stm32f0根据外部上升沿中断下降沿中断来测量输入信号的高电平时间（之前用TIMx_chx做过可以，为什么这种思路行不通）

小小飞行器 · 发表于 2015-2-11 19:39:27

思路是：
外部上升沿中断给定时器计数器的值置0 ，下降沿读出定时器的值。如果超过20ms这进入定时器中断，表示没有信号输入

[mw_shl_code=c,true]#include "PPM.h" #include "USART1.h" int ppm=0; void TIM14_PPM_Init(void) { TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure; NVIC_InitTypeDef NVIC_InitStructure; RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM14, ENABLE); NVIC_InitStructure.NVIC_IRQChannel = TIM14_IRQn; NVIC_InitStructure.NVIC_IRQChannelPriority = 0; NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; NVIC_Init(&NVIC_InitStructure); TIM_TimeBaseStructure.TIM_Period = 30000; // ×?????×°???????÷????????(??????) TIM_TimeBaseStructure.TIM_Prescaler = (45); //?±???¤·????? TIM_TimeBaseStructure.TIM_ClockDivision = 0; TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;//?ò?????????? TIM_TimeBaseInit(TIM14, &TIM_TimeBaseStructure); TIM_ClearFlag(TIM14, TIM_FLAG_Update); // ????????????±ê?? TIM_ITConfig(TIM14,TIM_IT_Update,ENABLE); TIM_Cmd(TIM14, ENABLE); } void PPM_EXTI_Init(void) { GPIO_InitTypeDef GPIO_InitStruct; EXTI_InitTypeDef EXTI_InitStruct; NVIC_InitTypeDef NVIC_InitStruct; RCC_APB2PeriphClockCmd(RCC_APB2Periph_SYSCFG, ENABLE); RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA, ENABLE); GPIO_InitStruct.GPIO_Pin = GPIO_Pin_4; GPIO_InitStruct.GPIO_Mode = GPIO_Mode_IN; GPIO_InitStruct.GPIO_Speed = GPIO_Speed_Level_2; GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_UP; GPIO_Init(GPIOA, &GPIO_InitStruct); SYSCFG_EXTILineConfig(EXTI_PortSourceGPIOA, EXTI_PinSource4); EXTI_ClearITPendingBit(EXTI_Line4); EXTI_InitStruct.EXTI_Line = EXTI_Line4; EXTI_InitStruct.EXTI_Mode = EXTI_Mode_Interrupt; EXTI_InitStruct.EXTI_Trigger = EXTI_Trigger_Rising; EXTI_InitStruct.EXTI_LineCmd = ENABLE; EXTI_Init(&EXTI_InitStruct); NVIC_InitStruct.NVIC_IRQChannel = EXTI4_15_IRQn; NVIC_InitStruct.NVIC_IRQChannelPriority = 0x01; NVIC_InitStruct.NVIC_IRQChannelCmd = ENABLE; NVIC_Init(&NVIC_InitStruct); } void Falling_() { EXTI_InitTypeDef EXTI_InitStruct; EXTI_InitStruct.EXTI_Line = EXTI_Line4; EXTI_InitStruct.EXTI_Mode = EXTI_Mode_Interrupt; EXTI_InitStruct.EXTI_Trigger = EXTI_Trigger_Falling; EXTI_InitStruct.EXTI_LineCmd = ENABLE; EXTI_Init(&EXTI_InitStruct); } void Rising_() { EXTI_InitTypeDef EXTI_InitStruct; EXTI_InitStruct.EXTI_Line = EXTI_Line4; EXTI_InitStruct.EXTI_Mode = EXTI_Mode_Interrupt; EXTI_InitStruct.EXTI_Trigger = EXTI_Trigger_Rising; EXTI_InitStruct.EXTI_LineCmd = ENABLE; EXTI_Init(&EXTI_InitStruct); } //============================================================================= //??????????EXTI4_15_IRQHandler //??????????°??ü???????? //???????÷???? //????·??????? //============================================================================= char Rising; char Falling; char Rising=1; char Falling=0; int now; int last; void EXTI4_15_IRQHandler(void) { if ( EXTI_GetITStatus(EXTI_Line4)!= RESET ) { if(Rising==1) { TIM_SetCounter(TIM14,0); Falling_(); Rising=0; Falling=1; } if(Falling==1) { now=TIM_GetCounter(TIM14);Rising_(); printf("last????%d\r\n",TIM_GetCounter(TIM14)); Rising=1; Falling=0; } EXTI_ClearITPendingBit(EXTI_Line4); } } void TIM14_IRQHandler(void) { if (TIM_GetITStatus(TIM14, TIM_IT_Update) != RESET) { TIM_ClearITPendingBit(TIM14,TIM_FLAG_Update); ppm=0; printf("???± %d\r\n",ppm); } } [/mw_shl_code]

为啥这样采集的读出的结果的值不正确？？