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为了测试，现在LCD前后都放了，不知过了多长时间，怪了。。。

明显的，SRAM读写速度慢了很多（有点无法容忍了），具体到使用时还要再找找原因了。

 DAC的实验 （输出正弦波）

没有示波器，是不是有说不清的感觉.

DAC输出：PA4，PA5
输出波形：正弦波
幅值范围：0~3.3V

部分代码：

//32点的正弦波数据，从0~4095，如需要可以再加密：

const uint16_t Sine12bit[32] = {
                      2047, 2447, 2831, 3185, 3498, 3750, 3939, 4056, 4095, 4056,
                      3939, 3750, 3495, 3185, 2831, 2447, 2047, 1647, 1263, 909,
                      599, 344, 155, 38, 0, 38, 155, 344, 599, 909, 1263, 1647};

//外设的种类动用了不少：

/* Enable peripheral clocks --------------------------------------------------*/
  /* DMA clock enable */
  RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA2, ENABLE);
  /* GPIOA Periph clock enable */
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);
  /* DAC Periph clock enable */
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_DAC, ENABLE);
  /* TIM2 Periph clock enable */
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);

// 主程序，搞定了定时器，DMA，让它自己跑去吧：

  /* TIM2 Configuration */
  /* Time base configuration */
  TIM_TimeBaseStructInit(&TIM_TimeBaseStructure);
  TIM_TimeBaseStructure.TIM_Period = 0x19;         
  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_1, &DAC_InitStructure);

  /* DAC channel2 Configuration */
  DAC_Init(DAC_Channel_2, &DAC_InitStructure);

  /* Fill Sine32bit table */
  for (Idx = 0; Idx < 32; Idx++)
  {
    DualSine12bit[Idx] = (Sine12bit[Idx] << 16) + (Sine12bit[Idx]);
  }

  /* DMA2 channel4 configuration */
  DMA_DeInit(DMA2_Channel4);
  DMA_InitStructure.DMA_PeripheralBaseAddr = DAC_DHR12RD_Address;
  DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)&DualSine12bit;
  DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;
  DMA_InitStructure.DMA_BufferSize = 32;
  DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
  DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
  DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Word;
  DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Word;
  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);

  /* Enable DAC Channel1: Once the DAC channel1 is enabled, PA.04 is
     automatically connected to the DAC converter. */
  DAC_Cmd(DAC_Channel_1, ENABLE);
  /* Enable DAC Channel2: Once the DAC channel2 is enabled, PA.05 is
     automatically connected to the DAC converter. */
  DAC_Cmd(DAC_Channel_2, ENABLE);

  /* Enable DMA for DAC Channel2 */
  DAC_DMACmd(DAC_Channel_2, ENABLE);

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


没有示波器，用万用表的直流、交流可测PA4，PA5的电压，估计是有波形出来了。

具体实际波形，还等看楼下后续。

这个自然，心中有数，我是特指“正弦波”