Colibri iMX8X: About the USB 2.0 eye pattern

Hi team, a customer measured the USB eye pattern and got some not ideal results.

They basically got the same results using their carrier board and using the Viola.

  1. For this custom CB, is it OK? Kindly check below:

  2. As for the Viola eye pattern, kindly comment?
    ie. “There is no problem because X” or “There is a problem and the customer should Y”.
    The eye pattern is the following (very similar)


Hello Alvaro,

it is always helpful to know the customer’s measurement setup.
So sometimes the setup is the Problem. e.g. does he use a diffrential probe.
Best Regards,

Thanks Matthias! Let me reach out to the customer.


One more thing.
which version of the viola is the customer using and I need the schematic part of the customer’s USB on his carrier board. on older vilola designs we used pull down in the data lines which was required back in the days for the PXA-based modules.

Best Regards,


HI Matthias,

The info from the customer:

They used 01421201 Viola Plus Carrier Board V1.2B for their test and copied the schematics for their own carrier board, so there is basically no difference.

As for the test info:
Oscilloscope: Tektronix DSA70804
Probe: Differential probe P7380A

Kindly let me know if you need more info.

Thanks and best regards,

The following changes should improve the signal quality: Remove the following resistors (and leave it as an open circuit to GND)

We are checking with the customer if this is the case.

We have confirmed that the above change doesn’t make any difference. For the shield, an RC would help, but mostly for EMC/EMI not signal integrity.

We are further checking.