PWM 怎么去掉毛刺啊

niuxiaohua · 发表于 2014-6-5 13:56:45

用PWM发送一串数据 data=0x12345678，前面有一段引导码，我写的程序
主函数的

#define Te 400
#define getbit( b, n) (((b) & (1L<<n)) ? 1 : 0) //读取b的第n位
#define dword unsigned long

dword d=0x12345678;

void Lead_code(void);
int main(void)
{
// u16 led0pwmval=0;
// u8 dir=1;
int i;
SystemInit();
delay_init(72);      //延时初始化
NVIC_Configuration();
uart_init(9600);
  LED_Init();
KEY_Init();          //按键初始化
// WM_On(863,100); //不分频。PWM频率=72000/900=800hz
while(1)
{
  Lead_code();
  WM_On(863,100);
  delay_us(5);
  for (i=31;i>=0;i--)
  {
   if (getbit(d,i)==1)
   {
     TIM_SetCompare2(TIM3,300);
     delay_us(1200);
   }
   else
   {
    TIM_SetCompare2(TIM3,600);
    delay_us(1200);
   }
  }
  TIM_SetCompare2(TIM3,0);
  delay_us(1200*13);
}

}

void Lead_code()
{
int i;
WM_On(576,100);
delay_us(5);
for (i=0;i<12;i++)
{
TIM_SetCompare2(TIM3,288);
delay_us(2*Te);
}
TIM_SetCompare2(TIM3,0);
delay_us(9*Te);
}

PWM配置的

void PWM_On(u16 arr,u16 psc)
{
GPIO_InitTypeDef GPIO_InitStructure;
TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
TIM_OCInitTypeDef TIM_OCInitStructure;

RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOC | RCC_APB2Periph_AFIO, ENABLE); //使能GPIO外设和AFIO复用功能模块时钟使能
                                                                          //用于TIM3的CH2输出的PWM通过该LED显示

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_5;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOC, &GPIO_InitStructure);

//设置该引脚为复用输出功能,输出TIM3 CH2的PWM脉冲波形
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_7; //TIM_CH2
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP; //复用推挽输出
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOA, &GPIO_InitStructure);
//GPIO_WriteBit(GPIOA, GPIO_Pin_7,Bit_SET); // PA7上拉

TIM_TimeBaseStructure.TIM_Period = arr; //设置在下一个更新事件装入活动的自动重装载寄存器周期的值 80K
TIM_TimeBaseStructure.TIM_Prescaler =psc; //设置用来作为TIMx时钟频率除数的预分频值不分频
TIM_TimeBaseStructure.TIM_ClockDivision = 0; //设置时钟分割:TDTS = Tck_tim
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up; //TIM向上计数模式
TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure); //根据TIM_TimeBaseInitStruct中指定的参数初始化TIMx的时间基数单位

TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM2; //选择定时器模式:TIM脉冲宽度调制模式2
TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable; //比较输出使能
TIM_OCInitStructure.TIM_Pulse = 0; //设置待装入捕获比较寄存器的脉冲值
TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low; //输出极性:TIM输出比较极性高
TIM_OC2Init(TIM3, &TIM_OCInitStructure); //根据TIM_OCInitStruct中指定的参数初始化外设TIMx
TIM_OC2PreloadConfig(TIM3, TIM_OCPreload_Enable); //使能TIMx在CCR2上的预装载寄存器

TIM_ARRPreloadConfig(TIM3, ENABLE); //使能TIMx在ARR上的预装载寄存器

TIM_Cmd(TIM3, ENABLE); //使能TIMx外设