AIR32F103(六) ADC,I2S,DMA和ADPCM实现的录音播放功能

关于

使用AIR32的ADC, I2S 和 DMA 实现简单的语音录音和播放功能, 以及使用 ADPCM 编码提升录音时长. 使用的MCU型号为 AIR32F103CCT6. 如果用CBT6, 对应的音频数据数组大小需要相应减小.

音频录音和播放

工作方式

加电后开始录音, 录音结束后循环播放

录音: 麦克风模块 -> ADC采样(12bit, 8K, 11K 或 16K) -> 存储在内存
播放: I2S -> I2S外设(MAX98357A / PT8211) -> 喇叭

对中间每个环节的说明

存储

首先是存储, MCU的内存有限, 如果不借助AT24C, MX25L这类外部存储, 只用内存存储的数据是有限的, AIR32F103CCT6 带 64K Byte内存, 如果按原始采样值存储, 录音时长为

16bit
- 8K: 128kbps, 约4秒
- 11K: 176kbps, 约3秒
- 16K: 256kbps, 约2秒
8bit
- 8K: 64kbps, 约8秒
- 11K: 88kbps, 约6秒
- 16K: 128kbps, 约4秒

采样

使用AIR32的ADC, 配合定时器实现精确的每秒8K, 11K和16K采样. AIR32的ADC分辨率和STM32F103一样都是固定的12bit(STM32F4之后才可以用寄存器调节分辨率)

如果使用ADC的中断, 可以向高位偏移做成16bit, 也可以去掉低位做成8bit
如果使用DMA, 因为AIR32不能像STM32那样, 在4字节地址上偏移一个字节取值, 所以只能按16bit(halfword)传值

音频采集设备如果直接用驻极体话筒, 采样的信号很弱(不是没有, 但是非常小), 需要加一个三极管做放大. 也可以买成品的 MAX9814 模块. 两者的效果区别不大, 但是在调试阶段, 建议用 MAX9814, 因为不用担心信号是否过饱和和失真问题, 在调通之后, 再换回低成本的驻极体话筒和三极管.

驻极体话筒放大的电路和元件参数可以参考这一篇 https://www.cnblogs.com/milton/p/15315783.html

播放

播放可以使用PWM转DAC, 也可以直接用I2S.

如果使用PWM, 因为PWM本身是方波, 会产生大量的谐振噪音, 只有将PWM频率设置到16KHz以上才能明显降低噪音(因为谐振频率超出人耳的听觉范围了), 用8KHz时的噪音非常明显.
因为AIR32F103全系列都支持I2S(数据手册上写只有RPT7才有, 实际上CBT6和CCT6也有), 所以直接用I2S输出是最简单的. 这时候需要一个能接收I2S输出并转为音频的模块.

I2S模块可以用 MAX98357A 模块, 自带I2S解码和放大可以直连喇叭, 也可以买PT8211/TM8211/GH8211, 0.3元一片非常便宜还是双声道, 缺点是不带功放, 如果直连喇叭得贴着耳朵才能听到, 可以再加一个LM386或者PAM8403做放大, 都非常便宜.

实现

硬件

AIR32F103CCT6
MAX9814
PT8211
8欧小喇叭

接线

  *   AIR32F103                  MAX98357A / PT8211
 *   PB13(SPI1_SCK/I2S_CK)       -> BCLK, BCK
 *   PB15(SPI1_MOSI/I2S_SD)      -> DIN
 *   PB12(SPI1_NSS/I2S_WS)       -> LRC, WS
 *                               GND  -> GND
 *                               VIN  -> 3.3V
 *                               +    -> speaker
 *                               -    -> speaker
 * 
 *   AIR32F103                  MAX9814
 *   PA2                        -> Out
 *   3.3V                       -> VDD
 *   GND                        -> GND
 *   GND                        -> A/R
 *                                 GAIN -> float:60dB, gnd:50dB, 3.3v:40dB

