請教有關於USART DMA的buffer size問題?

sappppp 提问时间：2016-4-15 12:47 /

想要請問，當我利用DMA做USART傳輸時，當我定義BufferSize大小為DataLen時，當我從PC端寫入一串數據如"123456"，但是傳送出來的數據一定是"0123456012"剛好填滿我設定的buffer 大小。請問是哪裡出問題呢?謝謝我的程式如下：

#define DataLen 10
u8 SendBuff[DataLen];
u8 RecviceBuff[DataLen];

void USART_DMA_Configuration(void)
{
DMA_InitTypeDef DMA_InitStructure;
DMA_DeInit(DMA1_Channel4);
DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)&USART1->DR;
DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)SendBuff;
DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;
DMA_InitStructure.DMA_BufferSize = DataLen;
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_High;
DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
DMA_Init(DMA1_Channel4, &DMA_InitStructure);
DMA_ITConfig(DMA1_Channel4, DMA_IT_TC, ENABLE);
DMA_ITConfig(DMA1_Channel4, DMA_IT_TE, ENABLE);
USART_DMACmd(USART1, USART_DMAReq_Tx, ENABLE);
DMA_Cmd(DMA1_Channel4, DISABLE);
DMA_DeInit(DMA1_Channel5);
DMA_InitStructure.DMA_PeripheralBaseAddr = USART1_DT_Base;
DMA_InitStructure.DMA_MemoryBaseAddr =  (uint32_t) RecviceBuff;
DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;
DMA_InitStructure.DMA_BufferSize = DataLen;
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_M2M = DMA_M2M_Disable;
DMA_Init(DMA1_Channel5, &DMA_InitStructure);
DMA_Cmd(DMA1_Channel5, ENABLE);

/*****************************************************************/
**************主流程  PC端寫入資料並由SMT32F1輸出至PC端
if(USART_GetITStatus(USART1, USART_IT_RXNE) != RESET)
{
      DMA_Cmd(DMA1_Channel5, DISABLE);
      DATA_LEN=DataLen - DMA_GetCurrDataCounter(DMA1_Channel5);
      if(DATA_LEN > 0)
      {
         for(i=0;i<DATA_LEN;i++)
         {
            SendBuff[i]= RecviceBuff[i];    // Let Memory receive data copy to Send memory
         }
         DMA_Cmd(DMA1_Channel4, DISABLE);
         DMA1_Channel4->CNDTR=DATA_LEN;
         USART_DMACmd(USART1, USART_DMAReq_Tx, ENABLE);
         DMA_Cmd(DMA1_Channel4, ENABLE);
      }