近几天 调试usb虚拟串口的程序，发现一些问题以及解决方法。和大家共享
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);
}
} |
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