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TPS65981: USB 2 Legacy Host Mode - Register Settings

Andy Goulbourne
Prodigy 245 points
Part Number: TPS65981
Other Parts Discussed in Thread: TPS65987

Hi we have the 69581 running as a DRP.  We have a specific application where our customer is unable to connect the CC signals and as such unable to do a PD power negotiation. 

We can change register settings in the TPS65981 but seem unable to force a legacy USB 2 Host mode where VBUS is always on but are not successful.

From our working DRP design, we are setting

  • Configuration Control 0x29 PD Mode to Legacy USB Host / Source
  • System Config 0x28 Port Information to Disabled.

What other registers need setting.  I attach my project file for the design tool for reference. 

Thanks.D1987.pjt

  • +1
    TI__Genius 12591 points

    Hi Andy, 

    Thank you for reaching out!

    Kindly clarify a few points for me so that I can best assist you with this issue.

    1- What is the issue with "unable to connect CC signals"? Is this a hardware issue or a configuration issue? What is the far-end device?

    2- VBUS should not always be "on" for Type-C or PD. What are you wanting the PD to do in this case?

    3- What do you mean by working DRP design? The PJT file attached does not have those settings set to what you described. 

    If you set System Config 0x28 Port Information to disabled, you will not get a connection on the CC lines(see image below). If you want to force a legacy USB 2 mode then you would need to set Port Information to Presents R_d on CC, no data/power role swap or Presents R_p on CC, no data/power role swap based on whether you want to source or sink. 

    4- Lastly, this device is not recommended for a new design. We highly recommend using the TPS65987.

    Best Regards,

    Aya 

  • 0 in reply to Aya Khedr
    Prodigy 245 points

    Hi , thanks for I did not get an email indicating that you had responded.

    We had had to use a 'plan b' and not resolve this issue. I have taken your comments on board and we may try this solution for our reference, 

  • 0 in reply to Andy Goulbourne
    TI__Genius 12591 points

    Hi Andy, 

    Thank you. Feel free to open a new thread if you have further questions about your new solution. 

    Best Regards,

    Aya