stm32
 f407 串口1 用DMA发送 发送400个数据 ，经常有数据没有发送完成
串口DMA配置函数
void Usart1_DMA_Config(void)
{ 
 
DMA_InitTypeDef  DMA_InitStructure;


RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA2,ENABLE);

DMA_DeInit(DMA2_Stream7);

while (DMA_GetCmdStatus(DMA2_Stream7) != DISABLE){}



DMA_InitStructure.DMA_Channel =DMA_Channel_4; 

DMA_InitStructure.DMA_PeripheralBaseAddr = USART1_DR_Base;

DMA_InitStructure.DMA_Memory0BaseAddr =(u32)SendBuff;

DMA_InitStructure.DMA_DIR = DMA_DIR_MemoryToPeripheral;

DMA_InitStructure.DMA_BufferSize = SENDBUFF_SIZE;

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_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_Cmd(DMA2_Stream7, DISABLE);    
    


DMA_ITConfig(DMA2_Stream7,DMA_IT_TC,ENABLE); 

} 



main函数调用函数


void USART1_DMA4_SendData(uint16_t CharLength)

   {

while (Flag_Uart_Send){;}


Flag_Uart_Send = 1;   

DMA_Cmd(DMA2_Stream7,DISABLE);

         while (DMA_GetCmdStatus(DMA2_Stream7) != DISABLE){}


DMA_SetCurrDataCounter(DMA2_Stream7,CharLength);  


DMA_Cmd(DMA2_Stream7,ENABLE);  


USART_DMACmd(USART1, USART_DMAReq_Tx, ENABLE);   
 
}



DMA传输完成中断函数


void DMA2_Stream7_IRQHandler(void)  
{  
   
    DMA_ClearFlag(DMA2_Stream7,DMA_FLAG_TCIF7);  
                                              
   DMA_Cmd(DMA2_Stream7,DISABLE);  

    Flag_Uart_Send = 0;  
}