stm32 usb audio 播放速度加快和噪音

遇见123 提问时间：2017-6-7 16:13 /

大家好。请问有没有用stm32接数字麦克风做usb audio的。
我用stm32f103RE接两个数字麦克风，经pdm转成pcm后通过usb发送到pc。整个板子相当一声卡。问题是用pc录音，出现播放速度加快，和噪音的显现。请大家帮我分析分析到底是哪里出问题了。谢谢

两个麦克风通过一根线接到i2s的 sd , 麦克风的clk 由i2s的sck产生。我是把i2s配置为主接收模式，用i2s来读取数据。目的是实现输出2通道16k采样。为此，我的i2s sck输出频率为 2.048M。  麦克风的输入频率为1.024M

现在不清楚到底问题出在采样阶段还是pdm 转pcm 还是usb audio发送阶段，请大家帮忙分析下。
部分代码如下

i2s配置如下：
switch(X_NUCLEO_CCA02M1_Handler.Sampling_Freq=AudioFreq){
  case AUDIOFREQ_8K:
{
   X_NUCLEO_CCA02M1_Handler.DecimationFactor=128;
   X_NUCLEO_CCA02M1_Handler.PdmBufferSize=256;
   break;
}
  case AUDIOFREQ_16K:
{
   X_NUCLEO_CCA02M1_Handler.DecimationFactor=64;
   X_NUCLEO_CCA02M1_Handler.PdmBufferSize=256;
   break;
}
  case AUDIOFREQ_32K:
{
   X_NUCLEO_CCA02M1_Handler.DecimationFactor=64;
   X_NUCLEO_CCA02M1_Handler.PdmBufferSize=512;

   break;
}
  case AUDIOFREQ_48K:
{
   X_NUCLEO_CCA02M1_Handler.DecimationFactor=64;
   X_NUCLEO_CCA02M1_Handler.PdmBufferSize=768;

   break;
}
  default:
{
   return AUDIO_ERROR;
}
  }

  /* Initialize the hAudioInI2s Instance parameter */
  hAudioInI2s.Instance       = AUDIO_IN_I2S_INSTANCE;

if(X_NUCLEO_CCA02M1_Handler.MicChannels==1)
  {
hAudioInI2s.Init.DataFormat = I2S_DATAFORMAT_16B;
  }
  else
  {
hAudioInI2s.Init.DataFormat = I2S_DATAFORMAT_32B;
  }

  if(AudioFreq == AUDIOFREQ_8K)
  {
hAudioInI2s.Init.AudioFreq = 4 * AudioFreq;
  }else
  {
hAudioInI2s.Init.AudioFreq = 2 * AudioFreq;
  }

  hAudioInI2s.Init.CPOL       = I2S_CPOL_LOW;
  hAudioInI2s.Init.MCLKOutput = I2S_MCLKOUTPUT_DISABLE;
  hAudioInI2s.Init.Mode       = I2S_MODE_MASTER_RX;
  hAudioInI2s.Init.Standard    = I2S_STANDARD_MSB;

  /* Initialize the I2S peripheral with the structure above */
  if(HAL_I2S_GetState(&hAudioInI2s) == HAL_I2S_STATE_RESET)
  {
AUDIO_IN_I2S_MspInit();
  }

  if(HAL_I2S_Init(&hAudioInI2s) != HAL_OK)
  {
return AUDIO_ERROR;
  }

}

static void AUDIO_IN_I2S_MspInit(void)
{
  static DMA_HandleTypeDef hdma_i2sRx;
  GPIO_InitTypeDef  GPIO_InitStruct;
  I2S_HandleTypeDef *hi2s = &hAudioInI2s;

/* Enable the I2S2 peripheral clock */
  AUDIO_IN_I2S_CLK_ENABLE();

__HAL_RCC_AFIO_CLK_ENABLE();

  /* Enable I2S GPIO clocks */
  AUDIO_IN_I2S_SCK_GPIO_CLK_ENABLE();
  AUDIO_IN_I2S_MOSI_GPIO_CLK_ENABLE();

GPIO_InitStruct.Pin = GPIO_PIN_13; // AUDIO_IN_I2S_SCK_PIN
GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;  // GPIO_SPEED_FREQ_HIGH;
HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);

GPIO_InitStruct.Pin = GPIO_PIN_15; /// AUDIO_IN_I2S_MOSI_PIN
GPIO_InitStruct.Mode = GPIO_MODE_INPUT;
GPIO_InitStruct.Pull = GPIO_NOPULL;
HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);

  /* Enable the DMA clock */
  AUDIO_IN_I2S_DMAx_CLK_ENABLE();

  hdma_i2sRx.Init.Direction = DMA_PERIPH_TO_MEMORY;       /* M2M transfer mode             */
  hdma_i2sRx.Init.PeriphInc = DMA_PINC_DISABLE;             /* Peripheral increment mode Enable */
  hdma_i2sRx.Init.MemInc = DMA_MINC_ENABLE;                /* Memory increment mode Enable    */
  hdma_i2sRx.Init.PeriphDataAlignment = AUDIO_IN_I2S_DMAx_PERIPH_DATA_SIZE; /* Peripheral data alignment : Word */
  hdma_i2sRx.Init.MemDataAlignment = AUDIO_IN_I2S_DMAx_MEM_DATA_SIZE; /* memory data alignment : Word    */
  hdma_i2sRx.Init.Mode = DMA_CIRCULAR;                      /* Normal DMA mode                */
  hdma_i2sRx.Init.Priority = DMA_PRIORITY_HIGH;             /* priority level : high          */

  if(hi2s->Instance == AUDIO_IN_I2S_INSTANCE)
  {
hdma_i2sRx.Instance = DMA1_Channel4;
   /* Configure the DMA Stream */
HAL_DMA_Init(&hdma_i2sRx);
/* Associate the DMA handle */
__HAL_LINKDMA(hi2s, hdmarx, hdma_i2sRx);
  }

  /* I2S DMA IRQ Channel configuration */

  HAL_NVIC_SetPriority(DMA1_Channel4_IRQn, 6, 6);
  HAL_NVIC_EnableIRQ(DMA1_Channel4_IRQn);

}