一、DAC简介

DAC(Digital-to-Analog Converter)，即数字/模拟转换模块，故名思议，它的作用就是把输入的数字编码，转换成对应的模拟电压输出，它的功能与 ADC 相反。在常见的数字信号系统中，大部分传感器信号被化成电压信号，而 ADC 把电压模拟信号转换成易于计算机存储、处理的数字编码，由计算机处理完成后，再由 DAC 输出电压模拟信号，该电压模拟信号常用来驱动某些执行器件，使人类易于感知。如音频信号的采集及还原就是这样一个过程。

STM32 具有片上 DAC 外设，它的分辨率可配置为 8 位或 12 位的数字输入信号，具有两个 DAC 输出通道，这两个通道互不影响，每个通道都可以使用 DMA 功能，都具有出错检测能力，可外部触发。

二、DAC通道选择

在 STM32 中具有 2 个这样的 DAC 部件，每个 DAC 有 1 个对应的输出通道连接到特定的引脚，即：PA4-通道 1，PA5-通道 2，为避免干扰，使用 DAC 功能时，DAC 通道引脚需要被配置成模拟输入功能（AIN）。

三、新建工程

1. 打开 STM32CubeMX 软件，点击“新建工程”

2. 选择 MCU 和封装

3. 配置时钟
RCC 设置，选择 HSE(外部高速时钟) 为 Crystal/Ceramic Resonator(晶振/陶瓷谐振器)

选择 Clock Configuration，配置系统时钟 SYSCLK 为 72MHz
修改 HCLK 的值为 72 后，输入回车，软件会自动修改所有配置

4. 配置调试模式
非常重要的一步，否则会造成第一次烧录程序后续无法识别调试器
SYS 设置，选择 Debug 为 Serial Wire

四、DAC1

4.1 参数配置

在 Analog 中选择 DAC 设置，并选择 OUT1 Configuration 通道1

或者在右边图找到 PA4 引脚，选择 DAC_OUT1

具体配置参数如下。

• OUT1/2 Configuration：
  对应两个输出通道。

• External Trigger：
  外部中断EXTI9 触发 就是使用外部中断来触发DAC。

• Output Buffer：
  使能DAC输出缓存。

DAC 集成了 2 个输出缓存，可以用来减少输出阻抗，无需外部运放即可直接驱动外部负载。每个 DAC 通道输出缓存可以通过设置 DAC_CR 寄存器的 BOFFx 位来使能或者关闭。如果带载能力还不行，后面就接一个电压跟随器，选择运放一定要选择电流大的型号。
使能输出缓冲后，DAC 输出的最小电压为 0.2V，最大电压为 VREF+-0.2，而未使能输出缓冲则输出可达到0V。

• Trigger：
  选择DAC的触发方式
  Timer 2/4/5/6/7/8 Trigger Out event 定时器触发，利用这种方式可以输出特定的波形。在这里我们选择定时器2。
  Software trigger 软件触发，在本模式下，向 DAC_SWTRIGR 寄存器写入配置即可触发信号进行转换。

• Wave generation mode：Disable（不使用波形发生器）。

4.2 配置DMA

点击 DMA Settings 添加 DAC_CH1 对应 DMA2 的通道3。DMA模式选择循环模式，方向选为内存到外设。

• Priority：
  当发生多个 DMA 通道请求时，就意味着有先后响应处理的顺序问题，这个就由仲裁器也管理。仲裁器管理 DMA 通道请求分为两个阶段。第一阶段属于软件阶段，可以在 DMA_CCRx 寄存器中设置，有 4 个等级：非常高、高、中和低四个优先级。第二阶段属于硬件阶段，如果两个或以上的 DMA 通道请求设置的优先级一样，则他们优先级取决于通 道编号，编号越低优先权越高，比如通道 0 高于通道 1。在大容量产品和互联型产品中，DMA1 控制器拥有高于 DMA2 控制器的优先级。

