项目使用了串口1发送了和接收数据， 接收数据用的是中断，众所周知，在相同效果下，程序进入中断的次数越少越好。 原来有接收一张数据，8个字节，那就要进八次中断，现在使用DAM 串口接收，接收8个字节只需要进一次中断。
       
        结论：串口发送不宜使用DMA,不方便， 串口接收应考虑使用DMA。  下面贴上DMA 程序函数。
      
 void STM32_Shenzhou_COMInit(USART_InitTypeDef* USART_InitStruct)
{
GPIO_InitTypeDef GPIO_InitStructure;
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE); /* Enable GPIO clock */
RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE); /* Enable UART clock */
GPIO_PinAFConfig(GPIOA, GPIO_PinSource9, GPIO_AF_USART1); /* Connect PXx to USARTx_Tx*/

/* Connect PXx to USARTx_Rx*/
GPIO_PinAFConfig(GPIOA, GPIO_PinSource10, GPIO_AF_USART1);

/* Configure USART Tx as alternate function  */
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOA, &GPIO_InitStructure);

/* Configure USART Rx as alternate function  */
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;
GPIO_Init(GPIOA, &GPIO_InitStructure);

USART_Init(USART1, USART_InitStruct); /* USART configuration */ 
USART_Cmd(USART1, ENABLE); /* Enable USART */
while(USART_GetFlagStatus(USART1, USART_FLAG_TC)==RESET);
USART_ClearFlag(USART1,USART_FLAG_TC);
}

void Printf_Init(void)
{
USART_InitTypeDef USART_InitStructure;   
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;
STM32_Shenzhou_COMInit(&USART_InitStructure);
}

void MYDMA_Config_Rx()
{ 
DMA_InitTypeDef  DMA_InitStructure;
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA2,ENABLE);
DMA_DeInit(DMA2_Stream5);
while (DMA_GetCmdStatus(DMA2_Stream5) != DISABLE){}

DMA_InitStructure.DMA_Channel = DMA_Channel_4;  
DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)USART1_DR_ADDRESS;
DMA_InitStructure.DMA_Memory0BaseAddr = (uint32_t)Rx_Buffer;
DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralToMemory;
DMA_InitStructure.DMA_BufferSize = 5;
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_InitStructure.DMA_Priority = DMA_Priority_Medium;
DMA_InitStructure.DMA_FIFOMode = DMA_FIFOMode_Disable;         
DMA_InitStructure.DMA_FIFOThreshold = DMA_FIFOThreshold_Full;
DMA_InitStructure.DMA_MemoryBurst = DMA_MemoryBurst_Single;
DMA_InitStructure.DMA_PeripheralBurst = DMA_PeripheralBurst_Single;
DMA_Init(DMA2_Stream5, &DMA_InitStructure);//??????DMA Stream

DMA_Cmd(DMA2_Stream5, DISABLE);
DMA_ITConfig(DMA2_Stream5, DMA_IT_TC, ENABLE);  
DMA_ClearITPendingBit(DMA2_Stream5, DMA_IT_TCIF5);    

USART_DMACmd(USART1,USART_DMAReq_Rx,ENABLE); 
DMA_Cmd(DMA2_Stream5, ENABLE);
DMA_NVIC_Configuration();
} 

void USART1_TX_01 (u16 ID)
{
u8 i=0;
Tx_Buffer[i++]=0xAA;
Tx_Buffer[i++]=0x70;
Tx_Buffer[i++]=(u8)(ID>>8);
Tx_Buffer[i++]=(u8)(ID);
Tx_Buffer[i++]=0xCC;
Tx_Buffer[i++]=0x33;
Tx_Buffer[i++]=0xC3;
Tx_Buffer[i++]=0x3C;
 for(i=0;i<8;i++)
{    
USART_SendData(USART1,Tx_Buffer);
while( USART_GetFlagStatus(USART1, USART_FLAG_TXE) == RESET );
}
}
void USART1_TX_02 (u8 timer)
{
u8 i=0;
Tx_Buffer[i++]=0xAA;
Tx_Buffer[i++]=0x70;
    Tx_Buffer[i++]=timer;
Tx_Buffer[i++]=0xCC;
Tx_Buffer[i++]=0x33;
Tx_Buffer[i++]=0xC3;
Tx_Buffer[i++]=0x3C;
 for(i=0;i<8;i++)
{    
 USART_SendData(USART1,Tx_Buffer);
while( USART_GetFlagStatus(USART1, USART_FLAG_TXE) == RESET );
}
}

int main(void)
{
flag_rx=0;
Printf_Init();
MYDMA_Config_Rx(); 
USART1_TX_02 (100);
USART1_TX_01(1);
while(1)
{
if(flag_rx==1)
{
flag_rx=0;
printf(" STM32F407ZGT ");
        }
    }
return(0);  
}

void DMA2_Stream5_IRQHandler(void)
{
if(DMA_GetITStatus(DMA2_Stream5, DMA_IT_TCIF5))  
{
flag_rx=1;
DMA_ClearITPendingBit(DMA2_Stream5, DMA_IT_TCIF5) ;
}
}