m_a_d_i_s wrote on Thursday, October 04, 2007:


I have a question about the USB CDC. Is it possible to create two RS232 ports on the PC side instead of one? I checked that CDC uses 4 enpoints (0, one I dont understand that well and in/out). As there are 2 more enpoints available, can I use them for additional serial port? hints and guidelines are very welcome.

Thanks, Madis

jakbird wrote on Thursday, October 04, 2007:

If you are using Windows on the PC side then you will run into problems with the USBSER CDC class driver.  You might want to search on USBSER as it does not like multiple interfaces on a single device.  (Rumor has it that this might be fixed in Vista.)
  Jack Peacock

m_a_d_i_s wrote on Friday, October 05, 2007:

Ok, thank you for the information. I got another question. Do you see anything wrong in the idea that I create one com port (which uses usbser.sys) and use another two free enpoints to create audio device (using usbaudio.sys)? I.e. they share enpoint 0, audio device has two enpoints more (in and out) and com device has three enpoints (as freeRTOS USB demo), total 6 as supported by sam7x? Is it normal way of thinking or total nonsense?


jakbird wrote on Friday, October 05, 2007:

You will still have the same problem with USBSER.  One CDC com port and an audio device is a “composite” device, multiple interfaces, which USBSER doesn’t handle.
  Jack Peacock