• Mode：
  Normal 表示单次传输，传输一次后终止传输。
  Circular 表示循环传输，传输完成后又重新开始继续传输，不断循环永不停止。

• Increment Address：
  Peripheral 表示外设地址自增。
  Memory 表示内存地址自增。

• Data Width：
  Byte 一个字节。
  Half Word 半个字，等于两字节。
  Word 一个字，等于四字节。

五、TIM2通用定时器

5.1 参数配置

在 Timers 中选择 TIM2 设置，时钟源 Clock Source 选择内部时钟 Internal Clock

在 Parameter Settings 进行具体参数配置。

• Prescaler（时钟预分频数）：0 则驱动计数器的时钟 CK_CNT = CK_INT(即72MHz)/(0+1) = 72MHz 即不分频

• Counter Mode（计数模式）：Up（向上计数模式）

• Counter Period（自动重装载值）：20-1

• auto-reload-preload（自动重装载）：Disable（不使能）

• TRGO Parameters（触发输出）：Update Event（更新事件） 在定时器的定时时间到达的时候输出一个信号(如：定时器更新产生TRGO信号来触发ADC的同步转换)

5.2 生成代码

输入项目名和项目路径

选择应用的 IDE 开发环境 MDK-ARM V5

每个外设生成独立的 ’.c/.h’ 文件
不勾：所有初始化代码都生成在 main.c
勾选：初始化代码生成在对应的外设文件。 如 GPIO 初始化代码生成在 gpio.c 中。

点击 GENERATE CODE 生成代码

六、库函数

/* IO operation functions *****************************************************/

HAL_StatusTypeDef HAL_DAC_Start(DAC_HandleTypeDef* hdac, uint32_t Channel);     //开启DAC输出

HAL_StatusTypeDef HAL_DAC_Stop(DAC_HandleTypeDef* hdac, uint32_t Channel);   //关闭DAC输出

HAL_StatusTypeDef HAL_DAC_Start_DMA(DAC_HandleTypeDef* hdac, uint32_t Channel, uint32_t* pData, uint32_t Length, uint32_t Alignment); //需要函数中不断开启   //开启DAC的DMA输出

HAL_StatusTypeDef HAL_DAC_Stop_DMA(DAC_HandleTypeDef* hdac, uint32_t Channel); //关闭DAC的DMA输出

HAL_StatusTypeDef HAL_DAC_SetValue(DAC_HandleTypeDef* hdac, uint32_t Channel, uint32_t Alignment, uint32_t Data);  //设置DAC输出值

uint32_t HAL_DAC_GetValue(DAC_HandleTypeDef* hdac, uint32_t Channel);  //获取DAC输出值

/**

  * @brief  Starts the TIM Base generation.

  * @param  htim TIM Base handle

  * @retval HAL status

  */

HAL_StatusTypeDef HAL_TIM_Base_Start(TIM_HandleTypeDef *htim);

