void uart_init(u32 bound){
   //GPIO端口设置
    GPIO_InitTypeDef GPIO_InitStructure;
        USART_InitTypeDef USART_InitStructure;
    //NVIC_InitTypeDef NVIC_InitStructure;
       
        RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA,ENABLE); //使能GPIOA时钟
        RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1,ENABLE);//使能USART1时钟

        //串口1对应引脚复用映射
        GPIO_PinAFConfig(GPIOA,GPIO_PinSource9,GPIO_AF_USART1); //GPIOA9复用为USART1
        GPIO_PinAFConfig(GPIOA,GPIO_PinSource10,GPIO_AF_USART1); //GPIOA10复用为USART1
       
        //USART1端口配置
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9 | GPIO_Pin_10; //GPIOA9与GPIOA10
        GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;//复用功能
        GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;        //速度50MHz
        GPIO_InitStructure.GPIO_OType = GPIO_OType_PP; //推挽复用输出
        GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP; //上拉
        GPIO_Init(GPIOA,&GPIO_InitStructure); //初始化PA9，PA10

   //USART1 初始化设置
        USART_InitStructure.USART_BaudRate = bound;//波特率设置
        USART_InitStructure.USART_WordLength = USART_WordLength_8b;//字长为8位数据格式
        USART_InitStructure.USART_StopBits = USART_StopBits_1;//一个停止位
        USART_InitStructure.USART_Parity = USART_Parity_No;//无奇偶校验位
        USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;//无硬件数据流控制
        USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;        //收发模式
    USART_Init(USART1, &USART_InitStructure); //初始化串口1
       
        USART_ITConfig(USART1, USART_IT_IDLE, ENABLE);//开启相关中断
    USART_ITConfig(USART1, USART_IT_RXNE, ENABLE);        /* 使能接收中断 */
       
        USART_Cmd(USART1, ENABLE);  //使能串口1
       
        //USART_ClearFlag(USART1, USART_FLAG_TC);
       
}

void MYDMA_Config(DMA_Stream_TypeDef *DMA_Streamx,u32 chx,u32 par,u32 mar,u16 ndtr)
{
    NVIC_InitTypeDef NVIC_InitStructure;
        DMA_InitTypeDef  DMA_InitStructure;
       

    /* CPU的小缺陷：串口配置好，如果没法直接Send，则第一个字节发送不出去
        如下语句解决第一个字节无法正确发送出去的问题 */
        USART_ClearFlag(USART1, USART_FLAG_TC);         /*清发送完成标志，Transmission Complete flag */

        /****        DMA ****配置***********/
        USART_DMACmd(USART1,USART_DMAReq_Tx,ENABLE);  //使能串口1的DMA发送
        USART_DMACmd(USART1,USART_DMAReq_Rx,ENABLE);  //使能串口1的DMA接收
       
    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA2,ENABLE);//DMA2时钟使能
               
       
    DMA_DeInit(DMA2_Stream7);
        while (DMA_GetCmdStatus(DMA2_Stream7) != DISABLE){}//等待DMA可配置
        /* 配置 DMA Stream */
        DMA_InitStructure.DMA_Channel = DMA_Channel_4;  //通道选择
        DMA_InitStructure.DMA_PeripheralBaseAddr = (u32)&USART1->DR;//DMA外设地址
        DMA_InitStructure.DMA_Memory0BaseAddr = (u32)COM1_SendBuff;//DMA 存储器0地址
        DMA_InitStructure.DMA_DIR = DMA_DIR_MemoryToPeripheral;//存储器到外设模式
        DMA_InitStructure.DMA_BufferSize = COM1_SEND_BUF_SIZE;//数据传输量
        DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;//外设非增量模式
        DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;//存储器增量模式
        DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;//外设数据长度:8位
        DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte;//存储器数据长度:8位
        DMA_InitStructure.DMA_Mode = DMA_Mode_Normal;// 使用普通模式
        DMA_InitStructure.DMA_Priority = DMA_Priority_Medium;//中等优先级
        DMA_InitStructure.DMA_FIFOMode = DMA_FIFOMode_Disable;         
        DMA_InitStructure.DMA_FIFOThreshold = DMA_FIFOThreshold_Full;
        DMA_InitStructure.DMA_MemoryBurst = DMA_MemoryBurst_Single;//存储器突发单次传输
        DMA_InitStructure.DMA_PeripheralBurst = DMA_PeripheralBurst_Single;//外设突发单次传输
        DMA_Init(DMA_Streamx, &DMA_InitStructure);//初始化DMA Stream
        DMA_ITConfig(DMA2_Stream7,DMA_IT_TC,ENABLE);

