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TUSB8041EVM: Tablet <-> TUSB8041 <-> USB Memory

Darren (FAE)
Expert 5483 points
Part Number: TUSB8041EVM
Other Parts Discussed in Thread: TPS65981, , TUSB8041, HD3SS3212

I have a customer that has been struggling to get a USB3.x memory stick to communicate with a tabet (2018 iPad Pro, Galaxy Tab) at USB3.x SuperSpeed datarates. They see the connection at USB2.0 (passed through via TPS65981)

When the connect a PC, they are seeing USB3.x speeds. Maybe this is a OTG / Tablet compatibility issue with USB3.x memory sticks...

But it would be extremely helpful if somebody on your team could plug in a Tablet to the TUSB8041EVM, and a USB3.x memory stick, and see if they communicate with the SSRX / SSTX lines as opposed to the D+ / D- for USB2.0

I would also appreciate some advice on tablet specifications that might make communicating possible...(OTG? cable choice?)

  • 0
    TI__Guru 60865 points

    Hi Darren,

    How is your customer connecting the Tablet and TUSB8041EVM?  What type of cable?

    The TUSB8041 doesn't support OTG / role swap and its behavior is going to be dependent on how it is connected to the type-C / lightning receptacle.

    Regards,

    JMMN

  • 0 in reply to JMMN
    TI__Expert 5483 points

    Hi JMMN,

    The customer has actually designed their own board.
    They are hoping the EVM can show if there are any problems in their design, or if this is a device-related function issue.

    Tablet is connected by USB Type-C connector to the board.
    The tablet-side USB-C connector runs the D+/D- connections through the TPS65981 internal MUX, then into the TUSB8041 Hub, then to the USB Memory D+/D- connections.

    The tablet-side USB-C connector runs the  SSTX/SSRX connections through a separate MUX (HD3SS3212) which is controlled by the TPS65981, then into the TUSB8041 Hub, then to the USB Memory SSTX/SSRX connections.

    The TPS65981 sets the MUX signals to control which path the signals to take. 

    It seems like connecting a notebook via USB-C connector connects at USB3.x speeds, but not the tablet...

    USB Memory stick is connected with a USB3.x capable Type-A style connector.
    The board has it's own power supply, and doesn't rely on the Tablet for power.

    Let me change the question...Do you know what conditions would a Tablet/cable have to meet, in order to communicate through the TUSB8041 at SuperSpeed?

  • 0 in reply to Darren (FAE)
    TI__Guru 60865 points

    Hi Darren,

    Is the customer using the same board and cable to connect to a tablet that it is to connect to a notebook?  I just want to be sure that they aren't using a type-C adapter or cable that doesn't support USB 3.0.  

    Can they confirm that the TPS65981 is enabling the SS connection to the hub?  The hub is Type-C unaware and will connect as long as the SS lines are enabled.  Another debug step would be to connect the hub to the tablet and then generate a hard reset to the hub using GRSTz, this would allow the hub to exit compliance mode if it entered it unexpectedly.

    Regards,

    JMMN

  • 0 in reply to JMMN
    TI__Guru 60865 points

    Resolving through direct email.