代码

完整的示例代码

定义了全局变量

 // 定义不同的AUDIO_FREQ值, 可以切换不同的采样频率, 8K, 11K, 16K, 越高的采样频率, 音质越好, 录音时长越短
#define AUDIO_FREQ 8000
//#define AUDIO_FREQ 11000
//#define AUDIO_FREQ 16000
 
// 定义存储的音频数据大小, CCT6用的是30000, CBT6 或 RPT6 可以相应的减小或增大
#define BUFF_SIZE 30000
 
// 音频数据数组, 同时用于DMA的接收地址
uint16_t dma_buf[BUFF_SIZE];
 
// I2S传输时, 用于记录传输的位置
uint32_t index;
// I2S传输时, 用于区分左右声道
__IO uint8_t lr = 0;

初始化GPIO, PA2是采样输入, PB12, PB13, PB15 用于I2S传输, PC13 是板载的LED, 用于指示录音开始和结束. 如果使用的不是Bluepill而是合宙的开发板, 可以修改为开发板对应的LED GPIO.

 void GPIO_Configuration(void)
{
    GPIO_InitTypeDef GPIO_InitStructure;
    // PA2 as analog input
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AIN;
    GPIO_Init(GPIOA, &GPIO_InitStructure);
    // PB12,PB13,PB15 as I2S AF output
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_12 | GPIO_Pin_13 | GPIO_Pin_15; 
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
    GPIO_Init(GPIOB, &GPIO_InitStructure);
    // PC13 as GPIO output
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_13;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
    GPIO_Init(GPIOC, &GPIO_InitStructure);
}

初始化ADC, 设置为外部触发模式, 这里使用TIM3的Update中断作为触发源, 初始化之后ADC并不会立即开始转换, 而是在TIM3的每次Update中断时进行转换. 所以如果要停止ADC, 需要先停掉TIM3

 void ADC_Configuration(void)
{
    ADC_InitTypeDef ADC_InitStructure;
 
    // Reset ADC1
    ADC_DeInit(ADC1);
    ADC_InitStructure.ADC_Mode = ADC_Mode_Independent;
    ADC_InitStructure.ADC_ScanConvMode = DISABLE;
    ADC_InitStructure.ADC_ContinuousConvMode = DISABLE;
    // 设置 TIM3 为外置触发源
    ADC_InitStructure.ADC_ExternalTrigConv = ADC_ExternalTrigConv_T3_TRGO;
    // 结果右对齐
    ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right;
    // 只使用一个通道
    ADC_InitStructure.ADC_NbrOfChannel = 1;
    ADC_Init(ADC1, &ADC_InitStructure);
    // PA2对应的channel是 ADC_Channel_2
    ADC_RegularChannelConfig(ADC1, ADC_Channel_2, 1, ADC_SampleTime_239Cycles5);
 
    // 启用ADC1的外部触发源
    ADC_ExternalTrigConvCmd(ADC1, ENABLE);
 
    // 在 ADC1 上启用 DMA
    ADC_DMACmd(ADC1, ENABLE);
    ADC_Cmd(ADC1, ENABLE);
 
    // 校准
    ADC_ResetCalibration(ADC1);
    while (ADC_GetResetCalibrationStatus(ADC1));
    ADC_StartCalibration(ADC1);
    while (ADC_GetCalibrationStatus(ADC1));
}

初始化DMA, 用 ADC1->DR 作为外设地址, dma_buf作为内存地址, 内存地址递增, 数据大小为16bit, 循环填充. 同时打开DMA的填充完成中断 DMA_IT_TC

 //调用
DMA_Configuration(DMA1_Channel1, (uint32_t)&ADC1->DR, (uint32_t)dma_buf, BUFF_SIZE);
 
// 函数实现
void DMA_Configuration(DMA_Channel_TypeDef *DMA_CHx, uint32_t ppadr, uint32_t memadr, uint16_t bufsize)
{
    DMA_InitTypeDef DMA_InitStructure;
 
