嵌入式系统设计(基于STM32F4)徐灵飞习题解答 第十三章

《嵌入式系统设计（基于STM32F4213章课后题参考答案DAC答：DAC、2RTDADAC123.3VDAC1.2V字信号是多少？答：(1.2/3.3)*4095=1489STM32F429微控制器的DAC有哪些触发方式（转换启动方式答：DACDAC转换、硬件信号触发：通过定时器TRGO事件或外部中断线9触发。DHRDOR答：DHRDOR：数据输出寄存器。只读。DHR寄存器。DAC答：DACx，有三种可能的方式。8DAC_DHR8Rx[7:0]位（DHRx[11:4]位。12DAC_DHR12Lx[15:4]位（DHRx[11:0]位。12DAC_DHR12Rx[11:0]位（DHRx[11:0]位。DAC双通道，有以下可能的方式。8位右对齐：将DAC通道1的数据加载到DAC_DHR8RD[7:0]位（存储到DHR1[11:4]位DAC2DAC_DHR8RD[15:8]位（DHR2[11:4]位。12位左对齐：将DAC通道1的数据加载到DAC_DHR12RD[15:4]位（存储到DHR1[11:0]位，将DAC通道2的数据加载到DAC_DHR12RD[31:20]位（存储到DHR2[11:0位。12位右对齐：将DAC通道1的数据加载到DAC_DHR12RD[11:0]位（存储到DHR1[11:0]位，将DAC通道2的数据加载到DAC_DHR12RD[27:16]位（存储到DHR2[11:0位。DAC答：DACDHR有以下函数：voidDAC_SetChannel1Data(uint32_tDAC_Align,uint16_tData)voidDAC_SetChannel2Data(uint32_tDAC_Align,uint16_tData)voidDAC_SetDualChannelData(uint32_tDAC_Align,uint16_tData2,uint16_tData1)DACGPIODAC1答：GPIO_InitTypeDefGPIO_InitStructure;/*-------------------第1步 *//*使能GPIOA时钟*/RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA,ENABLE);/*使能DAC时钟*/RCC_APB1PeriphClockCmd(RCC_APB1Periph_DAC,ENABLE);/*-------------------第2步 *//*DAC的GPIO配置，模拟*/GPIO_InitStructure.GPIO_Pin=GPIO_Pin_4;GPIO_InitStructure.GPIO_Mode=GPIO_Mode_AIN;GPIO_InitStructure.GPIO_PuPd=GPIO_PuPd_NOPULL;GPIO_Init(GPIOA,&GPIO_InitStructure);STM32F429DAC12kHz答：结合定时器中断实现。在每次DACDAC13.5TIM_Config(void)。TIM_TimeBaseStructure.TIM_Period=2250-1; //采样频率=40KHzTIM_TimeBaseStructure.TIM_Prescaler=0x0; //预分频，不分频90M/(0+1)=TIM_TimeBaseStructure.TIM_ClockDivision=0x0; //时钟分频系数TIM_TimeBaseStructure.TIM_CounterMode=TIM_CounterMode_Up;TIM_TimeBaseInit(TIM2,&TIM_TimeBaseStructure);

