PDM

PDM (Pulse Density Modulation)模塊是用于將外部pdm麥克風(fēng)輸出的pdm信號進(jìn)行濾波轉(zhuǎn)化為PCM信號并提供給CPU進(jìn)行后續(xù)的處理.

支持的配置

• 單聲道(左/右), 立體聲
• 采樣率 8/12/16//24/32/48KHz
• 24bit 采樣深度
• 左右聲道 增益調(diào)節(jié)
• 循環(huán)buffer/ 單次buffer

輸出數(shù)據(jù)格式

• 8bit + 單聲道
• 16bit + 單聲道
• 32bit + 單聲道 : 高8位為0, 實(shí)際有效數(shù)據(jù)為低24bit
• 16bit + 雙聲道 : 左右聲道各占16bit組成一個(gè)32bit數(shù)據(jù)(支持左右聲道對換)
• 32bit + 雙聲道 : 僅支持左右聲道分開2個(gè)buffer存儲

示例

PDM1單聲道16KHz , 16bit位深，用DMA讀取1024字節(jié)數(shù)據(jù)

static PDM_HandleTypeDef PDM_Handle = {0};
static DMA_HandleTypeDef DMA_Handle = {0};
static uint32_t DMA_cplt_flag = 0;
 
void DMAC1_CH3_IRQHandler(void)
{
    HAL_DMA_IRQHandler(PDM_Handle.hdmarx);
}
 
 
 
void HAL_PDM_RxCpltCallback(PDM_HandleTypeDef *hpdm)
{
    if(hpdm == &PDM_Handle)
        DMA_cplt_flag = 1;
}
 
 
void pdm_recieve(void)
{
 
    DMA_Handle.Instance = DMA1_Channel3;
    DMA_Handle.Init.Request = DMA_REQUEST_18;
 
 
    PDM_Handle.hdmarx = &DMA_Handle;
    PDM_Handle.Instance = hwp_pdm1;
    PDM_Handle.Init.Mode = PDM_MODE_LOOP; //Ring buffer mode
    PDM_Handle.Init.Channels = PDM_CHANNEL_LEFT_ONLY;
    PDM_Handle.Init.SampleRate = PDM_SAMPLE_16KHZ;
    PDM_Handle.Init.ChannelDepth = PDM_CHANNEL_DEPTH_16BIT;
    PDM_Handle.RxXferSize = 1024;
    PDM_Handle.pRxBuffPtr = (uint8_t *) 0x2000c000;
    
 
 
    HAL_PDM_Init(&PDM_Handle);
    HAL_NVIC_EnableIRQ(DMAC1_CH3_IRQn);
 
 
    HAL_PDM_Receive_DMA(&PDM_Handle, PDM_Handle.pRxBuffPtr, PDM_Handle.RxXferSize);
 
    while(DMA_cplt_flag == 0);
 
 
    HAL_NVIC_DisableIRQ(DMAC1_CH3_IRQn);
    HAL_PDM_DMAStop(&PDM_Handle);
    HAL_PDM_DeInit(&PDM_Handle);
}
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