void TIM3_IRQHandler(void) //TIM3
{
static u8 CapStatus=0; //捕获状态,CapStatus=0未捕获到第1个下降沿,CapStatus=1捕获到第1个下降沿
static u8 TIM3_CH3_Capture=0; //总的计数次数
u32 FrequencyTemp=0;
if(TIM_GetITStatus(TIM3,TIM_IT_Update)) //TIM3定时溢出更新中断
{
TIM_ClearITPendingBit(TIM3,TIM_IT_Update); //清除中断标志位
if(CapStatus)
TIM3_CH3_Capture++;
}
if(TIM_GetITStatus(TIM3,TIM_IT_CC3)) //RB0输入捕获中断
{
TIM_ClearITPendingBit(TIM3,TIM_IT_CC3); //清除中断标志位
if(!CapStatus)
{
CapStatus=1;
TIM_SetCounter(TIM3,0); //计数器清零
}
else if(CapStatus) //已经捕获到第1个下降沿
{
CapStatus=0;
FrequencyTemp=TIM_GetCapture3(TIM3)+TIM3_CH3_Capture*65536; //计算两个下降沿总计数
TIM3_CH3_Capture=0; //溢出次数清零
TIM_SetCounter(TIM3,0); //计数器清零
FrequencyValue=400000000/FrequencyTemp; //计算频率,比如5000,单位0.01Hz
}
}
}
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附录1:测频法计算频率
网上找的资料,不保证正确性,没有实际测试过,仅供参考。
通过在一定时间内检测跳边沿的个数可计算出频率 频率=上升沿或下降沿个数/统计时间。
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方法1:利用外部中断统计跳边沿个数,配置一个定时器每隔一定时间对频率进行计算。部分代码如下。
void exti_init() //外部中断初始化函数
{
GPIO_InitTypeDef GPIO_InitStructure;
EXTI_InitTypeDef EXTI_InitStructure;
NVIC_InitTypeDef NVIC_InitStructure;
RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO,ENABLE);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOC,ENABLE);
GPIO_InitStructure.GPIO_Pin=GPIO_Pin_2;
GPIO_InitStructure.GPIO_Mode=GPIO_Mode_IN_FLOATING;
GPIO_InitStructure.GPIO_Speed=GPIO_Speed_50MHz;
GPIO_Init(GPIOC,&GPIO_InitStructure);
GPIO_EXTILineConfig(GPIO_PortSourceGPIOC, GPIO_PinSource2);//选择GPIO引脚用作外部中段线路
//此处一定要记住给端口管脚加上中断外部线路
EXTI_InitStructure.EXTI_Line=EXTI_Line2;
EXTI_InitStructure.EXTI_Mode=EXTI_Mode_Interrupt;
EXTI_InitStructure.EXTI_Trigger=EXTI_Trigger_Falling; //下降沿进中断
EXTI_InitStructure.EXTI_LineCmd = ENABLE;
EXTI_Init(&EXTI_InitStructure);
NVIC_PriorityGroupConfig(NVIC_PriorityGroup_1);
NVIC_InitStructure.NVIC_IRQChannel = EXTI2_IRQn; //打开EXTI2的全局中断
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1; //设置优先级
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; //使能
NVIC_Init(&NVIC_InitStructure);
}
外部中断中断函数
void EXTI2_IRQHandler()
{
if(EXTI_GetITStatus(EXTI_Line2)==SET)
{
EXTI_ClearITPendingBit(EXTI_Line0);//清中断
if(GPIO_ReadInputDataBit(GPIOC,GPIO_Pin_2)==Bit_RESET) //确定沿
{
cnt++;
}
}
}
定时器中断函数
void TIM3_IRQHandler()
{
frequent=cnt; //定时器设置时间为1s时
cnt=0; //清零计数cnt
TIM_ClearITPendingBit(TIM3,TIM_IT_Update); //清标志位
}
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方法2:采用定时器外部计数的方法,另外一个定时器负责每隔一段时间计算频率,部分代码如下。
void time_init()
{
GPIO_InitTypeDef GPIO_InitStructure;
TIM_TimeBaseInitTypeDef TIM2_TimeBaseInitStructure;
TIM_TimeBaseInitTypeDef TIM3_TimeBaseInitStructure;
NVIC_InitTypeDef NVIC_InitStructure;
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA,ENABLE);
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3,ENABLE);
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2,ENABLE);
GPIO_InitStructure.GPIO_Pin=GPIO_Pin_0;
GPIO_InitStructure.GPIO_Mode=GPIO_Mode_IPU;
GPIO_InitStructure.GPIO_Speed=GPIO_Speed_50MHz;
GPIO_Init(GPIOA,&GPIO_InitStructure);
TIM_ClearITPendingBit(TIM2,TIM_IT_Update);//清除TIM2中断标志位
TIM2_TimeBaseInitStructure.TIM_Period = 0xFFFF;//设置自动重装载值
TIM2_TimeBaseInitStructure.TIM_Prescaler = 0;//设置分频
TIM2_TimeBaseInitStructure.TIM_ClockDivision = TIM_CKD_DIV1;
TIM2_TimeBaseInitStructure.TIM_CounterMode = TIM_CounterMode_Up;//向上计数
TIM_TimeBaseInit(TIM2,&TIM2_TimeBaseInitStructure);
TIM_ETRClockMode1Config(TIM2, TIM_ExtTRGPSC_OFF,TIM_ExtTRGPolarity_NonInverted, 0x00); //设置为采用外部时钟计数,可设定滤波参数消除信号干扰
TIM_Cmd(TIM2,ENABLE);
TIM_ClearITPendingBit(TIM3,TIM_IT_Update);
TIM3_TimeBaseInitStructure.TIM_Period = 999;
TIM3_TimeBaseInitStructure.TIM_Prescaler = 3599;
TIM3_TimeBaseInitStructure.TIM_ClockDivision = TIM_CKD_DIV1;
TIM3_TimeBaseInitStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseInit(TIM3,&TIM3_TimeBaseInitStructure);
TIM_Cmd(TIM3,ENABLE);
TIM_ITConfig(TIM3, TIM_IT_Update, ENABLE );
NVIC_PriorityGroupConfig(NVIC_PriorityGroup_1);
NVIC_InitStructure.NVIC_IRQChannel=TIM3_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority=0;
NVIC_InitStructure.NVIC_IRQChannelSubPriority=0;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);
}
定时器中断函数
void TIM3_IRQHandler()
{
static u8 i;
static u32 frequent_sum;
TIM_ClearITPendingBit(TIM3,TIM_IT_Update); //清中断
if(i<19)
{
cnt += TIM_GetCounter(TIM2); //,获取计数器的值,累加减少误差
TIM_SetCounter(TIM2,0); //计数器清零
i++;
}
else
{
cnt += TIM_GetCounter(TIM2);
TIM_SetCounter(TIM2,0);
cnt += cnt*0.000025; //根据实际情况修改系数线性补偿
frequent = cnt;
i = 0;
cnt = 0;
}
}
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