- 基于stm32的FSK调制解调器的设计（原理及程序）

...                                          //省去无关代码

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

{

Sine12bit[Idx] = Sine12bit[Idx]*8/10+500;        //防止出现底部失真

}

...                                          //省去无关代码

}

为什么要这么处理呢？在讲到DAC的配置时还会再提到这一点，在这里先不做解释。经过处理后的正弦波数据可以直接传送到DMA通道，等TIM2的触发时间一到，就可以依次把数据给到DAC，转换成正弦波输出。笔者用DAC通道2（对应PA5引脚）输出波形，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;//配置为模拟输入，抗噪声干扰

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位右对齐寄存器地址

DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)&Sine12bit;

DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;

DMA_InitStructure.DMA_BufferSize = 64;//采样64点，故缓存大小为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;  //设为向下计数

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;  //使能输出缓存

DAC_Init(DAC_Channel_2, &DAC_InitStructure);

DAC_Cmd(DAC_Channel_2, ENABLE);

DAC_DMACmd(DAC_Channel_2, ENABLE);        

TIM_Cmd(TIM2, ENABLE);        

}