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TUSB8042: Detection of upstream 3.0

FRANK1
Expert 8955 points

Part Number: TUSB8042

Hi Sir,

A customer has a query on detection of upstream 3.0.
After hub overspeed is detected,
Once unplugged and reconnected, it will be detected as a non overspeed hub.
And at that time, no downstream devices were detected.
Do you know the reason?
Feel free to contact me If you need more details.

Thanks for your clarification.
Regards,

  • 0
    TI__Guru 60870 points

    Hi Frank,

    What is meant by "hub ovespeed"?  Does it mean overcurrent?  If the hub reported an overcurrent event, the host may not re-enable port power until the system is power cycled.  Can you confirm if VBUS(5V power) is enabled on the downstream ports?

    Regards,

    JMMN

  • 0 in reply to JMMN
    TI__Expert 8955 points

    Hi JMMN,

    sorry, it's not overspeed, but 'Superspeed'.

    Superspeed refers to the name (Universal superspeed USB hub) displayed in the device manager of windows when the TUSB8042 hub IC is connected to the windows USB3.0 port.
    It is detected and displayed for the first time as a general-purpose superspeed USB hub.
    For the second time, it was somehow detected as a universal USB hub.

    The VBUS of the second downstream port is also enabled with 5V.

    Thanks.

  • 0 in reply to FRANK1
    TI__Guru 60870 points

    Hi Frank,

    When the hub connects to the host, it should report both a Generic SuperSpeed Hub instance and a Generic USB Hub instance since the hub connects at both USB 2.0 and USB 3.0 speeds simultaneously.

    Can you confirm that USB_VBUS input to the hub toggles when the hub is disconnect and reconnected?  If it doesn't this can prevent the SuperSpeed hub from reconnecting properly.

    Regards,

    JMMN

  • 0 in reply to JMMN
    TI__Expert 8955 points

    Hi JMMN,

    In addition, USB VBUS supplies voltage from different lines without supplying via USB cable.
    This voltage is always in. In this situation, the USB signal is only connected to the host and the cable.

    To enable reconnection correctly,
    do I always have to separate USB_VBUS?
    (Keep giving USB_ Is VBUS power supply wrong?)

    Thanks.

  • 0 in reply to FRANK1
    TI__Guru 60870 points

    USB_VBUS should be HIGH only when the hub is connected to a host.  It should toggle low then high again when a host is disconnected and reconnected. The downstream port connection states do not impact the USB_VBUS setting.

    Regards,

    JMMN

  • 0 in reply to JMMN
    TI__Expert 8955 points

    Hi JMMN,

    Thank you.

    When the host is disconnected and reconnected, the VBUS of the hub must be set to low level, and then high level. Do I think so?

    If so,

    What are the different actions when reconnecting with USB 2.0 host and USB 3.0 host?

    For example, in case 1 below, the host will normally detect the hub after reconnection.

    In case 2 below, the host cannot normally detect the hub after reconnection.

    In either case, VBUS is verified with high level.

    When connecting again, VBUS must be set to low level and then high level,

    Why does the detection succeed in case 1 below and fail in case 2 below?

    Case1. Connect USB 2.0 host and hub → disconnect → reconnect USB 2.0 host and hub

    Case2. Connect USB 3.0 host and hub → disconnect → reconnect USB 3.0 host and hub

  • 0 in reply to FRANK1
    TI__Guru 60870 points

    HI Frank,

    Yes, this is expected.  Usually a USB 2.0 connection can recover if VBUS is left high during a disconnect / reconnect since it will go to suspend and then the host will send a usb reset during enumeration.  It is much more difficult to recover a USB 3.0 connection if the hub is left with USB_VBUS during a disconnect / reconnect since the state machine is much more complex.

    Regards,

    JMMN