[求助] STM32F103C6T6的串口发送出现奇怪问题！

STM32F103C6T6的串口发送出现奇怪问题！与CC2530通讯是能收到数据，但发送的数据有几个字节是错误的，好奇怪！而且无法用DMA发送，最奇怪的是，程序下载完成后。用锂电池供电，运行指示灯正常闪烁。但串口则没有数据（用示波器测试），连接JTAG就有数据。超级奇怪！

DMA配置：

    DMA_DeInit(DMA1_Channel2); 
    DMA_InitStructure.DMA_PeripheralBaseAddr = (u32)SRC_USART1_DR;
    DMA_InitStructure.DMA_MemoryBaseAddr = (u32)&USARTSendBuff;
    DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;
    DMA_InitStructure.DMA_BufferSize = Len;
    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_InitStructure.DMA_Priority = DMA_Priority_Medium;
    DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
    DMA_Init(DMA1_Channel2, &DMA_InitStructure);
   
    USART_DMACmd(USART1, USART_DMAReq_Tx, ENABLE);
    // Enable DMA1 channel2
    DMA_Cmd(DMA1_Channel2, ENABLE);