void USART_Config()
{GPIO_InitTypeDef GPIO_InitStructure;USART_InitTypeDef USART_InitStructure;//配置串口1时钟RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1 | RCC_APB2Periph_GPIOA, ENABLE);//配置串口2时钟，使用复用功能，打开AFIO，管脚重映射到PD5，PD6
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO, ENABLE);RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART2, ENABLE);GPIO_PinRemapConfig(GPIO_Remap_USART2, ENABLE);RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOD, ENABLE);/*配置串口1（USART1 Tx(PA.09)）*/GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9;GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;GPIO_Init(GPIOA, &GPIO_InitStructure);    /* 配置串口1（USART1 Tx(PA.10)）*/GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;GPIO_Init(GPIOA, &GPIO_InitStructure);/*串口1工作模式（USART1 mode）配置 */USART_InitStructure.USART_BaudRate = 115200;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;USART_Init(USART1, &USART_InitStructure); USART_Cmd(USART1, ENABLE);//使能串口/*配置串口2（USART2 Tx(PD.05)）*/GPIO_InitStructure.GPIO_Pin = GPIO_Pin_5;GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;GPIO_Init(GPIOD, &GPIO_InitStructure);/*配置串口2（USART2 Tx(PD.05)）*/GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6;GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;GPIO_Init(GPIOD, &GPIO_InitStructure);/*串口2工作模式（USART2 mode）配置 */USART_InitStructure.USART_BaudRate = 115200;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;    USART_Init(USART2, &USART_InitStructure); USART_ITConfig(USART2, USART_IT_RXNE, ENABLE);USART_Cmd(USART2, ENABLE);NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2); /*串口2中断配置*/                                NVIC_InitStructure.NVIC_IRQChannel = USART2_IRQn;NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority =2;NVIC_InitStructure.NVIC_IRQChannelSubPriority =2;NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;NVIC_Init(&NVIC_InitStructure);
}/*printf()函数重定向*/
int fputc(int ch, FILE *f)
{//将printf()内容发往串口1USART_SendData(USART1, (unsigned char) ch);while( USART_GetFlagStatus(USART1,USART_FLAG_TC)!= SET);    return (ch);
} 

/*
* 函数名：itoa
* 描述  ：将整形数据转换成字符串
* 输入  ：-radix =10 表示10进制，其他结果为0
*         -value 要转换的整形数
*         -buf 转换后的字符串
*         -radix = 10
* 输出  ：无
* 返回  ：无
* 调用  ：被USART_printf()调用
*/
static char *itoa(int value, char *string, int radix)
{int     i, d;int     flag = 0;char    *ptr = string;/* This implementation only works for decimal numbers. */if (radix != 10){*ptr = 0;return string;}if (!value){*ptr++ = 0x30;*ptr = 0;return string;}/* if this is a negative value insert the minus sign. */if (value < 0){*ptr++ = '-';/* Make the value positive. */value *= -1;}for (i = 10000; i > 0; i /= 10){d = value / i;if (d || flag){*ptr++ = (char)(d + 0x30);value -= (d * i);flag = 1;}}/* Null terminate the string. */*ptr = 0;return string;} /*
* 函数名：USART_printf
* 描述  ：格式化输出，类似于C库中的printf，但这里没有用到C库
* 输入  ：-USARTx 串口通道
*                     -Data   要发送到串口的内容的指针
*                           -...    其他参数
* 输出  ：无
* 返回  ：无
* 调用  ：外部调用
*         典型应用USART_printf( USART1, "\r\n this is a demo \r\n" );
*                             USART_printf( USART2, "\r\n %d \r\n", i );
*                             USART_printf( USART3, "\r\n %s \r\n", j );
*/
void USART_printf(USART_TypeDef* USARTx, uint8_t *Data,...)
{const char *s;int d;   char buf[16];va_list ap;va_start(ap, Data);while ( *Data != 0)     // 判断是否到达字符串结束符
      {                                                          if ( *Data == 0x5c )  //'\'
                {                                                                          switch ( *++Data ){case 'r':                   //回车符                                                   USART_SendData(USARTx, 0x0d);Data ++;break;case 'n':                 //换行符                                                          //???USART_SendData(USARTx, 0x0a);        Data ++;break;default:Data ++;break;}                         }else if ( *Data == '%'){                                                                          //
                        switch ( *++Data ){                                case 's':                //字符串                                                                  s = va_arg(ap, const char *);for ( ; *s; s++) {USART_SendData(USARTx,*s);while( USART_GetFlagStatus(USARTx, USART_FLAG_TC) == RESET );}Data++;break;case 'd':                      //十进制                                                          d = va_arg(ap, int);itoa(d, buf, 10);for (s = buf; *s; s++) {USART_SendData(USARTx,*s);while( USART_GetFlagStatus(USARTx, USART_FLAG_TC) == RESET );}Data++;break;default:Data++;break;}                 } /* end of else if */else USART_SendData(USARTx, *Data++);while( USART_GetFlagStatus(USARTx, USART_FLAG_TC) == RESET );}
}