终于用PWM做成了DA

k4gjwl 提问时间：2008-9-3 19:44 /

之前不能得到正确的波形，主要是混淆了PWM频率和信号的采样频率，错误地使用了用DAC做输出时的8K频率，导致滤波电路无法正常工作.
以下的程序我使用TIMER4 channel3作为PWM输出，并使用TIMER2做8K定时去更新PWM占空比，输出了1KHz的正弦波。

/* ---------------------------------------------------------------
  TIM4 Configuration: Output Compare Inactive Mode:
  TIM4CLK = 72 MHz, Prescaler = 0, TIM2 counter clock = 72 KHz
  TIM4 frequency = TIM4CLK/(TIM1_Period + 1) = 70 KHz
--------------------------------------------------------------- */
void TIMER4_Configuration(void)
{
  TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
  TIM_OCInitTypeDef  TIM_OCInitStructure;

  /* Time base configuration */
  TIM_TimeBaseStructure.TIM_Period = 1023;
  TIM_TimeBaseStructure.TIM_Prescaler = 0x00;
  TIM_TimeBaseStructure.TIM_ClockDivision = 0x0;
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;

  TIM_TimeBaseInit(TIM4, &TIM_TimeBaseStructure);

  TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
  TIM_OCInitStructure.TIM_Channel = TIM_Channel_3;
  TIM_OCInitStructure.TIM_Pulse = 512;
  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
  TIM_OCInit(TIM4, &TIM_OCInitStructure);

  TIM_OC3PreloadConfig(TIM4, TIM_OCPreload_Enable);

  TIM_ARRPreloadConfig(TIM4, ENABLE);

  /* TIM4 enable counter */
  TIM_Cmd(TIM4, ENABLE);

}

void TIMER2_Configuration(void)
{
  TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
  TIM_OCInitTypeDef  TIM_OCInitStructure;

/* ---------------------------------------------------------------
  TIM2 Configuration: Output Compare Inactive Mode:
  TIM2CLK = 72 MHz, Prescaler = 1000, TIM2 counter clock = 72 KHz
  TIM2 frequency = TIM2CLK/(TIM2_Period + 1) = 8KHz
--------------------------------------------------------------- */

  /* Time base configuration */
  TIM_TimeBaseStructure.TIM_Period = 8;
  TIM_TimeBaseStructure.TIM_Prescaler = 1000-1;
  TIM_TimeBaseStructure.TIM_ClockDivision = 0x0;
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;

  TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);

  /* Prescaler configuration */
//  TIM_PrescalerConfig(TIM2, 1000-1, TIM_PSCReloadMode_Immediate);

  /* Output Compare Active Mode configuration: Channel1 */
  TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_Inactive;
  TIM_OCInitStructure.TIM_Channel = TIM_Channel_1;
  TIM_OCInitStructure.TIM_Pulse = 8;
  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;

  TIM_OCInit(TIM2, &TIM_OCInitStructure);

  TIM_OC1PreloadConfig(TIM2, TIM_OCPreload_Enable);

  TIM_ARRPreloadConfig(TIM2, ENABLE);

  /* TIM IT enable */
  TIM_ITConfig(TIM2, TIM_IT_CC1, ENABLE);

  /* Set PC.06, PC.07, PC.08 and PC.09 pins */
  GPIO_SetBits(GPIOC, GPIO_Pin_6);

  /* TIM2 enable counter */
  TIM_Cmd(TIM2, ENABLE);
}

u16 SINDATA[8]=
{
    512,874,1024,874,
    512,149,0,149
};

/*******************************************************************************
* Function Name  : TIM2_IRQHandler
* Description    : This function handles TIM2 global interrupt request.
* Input          : None
* Output         : None
* Return         : None
*******************************************************************************/
void TIM2_IRQHandler(void)
{
    static u16 i=0;
    static u8 j=0;

    if (TIM_GetITStatus(TIM2, TIM_IT_CC1) != RESET)
    {
    /* Clear TIM2 Capture Compare1 interrupt pending bit*/
    TIM_ClearITPendingBit(TIM2, TIM_IT_CC1);
    }
    if(i==0)
    {
         i = 1;
        GPIO_ResetBits(GPIOC, GPIO_Pin_6);
    }
    else
    {
         i = 0;
        GPIO_SetBits(GPIOC, GPIO_Pin_6);
    }

//  /* Set the Pulse value */
  TIM4->CCR3 = SINDATA[j++];
  if(j == 8)j = 0;
}

出处：a_bb