哪位朋友用过高级定时器的翻转模式产生PWM波的，进来帮看个问题了

pthread · 发表于 2016-6-15 15:52:09

背景是这样的：
我使用的TIM8，CH3和CH4因要输出频率可调的方波，所以使用了翻转模式配置。

目前情况是这样的(只看通道3)：
配置好后因通道输出电平不变化，我加了句 TIM_CtrlPWMOutputs(TIM8, ENABLE);然后就正常产生了方波，可是发现示波器显示的频率与我要求的2KHZ（CCR3的值为 (计数频率/1000)-1）差别很大（示波器显示的才不到100HZ）。我改变CCR3的值让其产生4KHZ的方波时，示波器显示的频率还是上次的值（小与100HZ）。我单步调试时，执行完定时器使能后就直接产生了方波，而不是进入CC中断函数才改变电平状态的。我觉着我的翻转模式未生效啊。使用PWM模式可正常输出匹配频率的方波。

以上情况就是这样，哪位朋友知道忽略了哪个地方么（问题出在用的是高级定时器这里）？？？？？？？？

#if TIMER8_EN
/* TIM8 clock enable */
RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM8 | RCC_APB2Periph_GPIOC | RCC_APB2Periph_AFIO, ENABLE);

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_8 | GPIO_Pin_9 ;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(GPIOC, &GPIO_InitStructure);
    PrescalerValue = (u16) (SystemCoreClock / 12000000) - 1;
Channel3Pulse =    (12000000/1000)-1;
Channel4Pulse = (12000000/1000)-1;
    /* Time base configuration */
    TIM_TimeBaseStructure.TIM_Period = TimerPeriod;
    TIM_TimeBaseStructure.TIM_Prescaler = PrescalerValue;
    TIM_TimeBaseStructure.TIM_ClockDivision = 0;
    TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;

    TIM_TimeBaseInit(TIM8, &TIM_TimeBaseStructure);

/* PWM1 Mode configuration: Channel3 */
  /* Channel 1, 2,3 and 4 Configuration in PWM mode */
    //TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM2;
TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_Toggle; //工作与翻转模式，当CCRx的值等于CNT的值时，电平翻转以此产生PWM波
    TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
    TIM_OCInitStructure.TIM_Pulse = Channel3Pulse;
    TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low;

    TIM_OC3Init(TIM8, &TIM_OCInitStructure);
TIM_OC3PreloadConfig(TIM8, TIM_OCPreload_Disable);

    TIM_OCInitStructure.TIM_Pulse = Channel4Pulse;
    TIM_OC4Init(TIM8, &TIM_OCInitStructure);
TIM_OC4PreloadConfig(TIM8, TIM_OCPreload_Disable);

TIM_OCInitStructure.TIM_Pulse = 12;
    TIM_OC1Init(TIM8, &TIM_OCInitStructure);
TIM_OC1PreloadConfig(TIM8, TIM_OCPreload_Disable);

TIM_OCInitStructure.TIM_Pulse = 10;
    TIM_OC2Init(TIM8, &TIM_OCInitStructure);
TIM_OC2PreloadConfig(TIM8, TIM_OCPreload_Disable);

//TIM_ClearITPendingBit(TIM3,TIM_IT_CC3|TIM_IT_CC4);    //清除中断Pending位，避免使能中断后立即进入中断
Drv_NVIC_IntPrioSet(TIM8_CC_IRQn,TIM8_PRIO);
Drv_NVIC_IRQSet(TIM8_CC_IRQn,&Drv_Time8_IntHandler);
#endif  /* TIM8_EN */
#if TIMER2_EN
Drv_Time2_Close();
#endif /* TIM2_EN */

#if TIMER3_EN
Drv_Time3_Close();
#endif /* TIM3_EN */

#if TIMER8_EN
TIM_ITConfig(TIM8,TIM_IT_CC3|TIM_IT_CC4,ENABLE);

/* TIM8 Main Output Enable */
TIM_CtrlPWMOutputs(TIM8, ENABLE);
TIM8->CNT = 0;
/* TIM8 enable counter */
    TIM_Cmd(TIM8, ENABLE);
#endif /* TIM8_EN */