The speed issue of USB Virtual COM port

[lillian_200601]

Posted on April 24, 2008 at 17:32

The speed issue of USB Virtual COM port

[lillian_200601]

Posted on May 17, 2011 at 09:52

I use Keil uVisition3 and MSBSTR9 EVAl board.

I run the demo of Virtual COM port from the ST site and it works fine.

However, the transfer speed between PC and the EVAL board is only 1KBytes/second whatever the baud rate is set.

How do I fix the source code so that I can achieve the speed up to 961200. Greatly appreciate your help.

Lillian

[michael]

Posted on May 17, 2011 at 09:52

hello,

well, I don't think the baud rate is of any importance for a virtual com port (I'm not 100% sure, it has been a while). try to check your descriptor and the rate at which your device is allowed to access the bus.

[lillian_200601]

Posted on May 17, 2011 at 09:52

Thank you for your response. More information for my issue.

USB bulk transfer mode is for communiation between PC and the EVAL board. The baud rate can be adjusted up to 115200. And the host application is Hyperterminal. Even though I revise the code and make the speed up to 961200bit/s, the real transfer speed is still 1KBytes/s. I suspect Hyperterminal caused this issue? Anyone has similiar experience with that? Thank you for your kind help.

[michael]

Posted on May 17, 2011 at 09:52

Are you sure that your UART's buad rate, as specificed by the STR9, is configured correctly? In my previous post I meant that the baud rate does not change anything for the virtual COM port (i.e. USB connection between laptop and STR9), of course it matter for the PC-STR9 link.

[lillian_200601]

Posted on May 17, 2011 at 09:52

The post here

http://www.st.com/mcu/forums-cat-6699-23.html

talks how to change the transfer speed between the labtop and Str9