七、生成模拟音频波形数据表

7.1 安装Adobe Audition

链接：https://pan.baidu.com/s/1iGMV7FPn-87KI9FnFUDx9A 提取码：4ahu

7.2 生成Wav文件

用 Adobe Audition 打开一个音频文件，选择一段区域。右键，存储选区为。

设置参数，然后导出

• 格式：Wave PCM

• 采样类型：8000 Hz，单声道，8位

• 去除包含标记和其他元数据，这样生成的文件更小

7.3 关于采样类型选择

看看采样频率和位深需要定时器频率的关系如下表格：

根据上面 五、TIM2通用定时器 的参数配置，定时器频率：

TIM2的定时器频率：f = Tclk/[(psc+1) * (cnt+1)] = 72MHz/[1*20] = 3.6MHz。

• 定时器时钟Tclk：72MHz

• 预分频器psc：0

• 自动重装载值cnt：19

所以我们采样频率选择 8000 Hz，位深选择 8位

7.4 安装DataToHex

链接：https://pan.baidu.com/s/1VZwq4zs5b3Mutn5p8rL2Uw 提取码：9d0h

7.5 生成十六进制数组

如：

/*----The Length of This Array is 1134 Byte.----*/

unsigned char Array[]={

0x52,0x49,0x46,0x46,0x66,0x04,0x00,0x00,0x57,0x41,0x56,0x45,0x66,0x6D,0x74,0x20,

0x10,0x00,0x00,0x00,0x01,0x00,0x01,0x00,0x40,0x1F,0x00,0x00,0x40,0x1F,0x00,0x00,

0x01,0x00,0x08,0x00,0x64,0x61,0x74,0x61,0x41,0x04,0x00,0x00,0x58,0x6D,0x7F,0x8F,

0xA5,0xB0,0xB9,0xBF,0xC0,0xB8,0xAF,0xA2,0x93,0x83,0x75,0x6B,0x63,0x61,0x63,0x6A,

0x72,0x7F,0x87,0x90,0x9A,0x9C,0x99,0x9A,0x97,0x8D,0x88,0x7E,0x73,0x69,0x60,0x58,

0x4B,0x47,0x43,0x46,0x4F,0x5B,0x6B,0x7D,0x8E,0x9F,0xAE,0xB5,0xBD,0xBB,0xB4,0xB0,

0x9E,0x92,0x85,0x74,0x6F,0x68,0x64,0x68,0x6E,0x74,0x80,0x8A,0x90,0x98,0x9D,0x9A,

0x97,0x91,0x8A,0x85,0x7A,0x75,0x70,0x66,0x62,0x5C,0x54,0x4F,0x4A,0x49,0x55,0x5A,

0x6B,0x80,0x89,0x9E,0xAD,0xB4,0xBE,0xBB,0xB4,0xAC,0x9F,0x8D,0x83,0x73,0x6B,0x68,

0x64,0x69,0x70,0x76,0x83,0x8D,0x93,0x9A,0x9D,0x99,0x97,0x8F,0x86,0x83,0x7A,0x71,

0x6F,0x65,0x61,0x5E,0x56,0x54,0x4E,0x48,0x53,0x5D,0x63,0x7D,0x8A,0x95,0xAD,0xB0,

0xB8,0xBE,0xB3,0xAB,0xA4,0x8E,0x83,0x77,0x6A,0x68,0x65,0x68,0x70,0x78,0x83,0x8F,

0x96,0x9B,0x9E,0x9B,0x96,0x8F,0x87,0x7E,0x7B,0x74,0x6D,0x71,0x67,0x67,0x64,0x5D,

0x57,0x53,0x49,0x52,0x5B,0x61,0x7C,0x87,0x95,0xA9,0xB3,0xB7,0xBD,0xB1,0xA9,0xA2,

0x8D,0x80,0x78,0x69,0x66,0x68,0x6A,0x74,0x7D,0x87,0x92,0x98,0x9A,0x9D,0x98,0x93,

0x8B,0x83,0x7B,0x79,0x74,0x6F,0x72,0x6E,0x6B,0x6A,0x62,0x5A,0x55,0x4B,0x4F,0x59,

0x5C,0x73,0x84,0x8E,0xA9,0xAE,0xB5,0xBB,0xB4,0xA8,0xA4,0x8D,0x7F,0x78,0x67,0x69,

0x6A,0x6F,0x78,0x85,0x8B,0x95,0x9D,0x9A,0x9B,0x94,0x88,0x83,0x7D,0x78,0x78,0x76,

0x74,0x78,0x73,0x74,0x6F,0x62,0x5B,0x4F,0x47,0x4D,0x57,0x5F,0x7E,0x87,0x9A,0xAA,

0xAE,0xAE,0xAE,0xA2,0x95,0x90,0x7C,0x79,0x74,0x71,0x79,0x81,0x87,0x94,0x97,0x9A,

0x9C,0x98,0x90,0x8B,0x81,0x79,0x78,0x76,0x79,0x79,0x7D,0x7B,0x7B,0x78,0x71,0x66,

