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TPS65982: Debug Accessory Mode Documentation

Hayden_Hast
Intellectual 1515 points
Part Number: TPS65982

Hi Team,

We are building a manufacturing test/debug board using the TPS65982. We have a TPS65982 controlling the USB-C port on our main project board and we are intending to use one on the debug board. I would like to have the debug board present itself as a debug accessory so that I can put the TPS65982 on the main board in to Debug Accessory Mode.

Do you have any more information other than the small section (7.2) in the FW User's Guide about how to use the Debug Accessory Mode? I’m assuming that I need a special/modified cable, probably directly attached to the debug board which does not break the connection on one of the CC pins so that the main board sees Rd on both CC wires.

Assuming that I can get the TPS65982 on the main board into Debug Accessory Mode, is it possible to do a normal USB-C PD negotiation while in Debug Accessory Mode? The TPS65982 in Debug accessory mode on the main board will configure its internal mux’s to expose some internal signals, is it possible to configure the mux’s in the TPS65982 on the Debug board in a similar way to break out those signals?

 There seems to be very little documentation about Debug Accessory Mode and I was only able to find one relevant E2E post  , so I’m hoping you can help me figure out how to get what we want out of it.

I've include a simple block diagram to show what we intend to do with only a small modification. Instead of discrete resistors we would like to use the TPS65982 internal resistors for the CC pins on the debug board. 

One last question... we plan to utilize the full 100W of power that PD offers, but have yet to find any 100W adapters/power bricks on the market to test our product with. Are you aware of any or is the only option to use a Power Supply & E-Load to test the 100W?

Please let me know what additional information you need and/or what questions you have.

Regards,
Hayden

  • 0
    TI__Mastermind 36756 points
    Hi Hayden,

    You would need to have a custom cable that connects both CC lines to the ANDROMEDA board. We can easily detect debug accessory mode on the TPS65982. However, I'm not sure if the TPS65982 supports acting as a debug accessory as you have described on the test/debug board. You may need to add a resistor option on that board to present Rd/Rd on both CC lines.
    Since, Debug Accessory Mode is a function of USB Type-C and not necessarily PD, I'm not sure if you could negotiate a PD contract in debug accessory mode. Debug Accessory Mode is covered in the USB Type-C specification which can be downloaded from the following link: www.usb.org/.../
    This will give you a good indication of what can be accomplished in debug accessory mode.

    to test 100W, you could use two TPS65982EVMs and program one as a 100W source and the other as a 100W sink using the Application Customization tool. The TPS65982EVM supports 100W on the external FET path on the board.

    Thank you,
    Eric
  • 0 in reply to Eric Beljaars
    Prodigy 30 points
    Hi Eric,
    I originally posed this question to Hayden.

    I was considering simply putting a male USB-C connector on my debug board that would connect directly to the main board, avoiding the issues with getting both CC pins. Could I just use some multiplexers to break off the CC wires between the connector and the TPS65982 to allow me to select between having the TPS65982 connected for charging test and Debug Accessory mode? If I do this and configure the TPS65982 as having a tethered fully featured cable will it negotiate 100W correctly? In particular, as I understand it, normally to source 100W to the TPS65982 will check that an e-marked cable rated for 5A is present. If I configure it with a tethered cable will it do 100W without checking for the 5A cable?

    Thanks,
    Theo
  • 0 in reply to Theodore Dahlen38
    TI__Mastermind 36756 points
    Hi Theo,

    Welcome to E2E!
    When using a tethered cable, you could configure the TPS65982 for use with a tethered cable when you want to source 100W through PD. Using a multiplexer to mux the CC lines to Rd/Rd could potentially work here. However, you would be bypassing the control of the TPS65982 in that use case. The TPS65982 would not control VBUS or offer Sink PDOs when the CC lines are externally connected to Rd/Rd. If you could achieve the debug modes that your design requires with this limitation then that solution would be sufficient.

    Thank you,
    Eric