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TUSB2077A: Remains in Suspend mode & no downstream Ports are Enumerated.

Siddharth Mishra
Prodigy 10 points
Part Number: TUSB2077A

Hello Team

We are using TUSB2077A with custom board & problem we are facing is no downstream ports are getting enumerated with this USB Hub. When measured we found that pin no.1 i.e Suspend pin remains high i.e between 2.7V to 3.3V whenever external host is plugged in on Upstream port I have attached snap of my Schematic design All downstream ports have a pull-up on OVERCURRENT pin & setting as mentioned in my Schematic.

1) What are the sequence required to be followed detect the downstream port on TUSB2077A and getting it enumerated ?

2) Is there any specific drivers/commands required to be installed/followed on Linux/Windows PC for the same?

3) Do you suspect any issue in the hardware design here? We already followed all the guideline provided.

Appreciate your help in Advance.

  • 0
    TI__Guru 60865 points

    Hi Siddharth,

    Does the host enumerate the USB hub?  I see a USB termination block on the downstream ports - does that include the 15K pulldowns that are required?

    Regards,

    JMMN

  • 0 in reply to JMMN
    Prodigy 10 points

    Yes host is able to enumerate USB Hub every time.

    Yes it has the 15k pull down & 27 ohm series resistor provision same as per the EVK.

    Couple of more queries as below:

    - How to know that whether hub is operating on Ganged mode or not ?

    - Do we need pull up also on overcurrent pin of unused port ?

    We have tried every possible ways but still no luck to see downstream port working. Awaiting to hear from you

  • 0 in reply to Siddharth Mishra
    TI__Guru 60865 points

    Every OVERCURRENT pin needs to be pulled up <- this is the likely issue.

    Your hub is not using power switches so the GANGED setting will have no impact.

    If you are still seeing issues after adding the overcurrent pullup, please check the DP/DM lines on one of the downstream ports and confirm the line states.

    Regards,

    JMMN