//向上计数模式DMA实现。使用定时器溢出事件作为DAC的转换触发信号。使用DMA将波形数据缓冲区中的数据源转移到DAC数据保持寄存器中。#definePi3.1415926#definef1000//正弦波频率2KHz#define fs 20000//采样频率 40KHz/*波形数据 */uint16_tSine_Table[20];DAC配置函数DAC自动转换，DMAvoidDAC_Mode_Init(void){uint32_tIdx=0;/*填充正弦波形数据，双通道右对齐*/for(i=0;i<20;i++){Sine_Table[i]=(uint16_t)((float)4095*(1+sin(2*i*Pi*f/fs))/2);}DAC_Config();//DAC初始化DAC_TIM_Config();//定时器初始化DAC_DMA_Config();/DMA初始化}DAC初始化函数staticvoidDAC_Config(void){GPIO_InitTypeDefGPIO_InitStructure;DAC_InitTypeDefDAC_InitStructure;/*使能GPIOA时钟*/RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA,ENABLE);/*使能DAC时钟*/RCC_APB1PeriphClockCmd(RCC_APB1Periph_DAC,ENABLE);/*DAC的GPIO配置，模拟输入*//*DAC的GPIO配置，模拟*/GPIO_InitStructure.GPIO_Pin=GPIO_Pin_4;GPIO_InitStructure.GPIO_Mode=GPIO_Mode_AIN;GPIO_InitStructure.GPIO_PuPd=GPIO_PuPd_NOPULL;GPIO_Init(GPIOA,&GPIO_InitStructure);/*配置DAC通道1*/DAC_InitStructure.DAC_Trigger=DAC_TRIGGER;//使用TIM2的溢出触发DACDAC_InitStructure.DAC_LFSRUnmask_TriangleAmplitude=DAC_LFSRUnmask_Bit0;//屏蔽幅值设置DAC_InitStructure.DAC_WaveGeneration=DAC_WaveGeneration_None;//不使用波形发生器DAC_InitStructure.DAC_OutputBuffer=DAC_OutputBuffer_Enable;//启用输出缓冲DAC_Init(DAC_CH1_CHANNEL,&DAC_InitStructure);/*使能通道1由PA4输出*/DAC_Cmd(DAC_CH1_CHANNEL,ENABLE);}定时器初始化staticvoidDAC_TIM_Config(void){TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;/*使能TIM2时钟，TIM2CLK为180M*/RCC_APB1PeriphClockCmd(DAC_TIM_CLK,ENABLE);/*TIM2基本定时器配置*/TIM_TimeBaseStructure.TIM_Period=2250-1; //采样频率=40KHzTIM_TimeBaseStructure.TIM_Prescaler=0x0; //预分频，不分频90M/(0+1)=90MTIM_TimeBaseStructure.TIM_ClockDivision=0x0; //时钟分频系数TIM_TimeBaseStructure.TIM_CounterMode=TIM_CounterMode_Up;TIM_TimeBaseInit(DAC_TIM,&TIM_TimeBaseStructure);/*配置TIM2触发源*/TIM_SelectOutputTrigger(DAC_TIM,TIM_TRGOSource_Update);/*使能TIM2*/TIM_Cmd(DAC_TIM,ENABLE);

//向上计数模式}DMA初始化staticvoidDAC_DMA_Config(void){DMA_InitTypeDefDMA_InitStructure;/*DAC1使用DMA1通道7数据流5时钟*/RCC_AHB1PeriphClockCmd(DAC_DMA_CLK,/*配置DMA2*/DMA_InitStructure.DMA_Channel=DAC_CHANNEL;DMA_InitStructure.DMA_PeripheralBaseAddr=(uint32_t)(DAC_BASE+0x20); //外设数据地址DMA_InitStructure.DMA_Memory0BaseAddr=(uint32_t)Sine_Table;//内存数据地DMA_InitStructure.DMA_DIR=DMA_DIR_MemoryToPeripheral;//数据传输方向内存至外设DMA_InitStructure.DMA_BufferSize=20; //缓存大小为20DMA_InitStructure.DMA_PeripheralInc=DMA_PeripheralInc_Disable;外设数据地址固定DMA_InitStructure.DMA_MemoryIncDMA_MemoryInc_Enable; //内存数据地址自增DMA_InitStructure.DMA_PeripheralDataSize=DMA_PeripheralDataSize_HalfWord;//半字为单位DMA_InitStructure.DMA_MemoryDataSize=DMA_PeripheralDataSize_HalfWord; //半字为单位DMA_InitStructure.DMA_Mode=DMA_Mode_Circular;DMA_InitStructure.DMA_Priority=

//循环模式//高DMA通道优先级DMA_InitStructure.DMA_FIFOMode=DMA_FIFOMode_Disable;DMA_InitStructure.DMA_FIFOThreshold=DMA_FIFOThreshold_Full;DMA_InitStructure.DMA_MemoryBurst=DMA_MemoryB