/**
  ******************************************************************************
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  * Copyright (C) Shanghai Eastsoft Microelectronics Co., Ltd. ALL rights reserved.
  *******************************************************************************
  */

<--------------------------------------------------------------------------------
Version history:
--------------------------------------------------------------------------------->
2021-12-31	V1.0.0	AE TEAM


<--------------------------------------------------------------------------------
Demo introduction:
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I2S 播放/录音

PZ-WM8978
    SPI0 I2S0
        SDA (放音)  --- PB5   [I2S_SD   = SPI0_MOSI]
        SDB (录音)  --- PB5   [I2S_SD   = SPI0_MOSI]
        SCKA        --- PD3   [I2S_CK   = SPI0_SCK ]
        MCLKA       --- PB4   [I2S_MCLK = SPI0_MISO]
        FSA         --- PA4   [I2S_WS   = SPI0_NSS ]
    I2C
        IIC_SCL     --- PB6   [I2C0_SCL]
        IIC_SDA     --- PB7   [I2C0_SDA]

PC的USB口 --- 开发板的USB_OTG接口
在例程中，MCU作为USB复合设备:扬声器和麦克风。但不支持同时放音和录音。
放音时的连接方式：PZ-WM8978模块_SDA (放音)  --- MCU_PB5
录音时的连接方式：PZ-WM8978模块_SDB (录音)  --- MCU_PB5
<--------------------------------------------------------------------------------
System clock:
--------------------------------------------------------------------------------->
External HOSC[12MHz] divided by 3, then PLL to 72MHz.

<--------------------------------------------------------------------------------
Pin connection: 
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I2C0_SCL   ---- (PB6, GPIO_FUNC_5)
I2C0_SDA   ---- (PB7, GPIO_FUNC_5)
I2S0_LRCK  ---- (PA4, GPIO_FUNC_6)
I2S0_SCLK  ---- (PD3, GPIO_FUNC_4)
I2S0_SD    ---- (PB5, GPIO_FUNC_4)
I2S0_MCLK  ---- (PB4, GPIO_FUNC_4)
UART2_TX   ---- (PE2, GPIO_FUNC_3)
UART2_RX   ---- (PE3, GPIO_FUNC_3)
