Question

我用stm32的PWM输入捕获模式测PWM波的频率，在keil上硬件仿真是对的，但是实际运行时却不行

extern float Rightf;
TIM_ICInitTypeDef TIM_ICInitStructure;
void TIM3_Input(void)
{
GPIO_InitTypeDef GPIO_InitStructure;
NVIC_InitTypeDef NVIC_InitStructure;
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);
NVIC_InitStructure.NVIC_IRQChannel = TIM3_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_7;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOA, &GPIO_InitStructure);
TIM_ICInitStructure.TIM_Channel = TIM_Channel_2;
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 = 0x0;
TIM_PWMIConfig(TIM3, &TIM_ICInitStructure);
TIM_SelectInputTrigger(TIM3, TIM_TS_TI2FP2);
TIM_SelectSlaveMode(TIM3, TIM_SlaveMode_Reset);
TIM_SelectMasterSlaveMode(TIM3, TIM_MasterSlaveMode_Enable);
TIM_Cmd(TIM3, ENABLE);
TIM_ITConfig(TIM3, TIM_IT_CC2, ENABLE);

}
void TIM3_IRQHandler(void)
{
uint16_t IC2Value = 0;
uint16_t DutyCycle = 0;
TIM_ClearITPendingBit(TIM3, TIM_IT_CC2);
IC2Value = TIM_GetCapture2(TIM3);
if (IC2Value != 0)
{
DutyCycle = (TIM_GetCapture1(TIM3) * 100) / IC2Value;
Rightf = 72000000 / IC2Value;
}
else
{
DutyCycle = 0;
Rightf = 0;
}
}

__IO float Left_f = 0;
__IO float Rightf = 1;
int main(void)
{
SystemInit();
delay_init(72);
TIM3_Input();

LED1=0;
while(Rightf < 9990 );
LED1=1;
while(1)
{
LED0=!LED0;
delay_ms(250);
}
}
在 while(Rightf < 9990 );语句判断值一直为假

Answer 1

外部PWM用示波器测过吗？

追问

测过，正常的方波，很稳定，程序步步编译测出值也很准确

追答

IC2Value观察这个值，如果正常，一步步往上推。

Answer 2

外部PWM采样波形什么样的