有段求方波频率的代码很迷，求各位路过的

椰子皮djc · 发表于 2018-8-22 18:02:59

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;
}
}

为什么要if(i<19)

为什么frequent=cnt