执行下面的代码后，DMA1_Channel2会循环将Send_Buf1的数据发送出去。发送过程中，如果调用USART_DMACmd(USART1, USART_DMAReq_Tx, DISABLE); 这时DMA1_Channel2会停止发送数据（假如这时正在发送Send_Buf1[300]）。这时，调用USART_DMACmd(USART1, USART_DMAReq_Tx, ENABLE);，DMA1_Channel2会从Send_Buf1[301]开始发送数据。
问题：我想在接下去调用USART_DMACmd(USART1, USART_DMAReq_Tx, ENABLE); 时，从Send_Buf1[0]开始发送，我该如何做？

unsigned char Send_Buf1[1000] = {0};
          DMA_InitTypeDef  DMA_InitStructure;
       
          //DMA_Cmd(DMA1_Channel2, DISABLE);       
                DMA_DeInit(DMA1_Channel2);
          DMA_InitStructure.DMA_BufferSize = SENDBUF_SIZE_USART1;
    DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;
    DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte;
    DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
    DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
    //DMA_InitStructure.DMA_Mode = DMA_Mode_Normal;
                DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;
    DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;

    DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)Send_Buf1;
    DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;
    DMA_InitStructure.DMA_Priority = DMA_Priority_VeryHigh;
    DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)&(USART1->TDR);
    DMA_Init(DMA1_Channel2, &DMA_InitStructure);
    DMA_Cmd(DMA1_Channel2, DISABLE);               
    DMA_Cmd(DMA1_Channel2, ENABLE);       

地址必须要在DMA初始化的时候写入到DMA配置中.
USART_DMACmd(USART1, USART_DMAReq_Tx,ENABLE);
  USART_DMACmd(USART1, USART_DMAReq_Rx, ENABLE);
  USART_ITConfig(USART1,USART_IT_IDLE,ENABLE);
看看这个帖子参考下
http://blog.csdn.net/jutun5887/article/details/78652367

好的，我再学习一下，谢谢！