f405的定时器问题（求大神解答！！！）

只看该作者 · 2017-6-26 09:44

想写一个tim定时器输出一个频率可变的pwm波形的程序，用for循环改变tim定时器的自动重载值。可是从第一个for循环跳到第二个for循环的时候tim定时器不输出pwm波形了，用断点判断程序是执行了tim的初始化和配置步骤的。
for(freq=3000;freq<=7000;freq+=100)
{
TIM2_Init(freq);
  }
for(freq=freq-100;freq<=freq+100;freq+=10)
{
  TIM2_Init(freq);
}

下面是定时器的配置函数
void TIM2_cfg(int freq)
{

  PrescalerValue = 0;
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);

  freq=42000000/freq-1;
  TIM_TimeBaseStructure.TIM_Period =freq;
  TIM_TimeBaseStructure.TIM_Prescaler = PrescalerValue;
  TIM_TimeBaseStructure.TIM_ClockDivision = 0;
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;

  TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);

  TIM_PrescalerConfig(TIM2, PrescalerValue, TIM_PSCReloadMode_Immediate);

  TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_Timing;
  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;

  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
  TIM_OCInitStructure.TIM_Pulse = freq/2;

  TIM_OC1Init(TIM2, &TIM_OCInitStructure);

  TIM_OC1PreloadConfig(TIM2, TIM_OCPreload_Disable);

  TIM_ARRPreloadConfig(TIM2, ENABLE);

  TIM_ClearITPendingBit(TIM2, TIM_IT_Update);

  TIM_ITConfig(TIM2, TIM_IT_Update, ENABLE);

  TIM_Cmd(TIM2, ENABLE);
}