        //****************************配置UART1接收
        DMA_DeInit(DMA2_Stream5);
        while (DMA_GetCmdStatus(DMA2_Stream5) != DISABLE);//等待DMA配置
        /* 配置 DMA Stream */
        DMA_InitStructure.DMA_Channel = DMA_Channel_4;        //选择通道
        DMA_InitStructure.DMA_PeripheralBaseAddr = (u32)&USART1->DR;//DMA外设地址
        DMA_InitStructure.DMA_Memory0BaseAddr = (u32)COM1_ReceiveBuff;//DMA存储器0地址
        DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralToMemory ;//外设到存储器模式
        DMA_InitStructure.DMA_BufferSize = COM1_RECEIVE_BUF_SIZE;//数据传输量
        DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;//外设非增量模式
        DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;//存储器模式
        DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;//外设数据位长度
        DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte;//存储器数据位长度
        DMA_InitStructure.DMA_Mode = DMA_Mode_Normal;// 使用普通模式
        DMA_InitStructure.DMA_Priority = DMA_Priority_Medium;//中等优先级
        DMA_InitStructure.DMA_FIFOMode = DMA_FIFOMode_Disable;                  
        DMA_InitStructure.DMA_FIFOThreshold = DMA_FIFOThreshold_Full;
        DMA_InitStructure.DMA_MemoryBurst = DMA_MemoryBurst_Single;  //存储器突发单词传输
        DMA_InitStructure.DMA_PeripheralBurst = DMA_PeripheralBurst_Single;//外设突发单词传输
        DMA_Init(DMA2_Stream5, &DMA_InitStructure);//初始化DMA Stream
        DMA_Cmd(DMA2_Stream5, ENABLE);        //开始DMA传输
        DMA_ITConfig(DMA2_Stream5,DMA_IT_TC,ENABLE);
    DMA_ClearITPendingBit(DMA2_Stream5, DMA_IT_TCIF5);      //清标志


        /*********************DMA NVIC        ***************************************************/

        NVIC_PriorityGroupConfig(NVIC_PriorityGroup_0);
        //DMA NVIC
        NVIC_InitStructure.NVIC_IRQChannel = DMA2_Stream7_IRQn;  
        NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1;  
        NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;       
        NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;  
        //DMA NVIC       
        NVIC_Init(&NVIC_InitStructure);  
        NVIC_InitStructure.NVIC_IRQChannel = DMA2_Stream5_IRQn;  
        NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1;  
        NVIC_InitStructure.NVIC_IRQChannelSubPriority = 4;       
        NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;  
        NVIC_Init(&NVIC_InitStructure);  

        /*DMA_usart1 */
        NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQn;
        NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1;
        NVIC_InitStructure.NVIC_IRQChannelSubPriority = 6;

        NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
        NVIC_Init(&NVIC_InitStructure);
}



void USART1_IRQHandler(void)                        //串口1中断服务程序
{
        u16 data;
        u8 Res;
   if(USART_GetITStatus(USART1,USART_IT_IDLE) != RESET)
   {
                DMA_Cmd(DMA2_Stream5, DISABLE); //关闭DMA，防止处理其间数据
                data = USART1->SR;
                data = USART1->DR;
                //USART_ClearFlag(USART1,USART_IT_IDLE);
                UART1_ReceiveSize = 32-DMA_GetCurrDataCounter(DMA2_Stream5);
            Res=COM1_ReceiveBuff[0];
          
                DMA_ClearFlag(DMA2_Stream5,DMA_FLAG_TCIF5 | DMA_FLAG_FEIF5 | DMA_FLAG_DMEIF5 | DMA_FLAG_TEIF5 | DMA_FLAG_HTIF5);//清除DMA2_Steam7传输标志
                DMA_SetCurrDataCounter(DMA2_Stream5, 32);
                DMA_Cmd(DMA2_Stream5, ENABLE);     //打开DMA
   }

}


只能中断一次，第二次进入不了，是什么问题呢