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TPS65981: Create Firmware For User Alternate Mode

Viktor Bergen
Prodigy 130 points
Part Number: TPS65981
Other Parts Discussed in Thread: , HD3SS460

Hello,

I'm trying to create a firmware for TPS65981 that enables a User Alternate Mode.
For this I tried to follow the recommendations in the document SLVA841 but did not succeed.
In order to make sure the hardware is ok, I’m using two evaluation boards TPS65981EVM from TI and connect them with a standard USB-C to USB-C cable.

How do I need to configure the TPS65981 so that when I connect the two TPS65981EVM with USB-C cable it configures the HD3SS460 for “4CH AM”? For this it is necessary that the lines AMSEL and EN would be high. Whatever I do this is never the case.
Could someone help me to figure out what I’m doing wrong. I could share the TPL project file I created.

Is there an example project somewhere available?

Thank you.

Regards,

Viktor

  • 0
    TI__Mastermind 36756 points
    Hi Viktor,

    Do you have a PD analyzer available to read back the PD messaging? This would let you know whether the alternate mode is entered correctly or not. The HD3SS460 mux is used for DisplayPort alternate mode, this is separate from User Alt Mode. I would suggest reading the following App Note on DisplayPort alternate mode to configure your EVMs for DP alt mode:

    www.ti.com/.../slva844b.pdf

    If this answers your question, PLEASE select "This resolved my issue"

    Thank you,
    Eric
  • 0 in reply to Eric Beljaars
    Prodigy 130 points
    Hi Eric,

    No, I do not have a PD analyzer.
    There is no problem with DisplayPort Alt mode, but I would like using the HD3SS460 MUX also for User Alt mode. I do not see a reason why it should not work for User Alt mode as long as the signal is compatible. Do you see a problem with that?

    Thank you,
    Viktor
  • 0 in reply to Viktor Bergen
    TI__Mastermind 36756 points
    Hi Viktor,

    The AMSEL event would only be enabled during DisplayPort Alt Mode and would not do anything for user alt mode. You can read about the GPIO events available here: www.ti.com/.../slva838.pdf
    I'm not sure about the HD3SS460 mux for user alt mode. I think it is dependent on the signal you are passing through. I would suggest asking a question with HD3SS460 as the part number if you have more concerns so that the device expert can answer your question.

    Thank you,
    Eric