I am experiencing a problem related with CDC communications on a XMega-64A33U.
My board is connected, through a hub, to a PC. On the same hub I also have an USB camera. Recently we upgraded to a faster camera, and started having problems.
Analysing USB traffic with USBlyzer, I discovered that my board sends to the PC a message circa each ms, even if the board has nothing to send and if the virtual port is closed on the PC side.
In short, these packets disrupt the operations of the camera.
I fear that the behaviour is not related with ASF or XMega, but with the nature of CDC itself. According to what I read, these are periodical requests from the PC, because there is no other way to know if the CDC device has something to send.
Now I would like to know:
1) can you confirm that this is really a CDC-related behaviour?
2) if there is a way to reduce the polling frequency?
3) if not, can you suggest a workaround?
I understand the best solution is "use a dedicated port", but at the moment this is not possible.