输出(TIM4_CR2寄存器的MMS=’010’)
  /* Enable the TIM4 Master Slave Mode */
  TIM_SelectMasterSlaveMode(TIM4, TIM_MasterSlaveMode_Enable);//配置定时器4为主模式
  /* Enable and set EXTI Line0 Interrupt to the lowest priority */
  NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);//第2组：最高2位用于指定抢占式优先级，后面2位用于指定响应优先级；
  NVIC_InitStructure.NVIC_IRQChannel = TIM4_IRQn;
  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;//rTIM4
  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;//
  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
  NVIC_Init(&NVIC_InitStructure);
  TIM_Cmd(TIM4, ENABLE);
}
//******************************************************************************************
//1000毫秒 定时查询！
void TIM4_IRQHandler_Lib(void){

        if(TIM_GetITStatus(TIM4, TIM_IT_Update) == SET){
                Freq=(float)TIM_GetCapture1(TIM2);
                Freq *=FREQ_DIV_K*(1000/MEASURE_ms);               
                TIM_ClearITPendingBit(TIM4, TIM_IT_Update);  
        }                
}
//**********************************************************************************************************
// 初始化TIM2  它作为外部脉冲计数器，同时也是由TIM4 内部触发复位控制的从计数器
//**********************************************************************************************************
void  TIM2_Config(void){
TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
TIM_ICInitTypeDef                     TIM_ICInitStructure;
       
        RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);
        TIM_DeInit(TIM2);       
        /*---------------------------- TIM2 Configuration ----------------------------*/
        /* Time base configuration */
        TIM_TimeBaseStructure.TIM_Period = 0xffffffff;//fCK_PSC/(PSC[15:0]+1)。
        TIM_TimeBaseStructure.TIM_Prescaler = 0;
        TIM_TimeBaseStructure.TIM_ClockDivision = 0;
        TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
        TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);
        TIM_SelectInputTrigger(TIM2, TIM_TS_ITR3);                                        //定时器2选择定时器4获得输入触发(TIM2_SMCR寄存器的TS=011)
        /* Use the External Clock as TIM2 Slave Mode */
        TIM_SelectSlaveMode(TIM2, TIM_SlaveMode_Reset);                        //配置定时器2使用复位模式(TIM2_SMCR寄存器的SMS=100)
        //--------------------------------------------------------------------------------
        //设置外部输入: x分频，上升沿，不过滤！
        TIM_ETRClockMode2Config(TIM2,FREQ_DIV,TIM_ExtTRGPolarity_Inverted,0);
        //TIM_ITRxExternalClockConfig(TIM2,TIM_TS_ITR3);
        //----------------------------------------------------------------------------
        //TIM4-tigo  同时产生 TIM2的输入扑捉
TIM_ICInitStructure.TIM_Channel=TIM_Channel_1;
TIM_ICInitStructure.TIM_ICPolarity=TIM_ICPolarity_Rising;
TIM_ICInitStructure.TIM_ICSelection=TIM_ICSelection_TRC;        //TIM_ICSelection_DirectTI;
TIM_ICInitStructure.TIM_ICPrescaler=TIM_ICPSC_DIV1;
TIM_ICInitStructure.TIM_ICFilter=0;                                                                                        //Fsampling=Fdts/4 N=8  滤除32ms的抖动
TIM_ICInit(TIM2,&TIM_ICInitStructure);
TIM_SetCounter(TIM2,0);
TIM_Cmd(TIM2, ENABLE);
}
//-------------------------------------------------------------------------------------------
//初始化 TIM2,TIM4.ETR
void FREQ_Measure_Init(void){
        TIM4_Config();
        TIM2_Config();
}
//---------------------------------------------------------------------------------------------
//得到频率值
float Get_Freq_Value(void){
        return Freq;
}

上面是高精度测频程序。全部定时器自动扑捉测量。主程序只是定时读数据。