0x58,0x4C,0x40,0x41,0x4E,0x58,0x74,0x89,0x98,0xAB,0xB4,0xB3,0xB1,0xA9,0x95,0x8F,

0x7F,0x77,0x74,0x74,0x7A,0x83,0x8B,0x96,0x9A,0x9D,0x9D,0x97,0x8E,0x83,0x7E,0x76,

0x74,0x76,0x76,0x79,0x7E,0x7C,0x7C,0x7B,0x73,0x68,0x59,0x4A,0x41,0x3C,0x4B,0x57,

0x6E,0x89,0x97,0xA9,0xB7,0xB6,0xB0,0xAE,0x97,0x8E,0x81,0x76,0x73,0x77,0x79,0x84,

0x8F,0x95,0x9E,0x9E,0x9C,0x97,0x90,0x83,0x80,0x76,0x73,0x75,0x77,0x79,0x7F,0x80,

0x7E,0x7D,0x76,0x69,0x5A,0x4D,0x40,0x3B,0x47,0x52,0x66,0x82,0x91,0xA4,0xB2,0xB4,

0xB3,0xAE,0x9C,0x91,0x84,0x78,0x76,0x75,0x7B,0x84,0x8C,0x95,0x9B,0x9E,0x9C,0x99,

0x90,0x86,0x83,0x77,0x74,0x76,0x74,0x78,0x7C,0x7C,0x7D,0x7A,0x73,0x69,0x5D,0x4E,

0x47,0x41,0x49,0x56,0x65,0x7D,0x8E,0xA0,0xAB,0xB2,0xAE,0xAC,0x9E,0x93,0x88,0x7F,

0x7B,0x7A,0x7D,0x84,0x8B,0x92,0x9A,0x9A,0x9B,0x99,0x90,0x89,0x87,0x7A,0x78,0x78,

0x73,0x79,0x79,0x78,0x78,0x74,0x6A,0x62,0x57,0x4E,0x47,0x47,0x50,0x5C,0x6F,0x82,

0x91,0xA0,0xA9,0xAB,0xAE,0xA5,0x9F,0x96,0x8A,0x86,0x82,0x7F,0x83,0x87,0x8A,0x93,

0x96,0x97,0x96,0x94,0x8C,0x88,0x83,0x7C,0x78,0x76,0x72,0x73,0x73,0x6E,0x6E,0x66,

0x5E,0x58,0x52,0x4C,0x54,0x57,0x64,0x75,0x7F,0x8F,0x9C,0xA0,0xA6,0xA8,0xA1,0xA1,

0x98,0x90,0x8C,0x87,0x84,0x89,0x87,0x8B,0x90,0x91,0x92,0x92,0x8F,0x8B,0x89,0x82,

0x7F,0x7B,0x76,0x73,0x72,0x6C,0x69,0x63,0x5C,0x57,0x53,0x4F,0x56,0x59,0x62,0x71,

0x7B,0x88,0x96,0x9A,0xA1,0xA6,0xA3,0xA3,0x9F,0x98,0x95,0x90,0x8B,0x8D,0x8A,0x8C,

0x8E,0x8D,0x8E,0x8E,0x8B,0x8A,0x87,0x81,0x7F,0x7B,0x75,0x72,0x6D,0x68,0x62,0x5D,

0x58,0x53,0x51,0x52,0x58,0x60,0x6A,0x74,0x80,0x8B,0x95,0x9C,0xA1,0xA3,0xA4,0xA1,

0x9F,0x9C,0x97,0x95,0x91,0x90,0x8E,0x8F,0x8E,0x8E,0x8C,0x8C,0x88,0x87,0x83,0x7E,

0x7B,0x76,0x71,0x6B,0x67,0x5F,0x5B,0x55,0x53,0x51,0x54,0x57,0x5F,0x69,0x72,0x7F,

0x89,0x91,0x9B,0xA1,0xA3,0xA7,0xA5,0xA3,0xA1,0x9D,0x99,0x96,0x92,0x90,0x8F,0x8D,

0x8C,0x8B,0x89,0x86,0x86,0x7F,0x7C,0x77,0x71,0x6B,0x66,0x5E,0x5A,0x56,0x52,0x52,

0x54,0x57,0x5F,0x67,0x6F,0x7B,0x83,0x8C,0x96,0x9C,0xA0,0xA6,0xA6,0xA6,0xA6,0xA1,

0x9E,0x9C,0x96,0x94,0x92,0x8F,0x8C,0x8B,0x86,0x85,0x81,0x7D,0x7B,0x76,0x70,0x6D,

0x66,0x60,0x5D,0x58,0x56,0x55,0x56,0x58,0x5F,0x64,0x6D,0x77,0x7F,0x88,0x91,0x97,

0x9E,0xA2,0xA5,0xA8,0xA7,0xA5,0xA3,0x9F,0x9B,0x98,0x93,0x91,0x8E,0x8B,0x88,0x83,

0x80,0x7B,0x78,0x72,0x6E,0x68,0x64,0x5E,0x5A,0x56,0x53,0x53,0x55,0x58,0x5E,0x66,

