TIM1测频得到的数值了但是我的时钟定义的是72M为什么是36M中间我都没有设置分频

pk3725069

TIM1测频得到的数值了但是我的时钟定义的是72M为什么是36M中间我都没有设置分频 [复制链接]

/*******************TIM1定义***************************?

void Timer_Configuration(void) 

{ 

  TIM_TimeBaseInitTypeDef   TIM_TimeBaseStructure; 

  TIM_ICInitTypeDef     TIM_ICInitStructure; 

  //TIM1时基设定--捕获填充频率 

  TIM_DeInit(TIM1); 

  TIM_TimeBaseStructure.TIM_Period=0xFFFF;  //ARR的值 

  TIM_TimeBaseStructure.TIM_Prescaler=0; 

  TIM_TimeBaseStructure.TIM_ClockDivision=TIM_CKD_DIV1; //采样不分频,频率72M 

  TIM_TimeBaseStructure.TIM_CounterMode=TIM_CounterMode_Up; //向上计数模式 

 // TIM_TimeBaseStructure.TIM_RepetitionCounter=TIM_EncoderMode_TI2;

  TIM_TimeBaseInit(TIM1, &TIM_TimeBaseStructure); 

  TIM_PrescalerConfig(TIM1,0,TIM_PSCReloadMode_Immediate);//时钟分频系数0,系统时钟72MHZ 

  TIM_ARRPreloadConfig(TIM1, ENABLE);   //使能ARR预装载缓冲器 

   

//定时器1捕获设置 

 

  TIM_ICInitStructure.TIM_Channel=TIM_Channel_1; 

  TIM_ICInitStructure.TIM_ICPolarity=TIM_ICPolarity_Rising; 

  TIM_ICInitStructure.TIM_ICSelection=TIM_ICSelection_DirectTI; 

  TIM_ICInitStructure.TIM_ICPrescaler=TIM_ICPSC_DIV1; 

  TIM_ICInitStructure.TIM_ICFilter=0;  

  TIM_ICInit(TIM1,&TIM_ICInitStructure); 

  //清中断，以免一启用中断后立即产生中断  

  TIM_ClearFlag(TIM1, TIM_IT_Update);//  TIM_FLAG_Update

//使能TIM1溢出中断源  

  TIM_ITConfig(TIM1, TIM_IT_Update, ENABLE);  

//TIM_ITConfig(TIM1, TIM_FLAG_CC1OF, ENABLE);

  TIM_ITConfig(TIM1, TIM_IT_CC1, ENABLE);//使能捕获中断 

  TIM_GenerateEvent(TIM1,TIM_EventSource_Update);

  TIM_Cmd(TIM1, ENABLE);  //使能定时器1 

} 

void NVIC_Configuration(void) 

{ 

  NVIC_InitTypeDef NVIC_InitStructure; 

  /* Enable the TIM2 global Interrupt */ 

  NVIC_InitStructure.NVIC_IRQChannel = TIM1_CC_IRQn; 

  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0; 

  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0; 

  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; 

  NVIC_Init(&NVIC_InitStructure); 

  

  NVIC_InitStructure.NVIC_IRQChannel =  TIM1_UP_IRQn; 

  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0; 

  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1; 

  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; 

  NVIC_Init(&NVIC_InitStructure);  

} 

void GPIO_Configuration(void) 

{ 

  GPIO_InitTypeDef GPIO_InitStructure; 

  GPIO_DeInit(GPIOA);

  /* TIM2 channel 2 pin (PA.01) configuration */ 

  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_8; 

  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING; 

  

  GPIO_Init(GPIOA, &GPIO_InitStructure);

 }

/****************定时器中断服务函数 *******************************/

//要想得到足够大的测频范围，只要定义相应的OV_count，cap_diff足够大就可以了 

//建议freq_1array[]可以设置成double类型的变量，那样可以有小数频率！ 

void TIM1_CC_IRQHandler(void) 

{  

//捕获处理 

if(TIM_GetITStatus(TIM1,TIM_IT_CC1)!=RESET) 

{ 

  TIM_ClearITPendingBit(TIM1,TIM_IT_CC1); 

if(1==cap_count) //捕获频率 

{

OV_count=0; 

old_cap=TIM_GetCapture1(TIM1);//TIM_GetCounter

} 

else if(cap_count>10)        //捕获十次

{ 

new_cap=TIM_GetCapture1(TIM1);// TIM_GetCounter

cap_diff=new_cap-old_cap+65535*OV_count;

freq_1array=720000000.0/cap_diff;//这里72000000*10是对10次捕获求平均值 *100是求小数后两位

cap_count=1; 

OV_count=0; 

} 

cap_count++;

} 

} 

//TIM1溢出中断服务子程序：TIM1_FLAG_CC1OF  

void TIM1_UP_IRQHandler(void)  

{  

TIM_ClearITPendingBit(TIM1, TIM_IT_Update); //清中断  

OV_count++;

} 

void main(void)

  {

  /* config the sysclock to 72m */

  SystemInit();

  RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA | RCC_APB2Periph_TIM1|

                         RCC_APB2Periph_AFIO,ENABLE);  

 Timer_Configuration();

 GPIO_Configuration();

 NVIC_Configuration();

 

 while(1);

   

  }    

要把中断中的 freq_1array=720000000.0/cap_diff 改成360000000.0才正确

为什么呢。。

/**************"stm32f10x.h"**********************************/

#if defined (STM32F10X_LD_VL) || (defined STM32F10X_MD_VL) || (defined STM32F10X_HD_VL)

/* #define SYSCLK_FREQ_HSE    HSE_VALUE */

 #define SYSCLK_FREQ_24MHz  24000000

#else

/* #define SYSCLK_FREQ_HSE    HSE_VALUE */

/* #define SYSCLK_FREQ_24MHz  24000000 */ 

/* #define SYSCLK_FREQ_36MHz  36000000 */

/* #define SYSCLK_FREQ_48MHz  48000000 */

/* #define SYSCLK_FREQ_56MHz  56000000 */

#define SYSCLK_FREQ_72MHz  72000000

#endif

[ 本帖最后由 pk3725069 于 2012-3-14 18:06 编辑 ]