    DMA_DeInit(DMA_CHx);
    DMA_InitStructure.DMA_PeripheralBaseAddr = ppadr;
    DMA_InitStructure.DMA_MemoryBaseAddr = memadr;
    DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;
    DMA_InitStructure.DMA_BufferSize = bufsize;
    // Addresss increase - peripheral:no, memory:yes
    DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
    DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
    // Data unit size: 16bit
    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_Medium;
    // Memory to memory: no
    DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
    DMA_Init(DMA_CHx, &DMA_InitStructure);
    // Enable 'Transfer complete' interrupt
    DMA_ITConfig(DMA1_Channel1, DMA_IT_TC, ENABLE);
    // Enable DMA
    DMA_Cmd(DMA_CHx, ENABLE);
}

打开外设的中断控制, DMA用于转换结束, SPI2的中断用于每次的数据发送

 void NVIC_Configuration(void)
{
    // DMA1 interrupts
    NVIC_InitTypeDef NVIC_InitStructure;
    NVIC_InitStructure.NVIC_IRQChannel = DMA1_Channel1_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 6;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStructure);
    // SPI2 interrupts
    NVIC_InitStructure.NVIC_IRQChannel = SPI2_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 6;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStructure);
}

初始化定时器TIM3, 根据MCU频率72MHz, 计算得到分别在8K, 11K, 16K时的定时器周期和预分频系数. 启用计时器的Update中断, 但是不启动定时器, 因为启动后就会产生中断, 就会触发ADC转换. 需要将计时器的启动放到main()中.

 void TIM_Configuration(void)
{
    TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
 
    TIM_TimeBaseStructure.TIM_Period = 9 - 1;
#if AUDIO_FREQ == 8000
    // Period = 72,000,000 / 8,000 = 1000 * 9
    TIM_TimeBaseStructure.TIM_Prescaler = 1000 - 1;
#elif AUDIO_FREQ == 11000
    // Period = 72,000,000 / 11,000 = 727 * 9
    TIM_TimeBaseStructure.TIM_Prescaler = 727 - 1;
#else
    // Period = 72,000,000 / 16,000 = 500 * 9
    TIM_TimeBaseStructure.TIM_Prescaler = 500 - 1;
#endif
    TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;
    TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
    TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);
    // Enable TIM3 'TIM update' trigger for adc
    TIM_SelectOutputTrigger(TIM3, TIM_TRGOSource_Update);
    // Timer will be started in main()
}

初始化I2S, 如果使用的是PT8211, 需要将 I2S_Standard 设置为 I2S_Standard_LSB. 否则双声道传数据时工作不正常

 void IIS_Configuration(void)
{
    I2S_InitTypeDef I2S_InitStructure;
 
    SPI_I2S_DeInit(SPI2);
    I2S_InitStructure.I2S_Mode = I2S_Mode_MasterTx;
    // PT8211:LSB,  MAX98357A:Phillips
    I2S_InitStructure.I2S_Standard = I2S_Standard_Phillips;
    // 16-bit data resolution
    I2S_InitStructure.I2S_DataFormat = I2S_DataFormat_16b;
#if AUDIO_FREQ == 8000
    // 8K sampling rate
    I2S_InitStructure.I2S_AudioFreq = I2S_AudioFreq_8k;
#elif AUDIO_FREQ == 11000
    // 11K sampling rate
    I2S_InitStructure.I2S_AudioFreq = I2S_AudioFreq_11k;
#else
    // 16K sampling rate
    I2S_InitStructure.I2S_AudioFreq = I2S_AudioFreq_16k;
#endif
    I2S_InitStructure.I2S_CPOL = I2S_CPOL_Low;
    I2S_InitStructure.I2S_MCLKOutput = I2S_MCLKOutput_Disable;
    I2S_Init(SPI2, &I2S_InitStructure);
 
