STM32F4 DMA+空闲中断 不能每次都进空闲中断 求原因

void USART3_Configuration(void)    // 串口配置函数

{

   GPIO_InitTypeDef GPIO_InitStructure;      

   NVIC_InitTypeDef NVIC_InitStructure;

   USART_InitTypeDef USART_InitStructure;  



   RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOC,ENABLE); //使能GPIOC时钟

  RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART3,ENABLE);//使能USART3时钟，挂在APB1上



    GPIO_PinAFConfig(GPIOC,GPIO_PinSource10,GPIO_AF_USART3); //GPIOC10复用USART3_TX

    GPIO_PinAFConfig(GPIOC,GPIO_PinSource11,GPIO_AF_USART3); //GPIOC11复用USART3_RX

//发送TXPIN  

    GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;  

     GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;  

     GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;  

     GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;  

     GPIO_Init(GPIOC, &GPIO_InitStructure);  

//接收RXPIN  

     GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;  

     GPIO_InitStructure.GPIO_Pin = GPIO_Pin_11;  

     GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL; //上拉   

     GPIO_Init(GPIOC, &GPIO_InitStructure);



    USART_InitStructure.USART_BaudRate = 115200;//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;//1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_Tx | USART_Mode_Rx; //收发模式

   USART_Init(USART3, &USART_InitStructure); //初始化串口3

   USART_ITConfig(USART3, USART_IT_IDLE, ENABLE);

   USART_DMACmd(USART3, USART_DMAReq_Rx, ENABLE);



  NVIC_InitStructure.NVIC_IRQChannel = USART3_IRQn; //串口3中断通道

  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority=3;//抢占优先级2

  NVIC_InitStructure.NVIC_IRQChannelSubPriority =3;  //子优先级0

  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;   //IRQ通道使能

  NVIC_Init(&NVIC_InitStructure); //根据指定的参数初始化VIC寄存器

  USART_Cmd(USART3, ENABLE);  //使能串口3

}



void DMA_Usart_Init()

{

  DMA_InitTypeDef DMA_InitStructure;

   RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA1, ENABLE); // 开启DMA1时钟

DMA_InitStructure.DMA_Channel =  DMA_Channel_4;    //外设的接收通道

  DMA_InitStructure.DMA_PeripheralBaseAddr =  (int32_t)&USART3->DR; //source  buf

  DMA_InitStructure.DMA_Memory0BaseAddr = (int32_t)&USART3_R_BUF; //target buf

  DMA_InitStructure.DMA_DIR =  DMA_DIR_PeripheralToMemory;  //外设寄存器 -> 内存缓冲区?

  DMA_InitStructure.DMA_BufferSize = 18;  //BuffSize;

  DMA_InitStructure.DMA_PeripheralInc =  DMA_PeripheralInc_Disable;

  DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;

  DMA_InitStructure.DMA_PeripheralDataSize =   DMA_PeripheralDataSize_Byte;

  DMA_InitStructure.DMA_MemoryDataSize =  DMA_MemoryDataSize_Byte;

  DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;//DMA_Mode_Circular;  //DMA_Mode_Normal; //接收设计为循环收，否则接收一次后，无法正常接收到数据

  DMA_InitStructure.DMA_Priority = DMA_Priority_High;

  

  DMA_InitStructure.DMA_FIFOMode =  DMA_FIFOMode_Disable;

  DMA_InitStructure.DMA_FIFOThreshold = DMA_FIFOThreshold_HalfFull; //指定FIFO阈值水平

//  DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;

  DMA_InitStructure.DMA_MemoryBurst =  DMA_MemoryBurst_Single;// DMA_MemoryBurst_Single;      //指定Burst转移配置内存传输，单次传输

  DMA_InitStructure.DMA_PeripheralBurst = DMA_PeripheralBurst_Single; // 指定的burst转移配置外围转移

  

  DMA_Init(DMA1_Stream1,  &DMA_InitStructure);

  DMA_Cmd(DMA1_Stream1, ENABLE);

}



void USART3_IRQHandler(void)

{



      uint32_t temp = 0;  

       uint16_t i = 0;

       unsigned char r = 0;   

if((USART_GetFlagStatus(USART3,USART_IT_IDLE)) != RESET)

  {

   DMA_Cmd(DMA1_Stream1, DISABLE);

   temp = USART3->SR;  

   temp = USART3->DR;

   i = 16 - DMA_GetCurrDataCounter(DMA1_Stream1);

   DMA_ClearFlag(DMA1_Stream1,DMA_FLAG_TCIF1 | DMA_FLAG_FEIF1 | DMA_FLAG_DMEIF1 | DMA_FLAG_TEIF1 | DMA_FLAG_HTIF1);//清除DMA1_Steam1传输完成标志

    DMA_SetCurrDataCounter(DMA1_Stream1, 16);

     receive_flag = 1; //????????1DMA_Cmd(DMA1_Stream1, ENABLE);

  }

}