About improve the eye pattern of USB OTG in i.MX6DQ.

[keitanagashima]

Dear All,

My customer is using the USB OTG with Full speed in i.MX6DQ.

But, eye pattern was bad quality.

In case of High speed mode, the signal quality was improved by changing the D_CAL & TXCAL.

But, the quality wasn't improved in Full speed mode.

[Q1]

Is there register to improve the signal quality with Full speed mode?

And, the signal quality was worse by increasing the value of TXCAL in Full speed mode.

(In High speed mode, the quality was better by above setting...)

[Q2]

Are HS mode and FS mode the relation of the inverse proportion by increasing the TXCAL value?

Best Regards,

Keita

[igorpadykov]

Hi Keita

please check AN4589 Configuring USB on i.MX 6 Series Processors

http://cache.nxp.com/files/32bit/doc/app_note/AN4589.pdf 

below certification report

USB Certification report of i.Mx6 | NXP Community 

Issues with eye pattern may be caused by customer board layout

and measuring equipment/procedures, so may be recommended to apply

to local fae for on site checking.

Best regards
igor
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[keitanagashima]

Hi Igor,

Yes. I already read these document.

But, I didn't find the adjust register in FS mode.

So, please check again below questions.

[Q1]
Is there register to improve the signal quality in Full speed mode?

[Q2]
Are HS and FS mode the relation of the inverse proportion by increasing the TXCAL value?

Best Regards,

Keita

[igorpadykov]

Hi Keita

what official usb.org documentation customer is following when doing these tests ?

Had he read usb.org official "USB-IF USB 2.0 Electrical Test Specification"

http://www.usb.org/developers/compliance/USB-IF_USB_2_0_Electrical_Test_Spec081005.pdf 

According to this document there are no tests for "signal quality in Full speed mode" ?

Please recheck documents:

Patch to make i.MX6DQ USB to support test modes for certification test 

Best regards
igor

[keitanagashima]

Hi Igor,

The below signal quality in Full speed mode was very good.

USB Certification report of i.Mx6 | NXP Community

I compared the above NXP's quality signal and customer's one.

The p-p voltage was different.

So, I suggested my customer increase the voltage of USB_LDO from 3.0V to 3.3V.  

But, we want to know the existence of the register to adjust signal quality in FS mode beforehand.

If the register wasn't exist, please tell me it.

Best Regards,

Keita

[igorpadykov]

Hi Keita

in FS mode eye pattern test is not performed, it is

only for HS mode according to USB 2.0 specification

sect.7.1.2 Data Signal Rise and Fall, Eye Patterns,
sect.7.1.2.2 High-speed Signaling Eye Patterns and Rise and Fall Time

http://www.usb.org/developers/compliance/USB-IF_USB_2_0_Electrical_Test_Spec081005.pdf

There are no register settings for changing signal levels in FS mode.

Termination resistors TXCAL45 are used only in HS mode, below part of AN4589

Best regards
igor