    I2S_Cmd(SPI2, ENABLE);
}

中断处理

DMA中断: DMA中断时表示内存数组已经装满了, 此时要停掉TIM3和ADC1, 并关掉PC13 LED指示录音结束

 void DMA1_Channel1_IRQHandler(void)
{
    // DMA1 Channel1 Transfer Complete interrupt
    if (DMA_GetITStatus(DMA1_IT_TC1))
    {
        DMA_ClearITPendingBit(DMA1_IT_GL1);
        // Stop ADC(by stopping TIM3)
        TIM_Cmd(TIM3, DISABLE);
        ADC_Cmd(ADC1, DISABLE);
        GPIO_SetBits(GPIOC, GPIO_Pin_13);
    }
}

SPI2(I2S)中断, 用于每个I2S数据的传输, 因为传输时左右声道的数据是交替传输的, 所以这里需要用一个全局变量切换当前的声道. 因为录音是单声道, 所以传输时对应两个声道, 每个值会被传输两遍. 到达最后一个值后, 会停掉I2S.

 void SPI2_IRQHandler(void)
{
    // If TX Empty flag is set
    if (SPI_I2S_GetITStatus(SPI2, SPI_I2S_IT_TXE) == SET)
    {
        // Put data to both channels
        if (lr == 0)
        {
            lr = 1;
            SPI_I2S_SendData(SPI2, (uint16_t)dma_buf[index] << 3);
        }
        else
        {
            lr = 0;
            SPI_I2S_SendData(SPI2, (uint16_t)dma_buf[index++] << 3);
            if (index == BUFF_SIZE)
            {
                index = 0;
                // Disable the I2S1 TXE Interrupt to stop playing
                SPI_I2S_ITConfig(SPI2, SPI_I2S_IT_TXE, DISABLE);
            }
        }
    }
}

主函数. 在主函数中, 先开启录音, 然后等待4秒(对应 3万个样本, 8K采样, 4秒之内就结束了), 然后开始播放. 每个循环等待5秒. 播放会在中断中判断是否结束, 结束就停止.

 int main(void)
{
    Delay_Init();
    USART_Printf_Init(115200);
    printf("SystemClk:%ld\r\n", SystemCoreClock);
 
    RCC_Configuration();
    GPIO_Configuration();
    ADC_Configuration();
    DMA_Configuration(DMA1_Channel1, (uint32_t)&ADC1->DR, (uint32_t)dma_buf, BUFF_SIZE);
    NVIC_Configuration();
    TIM_Configuration();
    IIS_Configuration();
    GPIO_SetBits(GPIOC, GPIO_Pin_13);
    Delay_S(1);
    // Start timer to start recording
    printf("Start recording\r\n");
    TIM_Cmd(TIM3, ENABLE);
    // Turn on LED, DMA TC1 interrupt will turn it off 
    GPIO_ResetBits(GPIOC, GPIO_Pin_13);
    Delay_S(4);
    printf("Start playing\r\n");
    while (1)
    {
        // Restart the playing
        SPI_I2S_ITConfig(SPI2, SPI_I2S_IT_TXE, ENABLE);
        Delay_S(5);
    }
}

使用ADPCM压缩音频数据

ADPCM 的原理和计算方式可以参考这一篇 https://www.cnblogs.com/milton/p/16914797.html.

使用ADPCM可以将16bit的数据压缩为4bit, 同时保持基本一致的听觉信息. 这样对于64kB的CCT6, 可以在12bit的效果下记录接近16秒的语音(64K = 16 * 8K * 0.5). 而且 ADPCM 的计算简单, AIR32这种M3核心的MCU处理起来非常轻松.

工作机制调整

如果使用ADPCM, 需要对前面的例子进行一些调整. 硬件和前面的一致, 改动都在代码.

