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TPS65981EVM: TPS65981EVM USB source and DP sink

Kenneth Mayer
Prodigy 50 points
Part Number: TPS65981EVM
Other Parts Discussed in Thread: TPS65981

I have a question about a potential system configuration using two TPS65981 devices. I need each side of the device to perform both source and sink functions. The system-side sources DP and sinks USB, while the host (PC)-side sinks DP (to be connected to a display) and sources USB. I have attached an edited version of Figure 5 from the TPS65981EVM user manual to illustrate the system. Is this configuration possible with the TPS, or can one TPS device only source or sink both types of signals?

  • 0
    TI__Mastermind 30000 points

    Hello Kenneth,

    The TPS65981 on its own is able to support this functionality. It can be configured as a DRP for whatever system you design it to. However, the hardware for the expansion EVM do not allow for bi directional data flow like what you are asking for. 

  • 0 in reply to Adam Mc Gaffin
    Prodigy 50 points

    Hi Adam.

    Thank you for your reply. Off the top of your head, do you know of any other device I could use or, any way that I could build this setup using the EVM?

    Thanks,

    Kenneth

  • 0 in reply to Kenneth Mayer
    TI__Mastermind 30000 points

    Hi Kenneth,

    After looking at your diagram again, are you wanting the system to act as a DP source and USB sink at the same time? If so, this is not possible. A type-C PD device allows for your system to be both a DFP and UFP (DRP), but not at the same time. At any given time between two connected devices, one will be transmitting the data (DFP) and the other will be receiving data (UFP)

  • 0 in reply to Adam Mc Gaffin
    Prodigy 50 points

    So it isn't possible to both have an active DisplayPort link from the source and to have a USB 2.0 sink device on the same side of the cable simultaneously? That is unfortunate, as we had hoped that we see the DisplayPort output and also reprogram the FPGA and communicate with its UARTs using only a single cable.

    Is it possible to switch between port directions at runtime without reprogramming the TPS65981's firmware? For example, disabling the DisplayPort link, communicating with the application board as a USB 2.0 sink over the same cable, and then switching back, perhaps with an onboard switch or I2C device?

  • 0 in reply to Kenneth Mayer
    TI__Mastermind 30000 points

    Correct, this is not possible. 

    Yes, this is possible. You could issue a port disconnect and then change the configuration where the TPS65981 now only acts as a UFP instead of a DFP.