遇到串口发送要点几下发送的问题：
注意当DMA缓冲区即自己定义的数组的大小大于传输字节时，需要累积传输个数达到数组大小才能产生DMA中断，也就是DMA中断只有在数组填满时才会产生。
main.c

#include "system.h"
#include "SysTick.h"
#include "led.h"
#include "usart.h"
#include "dma.h"


#define send_buf_len 10
u8 send_buf[send_buf_len];



/*******************************************************************************
* 函 数 名         : main
* 函数功能         : 主函数
* 输    入         : 无
* 输    出         : 无
*******************************************************************************/
int main()
{
    u8 i=0;
    
    SysTick_Init(72);
    NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);  //中断优先级分组 分2组
    LED_Init();
    USART1_Init(9600);
    DMAx_Init((u32)&USART1->DR,(u32)send_buf,10);
    
    printf("开始");
    while(1)
    {
        if(flag)
        {
            for(i=0;i<10;i++)
            {
                printf("0x%02X",send_buf[i]);
            }
            flag=0;
        }
    }
}

usart.c

#include "usart.h"       

int fputc(int ch,FILE *p)  //函数默认的，在使用printf函数时自动调用
{
    USART_SendData(USART1,(u8)ch);  
    while(USART_GetFlagStatus(USART1,USART_FLAG_TXE)==RESET);
    return ch;
}

/*******************************************************************************
* 函 数 名         : USART1_Init
* 函数功能         : USART1初始化函数
* 输    入         : bound:波特率
* 输    出         : 无
*******************************************************************************/ 
void USART1_Init(u32 bound)
{
   //GPIO端口设置
    NVIC_InitTypeDef NVIC_InitStructure;
    USART_InitTypeDef USART_InitStructure;
    GPIO_InitTypeDef  GPIO_InitStructure;
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA,ENABLE);
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1,ENABLE);
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO,ENABLE);
    
    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);
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
    GPIO_Init(GPIOA,&GPIO_InitStructure);
    
    NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 2;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 2;
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStructure);
    
    USART_InitStructure.USART_BaudRate = bound;
    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_ITConfig(USART1,USART_IT_IDLE,ENABLE);
    USART_DMACmd(USART1,USART_DMAReq_Rx,ENABLE);
    USART_Cmd(USART1,ENABLE);
    //USART_ClearFlag(USART1, USART_FLAG_TC);
}

dma.c

#include "dma.h"
u8 flag=0;
/*******************************************************************************
* 函 数 名         : DMAx_Init
* 函数功能         : DMA初始化函数
* 输    入         : 
                     DMAy_Channelx:DMA通道选择,@ref DMA_channel DMA_Channel_0~DMA_Channel_7
                     par:外设地址
                     mar:存储器地址
                     ndtr:数据传输量
* 输    出         : 无
*******************************************************************************/ 
void DMAx_Init(u32 par,u32 mar,u16 ndtr)
{
    DMA_InitTypeDef DMA_InitStructure;
    NVIC_InitTypeDef NVIC_InitStructure;
    RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE); //DMA1 时钟使能
    DMA_DeInit(DMA1_Channel5);
    DMA_InitStructure.DMA_MemoryBaseAddr = mar;
    DMA_InitStructure.DMA_PeripheralBaseAddr = par;
    DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;
    DMA_InitStructure.DMA_BufferSize = ndtr;
    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_Normal; //DMA_Mode_Normal
    DMA_InitStructure.DMA_Priority = DMA_Priority_Medium;
    DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
    DMA_Init(DMA1_Channel5,&DMA_InitStructure);
    DMA_Cmd(DMA1_Channel5,ENABLE);
    
    NVIC_InitStructure.NVIC_IRQChannel = DMA1_Channel5_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 2;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 2;
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStructure);
    
    DMA_ITConfig(DMA1_Channel5,DMA_IT_TC,ENABLE);
    
    
}

void DMA1_Channel5_IRQHandler(void)

{

if(DMA_GetFlagStatus(DMA1_FLAG_TC5)==SET)

   {
        flag=1;
        DMA_ClearFlag(DMA1_FLAG_TC5);//清中断标志，否则会一直中断

        printf("进入DMA发送中断！\r\n");       

   }

}