之前想用stm32的DAC输出正弦波，才用的方案是在死循环里面用for循环输出36点的电压值模拟成一个完整的正弦波。发现最多只能输出个20KHz的波形，在示波器下面能够看到明显的梯度。后来用DMA+ADC的模式发现可以上100K（不过频率有点飘），下面吧代码贴出来

void DAC_DMA_Configuration(void)
{
DAC_InitTypeDef            DAC_InitStructure;
DMA_InitTypeDef            DMA_InitStructure;
TIM_TimeBaseInitTypeDef    TIM_TimeBaseStructure;
GPIO_InitTypeDef GPIO_InitStructure;

  RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA2, ENABLE);
  RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);
  /* GPIOA Periph clock enable */
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_DAC, ENABLE);
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2|RCC_APB1Periph_TIM4, ENABLE);

  GPIO_InitStructure.GPIO_Pin =  GPIO_Pin_4 | GPIO_Pin_5;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AIN;
  GPIO_Init(GPIOA, &GPIO_InitStructure);
 /* TIM2 Configuration */
  /* Time base configuration */
  TIM_TimeBaseStructInit(&TIM_TimeBaseStructure); 
  TIM_TimeBaseStructure.TIM_Period = 50;          
  TIM_TimeBaseStructure.TIM_Prescaler = 0x0;       
  TIM_TimeBaseStructure.TIM_ClockDivision = 0x0;    
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;  
  TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);

  /* TIM2 TRGO selection */
  TIM_SelectOutputTrigger(TIM2, TIM_TRGOSource_Update);

  /* DAC channel1 Configuration */
  DAC_InitStructure.DAC_Trigger = DAC_Trigger_T2_TRGO;
  DAC_InitStructure.DAC_WaveGeneration = DAC_WaveGeneration_None;
  DAC_InitStructure.DAC_OutputBuffer = DAC_OutputBuffer_Disable;
  DAC_Init(DAC_Channel_2, &DAC_InitStructure);


  DMA_DeInit(DMA2_Channel4);

  DMA_InitStructure.DMA_PeripheralBaseAddr = DAC_DHR12RD_Address;
  DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)&Sine12bit;
  DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;
  DMA_InitStructure.DMA_BufferSize = 36;
  DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
  DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
  DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_HalfWord;
  DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord;
  DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;
  DMA_InitStructure.DMA_Priority = DMA_Priority_High;
  DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;

  DMA_Init(DMA2_Channel4, &DMA_InitStructure);
  /* Enable DMA2 Channel4 */
  DMA_Cmd(DMA2_Channel4, ENABLE);
  DAC_Cmd(DAC_Channel_2, ENABLE);
  DAC_DMACmd(DAC_Channel_2, ENABLE);


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


  TIM_TimeBaseStructInit(&TIM_TimeBaseStructure); 
  TIM_TimeBaseStructure.TIM_Period = 40;          
  TIM_TimeBaseStructure.TIM_Prescaler = 0x0;       
  TIM_TimeBaseStructure.TIM_ClockDivision = 0x0;    
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;  
  TIM_TimeBaseInit(TIM4, &TIM_TimeBaseStructure);
  /* TIM2 TRGO selection */
  TIM_SelectOutputTrigger(TIM4, TIM_TRGOSource_Update);
  /* DAC channel1 Configuration */
  DAC_InitStructure.DAC_Trigger = DAC_Trigger_T4_TRGO;
  DAC_InitStructure.DAC_WaveGeneration = DAC_WaveGeneration_None;
  DAC_InitStructure.DAC_OutputBuffer = DAC_OutputBuffer_Disable;
  DAC_Init(DAC_Channel_1, &DAC_InitStructure);

  DMA_DeInit(DMA2_Channel3);
  DMA_InitStructure.DMA_PeripheralBaseAddr = DAC_DHR12R2_Address;
  DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)&Sine12bit;
  DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;
  DMA_InitStructure.DMA_BufferSize =36;
  DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
  DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
  DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_HalfWord;
  DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord;
  DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;
  DMA_InitStructure.DMA_Priority = DMA_Priority_High;
  DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;

  DMA_Init(DMA2_Channel3, &DMA_InitStructure);
  /* Enable DMA2 Channel4 */
  DMA_Cmd(DMA2_Channel3, ENABLE);


  DAC_Cmd(DAC_Channel_1, ENABLE);
  DAC_DMACmd(DAC_Channel_1, ENABLE);
  TIM_Cmd(TIM4, ENABLE);

}

代码输出的频率是40K和50K两路。示波器下面看起来还蛮不错的。