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AM335x: Problem with USB Composite Dual CDC and Hi-Speed of StarterWare 2.0.0.7

Ruediger Wesche
Prodigy 140 points

Hi, all!

To add USB functionality to an existing firmware for a custom AM335x hardware, I added the sources of the "Composite Dual CDC Serial Port device Example Application" of StarterWare 2.0.0.7. This works fine after I #defined USB_MODE_FULLSPEED for UsbPhyOn() usbphyGS70.c. Without this #define the USB-Host (Windows XP in my case) shows an USB error on an unknown device with VID and PID being 0. As mentioned in the Limitation at the bottom of the StarterWare USB documentation, I noticed the SOF counter incrementing with 8kHz. With the #define it increments with 1kHz. The StarterWare USB documentation states "The CDC class is configured and tested for Hi-Speed PIO mode only". So I assume Hi-Speed should work generally.

Is there a problem with the Composite Class added in StarterWare 2.0.0.7?

Or may this problem arise from the board layout between AM335x and the USB-connector?

Thanks, Rudi

  • 0
    Prodigy 140 points

    Hi all again!

    Finally I found the reason: someone place two 15pF capacitors on the DP and DM signals. After removing these capacitors the board works with Hi-Speed. So the longer stub traces in our board layout did not cause this problem and the "Composite Dual CDC Serial Port device Example Application" of StarterWare 2.0.0.7 is OK, too.

    Best Regards,

    Rudi