去掉DMA

因为DMA必须是硬件到硬件, 如果想做成双缓冲, 比如做一个1K左右的DMA数组, 一半结束后批量编码, 再等另一半结束再编码? 这样其实不行, 因为集中编码时ADC也还在进行, 一边在计算一边在转换和中断, 会互相影响, 导致采样不均匀. 因为ADC转换使用定时器触发, 定时器两个中断之间, ADC转换的时间很短, 中间间隔的时间完全可以用于编码, 所以需要将DMA去掉, 改成使用ADC的转换完成中断, 在完成中断的处理函数中对采样值进行编码

调整数组

为了计算方便, 将语音数组转换为uint8_t, 这样每个值记录的是两个采样点, 相应的数组大小扩充到了60000

调整I2S传输

因为每个值存储的是两个采样, 因此在I2S的TXE中断处理中, 原先的左右声道判断需要叠加4bit偏移判断, 变成4种情况.

代码

完整的示例代码

ADC启用中断

 void ADC_Configuration(void)
{
    ADC_InitTypeDef ADC_InitStructure;
 
    // Reset ADC1
    ADC_DeInit(ADC1);
    ADC_InitStructure.ADC_Mode = ADC_Mode_Independent;
    ADC_InitStructure.ADC_ScanConvMode = DISABLE;
    ADC_InitStructure.ADC_ContinuousConvMode = DISABLE;
    // Select TIM3 trigger output as external trigger
    ADC_InitStructure.ADC_ExternalTrigConv = ADC_ExternalTrigConv_T3_TRGO;
    ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right;
    ADC_InitStructure.ADC_NbrOfChannel = 1;
    ADC_Init(ADC1, &ADC_InitStructure);
    // ADC_Channel_2 for PA2
    ADC_RegularChannelConfig(ADC1, ADC_Channel_2, 1, ADC_SampleTime_7Cycles5);
 
    // Enable ADC1 external trigger
    ADC_ExternalTrigConvCmd(ADC1, ENABLE);
    ADC_ITConfig(ADC1, ADC_IT_EOC, ENABLE);
 
    // Enable ADC1
    ADC_Cmd(ADC1, ENABLE);
 
    // Calibration
    ADC_ResetCalibration(ADC1);
    while (ADC_GetResetCalibrationStatus(ADC1));
    ADC_StartCalibration(ADC1);
    while (ADC_GetCalibrationStatus(ADC1));
}

在ADC中断中, 对ADC结果值的编码

 void Audio_Encode(void)
{
    static uint32_t idx = 0;
    static uint8_t msb = 0;
    uint8_t val;
 
    val = ADPCM_Encode((uint16_t)(ADC1->DR << 2)) & 0x0F;
    if (msb == 0)
    {
        voice[idx] = val;
        msb = 1;
    }
    else
    {
        voice[idx] |= (val << 4);
        msb = 0;
        idx++;
        if (idx == BUFF_SIZE)
        {
            // Stop ADC(by stopping TIM3)
            TIM_Cmd(TIM3, DISABLE);
            ADC_Cmd(ADC1, DISABLE);
            ADC_ExternalTrigConvCmd(ADC1, DISABLE);
            GPIO_SetBits(GPIOC, GPIO_Pin_13);
            idx = 0;
            finish = 1;
        }
    }
}

在I2S传输中断中, 对值的解码. 每传输四个数据(低4位左右声道, 高4位左右声道)下标才加1, 传输结束后重置下标.

 uint16_t Audio_Decode(void)
{
    static uint32_t idx = 0;
    static __IO uint8_t msb = 0, lr = 0;
    static uint16_t val;
 
    if (msb == 0)
    {
        // Put data to both channels
        if (lr == 0)
        {
            val = ADPCM_Decode(voice[idx] & 0x0F);
            lr = 1;
        }
        else if (lr == 1)
        {
            lr = 0;
            msb = 1;
        }
    }
    else
    {
        if (lr == 0)
        {
            val = ADPCM_Decode((voice[idx] >> 4) & 0x0F);
            lr = 1;
        }
        else if (lr == 1)
        {
            lr = 0;
            msb = 0;
            idx++;
            if (idx == BUFF_SIZE)
            {
                idx = 0;
                ADPCM_Reset();
            }
        }
    }
    return val;
}

使用ADPCM后, 在8K采样下语音音质没有明显下降, 但是录音时长增长到了15秒, 提升明显.

