1、蓝桥杯嵌入式开发板串口USART2占用PA2、3
在嵌入式设计与开发\STM32固件库v3.5\STM32F10x_StdPeriph_Lib_V3.5.0\Project\STM32F10x_StdPeriph_Examples\USART\Interrupt\main函数复制初始化函数

```css
void usart_init(void)
{
 
   GPIO_InitTypeDef GPIO_InitStructure;    
   USART_InitTypeDef USART_InitStructure;

  RCC_APB2PeriphClockCmd( RCC_APB2Periph_GPIOA|RCC_APB2Periph_GPIOF , ENABLE);
  RCC_APB2PeriphClockCmd( RCC_APB1Periph_USART2 , ENABLE);
						  
  /* Configure USARTy Rx as input floating */
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_3;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
  GPIO_Init(GPIOA, &GPIO_InitStructure);
  
  /* Configure USARTy Tx as alternate function push-pull */
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
  GPIO_Init(GPIOA, &GPIO_InitStructure);
 
  USART_InitStructure.USART_BaudRate = 119200;
  USART_InitStructure.USART_WordLength = USART_WordLength_8b;
  USART_InitStructure.USART_StopBits = USART_StopBits_1;
  USART_InitStructure.USART_Parity = USART_Parity_No;
  USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
  USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;

  /* Configure USARTy */
  USART_Init(USART2, &USART_InitStructure);
 
  /* Enable USARTy Receive and Transmit interrupts */
  USART_ITConfig(USART2, USART_IT_RXNE, ENABLE);
  USART_ITConfig(USART2, USART_IT_TXE, ENABLE);//按需求填

  /* Enable the USARTz */
  USART_Cmd(USART2, ENABLE);

}

2、编写发送和接收函数
复制嵌入式设计与开发\STM32固件库v3.5\STM32F10x_StdPeriph_Lib_V3.5.0\Project\STM32F10x_StdPeriph_Examples\USART\Printf的

```css
PUTCHAR_PROTOTYPE
{
  /* Place your implementation of fputc here */
  /* e.g. write a character to the USART */
  USART_SendData(EVAL_COM1, (uint8_t) ch);

  /* Loop until the end of transmission */
  while (USART_GetFlagStatus(EVAL_COM1, USART_FLAG_TC) == RESET)
  {}

  return ch;
}

更改为（注意是USART_FLAG_TXE）这个最好记住、有时候改动格式会乱

void send_data(uint8_t *str)
{
    uint8_t index = 0;
    
    do
    {
        USART_SendData(USART2,str[index]);
        while(USART_GetFlagStatus(USART2,USART_FLAG_TXE) == RESET);
        index++;        
    }
    while(str[index] != 0);  //?ì2é×?·?′??áê?±ê??
    
}

3、测试，主函数加入

 USART_SendString("Welcome to GXCT\r\n");

串口调试助手可收到

二、蜂鸣器（PB4重映射）
第十一届蓝桥杯大赛个人赛（电子类）模拟题\嵌入式设计与开发\STM32固件库v3.5\STM32F10x_StdPeriph_Lib_V3.5.0\Project\STM32F10x_StdPeriph_Examples\GPIO\JTAG_Remap
复制

 STM_EVAL_LEDOn(LED1);

    /* Disable the Serial Wire Jtag Debug Port SWJ-DP */
    GPIO_PinRemapConfig(GPIO_Remap_SWJ_Disable, ENABLE);

    /* Configure PA.13 (JTMS/SWDAT), PA.14 (JTCK/SWCLK) and PA.15 (JTDI) as 
       output push-pull */
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_13 | GPIO_Pin_14 | GPIO_Pin_15;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
    GPIO_Init(GPIOA, &GPIO_InitStructure);

    /* Configure PB.03 (JTDO) and PB.04 (JTRST) as output push-pull */
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_3 | GPIO_Pin_4;
    GPIO_Init(GPIOB, &GPIO_InitStructure);
   

修改为PB4、配置端口复用时钟和重映射、GPIO_Mode_Out_PP改为GPIO_Mode_Out_PP

 void beep_init(void)
{
   
  GPIO_InitTypeDef GPIO_InitStructure;    
  RCC_APB2PeriphClockCmd( RCC_APB2Periph_GPIOB|RCC_APB2Periph_AFIO , ENABLE);
  GPIO_PinRemapConfig(GPIO_Remap_SWJ_NoJTRST, ENABLE);

  /* Configure USARTy Tx as alternate function push-pull */
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_4;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
  GPIO_Init(GPIOB, &GPIO_InitStructure);
   
  GPIO_SetBits(GPIOB,GPIO_Pin_4);	//不响	 
}

2、主函数调用

    GPIO_SetBits(GPIOB,GPIO_Pin_4);//不响
	Delay_Ms(4000);
   	GPIO_ResetBits(GPIOB,GPIO_Pin_4);//响
	Delay_Ms(1000);