Mini MP3 Player

void SystemClock_Config(void)
{
  RCC_OscInitTypeDef RCC_OscInitStruct = {0};
  RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};

  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
  RCC_OscInitStruct.HSEState       = RCC_HSE_ON;
  RCC_OscInitStruct.HSEPredivValue  = RCC_HSE_PREDIV_DIV1;
  RCC_OscInitStruct.PLL.PLLState   = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource  = RCC_PLLSOURCE_HSE;
  RCC_OscInitStruct.PLL.PLLMUL     = RCC_PLL_MUL9;  // 8MHz x 9 = 72MHz

  if(HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
    Error_Handler();

  RCC_ClkInitStruct.ClockType      = RCC_CLOCKTYPE_HCLK | RCC_CLOCKTYPE_SYSCLK
                                  | RCC_CLOCKTYPE_PCLK1 | RCC_CLOCKTYPE_PCLK2;
  RCC_ClkInitStruct.SYSCLKSource   = RCC_SYSCLKSOURCE_PLLCLK;
  RCC_ClkInitStruct.AHBCLKDivider  = RCC_SYSCLK_DIV1;   // AHB = 72MHz
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV2;      // APB1 = 36MHz
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;      // APB2 = 72MHz

  if(HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_2) != HAL_OK)
    Error_Handler();
}

void MX_GPIO_Init(void)
{
  GPIO_InitTypeDef GPIO_InitStruct = {0};

  __HAL_RCC_GPIOD_CLK_ENABLE();
  __HAL_RCC_GPIOA_CLK_ENABLE();

  /* K1(PA4) K2(PA5) K3(PA6) — 上拉输入 */
  GPIO_InitStruct.Pin   = K1_Pin | K2_Pin | K3_Pin;
  GPIO_InitStruct.Mode  = GPIO_MODE_INPUT;
  GPIO_InitStruct.Pull  = GPIO_PULLUP;
  HAL_GPIO_Init(K1_GPIO_Port, &GPIO_InitStruct);
}

UART_HandleTypeDef huart2;

void MX_USART2_UART_Init(void)
{
  huart2.Instance        = USART2;
  huart2.Init.BaudRate   = 9600;                  // DFPlayer标准波特率
  huart2.Init.WordLength  = UART_WORDLENGTH_8B;     // 8位数据
  huart2.Init.StopBits    = UART_STOPBITS_1;        // 1停止位
  huart2.Init.Parity      = UART_PARITY_NONE;      // 无校验
  huart2.Init.Mode        = UART_MODE_TX_RX;        // 收发模式
  huart2.Init.HwFlowCtl   = UART_HWCONTROL_NONE;    // 无硬件流控
  huart2.Init.OverSampling= UART_OVERSAMPLING_16;

  if(HAL_UART_Init(&huart2) != HAL_OK)
    Error_Handler();
}

/* USART2 GPIO: PA2=TX(复用推挽), PA3=RX(浮空输入) */
void HAL_UART_MspInit(UART_HandleTypeDef* uartHandle)
{
  if(uartHandle->Instance == USART2)
  {
    __HAL_RCC_USART2_CLK_ENABLE();
    __HAL_RCC_GPIOA_CLK_ENABLE();

    // PA2 → USART2_TX (复用推挽输出)
    GPIO_InitStruct.Pin   = GPIO_PIN_2;
    GPIO_InitStruct.Mode  = GPIO_MODE_AF_PP;
    GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;
    HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

    // PA3 → USART2_RX (输入)
    GPIO_InitStruct.Pin   = GPIO_PIN_3;
    GPIO_InitStruct.Mode  = GPIO_MODE_INPUT;
    GPIO_InitStruct.Pull  = GPIO_NOPULL;
    HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

    HAL_NVIC_SetPriority(USART2_IRQn, 0, 0);
    HAL_NVIC_EnableIRQ(USART2_IRQn);
  }
}

uint8_t USART2_TX_BUF[200];
#define u2_printf(...)  HAL_UART_Transmit(&huart2, USART2_TX_BUF, \
                          sprintf((char *)USART2_TX_BUF, __VA_ARGS__), 0xffff)

/*
 * 发送8字节MP3指令帧
 * CMD: 0x01=下一首  0x02=上一首  0x0D=播放  0x0E=暂停
 */
void MP3_Send(uint8_t CMD)
{
  u2_printf("%c%c%c%c%c%c%c%c", 0x7E, 0xFF, 0x06, CMD, 0x00, 0x00, 0x00, 0xEF);
}

int main(void)
{
  HAL_Init();
  SystemClock_Config();
  MX_GPIO_Init();
  MX_USART2_UART_Init();
  OLED_Init();

  while (1)
  {
    /* —— 按键检测 —— */
    if(HAL_GPIO_ReadPin(K1_GPIO_Port, K1_Pin) &&
       HAL_GPIO_ReadPin(K2_GPIO_Port, K2_Pin) &&
       HAL_GPIO_ReadPin(K3_GPIO_Port, K3_Pin))
      flag_Key = 0;  // 所有按键松开，复位消抖标志

    if(!HAL_GPIO_ReadPin(K1_GPIO_Port, K1_Pin) && !flag_Key)  // 上一首
    {
      MP3_Send(0x02);
      (song == 0) ? (song = 5) : (song--);
      Flag_Play = 1;
      flag_Key = 1;
    }

    if(!HAL_GPIO_ReadPin(K2_GPIO_Port, K2_Pin) && !flag_Key)  // 下一首
    {
      MP3_Send(0x01);
      (song == 5) ? (song = 0) : (song++);
      Flag_Play = 1;
      flag_Key = 1;
    }

    if(!HAL_GPIO_ReadPin(K3_GPIO_Port, K3_Pin) && !flag_Key)  // 播放/暂停
    {
      if(Flag_Play == 0) { Flag_Play = 1; MP3_Send(0x0D); }  // 播放
      else               { Flag_Play = 0; MP3_Send(0x0E); }  // 暂停
      flag_Key = 1;
    }

    /* —— OLED屏幕显示（50ms刷新） —— */
    if(HAL_GetTick() - Time_Now >= 50)
    {
      OLED_Clear();
      switch(song)  // 显示歌名
      {
        case 0: OLED_CenterPrintf(12, "枫");            break;
        case 1: OLED_CenterPrintf(12, "蒲公英的约定");  break;
        case 2: OLED_CenterPrintf(12, "富士山下");      break;
        case 3: OLED_CenterPrintf(12, "瞬");            break;
        case 4: OLED_CenterPrintf(12, "唯一");          break;
        case 5: OLED_CenterPrintf(12, "特别的人");      break;
      }
      if(Flag_Play == 0) OLED_CenterPrintf(36, "暂停");
      else              OLED_CenterPrintf(36, "播放");
      OLED_Update();
      Time_Now = HAL_GetTick();
    }
  }
}

#define SCL_Port  GPIOB
#define SCL_Pin   GPIO_PIN_15
#define SDA_Port  GPIOB
#define SDA_Pin   GPIO_PIN_14

/* 字体大小参数 */
#define OLED_8X16   8    // 8x16像素字体
#define OLED_6X8    6    // 6x8像素字体

void OLED_Init(void);
void OLED_Clear(void);
void OLED_Update(void);
void OLED_CenterPrintf(int16_t Y, char *format, ...);