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2009-04-19 19:18:35 | 关于stm32 usb虚拟串口程序问题的讨论

转自 www.stmsky.com 在路上 stm32 论坛

http://www.stmsky.com/bbs/viewthread.php?tid=1168&extra=page%3D1

主要问题是  串口有时收到乱码有时收到丢包数据：
  关于乱码我们其实很容易想到奇偶校验的问题，而我们平常都是默认为没有奇偶校验。
请看程序：
      * USART1 default configuration */
  /* USART1 configured as follow:
      - BaudRate = 9600 baud
      - Word Length = 8 Bits
      - One Stop Bit
      - Parity Odd
      - Hardware flow control desabled
      - Receive and transmit enabled
      - USART Clock disabled
      - USART CPOL: Clock is active low
      - USART CPHA: Data is captured on the second edge
      - USART LastBit: The clock pulse of the last data bit is not output to
                     the SCLK pin
  */
  USART_InitStructure.USART_BaudRate = 9600;
  USART_InitStructure.USART_WordLength = USART_WordLength_8b;
  USART_InitStructure.USART_StopBits = USART_StopBits_1;
  USART_InitStructure.USART_Parity = USART_Parity_Odd;
  USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
  USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;
  USART_InitStructure.USART_Clock = USART_Clock_Disable;
  USART_InitStructure.USART_CPOL = USART_CPOL_Low;
  USART_InitStructure.USART_CPHA = USART_CPHA_2Edge;
  USART_InitStructure.USART_LastBit = USART_LastBit_Disable;

只要改成odd  或者程序里作修改即可

问题2 ：既然是虚拟串口，那么利用pc串口软件两边应该可以正常通信，但是源程序出现的情况是。
      真--虚  ok
         虚--真  则严重丢数据

  看了一下程序  原来捣鬼的是这里：
   void USB_To_USART_Send_Data(u8* data_buffer, u8 Nb_bytes)
{
  u32 i;

  for (i = 0; i < Nb_bytes; i++)
  {
USART_SendData(USART1, *(data_buffer + i));
   }
}
串口发送数据后没有等待串口发送完成

改为下边即可
void USB_To_USART_Send_Data(u8* data_buffer, u8 Nb_bytes)
{
  u32 i;

  for (i = 0; i < Nb_bytes; i++)
  {
USART_SendData(USART1, *(data_buffer + i));
   while(USART_GetFlagStatus(USART1, USART_FLAG_TXE) == RESET);

  }
}

原创 stm32 转载

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