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

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?)

  • 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.



  • 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?

  • 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.



  • Resolving through direct email.