最后

以上说明了如何使用AIR32自带的内存实现简单的语音录制和播放功能, 以及使用 ADPCM 对音频数据进行压缩, 提高录制时长. 通过这些机制, 可以快速扩充为实用的录制设备, 例如外挂I2C或SPI存储, 或提升无线传输的音质, 在同样的码率下使用更高采样率.

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原文地址：https://www.cnblogs.com/milton/p/16919589.html

	* AIR32F103 MAX98357A / PT8211
	* PB13(SPI1_SCK/I2S_CK) -> BCLK, BCK
	* PB15(SPI1_MOSI/I2S_SD) -> DIN
	* PB12(SPI1_NSS/I2S_WS) -> LRC, WS
	* GND -> GND
	* VIN -> 3.3V
	* + -> speaker
	* - -> speaker
	*
	* AIR32F103 MAX9814
	* PA2 -> Out
	* 3.3V -> VDD
	* GND -> GND
	* GND -> A/R
	* GAIN -> float:60dB, gnd:50dB, 3.3v:40dB

	// 定义不同的AUDIO_FREQ值, 可以切换不同的采样频率, 8K, 11K, 16K, 越高的采样频率, 音质越好, 录音时长越短
	#define AUDIO_FREQ 8000
	//#define AUDIO_FREQ 11000
	//#define AUDIO_FREQ 16000

	// 定义存储的音频数据大小, CCT6用的是30000, CBT6 或 RPT6 可以相应的减小或增大
	#define BUFF_SIZE 30000

	// 音频数据数组, 同时用于DMA的接收地址
	uint16_t dma_buf[BUFF_SIZE];

	// I2S传输时, 用于记录传输的位置
	uint32_t index;
	// I2S传输时, 用于区分左右声道
	__IO uint8_t lr = 0;

	void GPIO_Configuration(void)
	{
	GPIO_InitTypeDef GPIO_InitStructure;
	// PA2 as analog input
	GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2;
	GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AIN;
	GPIO_Init(GPIOA, &GPIO_InitStructure);
	// PB12,PB13,PB15 as I2S AF output
	GPIO_InitStructure.GPIO_Pin = GPIO_Pin_12 \| GPIO_Pin_13 \| GPIO_Pin_15;
	GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
	GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
	GPIO_Init(GPIOB, &GPIO_InitStructure);
	// PC13 as GPIO output
	GPIO_InitStructure.GPIO_Pin = GPIO_Pin_13;
	GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
	GPIO_Init(GPIOC, &GPIO_InitStructure);
	}

	void ADC_Configuration(void)
	{
	ADC_InitTypeDef ADC_InitStructure;

	// Reset ADC1
	ADC_DeInit(ADC1);
	ADC_InitStructure.ADC_Mode = ADC_Mode_Independent;
	ADC_InitStructure.ADC_ScanConvMode = DISABLE;
	ADC_InitStructure.ADC_ContinuousConvMode = DISABLE;
	// 设置 TIM3 为外置触发源
	ADC_InitStructure.ADC_ExternalTrigConv = ADC_ExternalTrigConv_T3_TRGO;
	// 结果右对齐
	ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right;
	// 只使用一个通道
	ADC_InitStructure.ADC_NbrOfChannel = 1;
	ADC_Init(ADC1, &ADC_InitStructure);
	// PA2对应的channel是 ADC_Channel_2
	ADC_RegularChannelConfig(ADC1, ADC_Channel_2, 1, ADC_SampleTime_239Cycles5);

	// 启用ADC1的外部触发源
	ADC_ExternalTrigConvCmd(ADC1, ENABLE);

	// 在 ADC1 上启用 DMA
	ADC_DMACmd(ADC1, ENABLE);
	ADC_Cmd(ADC1, ENABLE);

	// 校准
	ADC_ResetCalibration(ADC1);
	while (ADC_GetResetCalibrationStatus(ADC1));
	ADC_StartCalibration(ADC1);
	while (ADC_GetCalibrationStatus(ADC1));
	}

