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About the problem that USB 2.0 OTG port of i.MX25 is recognized as USB1.1

Question asked by yuuki on Mar 26, 2015
Latest reply on Jun 26, 2015 by yuuki

Dear all,

 

In our system, the USB 2.0 OTG port is used as Device mode.
And it is connected to a PC (USB2.0 Host port).

 

However, it may be recognized as USB1.1 after a soft reset of i.MX25.
  When a problem occurred, we confirmed the PSPD field of the PORTSC1 register.
  It is set in "00:Full Speed".

 

I tested connection with ten PCs.
As a result, four PCs have this problem.
This problem occurs at the rate of one of five times.

 

We made four kinds of original boards.
All these boards have the same problem.

 

We observed a waveform at the time of problem occurrence.
Please refer to attached file.

 

In the case of normal operation, after ChirpK was issued, ChirpKJ is observed.
- normal operation waveform.png

 

Howevwe, when a problem occurred, ChirpKJ is not observed after ChirpK.
- waveform with problem.png

 

We suspect that this is the cause of the problem.

Would you teach the probable cause for this problem?
Would you teach the workaround of this problem?

 

Best Regards,
Yuuki

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