stm32的TIMx捕获低频溢出问题嵌入式barretx的博客-

使用stm32的TIM4的通道1与通道2来主要实现捕获功能，低频是捕获值依旧准确。
环境使用的stm32f103vet6

一、贴出初始化部分的代码

void TIM4_Mode_Config(void) {  GPIO_InitTypeDef GPIO_InitStructure;  TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;  TIM_ICInitTypeDef TIM_ICInitStructure;     NVIC_InitTypeDef NVIC_InitStructure; //PB6 ch1  A,PB7 ch2  RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM4, ENABLE); //使能TIM4时钟   RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB, ENABLE); //使能GPIOA时钟 GPIO_StructInit(&GPIO_InitStructure); //将GPIO_InitStruct中的参数按缺省值输入  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6 | GPIO_Pin_7;           GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING; //PA6 PA7浮空输入    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; GPIO_Init(GPIOB, &GPIO_InitStructure); TIM_DeInit(TIM4);   TIM_TimeBaseStructure.TIM_Period = TIM4_TIM_Period;//55999;根据个人需求进行配置         TIM_TimeBaseStructure.TIM_Prescaler = 0; //预分频值  TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1; //输入时钟不分频  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up; //向上计数 TIM_TimeBaseInit(TIM4,&TIM_TimeBaseStructure); //输入捕捉方式  TIM_ICInitStructure.TIM_Channel = TIM_Channel_1;  TIM_ICInitStructure.TIM_ICPolarity = TIM_ICPolarity_Rising; //捕捉上升沿  TIM_ICInitStructure.TIM_ICSelection = TIM_ICSelection_DirectTI; //捕捉中断  TIM_ICInitStructure.TIM_ICPrescaler = TIM_ICPSC_DIV1; //捕捉不分频  TIM_ICInitStructure.TIM_ICFilter = 0x3; //捕捉输入滤波 TIM_ICInit(TIM4, &TIM_ICInitStructure);  TIM_ICInitStructure.TIM_Channel = TIM_Channel_2 ;  TIM_ICInitStructure.TIM_ICPolarity = TIM_ICPolarity_Rising; //捕捉上升沿  TIM_ICInitStructure.TIM_ICSelection = TIM_ICSelection_DirectTI; //捕捉中断  TIM_ICInitStructure.TIM_ICPrescaler = TIM_ICPSC_DIV1; //捕捉不分频  TIM_ICInitStructure.TIM_ICFilter = 0x3; //捕捉输入滤波 0x0-0xF TIM_ICInit(TIM4, &TIM_ICInitStructure); TIM_ClearFlag(TIM4, TIM_IT_CC1 | TIM_IT_CC2| TIM_IT_Update); /* Enable the TIM4Interrupt */  NVIC_InitStructure.NVIC_IRQChannel = TIM4_IRQn;  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; NVIC_Init(&NVIC_InitStructure); TIM_ClearFlag(TIM4,TIM_FLAG_Update); TIM_ARRPreloadConfig(TIM4,DISABLE); /* Enable the CC2 Interrupt Request */ TIM_ITConfig(TIM4, TIM_IT_CC1 | TIM_IT_CC2 | TIM_IT_Update , ENABLE); /* TIM enable counter */ TIM_Cmd(TIM4, ENABLE); } 

二、贴出中断处理函数，对于低频捕获必须要配置更新中断（TIM_IT_Update），当发生溢出中断时计数一次，最终算得的捕获时间需要加上（溢出次数*装载值），这样获得的低频捕获的值才是正确的。

void TIM4_IRQHandler(void) //定时器中断 { //频率缓冲区计数 static u32 this_time_CH1 = 0; static u32 last_time_CH1 = 0; static u8 capture_number_CH1 = 0;  vu32 tmp16_CH1; static u16 this_time_CH2 = 0; static u16 last_time_CH2 = 0; static u8 capture_number_CH2 = 0;  vu32 tmp16_CH2; if (TIM_GetITStatus(TIM4,TIM_IT_Update) != RESET) //计数器更新中断 { TIM_ClearITPendingBit(TIM4, TIM_IT_Update); //溢出次数通道1、2分开统计     CH1_Cycles_Count++;     CH2_Cycles_Count++; } if(TIM_GetITStatus(TIM4, TIM_IT_CC1) != RESET) //通道1脉冲检测中断 { TIM_ClearITPendingBit(TIM4, TIM_IT_CC1); if(capture_number_CH1 == 0) //收到第一个上升沿 {     capture_number_CH1 = 1;     last_time_CH1 = TIM_GetCapture1(TIM4); } else if(capture_number_CH1 == 1) //收到第二个上升沿 { //capture_number_CH1 = 0;     this_time_CH1 = TIM_GetCapture1(TIM4); if(this_time_CH1 > last_time_CH1) {      tmp16_CH1 = this_time_CH1 - last_time_CH1 + TIM4_TIM_Period * CH1_Cycles_Count; } else {      tmp16_CH1 = TIM4_TIM_Period * CH1_Cycles_Count - last_time_CH1 + this_time_CH1; }        CH1_Cycles_Count = 0;     last_time_CH1 = this_time_CH1; } } if(TIM_GetITStatus(TIM4, TIM_IT_CC2) != RESET) //通道2脉冲检测中断 { TIM_ClearITPendingBit(TIM4, TIM_IT_CC2);       pulse_count++; if(capture_number_CH2 == 0) {     capture_number_CH2 = 1;     last_time_CH2 = TIM_GetCapture2(TIM4); } else if(capture_number_CH2 == 1) { //capture_number_CH2 = 0;     this_time_CH2 = TIM_GetCapture2(TIM4); if(this_time_CH2 > last_time_CH2) {      tmp16_CH2 = this_time_CH2 - last_time_CH2 + TIM4_TIM_Period * CH2_Cycles_Count; } else {      tmp16_CH2 = TIM4_TIM_Period * CH2_Cycles_Count - last_time_CH2 + this_time_CH2; }     CH2_Cycles_Count = 0;     last_time_CH2 = this_time_CH2; } } } 

三、注意事项
初始化部分就不说了，看到很多网友在捕获过程中存在问题。基本上大部分网友都是下图中“圈1”中没有屏蔽，“圈2”内容没有。这样的配置会造成丢失百分之五十的脉冲没有统计。大家自己体会一下下面的操作 。