	//调用
	DMA_Configuration(DMA1_Channel1, (uint32_t)&ADC1->DR, (uint32_t)dma_buf, BUFF_SIZE);

	// 函数实现
	void DMA_Configuration(DMA_Channel_TypeDef *DMA_CHx, uint32_t ppadr, uint32_t memadr, uint16_t bufsize)
	{
	DMA_InitTypeDef DMA_InitStructure;

	DMA_DeInit(DMA_CHx);
	DMA_InitStructure.DMA_PeripheralBaseAddr = ppadr;
	DMA_InitStructure.DMA_MemoryBaseAddr = memadr;
	DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;
	DMA_InitStructure.DMA_BufferSize = bufsize;
	// Addresss increase - peripheral:no, memory:yes
	DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
	DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
	// Data unit size: 16bit
	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_Medium;
	// Memory to memory: no
	DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
	DMA_Init(DMA_CHx, &DMA_InitStructure);
	// Enable 'Transfer complete' interrupt
	DMA_ITConfig(DMA1_Channel1, DMA_IT_TC, ENABLE);
	// Enable DMA
	DMA_Cmd(DMA_CHx, ENABLE);
	}

	void NVIC_Configuration(void)
	{
	// DMA1 interrupts
	NVIC_InitTypeDef NVIC_InitStructure;
	NVIC_InitStructure.NVIC_IRQChannel = DMA1_Channel1_IRQn;
	NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 6;
	NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
	NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
	NVIC_Init(&NVIC_InitStructure);
	// SPI2 interrupts
	NVIC_InitStructure.NVIC_IRQChannel = SPI2_IRQn;
	NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 6;
	NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
	NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
	NVIC_Init(&NVIC_InitStructure);
	}

	void TIM_Configuration(void)
	{
	TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;

	TIM_TimeBaseStructure.TIM_Period = 9 - 1;
	#if AUDIO_FREQ == 8000
	// Period = 72,000,000 / 8,000 = 1000 * 9
	TIM_TimeBaseStructure.TIM_Prescaler = 1000 - 1;
	#elif AUDIO_FREQ == 11000
	// Period = 72,000,000 / 11,000 = 727 * 9
	TIM_TimeBaseStructure.TIM_Prescaler = 727 - 1;
	#else
	// Period = 72,000,000 / 16,000 = 500 * 9
	TIM_TimeBaseStructure.TIM_Prescaler = 500 - 1;
	#endif
	TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;
	TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
	TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);
	// Enable TIM3 'TIM update' trigger for adc
	TIM_SelectOutputTrigger(TIM3, TIM_TRGOSource_Update);
	// Timer will be started in main()
	}

	void IIS_Configuration(void)
	{
	I2S_InitTypeDef I2S_InitStructure;

	SPI_I2S_DeInit(SPI2);
	I2S_InitStructure.I2S_Mode = I2S_Mode_MasterTx;
	// PT8211:LSB, MAX98357A:Phillips
	I2S_InitStructure.I2S_Standard = I2S_Standard_Phillips;
	// 16-bit data resolution
	I2S_InitStructure.I2S_DataFormat = I2S_DataFormat_16b;
	#if AUDIO_FREQ == 8000
	// 8K sampling rate
	I2S_InitStructure.I2S_AudioFreq = I2S_AudioFreq_8k;
	#elif AUDIO_FREQ == 11000
	// 11K sampling rate
	I2S_InitStructure.I2S_AudioFreq = I2S_AudioFreq_11k;
	#else
	// 16K sampling rate
	I2S_InitStructure.I2S_AudioFreq = I2S_AudioFreq_16k;
	#endif
	I2S_InitStructure.I2S_CPOL = I2S_CPOL_Low;
	I2S_InitStructure.I2S_MCLKOutput = I2S_MCLKOutput_Disable;
	I2S_Init(SPI2, &I2S_InitStructure);

