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TUSB8020B: Hub physical layer testing fail

Dylan You
Intellectual 2630 points
Part Number: TUSB8020B


Dear teams,

My customer is using TUSB8020, and test its physical layer. However, they found testing item 1,2,and 5 failed showing in figure 1. Testing loop is SOC USB3.0 - TUSB8020 showing in figure 2. However, they short circuit the TUSB8020 first, then they found the testing item can be passed. Could you help share what kinds of parameters they need to configure to improve?

Figure 1

Figure 2

Schematic showing below:

TUSB8020.pdf

Testing item 1 waveform:

Testing item 2 waveform:

Testing item 5 waveform:

Thanks!

Dylan

  • 0
    TI__Guru 60870 points

    Hi Dylan,

    These test results are expected since the customer is using a repeated test packet.

    Repeated test packet = generated by a USB host and then measured at the downstream port of the hub (or generated by a USB device and then measured at the upstream port of the hub).  A repeated test packet will have EOP dribble and dropped SYNC bits as allowed per the USB 2.0 specification.

    You will need to use the USBHSET tool to have the hub generate the test packets directly on the downstream port in order to pass all the default signal quality compliance tests.

    Regards,

    JMMN

  • 0 in reply to JMMN
    TI__Intellectual 2630 points

    Hi JMMN,

    Thanks a lot for your strong support! Here is my customer feedback:

    They use USBHSET tool and found that the testing fail item is same as the sending pocket fail item showing in following picture:

    Thanks!

    Dylan

  • 0 in reply to Dylan You
    TI__Guru 60870 points

    Dylan,

    They need to generate the test packet on the downstream port itself:

    They need to load the hub portion of the XHCI HSET tool and generate the test packet on the port:

  • 0 in reply to JMMN
    TI__Intellectual 2630 points

    Hi JMMN,

    Customer told me they did actually tested it with the same method you mentioned.

    Thanks!

    Dylan

  • 0 in reply to Dylan You
    TI__Guru 60870 points

    The customer needs to measure Hub SYNC field and EOP width using a test packet not a SOF packet.  The tests they are running (EL_21, EL_22, EL_25) are all listed as "HOST" tests, why are they running them on a hub device?  They don't apply.

    Regards,

    JMMN