关键代码分析：
usart.H
#ifndef __USART_H
#define __USART_H
#include "stdio.h"
#include "sys.h" #define DMA_Rec_Len 200      //定义一个长度为200个字节的数据缓冲区。（建议定义的长度比你可能接收到的最长单帧数据长度长！）void uart_init(u32 bound);
void MYDMA_Enable(DMA_Channel_TypeDef*DMA_CHx);#endifusart.C
//初始化IO 串口1
//bound:波特率
void uart_init(u32 bound)
{//GPIO端口设置
    GPIO_InitTypeDef GPIO_InitStructure;USART_InitTypeDef USART_InitStructure;NVIC_InitTypeDef NVIC_InitStructure;DMA_InitTypeDef DMA_InitStructure;RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1|RCC_APB2Periph_GPIOA, ENABLE); //使能USART1，GPIOA时钟RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE); //使能DMA传输RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART2,ENABLE);//使能USART2时钟
USART_DeInit(USART1);  //复位串口1//USART1_TX   PA.9GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9; //PA.9GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP; //复用推挽输出GPIO_Init(GPIOA, &GPIO_InitStructure); //初始化PA9//USART1_RX  A.10GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;//浮空输入GPIO_Init(GPIOA, &GPIO_InitStructure);  //初始化PA10//Usart1 NVIC 配置NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQn;NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority=3 ;//抢占优先级3NVIC_InitStructure.NVIC_IRQChannelSubPriority = 3; //子优先级3NVIC_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 初始化设置USART_InitStructure.USART_BaudRate = bound;//一般设置为9600;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USART_ITConfig(USART1, USART_IT_IDLE, ENABLE);//开启空闲中断USART_DMACmd(USART1,USART_DMAReq_Rx,ENABLE);   //使能串口1 DMA接收USART_Cmd(USART1, ENABLE);                    //使能串口 //相应的DMA配置DMA_DeInit(DMA1_Channel5);   //将DMA的通道5寄存器重设为缺省值  串口1对应的是DMA通道5DMA_InitStructure.DMA_PeripheralBaseAddr = (u32)&USART1->DR;  //DMA外设ADC基地址DMA_InitStructure.DMA_MemoryBaseAddr = (u32)DMA_Rece_Buf;  //DMA内存基地址DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;  //数据传输方向，从外设读取发送到内存DMA_InitStructure.DMA_BufferSize = DMA_Rec_Len;  //DMA通道的DMA缓存的大小DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;  //外设地址寄存器不变DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;  //内存地址寄存器递增DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;  //数据宽度为8位DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte; //数据宽度为8位DMA_InitStructure.DMA_Mode = DMA_Mode_Normal;  //工作在正常缓存模式DMA_InitStructure.DMA_Priority = DMA_Priority_Medium; //DMA通道 x拥有中优先级 DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;  //DMA通道x没有设置为内存到内存传输DMA_Init(DMA1_Channel5, &DMA_InitStructure);  //根据DMA_InitStruct中指定的参数初始化DMA的通道
DMA_Cmd(DMA1_Channel5, ENABLE);  //正式驱动DMA传输
}//串口中断函数
void USART1_IRQHandler(void)                 //串口1中断服务程序
{if(USART_GetITStatus(USART1, USART_IT_IDLE) != RESET)  //接收中断(接收到的数据必须是0x0d 0x0a结尾)
      {USART_ReceiveData(USART1);//读取数据 注意：这句必须要，否则不能够清除中断标志位。Usart1_Rec_Cnt = DMA_Rec_Len-DMA_GetCurrDataCounter(DMA1_Channel5); //算出接本帧数据长度//***********帧数据处理函数************//
          printf ("The lenght:%d\r\n",Usart1_Rec_Cnt);printf ("The data:\r\n");Usart1_Send(DMA_Rece_Buf,Usart1_Rec_Cnt);printf ("\r\nOver! \r\n");//*************************************//
         USART_ClearITPendingBit(USART1, USART_IT_IDLE);         //清除中断标志MYDMA_Enable(DMA1_Channel5);                   //恢复DMA指针，等待下一次的接收
     } }