思路：普通IO口配置上升沿下降沿触发中断，然后配置一个定时器（周期大于等于PWM周期），在IO口中断中读取定时器计数。

定时器不需要配置中断

void TIM3_Configuration(void)

{

TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;

TIM_OCInitTypeDef TIM_OCInitStructure;

/* TIM2 clock enable */

RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);

TIM_TimeBaseStructure.TIM_Prescaler = 72-1; //72M/72=1M

TIM_TimeBaseStructure.TIM_Period = 20000; //20ms overflow

TIM_TimeBaseStructure.TIM_ClockDivision = 0x0; //

TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up; //

TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);

/*load */

TIM_ARRPreloadConfig(TIM3, ENABLE);

//clear IT bit

TIM_ClearITPendingBit(TIM3,TIM_IT_Update);

/* overflow interrupt*/

//TIM_ITConfig(TIM3, TIM_IT_Update, ENABLE);

/* allow*/

TIM_Cmd(TIM3, ENABLE);

}

IO口配置

GPIO_InitTypeDef GPIO_InitStructure;

EXTI_InitTypeDef EXTI_InitStructure;

RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOE, ENABLE);

RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO, ENABLE);

/*

PE9 CH1 DJ // PE10 CH2 MD // PE11 CH6 adjust */

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9|GPIO_Pin_10|GPIO_Pin_11;

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IPD;

GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; //50M

GPIO_Init(GPIOE, &GPIO_InitStructure);

GPIO_EXTILineConfig(GPIO_PortSourceGPIOE,GPIO_PinSource9);

GPIO_EXTILineConfig(GPIO_PortSourceGPIOE,GPIO_PinSource10);

GPIO_EXTILineConfig(GPIO_PortSourceGPIOE,GPIO_PinSource11);

EXTI_InitStructure.EXTI_Line = EXTI_Line9 | EXTI_Line10 |EXTI_Line11;

EXTI_InitStructure.EXTI_Mode = EXTI_Mode_Interrupt;

EXTI_InitStructure.EXTI_Trigger = EXTI_Trigger_Rising_Falling;

EXTI_InitStructure.EXTI_LineCmd = ENABLE;

EXTI_Init(&EXTI_InitStructure);

IO中断配置

NVIC_InitTypeDef NVIC_InitStructure;

/* Configure one bit for preemption priority */

NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);

/* PB6 PE5 interrupt */

NVIC_InitStructure.NVIC_IRQChannel = EXTI9_5_IRQn;

NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1; //highest priority

NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;

NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;

NVIC_Init(&NVIC_InitStructure);

/* PE3 interrupt */

NVIC_InitStructure.NVIC_IRQChannel = EXTI15_10_IRQn;

NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;

NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;

NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;

NVIC_Init(&NVIC_InitStructure);

中断处理函数（counter_reload是20000，TIM_TimeBaseStructure.TIM_Period = 20000;）

void EXTI9_5_IRQHandler(void)

{

static u16 C_tmp;

static u16 PE9_Counter;

static u16 PE9_last_count;

if(EXTI_GetITStatus(EXTI_Line9) != RESET)

{

EXTI_ClearITPendingBit(EXTI_Line9);

C_tmp=TIM_GetCounter(TIM3);

//Delay(1);

if(!(GPIOE->IDR & GPIO_Pin_9))

{ // PE6=0 falling

PE9_Counter=C_tmp;

PE9_Counter=(PE9_Counter-PE9_last_count)>0?

(PE9_Counter-PE9_last_count):(PE9_Counter-PE9_last_count+counter_reload);

if (PE9_Counter Max_duty) //1ms~2ms

return;

}

else

{ //Rising

PE9_last_count=C_tmp;

}

}

}

void EXTI15_10_IRQHandler(void)

{

static u16 C_tmp;

static u16 PE10_Counter;

static u16 PE10_last_count;

static u16 PE11_Counter;

static u16 PE11_last_count;

if(EXTI_GetITStatus(EXTI_Line10) != RESET)

{

EXTI_ClearITPendingBit(EXTI_Line10);

C_tmp=TIM_GetCounter(TIM3);

//Delay(1);

if(!(GPIOE->IDR & GPIO_Pin_10))

{ // PE6=0 falling

PE10_Counter=C_tmp;

PE10_Counter=(PE10_Counter-PE10_last_count)>0?

(PE10_Counter-PE10_last_count):(PE10_Counter-PE10_last_count+counter_reload);

if (PE10_Counter Max_duty) //1ms~2ms

return;

}

else

{ //Rising

PE10_last_count=C_tmp;

}

}

else if(EXTI_GetITStatus(EXTI_Line11) != RESET)

{

EXTI_ClearITPendingBit(EXTI_Line11);

C_tmp=TIM_GetCounter(TIM3);

if(!(GPIOE->IDR & GPIO_Pin_11))

{ // PE6=0 falling

PE11_Counter=C_tmp;

PE11_Counter=(PE11_Counter-PE11_last_count)>0?

(PE11_Counter-PE11_last_count):(PE11_Counter-PE11_last_count+counter_reload);

if (PE11_Counter Max_duty) //1ms~2ms

return;

}

else

{ //Rising

PE11_last_count=C_tmp;

}

}

}