CYUSB3326-88LTXI : USB Loopback mode

[KyLe_3407496]

Dear Support and Expert

We are using CYUSB3326-88LTXI on our product. And we want to test Signal Intergrity on USB Rx lines.

Is there any method to enter the USB HUB Loopback mode?

We are now trying, but we can't.

Please refer attached picutre that 'the DUT is not in Loopback'.

Thanks,

Lee

[Sananya_14 · Accepted solution]

Hello Lee,

-This error could be because the pattern sent and receive to DUT did not match and hence hub isnt going into loopback mode. Please refer to hardware guidelines for Rx and Tx lines from the Application Note to ensure there are no path losses in your board.

-Please check if the error is happening with other boards for us to understand if it is a device or board issue.

Best Regards,

Sananya

[KyLe_3407496]

Thanks for your comment Sananya.

=================================================================================================

-This error could be because the pattern sent and receive to DUT did not match and hence hub isnt going into loopback mode. Please refer to hardware guidelines for Rx and Tx lines from the Application Note to ensure there are no path losses in your board.

-Please check if the error is happening with other boards for us to understand if it is a device or board issue.

-> We will check out our board and notice that if it is a device or board issue.

=================================================================================

Well, I have another questions.

1) Getting into the USB hub's loopback mode and normal using is totally different? we couldn't find any issue from USB hub.

2) Is there any program need to enter the USB HUB Loopback mode and setting some value?

3) We are now testing a siganl intergrity with a equipment. If we want to get into the loopback mode, does the equipment has to send some particular packet?

Best regards

Lee

[Sananya_14]

Hello Lee,

The loopback tests are done in compliance mode under worst case conditions unlike the normal mode. So there is a possibility that the hub works fine in normal cases but fails sometimes in compliance tests.

Best Regards,

Sananya

[KyLe_3407496]

Thanks for your following, Sananya.

=========================================================================================================

The loopback tests are done in compliance mode under worst case conditions unlike the normal mode. So there is a possibility that the hub works fine in normal cases but fails sometimes in compliance tests.

=========================================================================================================

I understand your feedback. Loopback tests are worst case. So in the normal mode, we couldn't find some issues.

And I read your comment, and find 'compliance mode'. Do we have to set our product compliance mode?

In CYUSB3326-88LTXI datasheet, there is BC v1.2 for compliance mode. but there isn't any setup for loopback's compliance mode.

Best Regards,

Lee

[KyLe_3407496]

This issue has been solved.

Two things are different from before. Please refer it.

1) Using new equipment for test.

2) Testing in the BIOS mode.

Thanks for your help.

Best Regards,

Lee