... ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?//省去無關代碼

for (Idx = 0; Idx < 64; Idx++)

{

Sine12bit[Idx] = Sine12bit[Idx]*8/10+500; ? ? ? ?//防止出現底部失真

}

... ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?//省去無關代碼

}

為什么要這么處理呢？在講到DAC的配置時還會再提到這一點，在這里先不做解釋。經過處理后的正弦波數據可以直接傳送到DMA通道，等TIM2的觸發時間一到，就可以依次把數據給到DAC，轉換成正弦波輸出。筆者用DAC通道2（對應PA5引腳）輸出波形，所以需要使能和配置DMA2通道4，DMA的配置如下：

?

#define DAC_DHR12R2_Address ? ? ?0x40007414

void DMAx_Init(void)

{

DMA_InitTypeDef DMA_InitStructure;

GPIO_InitTypeDef GPIO_InitStructure;

/* DMA1 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);

?

/* Once the DAC channel is enabled, the corresponding GPIO pin is automatically?

connected to the DAC converter. In order to avoid parasitic consumption,?

the GPIO pin should be configured in analog */

GPIO_InitStructure.GPIO_Pin = ?GPIO_Pin_5;

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AIN;//配置為模擬輸入，抗噪聲干擾

GPIO_Init(GPIOA, &GPIO_InitStructure);

?

/* DMA1 channel4 configuration */

DMA_DeInit(DMA2_Channel4);

DMA_InitStructure.DMA_PeripheralBaseAddr = DAC_DHR12R2_Address;//DAC通道2的12位右對齊寄存器地址

DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)&Sine12bit;

DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;

DMA_InitStructure.DMA_BufferSize = 64;//采樣64點，故緩存大小為64

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);

DMA_Cmd(DMA2_Channel4, ENABLE);

}

TIM2和DAC的配置如下：

void TIM2_DAC_Init(u16 arr,u16 psc)

{

TIM_TimeBaseInitTypeDef ?TIM_TimeBaseStructure;

DAC_InitTypeDef DAC_InitStructure;

RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);

TIM_TimeBaseStructInit(&TIM_TimeBaseStructure);?

TIM_TimeBaseStructure.TIM_Period = arr; ? ? ? ? ?

TIM_TimeBaseStructure.TIM_Prescaler = psc; ? ? ??

TIM_TimeBaseStructure.TIM_ClockDivision = 0x0; ? ?

TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Down; ?//設為向下計數

TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);

TIM_SelectOutputTrigger(TIM2, TIM_TRGOSource_Update);

DAC_InitStructure.DAC_Trigger = DAC_Trigger_T2_TRGO;

DAC_InitStructure.DAC_WaveGeneration = DAC_WaveGeneration_None;

DAC_InitStructure.DAC_OutputBuffer = DAC_OutputBuffer_Enable; ?//使能輸出緩存

DAC_Init(DAC_Channel_2, &DAC_InitStructure);

DAC_Cmd(DAC_Channel_2, ENABLE);

DAC_DMACmd(DAC_Channel_2, ENABLE);? ? ? ??

TIM_Cmd(TIM2, ENABLE); ? ? ? ?

}