AnsweredAssumed Answered

USB CDC Code enumerates differently depending on the USB Port.

Question asked by Matt Lang on May 19, 2015
Latest reply on Aug 26, 2015 by Audi McAvoy



I'm using KDS with KSDK V1.1.0 and an MK22FN51212 MCU. I have bare metal projects with no OS. I use the USB hardware on the MCU with the example CDC code.


The problem:

When I plug my device into the front of a powered USB Hub, I enumerate as a normal com port, when I plug it into the back of the USB Hub I enumerate as a "Virtual COM Port Demo" from Freescale and tries to load a driver for it, and lastly I plug it into my desktop tower USB ports and it says it's an "unknown device" .


I do the same test with the same code only this time I put the code on the MK22 Freedom Dev Board. It does the same thing only this time when I plug it into my desktop tower port it comes up as a normal Com port.


When I load the dev_cdc_virtual_com_frdmk22f_bm_frdmk22f example demo onto the freedom board, it works perfect. It will enumerate as a com port no matter what port I put it in.


Lastly, When I put the dev_cdc_virtual_com_frdmk22f_bm_frdmk22f example demo on my hardware, the front and back of the USB hub works fine, but it still does not work with my desktop tower USB ports ("Unknown Device").



I'm using the same code as the cdc virtual com demo. What would cause this problem?