0x70,0x78,0x83,0x8C,0x94,0x9B,0xA0,0xA5,0xA8,0xA9,0xA9,0xA6,0xA5,0xA2,0x9E,0x9B,

0x97,0x92,0x8F,0x8B,0x85,0x80,0x7B,0x76,0x70,0x6B,0x65,0x60,0x5B,0x57,0x52,0x52,

0x51,0x53,0x58,0x5D,0x66,0x6E,0x79,0x82,0x8C,0x95,0x9C,0xA2,0xA7,0xA9,0xAC,0xAC,

0xAA,0xA8,0xA6,0xA1,0x9D,0x99,0x93,0x8F,0x89,0x83,0x7F,0x78,0x72,0x6C,0x65,0x5F,

0x5A,0x54,0x51,0x4E,0x4E,0x50,0x54,0x5A,0x61,0x6A,0x74,0x7D,0x88,0x92,0x9A,0xA2,

0xA8,0xAC,0xAF,0xAF,0xAF,0xAD,0xAA,0xA5,0xA0,0x9C,0x96,0x91,0x8A,0x83,0x7D,0x78,

0x70,0x6A,0x62,0x5C,0x57,0x52,0x4E,0x4C,0x4D,0x4F,0x53,0x5A,0x61,0x6C,0x76,0x7F,

0x8B,0x95,0x9D,0xA4,0xAA,0xAD,0xB0,0xB0,0xAF,0xAD,0xAA,0xA6,0xA0,0x9B,0x95,0x8E,

0x87,0x81,0x79,0x72,0x6A,0x63,0x5D,0x57,0x52,0x4F,0x4D,0x4D,0x4F,0x52,0x58,0x5F,

0x68,0x72,0x7D,0x87,0x91,0x99,0xA1,0xA8,0xAC,0xB0,0xB0,0xB0,0xAE,0xAB,0xA8,0xA3,

0x9D,0x97,0x8F,0x89,0x81,0x7A,0x72,0x6A,0x64,0x5D,0x58,0x53,0x4F,0x4E,0x4D,0x4F,

0x53,0x59,0x5F,0x68,0x72,0x7C,0x86,0x8F,0x99,0x9F,0xA6,0xAB,0xAE,0xAF,0xB0,0xAE,

0xAB,0xA8,0xA2,0x9D,0x96,0x8F,0x88,0x81,0x78,0x71,0x69,0x63,0x5C,0x57,0x53,0x51,

0x4F,0x50,0x53,0x57,0x5C,0x63,0x6C,0x75,0x7E,0x88,0x90,0x98,0xA0,0xA4,0xAA,0xAD,

0xAE,0xAE,0xAC,0xA9,0xA5,0xA1,0x9A,0x94,0x8D,0x86,0x7D,0x76,0x6F,0x68,0x61,0x5C,

0x58,0x54,0x53,0x53,0x54,0x57,0x5C,0x62,0x69,0x71,0x79,0x82,0x8A,0x92,0x98,0x9E,

0xA3,0xA7,0xA9,0xAA,0xAA,0xA7,0xA4,0xA1,0x9B,0x95,0x8E,0x88,0x81,0x7A,0x74,0x6D,

0x68,0x63,0x5F,0x5D,0x5A,0x5B,0x5C,0x5D,0x61,0x64,0x69,0x70,0x77,0x7D,0x84,0x8A,

0x8F,0x97,0x9A,0x9D,0x9F,0xA1,0xA2,0xA0,0x9F,0x9C,0x98,0x93,0x8F,0x89,0x84,0x7E,

0x79,0x75,0x70,0x6D,0x6A,0x67,0x66,0x66,0x66,0x67,0x69,0x6D,0x70,0x73,0x77,0x7C,

0x80,0x84,0x88,0x8B,0x8E,0x91,0x93,0x95,0x94,0x95,0x93,0x92,0x90,0x8E,0x8B,0x87,

0x84,0x81,0x7D,0x7A,0x78,0x76,0x73,0x73,0x71,0x70,0x70,0x71,0x73,0x00,

};

八、修改main函数

添加模拟音频波形数据表 Array[]
添加 HAL_TIM_Base_Start() 函数，启动定时器。
添加 HAL_DAC_Start_DMA()函数，启动 DAC 的 DMA 输出。

unsigned char Array[]={

0xFF,0xF3,0x28,0xC4,0x00,0x0C,0xC8,0x4E,0xA8,0xFF,0x58,0x10,0x00,0x80,0x2A,0x42,

0x52,0x34,0x03,0xF9,0xF5,0xE1,0xB6,0x06,0x17,0x39,0xFD,0xAB,0xB2,0x04,0xD6,0xAA,

0x52,0x0A,0x9C,0x32,0xF4,0x37,0xF6,0x7C,0x22,0xEC,0x59,0xD4,0xF2,0x1C,0xBB,0x30,

0xB7,0xA4,0xD2,0x7F,0xFD,0xBF,0xEB,0xFB,0x3E,0x51,0x63,0xFF,0xFF,0xD5,0x94,0x0C,

0x2A,0xC9,0xBA,0xE6,0xA2,0x98,0xAA,0x91,0xFF,0xF3,0x28,0xC4,0x07,0x0C,0x98,0x6A,