USB on K20D50 (versus D75)

[richardsabourin]

Hi folks, looking for a little advice:

We have a design based on K20D50 and the 4.1.1 bare metal USB stack implementing the CDC class. The device works fine when connected to a full-speed hub (built into my Dell keyboard), but doesn't enumerate in other places, such as the hi-speed ports on my laptop.

The K20D75 tower board, where we started development, works fine. The only relevant code changes are clocking (8 Mhz crystal PEE mode), and fixing the driver to match the syntax in the MK20D5.h file (i.e., USB0_ISTAT to USB0->ISTAT).

Anybody have any suggestions? Does it sound like it could be a noise or clock jitter issue?

Thanks!

[Kan_Li]

Hi Richard,

If you just change the code for clock configuration and syntax match, I think it is more likely a hardware issue. If you have any USB analyzer, would you please capture the data transaction between PC Host and CDC during enumeration? Thanks for your patience!

Have a great day,
Kan

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[richardsabourin]

Thank you for your reply - I have been planning to get a Total Phase analyzer to look into this.