文章目录
- 一、硬件原理
- 二、STM32CubeMX配置
- 2.1 RCC
- 2.2 SYS
- 2.3 I2C1
- 2.4 USART1
- 2.5 USB_OTG_FS
- 2.6 I2S2
- 2.7 USB_DEVICE
- 2.8 Clock Configuration
- 2.9 Project Manager
- 2.10 生成代码
- 三、代码完善
- 3.1 WM8978
- 3.2 usbd_audio_if
- 四、程序流程图
- 4.1 初始化流程
- 4.2 播放流程
一、硬件原理
基于正点原子STM32F407探索者开发板，其中音频部分硬件原理图如下
其中WM8978是一款全功能音频处理器，STM32通过控制WM8978即可实现扬声器/喇叭的音频播放，麦克风的音频录制等功能。
主要控制两个接口
- IIC控制接口，实现WM8978寄存器的读写
- I2S数字音频接口，实现音频数据传输（接收和发送）
二、STM32CubeMX配置
2.1 RCC
开发板外接了两个晶振
- 8MHz的高速晶振
- 32.768kHz的低速晶振
2.2 SYS
Debug Serial Wire
2.3 I2C1
- GPIO口是PB8/PB9
2.4 USART1
- 用来打印调试日志，波特率调到1000000，加快日志打印
- Data Direction: Transmit Only
- DMA Settings: USART1_TX
- PA9 / PA10
2.5 USB_OTG_FS
- Mode:Device Only
- global interrupt 勾选
2.6 I2S2
- mode: Full-Duplex Master
- Audio Frequency: 48KHz
- DMA Setting: SPI2_TX / I2S2_EXT_RX
- GPIO Setting
2.7 USB_DEVICE
- Class For FS IP: Audio Device Class
- USBD_AUDIO_FREQ: 48000 sample/s
- 描述符有些部分可以自定义
2.8 Clock Configuration
2.9 Project Manager
- 堆栈调大0x4000
2.10 生成代码
- 右上角
GENERATE CODE
3.1 WM8978
main.c
main函数增加WM8978_Init();
int main(void)
{
HAL_Init();
SystemClock_Config();
MX_GPIO_Init();
MX_DMA_Init();
MX_I2C1_Init();
MX_I2S2_Init();
MX_USART1_UART_Init();
MX_USB_DEVICE_Init();
WM8978_Init();
while (1)
{
}
}wm8978.c
#define DEVICE_ADDRESS 0x1A
#define WIRTE_ADDRESS (DEVICE_ADDRESS << 1 | 0)
extern I2C_HandleTypeDef hi2c1;
uint8_t WM8978_Write(uint8_t reg_addr, uint16_t data)
{
uint8_t pData[10] = { 0 };
pData[0] = (reg_addr << 1) | ((data >> 8) & 0x01);
pData[1] = data & 0xFF;
return HAL_I2C_Master_Transmit(&hi2c1, WIRTE_ADDRESS, pData, 2, 1000);
}
uint32_t WM8978_Init(void)
{
WM8978_Reset();
WM8978_Write(1, 0x0F); // 模拟放大器使能， 使能输出输入缓存区
WM8978_Write(3, 0x7F); // 使能左右声道和L\ROUT2
WM8978_Write(4, 0x10); // I2S 16bit
WM8978_Write(6, 0x00); // MCU提供时钟
WM8978_Write(10, 0x08); // 输出音质最好
WM8978_Write(43, 0x10); // ROUT2反相
WM8978_VolumeCtl(0x3F);
return 0;
}
uint32_t WM8978_Reset(void)
{
if(WM8978_Write(0, 0)!= HAL_OK)// 软复位
return 1;
HAL_Delay(10);
return 0;
}3.2 usbd_audio_if
AUDIO_AudioCmd_FS中对应AUDIO_CMD_START、AUDIO_CMD_PLAY和AUDIO_CMD_STOP的操作HAL_I2S_TxCpltCallback对应传输完成的USB同步操作
extern I2S_HandleTypeDef hi2s2;
/**
* @brief Handles AUDIO command.
* @param pbuf: Pointer to buffer of data to be sent
* @param size: Number of data to be sent (in bytes)
* @param cmd: Command opcode
* @retval USBD_OK if all operations are OK else USBD_FAIL
*/
static int8_t AUDIO_AudioCmd_FS(uint8_t* pbuf, uint32_t size, uint8_t cmd)
{
switch(cmd)
{
case AUDIO_CMD_START:
HAL_I2S_Transmit_DMA(&hi2s2, (uint16_t*)pbuf, size);
break;
case AUDIO_CMD_PLAY:
HAL_I2S_Transmit_DMA(&hi2s2, (uint16_t*)pbuf, size);
break;
case AUDIO_CMD_STOP:
HAL_I2S_DMAStop(&hi2s2);
break;
}
return (USBD_OK);
}
void HAL_I2S_TxHalfCpltCallback(I2S_HandleTypeDef *hi2s)
{
HalfTransfer_CallBack_FS();
}
void HAL_I2S_TxCpltCallback(I2S_HandleTypeDef *hi2s)
{
TransferComplete_CallBack_FS();
}4.1 初始化流程
main
hal库
stm32f4xx_hal_map
wx8978
usb_device
STM32_USB_DEVICE_Library
HAL_Init()
SystemClock_Config()
HAL_Delay(100)
MX_GPIO_Init()
MX_DMA_Init()
MX_I2C1_Init()
HAL_I2C_Init()
HAL_I2C_MspInit()
MX_I2S2_Init()
HAL_I2S_Init()
HAL_I2S_MspInit()
WM8978_Init()
MX_USB_DEVICE_Init()
USBD_Init(&hUsbDeviceFS, &FS_Desc, DEVICE_FS)
USBD_RegisterClass(&hUsbDeviceFS, &USBD_AUDIO)
USBD_AUDIO_RegisterInterface(&hUsbDeviceFS, &USBD_AUDIO_fops_FS)
USBD_Start(&hUsbDeviceFS)
HAL_Delay(100)
while(1)
main
hal库
stm32f4xx_hal_map
wx8978
usb_device
STM32_USB_DEVICE_Library
4.2 播放流程
STM32_USB_DEVICE_Library
usbd_audio_if
hal库
AudioCmd(uint8_t *pbuf, uint32_t size, uint8_t cmd)
HAL_I2S_Transmit_DMA
STM32_USB_DEVICE_Library
usbd_audio_if
hal库
