原因：當使用CC2530的串列埠時，協議棧會生成一個串列埠傳送事件，在執行該事件的時候也會觸發相應的串列埠回撥函式，導致回撥函式被重複呼叫。

        詳細程式碼如下：

/******************************************************************************
 * @fn      HalUARTPollDMA
 *
 * @brief   Poll a USART module implemented by DMA.
 *
 * @param   none
 *
 * @return  none
 *****************************************************************************/
static void HalUARTPollDMA(void)
{
  uint16 cnt = 0;
  uint8 evt = 0;

  if (HAL_UART_DMA_NEW_RX_BYTE(dmaCfg.rxHead))
  {
    uint16 tail = findTail();

    // If the DMA has transferred in more Rx bytes, reset the Rx idle timer.
    if (dmaCfg.rxTail != tail)
    {
      dmaCfg.rxTail = tail;

      // Re-sync the shadow on any 1st byte(s) received.
      if (dmaCfg.rxTick == 0)
      {
        dmaCfg.rxShdw = ST0;
      }
      dmaCfg.rxTick = HAL_UART_DMA_IDLE;
    }
    else if (dmaCfg.rxTick)
    {
      // Use the LSB of the sleep timer (ST0 must be read first anyway).
      uint8 decr = ST0 - dmaCfg.rxShdw;

      if (dmaCfg.rxTick > decr)
      {
        dmaCfg.rxTick -= decr;
        dmaCfg.rxShdw = ST0;
      }
      else
      {
        dmaCfg.rxTick = 0;
      }
    }
    cnt = HalUARTRxAvailDMA();
  }
  else
  {
    dmaCfg.rxTick = 0;
  }

  if (cnt >= HAL_UART_DMA_FULL)
  {
    evt = HAL_UART_RX_FULL;
  }
  else if (cnt >= HAL_UART_DMA_HIGH)
  {
    evt = HAL_UART_RX_ABOUT_FULL;
    PxOUT |= HAL_UART_Px_RTS;
  }
  else if (cnt && !dmaCfg.rxTick)
  {
    evt = HAL_UART_RX_TIMEOUT;
  }

/****************以下程式碼會重複觸發串列埠回撥函式，所以註釋掉*************************/
//  if (dmaCfg.txMT)
//  {
//    dmaCfg.txMT = FALSE;
//    evt |= HAL_UART_TX_EMPTY;
//  }
 /*********************************************************************************/

  if (dmaCfg.txShdwValid)
  {
    uint8 decr = ST0;
    decr -= dmaCfg.txShdw;
    if (decr > dmaCfg.txTick)
    {
      // No protection for txShdwValid is required
      // because while the shadow was valid, DMA ISR cannot be triggered
      // to cause concurrent access to this variable.
      dmaCfg.txShdwValid = FALSE;
    }
  }
  
  if (dmaCfg.txDMAPending && !dmaCfg.txShdwValid)
  {
    // UART TX DMA is expected to be fired and enough time has lapsed since last DMA ISR
    // to know that DBUF can be overwritten
    halDMADesc_t *ch = HAL_DMA_GET_DESC1234(HAL_DMA_CH_TX);
    halIntState_t intState;

    // Clear the DMA pending flag
    dmaCfg.txDMAPending = FALSE;
    
    HAL_DMA_SET_SOURCE(ch, dmaCfg.txBuf[dmaCfg.txSel]);
    HAL_DMA_SET_LEN(ch, dmaCfg.txIdx[dmaCfg.txSel]);
    dmaCfg.txSel ^= 1;
    HAL_ENTER_CRITICAL_SECTION(intState);
    HAL_DMA_ARM_CH(HAL_DMA_CH_TX);
    do
    {
      asm("NOP");
    } while (!HAL_DMA_CH_ARMED(HAL_DMA_CH_TX));
    HAL_DMA_CLEAR_IRQ(HAL_DMA_CH_TX);
    HAL_DMA_MAN_TRIGGER(HAL_DMA_CH_TX);
    HAL_EXIT_CRITICAL_SECTION(intState);
  }
  else
  {
    halIntState_t his;

    HAL_ENTER_CRITICAL_SECTION(his);
    if ((dmaCfg.txIdx[dmaCfg.txSel] != 0) && !HAL_DMA_CH_ARMED(HAL_DMA_CH_TX)
                                          && !HAL_DMA_CHECK_IRQ(HAL_DMA_CH_TX))
    {
      HAL_EXIT_CRITICAL_SECTION(his);
      HalUARTIsrDMA();
    }
    else
    {
      HAL_EXIT_CRITICAL_SECTION(his);
    }
  }

  if (evt && (dmaCfg.uartCB != NULL))
  {
    dmaCfg.uartCB(HAL_UART_DMA-1, evt);
  }
}