STM32 I2S单声道音频数据PCM解码C代码示例

以下是一个简单的示例代码，用于将I2S单声道音频数据解码为PCM格式：

#include "stm32f4xx.h"

#define I2S_BUFFER_SIZE 256

uint16_t I2S_Buffer[I2S_BUFFER_SIZE];
uint16_t PCM_Buffer[I2S_BUFFER_SIZE * 2];

int main(void)
{
    // 初始化I2S
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_SPI3, ENABLE);

    GPIO_InitTypeDef GPIO_InitStruct;
    SPI_InitTypeDef SPI_InitStruct;

    GPIO_InitStruct.GPIO_Pin = GPIO_Pin_3 | GPIO_Pin_5 | GPIO_Pin_7;
    GPIO_InitStruct.GPIO_Mode = GPIO_Mode_AF;
    GPIO_InitStruct.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_InitStruct.GPIO_OType = GPIO_OType_PP;
    GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_NOPULL;
    GPIO_Init(GPIOB, &GPIO_InitStruct);

    GPIO_PinAFConfig(GPIOB, GPIO_PinSource3, GPIO_AF_SPI3);
    GPIO_PinAFConfig(GPIOB, GPIO_PinSource5, GPIO_AF_SPI3);
    GPIO_PinAFConfig(GPIOB, GPIO_PinSource7, GPIO_AF_SPI3);

    SPI_InitStruct.SPI_Direction = SPI_Direction_2Lines_FullDuplex;
    SPI_InitStruct.SPI_Mode = SPI_Mode_Master;
    SPI_InitStruct.SPI_DataSize = SPI_DataSize_16b;
    SPI_InitStruct.SPI_CPOL = SPI_CPOL_High;
    SPI_InitStruct.SPI_CPHA = SPI_CPHA_2Edge;
    SPI_InitStruct.SPI_NSS = SPI_NSS_Soft;
    SPI_InitStruct.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_2;
    SPI_InitStruct.SPI_FirstBit = SPI_FirstBit_MSB;
    SPI_InitStruct.SPI_CRCPolynomial = 0;
    SPI_Init(SPI3, &SPI_InitStruct);

    SPI_Cmd(SPI3, ENABLE);

    // 初始化DMA
    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA1, ENABLE);

    DMA_InitTypeDef DMA_InitStruct;

    DMA_StructInit(&DMA_InitStruct);

    DMA_InitStruct.DMA_Channel = DMA_Channel_0;
    DMA_InitStruct.DMA_PeripheralBaseAddr = (uint32_t)&SPI3->DR;
    DMA_InitStruct.DMA_Memory0BaseAddr = (uint32_t)I2S_Buffer;
    DMA_InitStruct.DMA_DIR = DMA_DIR_PeripheralToMemory;
    DMA_InitStruct.DMA_BufferSize = I2S_BUFFER_SIZE;
    DMA_InitStruct.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
    DMA_InitStruct.DMA_MemoryInc = DMA_MemoryInc_Enable;
    DMA_InitStruct.DMA_PeripheralDataSize = DMA_PeripheralDataSize_HalfWord;
    DMA_InitStruct.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord;
    DMA_InitStruct.DMA_Mode = DMA_Mode_Circular;
    DMA_InitStruct.DMA_Priority = DMA_Priority_High;
    DMA_InitStruct.DMA_FIFOMode = DMA_FIFOMode_Disable;
    DMA_InitStruct.DMA_FIFOThreshold = DMA_FIFOThreshold_HalfFull;
    DMA_InitStruct.DMA_MemoryBurst = DMA_MemoryBurst_Single;
    DMA_InitStruct.DMA_PeripheralBurst = DMA_PeripheralBurst_Single;
    DMA_Init(DMA1_Stream0, &DMA_InitStruct);

    DMA_Cmd(DMA1_Stream0, ENABLE);

    // 开始I2S传输
    SPI_I2S_DMACmd(SPI3, SPI_I2S_DMAReq_Rx, ENABLE);
    SPI_I2S_ITConfig(SPI3, SPI_I2S_IT_RXNE, ENABLE);

    // 开始解码
    while (1)
    {
        for (int i = 0; i < I2S_BUFFER_SIZE; i++)
        {
            // 将I2S数据从16位转换为有符号的PCM数据（16位）
            int16_t pcm = (int16_t)I2S_Buffer[i] << 4;

            // 将单声道PCM数据复制到立体声PCM数据中
            PCM_Buffer[i * 2] = PCM_Buffer[i * 2 + 1] = pcm;
        }
    }
}

void SPI3_IRQHandler(void)
{
    if (SPI_I2S_GetFlagStatus(SPI3, SPI_I2S_FLAG_RXNE))
    {
        SPI_I2S_ClearFlag(SPI3, SPI_I2S_FLAG_RXNE);
    }
}

上述代码使用STM32的DMA和中断机制从I2S接口读取音频数据，并将其解码为PCM格式。这个示例代码只使用了单声道音频数据，但是可以轻松地扩展为立体声音频数据。在这个示例中，I2S的采样率为44.1kHz，PCM数据的位深度为16位。如果需要更高的采样率或更高的位深度，则需要相应地修改代码。