串口 DMA中断输出第一个显示为未知

wait小乖

打印5个A 结果出现这样*AAAA

 NVIC_InitTypeDef NVIC_InitStructure;
DMA_InitTypeDef DMA_InitStructure;
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA2,ENABLE);

NVIC_InitStructure.NVIC_IRQChannel = DMA2_Stream7_IRQn ;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority =2;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init( &NVIC_InitStructure);

DMA_DeInit(DMA2_Stream7);
DMA_InitStructure.DMA_Channel = DMA_Channel_5;
DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)(&(USART6)->DR);
DMA_InitStructure.DMA_Memory0BaseAddr = (uint32_t)SendBuff;
DMA_InitStructure.DMA_DIR = DMA_DIR_MemoryToPeripheral;
/*DMA传输大小*/
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_Normal;//只发一次/DMA_Mode_Circular;地址归位 一直发
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_Stream7,&DMA_InitStructure);
DMA_ITConfig(DMA2_Stream7,DMA_IT_TC,ENABLE);

DMA_Cmd(DMA2_Stream7, ENABLE); 



这是我的配置 不知道哪里有问题 请指导 谢谢!