USB OTG Eye Diagram test for i.MX6Q

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USB OTG Eye Diagram test for i.MX6Q

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fdact
Contributor I

Hi,

I referred to https://community.nxp.com/docs/DOC-105609I.MX6 series USB Certification Guides) to configure the eye Diagram test ,
With reference to https://community.nxp.com/docs/DOC-94460?commentID=17030#comment-17030,(Patch to make i.MX6DQ USB to support test modes for certification test)  the same result was found.
It was found that the amplitude of the output waveform was too large, and the amplitude could not be reduced by modifying 0x020c9010(TXCAL45DP, TXCAL45DN,D_CAL)。

Hardware information: i.MX6Q   USB: OTG

Android8.0.0   Linux 4.9.17

My test method is to switch the USB interface to Host mode, connect the U disk, and test GND d+ D-test points at the same time.
Attached is the picture of the test. Could you please help to see how to reduce the amplitude in High Speed test mode?
Thanks.
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igorpadykov
NXP TechSupport
NXP TechSupport

Hi zero

one can consider i.MX6Q SabreSD schematic p.11  spf-27392  L520

and compare custom board layout with reference design

Design files, including hardware schematics, Gerbers, and OrCAD files for i.MX 6Quad (i.MX 6Dual emu...

Best regards
igor
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fdact
Contributor I

Hi igorpadykov

Thank you for your suggestion. We're checking it now.
And when I tried to change the U disk , the test found that the amplitude decreased,
as shown in the attached picture.
However, there was a waveform with very low amplitude in the first half of the waveform.
This part of the waveform doesn't feel normal.

test0813.jpg

My question is:
1. Is there any relationship between eye Diagram test and what U disk is inserted?
2. The waveform with very low amplitude in the first half of the attachment may be caused by what reason?
3. For eye Diagram test, do I have to reduce the amplitude below 400mV?

Thanks.

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