TIM4通道三PWM驱动蜂鸣器问题，蜂鸣器不响，LED0竟然会渐亮渐灭，搞得我没脾气了！

liuyongliuyong · 发表于 2013-4-20 22:35:28

void TIM4_PWM_Init(u16 arr,u16 psc)
{
GPIO_InitTypeDef GPIO_InitStructure;
TIM_TimeBaseInitTypeDef TIM_TimeBaseInitStructure;
TIM_OCInitTypeDef TIM_OCInitStructure;
TIM_DeInit(TIM4);

RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM4,ENABLE);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB|RCC_APB2Periph_AFIO,ENABLE);

//GPIO_PinRemapConfig(GPIO_Remap_TIM4,ENABLE);

GPIO_InitStructure.GPIO_Pin=GPIO_Pin_8;
GPIO_InitStructure.GPIO_Mode=GPIO_Mode_AF_PP;
GPIO_InitStructure.GPIO_Speed=GPIO_Speed_50MHz;
GPIO_Init(GPIOB,&GPIO_InitStructure);

TIM_TimeBaseInitStructure.TIM_Period=arr;
TIM_TimeBaseInitStructure.TIM_Prescaler=psc;
TIM_TimeBaseInitStructure.TIM_ClockDivision=0x00;
TIM_TimeBaseInitStructure.TIM_CounterMode=TIM_CounterMode_Up;
TIM_TimeBaseInit(TIM4,&TIM_TimeBaseInitStructure);

TIM_OCInitStructure.TIM_OCMode=TIM_OCMode_PWM1;
TIM_OCInitStructure.TIM_OutputState=TIM_OutputState_Enable;
TIM_OCInitStructure.TIM_OCPolarity=TIM_OCPolarity_High;

TIM_OC3Init(TIM4,&TIM_OCInitStructure);
TIM_OC3PreloadConfig(TIM4,TIM_OCPreload_Enable);

TIM_Cmd(TIM4,ENABLE);
}

int main(void)
{
  u16 led0pwmval=0;
u8 dir=1;
delay_init();     //延时函数初始化
  TIM4_PWM_Init(899,0); //不分频。PWM频率=72000/900=8Khz
   while(1)
{
   delay_ms(10);
  if(dir)led0pwmval++;
  else led0pwmval--;

   if(led0pwmval>300)dir=0;
  if(led0pwmval==0)dir=1;
  TIM_SetCompare3(TIM4,led0pwmval);
}
}

搞了好久，程序应该没有问题的啊，可是结果是蜂鸣器不响，LED0做PWM现象，郁闷！麻烦谁帮忙分析一下