	I2S_Cmd(SPI2, ENABLE);
	}

	void DMA1_Channel1_IRQHandler(void)
	{
	// DMA1 Channel1 Transfer Complete interrupt
	if (DMA_GetITStatus(DMA1_IT_TC1))
	{
	DMA_ClearITPendingBit(DMA1_IT_GL1);
	// Stop ADC(by stopping TIM3)
	TIM_Cmd(TIM3, DISABLE);
	ADC_Cmd(ADC1, DISABLE);
	GPIO_SetBits(GPIOC, GPIO_Pin_13);
	}
	}

	void SPI2_IRQHandler(void)
	{
	// If TX Empty flag is set
	if (SPI_I2S_GetITStatus(SPI2, SPI_I2S_IT_TXE) == SET)
	{
	// Put data to both channels
	if (lr == 0)
	{
	lr = 1;
	SPI_I2S_SendData(SPI2, (uint16_t)dma_buf[index] << 3);
	}
	else
	{
	lr = 0;
	SPI_I2S_SendData(SPI2, (uint16_t)dma_buf[index++] << 3);
	if (index == BUFF_SIZE)
	{
	index = 0;
	// Disable the I2S1 TXE Interrupt to stop playing
	SPI_I2S_ITConfig(SPI2, SPI_I2S_IT_TXE, DISABLE);
	}
	}
	}
	}

	int main(void)
	{
	Delay_Init();
	USART_Printf_Init(115200);
	printf("SystemClk:%ld\r\n", SystemCoreClock);

	RCC_Configuration();
	GPIO_Configuration();
	ADC_Configuration();
	DMA_Configuration(DMA1_Channel1, (uint32_t)&ADC1->DR, (uint32_t)dma_buf, BUFF_SIZE);
	NVIC_Configuration();
	TIM_Configuration();
	IIS_Configuration();
	GPIO_SetBits(GPIOC, GPIO_Pin_13);
	Delay_S(1);
	// Start timer to start recording
	printf("Start recording\r\n");
	TIM_Cmd(TIM3, ENABLE);
	// Turn on LED, DMA TC1 interrupt will turn it off
	GPIO_ResetBits(GPIOC, GPIO_Pin_13);
	Delay_S(4);
	printf("Start playing\r\n");
	while (1)
	{
	// Restart the playing
	SPI_I2S_ITConfig(SPI2, SPI_I2S_IT_TXE, ENABLE);
	Delay_S(5);
	}
	}

	void Audio_Encode(void)
	{
	static uint32_t idx = 0;
	static uint8_t msb = 0;
	uint8_t val;

	val = ADPCM_Encode((uint16_t)(ADC1->DR << 2)) & 0x0F;
	if (msb == 0)
	{
	voice[idx] = val;
	msb = 1;
	}
	else
	{
	voice[idx] \|= (val << 4);
	msb = 0;
	idx++;
	if (idx == BUFF_SIZE)
	{
	// Stop ADC(by stopping TIM3)
	TIM_Cmd(TIM3, DISABLE);
	ADC_Cmd(ADC1, DISABLE);
	ADC_ExternalTrigConvCmd(ADC1, DISABLE);
	GPIO_SetBits(GPIOC, GPIO_Pin_13);
	idx = 0;
	finish = 1;
	}
	}
	}

	uint16_t Audio_Decode(void)
	{
	static uint32_t idx = 0;
	static __IO uint8_t msb = 0, lr = 0;
	static uint16_t val;

	if (msb == 0)
	{
	// Put data to both channels
	if (lr == 0)
	{
	val = ADPCM_Decode(voice[idx] & 0x0F);
	lr = 1;
	}
	else if (lr == 1)
	{
	lr = 0;
	msb = 1;
	}
	}
	else
	{
	if (lr == 0)
	{
	val = ADPCM_Decode((voice[idx] >> 4) & 0x0F);
	lr = 1;
	}
	else if (lr == 1)
	{
	lr = 0;
	msb = 0;
	idx++;
	if (idx == BUFF_SIZE)
	{
	idx = 0;
	ADPCM_Reset();
	}
	}
	}
	return val;
	}