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TUSB320: Configured as DRP

Danilo A.
Mastermind 28830 points
Part Number: TUSB320
Other Parts Discussed in Thread: TPS65987D, TPS25750

Hi Team,

We received this inquiry from our customer.

I have a very specific question about a component. It is about the TUSB320. One can configure it either as a DFP, UFP or DRP
I would like to know, what would happen if it is configured in DRP and a laptop (also a DRP) is connected
The reason for this is that at some point i want to supply the device with the power my laptop can provide and configure it over the Type-C interface. But at another point I would like for the device act as a host, for when I insert a flash drive.

But yeah, the scenario is the following: The Device should have a type C interface with the TUSB320, so it can be host and device (DFP,UFP). For when i connect a laptop to it, it shall be powered by the laptop alone. Then i can exchange data over usb2. but instead of the laptop a flashdrive should also be connectable. In this moment it needs to become the host. How does it work with the pulldowns/pullups? and is it a factor if it is a Type > to Type C cable?
Regards,
Danilo
  • 0
    TI__Guru**** 178036 points

    Hi,

    You need a PD controller such as TI TPS6598x family for this application. Any time you need data and power to flow in a opposite directions, a PD controller must be used to implement PR_SWAP and DR_SWAP. CC controllers such as TUS320 can not implement PR_SWAP and DR_SWAP.

    Thanks

    David

  • 0
    Prodigy 70 points

    Hi,
    i am the guys who did the original inquiry.
    Altough, I would like to thank David and the rest of the TI team for their help, I want to specify my question and add some minor details which I still am mildly confused about.

    Having mentioned that the to be developed device shall have DRP (actually Dual Role Data – Role -> DRD; DRP=Dual-Role-Power).

    The change from one mode to the other is achieved by the central logic communicating through i2c to the TUSB320. The TUSB doesn’t change the roles as USB PD does, it does it by actually

    Utilising a switch, toggling between Rp pulled up or down, right? I see how this makes it fundamentally different from a "proper" PD controller, utilising the PD protocol. So it would NOT be possible to imitate this behaviour of switching (maybe resetting, newly enumerating) with the TUSB320? This switch MUST come from "within" from the software/from central logic?

    General question about USB:

    1) For a device to be able to communicate to a usb, this device would have to have CC pins in specific pullup/pulldown position for it to become the power sourcing host, resulting by default in DFP role, too? 

    2) i have troubles understanding how a USB 3.0 or 2.0 Type-A to Type-C cable works in this regard.
    Is the direction/role dictacted by the fact, that the host must be connected to the Type-A, because the type-A ending of the cable doesnt feature CC lines, right? How does this Type-A host know that the Type-C connected device has Rp resistors connected for 5V at 3A connected if it doesnt have any CC lines itself.

  • 0 in reply to David (ASIC) Liu
    Prodigy 70 points

    Thanks for your reply. These components are for PD-level power levels. What components are mor suitable for <15W with USB PD Roleswap functionality?

  • 0 in reply to Michael Schichta
    TI__Guru**** 178036 points

    Hi

    Please see my response below.

    The change from one mode to the other is achieved by the central logic communicating through i2c to the TUSB320. The TUSB doesn’t change the roles as USB PD does, it does it by actually

    Utilising a switch, toggling between Rp pulled up or down, right? I see how this makes it fundamentally different from a "proper" PD controller, utilising the PD protocol. So it would NOT be possible to imitate this behaviour of switching (maybe resetting, newly enumerating) with the TUSB320? This switch MUST come from "within" from the software/from central logic?

    No, both the PR_SWAP (Power Role Swap) and DR_SWAP (Data Role Swap) are part of the PD control message. Below is an example of the PR_SWAP message sequence

    So the SWAP is an actual data packet, and not just toggling between Rp and Rd. The TUSB320 can't send/receive the SWAP control message.

    General question about USB:

    1) For a device to be able to communicate to a usb, this device would have to have CC pins in specific pullup/pulldown position for it to become the power sourcing host, resulting by default in DFP role, too? 

    It depends on the hub power and data implementation. The traditional USB has the power and data tied together -> the source acts as both a USB data host and power provider. But USB Type-C splits the power and data role. You can be a data sink or device while being a power provided or vice versa. The data and power role can also be changed separately using the PR_SWAP or DR_SWAP after the initial CC negotiation. 

    2) i have troubles understanding how a USB 3.0 or 2.0 Type-A to Type-C cable works in this regard.
    Is the direction/role dictacted by the fact, that the host must be connected to the Type-A, because the type-A ending of the cable doesnt feature CC lines, right? How does this Type-A host know that the Type-C connected device has Rp resistors connected for 5V at 3A connected if it doesnt have any CC lines itself.

    Please see the diagram below and in particular note #2. The CC pin of the Type-C plug has the Rp connected to the VBUS. For the host connected to the Type-A plug, it will always be host. For the Type-C device, upon seeing the Rp inside the cable, it will configure itself as a sink. 

    Thanks

    David

  • 0 in reply to David (ASIC) Liu
    Prodigy 70 points

    Thanks, David.
    This did clear some of my problems. Thanks alot. I would consider this question to be answered. @Danilo, may close it

  • +1 in reply to Michael Schichta
    TI__Mastermind 37855 points

    Hi Michael,

    I'm glad David was able to clear some of your problems. If you are interested in a PD controller, we would recommend you look at the TPS65987D family or the TPS25750. Those both support USB-C PD and power/data role swaps. If you have questions about those parts, feel free to open a new thread referencing those parts.

    Closing this thread now, please select the resolved button.

    Thanks and Regards,

    Chris

  • +1 in reply to Christopher Lim1
    Prodigy 70 points

    Hi Chris,

    I am unaware how i can mark it as resolved. openend the thread on my behalf