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Original question:

TUSB320: What's the difference between TUSB320 and TUSB320LI/HI and TUSB320LAI/HAI

TUSB320: Does TUSB320 _really_ support Try.SNK and/or Try.SRC via external SW?

Evan Shultz
Prodigy 30 points
Part Number: TUSB320

There seems to be incomplete or conflicting information on the forum on this topic. Perhaps you can help to clarify since I'm not able to sort it out.

https://e2e.ti.com/support/interface-group/interface/f/interface-forum/488015/difference-between-tusb320l-h-and-tusb320/1762458, from 8 years ago, has a PowerPoint attachment which says that Try.SNK is supported with SW intervention. There is no information I can see linking to this SW. Try.SRC and some other options are stated to be a WIP.

https://e2e.ti.com/support/interface-group/interface/f/interface-forum/561951/tusb320-does-tusb320-support-try-snk-try-src, from 7 years ago, says TUSB320 doesn't support Try.SNK and Try.SRC. However, this could be myopically considering only HW support for these mode preferences and ignoring a possible SW workaround.

https://e2e.ti.com/support/interface-group/interface/f/interface-forum/707926/tusb320-what-are-the-differences-between-the-following-parts-tusb320-tusb320li-tusb320hi-tusb320lai-tusb320hai/2608914, from 5 years ago, says both Try.SRC and Try.SNK are supported with external SW. Again, no SW info is linked.

Finally, https://e2e.ti.com/support/interface-group/interface/f/interface-forum/969379/tusb320-what-s-the-difference-between-tusb320-and-tusb320li-hi-and-tusb320lai-hai/3581699 from 3 years ago says TUSB320 doesn't support either mode preference. Again, it is not clear if this means only via hardware and is ignoring SW intervention.

So... what to make of this? As I said, the info looks incomplete or in conflict. My product is using the original TUSB320 on a DRP and I would like to prefer the sink/device role when connected with another DRP. I have the I2C bus connected to a processor, but I'm not currently using that interface.

If we look at the datasheets for the TUSB320 and later versions, page 19 shows the relevant register map on all datasheets. TUSB320 (https://www.ti.com/lit/ds/symlink/tusb320.pdf) shows no SOURCE_PREF register (used for Try.SRC and Try.SNK). TUSB320H / TUSB320L (https://www.ti.com/lit/ds/symlink/tusb320li.pdf) does as well as TUSB320HA / TUSB320LA (https://www.ti.com/lit/ds/symlink/tusb320lai.pdf). So does TUSB320 really support the SOURCE_PREF register but it's not shown in the datasheet? Is there some other SW song and dance which will simulate Try.SNK and Try.SRC? Is something else meant by "SW intervention" or "external SW"? I can only assume this means using the I2C interface for TUSB320.

Is there really a SW method to make the original TUSB320 perform Try.SRC and/or Try.SNK? If so, what is it? Is it in the latest Linux driver? If so, I am not seeing it and guidance would be valuable.

  • 0
    TI__Mastermind 30450 points

    Hi Evan,

    I will look into this and get back to you.

    Best,

    Shane

  • 0
    TI__Mastermind 30450 points

    Hi Evan,

    The TUSB320 does not support Try.SNK or Try.SRC. Whatever external software may have allowed this functionality in the past is no longer supported. If you require this feature, consider using the TUSB320LAI or TUSB320HAI. These devices have hardware support for Try.SNK and Try.SRC.

    Best,

    Shane

  • 0 in reply to Shane Hauser
    Prodigy 30 points

    Hi Shane,

    Thank you. I understand there is no TI-provided SW tool to do this.

    And to close the other possible line of question above: there's no way to simulate Try.SNK or Try.SRC using I2C with TUSB320? I must use either newer TUSB320 version if I want Try.SRC and/or Try.SNK?

  • +1 in reply to Evan Shultz
    TI__Mastermind 30450 points

    Hi Evan,

    I am not aware of any way to simulate Try.SNK/SRC on the TUSB320 with I2C and as such cannot support that use case. I recommend using either the 320LI, 320HI, 320LAI, or 320HAI if you want Try.SRC/SNK.

  • 0 in reply to Shane Hauser
    Prodigy 30 points

    Thanks again Shane.

    I do not mean to be irritating, but I want to be very clear. In your first technical reply, you wrote "TUSB320LAI or TUSB320HAI...have hardware support for Try.SNK and Try.SRC". Both the LI / HI and LAI / HAI datasheets say on page 11: "Try.SRC and Try.SNK are only available when TUSB320 is configured in I2C mode. When operating in GPIO mode, the TUSB320 will always operate as a standard DRP." That leads me to two clarifying questions: (1) Should your statement also include the LI and HI versions, not just LAI and HAI versions? (2) Also, what does "hardware support" mean if only the GPIO mode and not the I2C mode of the IC supports these preferred DRP features; do you mean the original TUSB320 does not have support in the IC (the IC's logic design being the 'hardware' you refer to) for these preferred DRP features even though in the 'hardware mode' (not the I2C mode) these preferred DRP features are never available?

  • 0 in reply to Evan Shultz
    TI__Mastermind 30450 points

    Hi Evan,

    I understand the need for clarity and assure you it is no problem to elaborate on your questions.

    1. Yes, the TUSB320LI, HI, LAI, and HAI have the same support for Try.SRC/SNK in I2C mode. My original response could have included all of these.

    2. “TUSB320LAI and HAI have hardware support”. By saying this I meant these devices do not require external software to support Try.SNK/SRC as the device comes with the ability to perform these functions. In order to use Try.SRC/SNK, the device must be in I2C mode and the SOURCE_PREF register should be written to as shown on the datasheet.

    3. The original TUSB320 may have the logical ability to support Try.SRC/SNK, however it would seem to need external software to allow this. After looking into the issue, I do not believe the software for this is available.

    Best,

    Shane

  • 0 in reply to Shane Hauser
    Prodigy 30 points

    Hi again Shane,

    Thanks again.

    On item #3 above, are you able to share what the external software would do? Even if the software/library or source code is not available (or no longer available), knowing how to control the original TUSB320 to perform Try.SRC and Try.SNK would alleviate my issue since I have the I2C interface connected to a processor. If you can share how to do this, with me creating the software independently, my question may be resolved.

  • 0 in reply to Evan Shultz
    TI__Mastermind 30450 points

    Hi Evan,

    Is there a reason you cannot switch to the TUSB320LAI/HAI device? From what I can see it would be cheaper than the original 320 and have Try.SRC/SNK.

    TUSB320:

    TUSB320LAI:

  • 0 in reply to Shane Hauser
    Prodigy 30 points

    Hi Shane,

    Switching involves testing and qualification. This can be done on future products, but it doesn't help with product already in the field. If the original TUSB320 can do Try.SRC and Try.SNK, there is just a single testing/qualification process and one set of hardware. The cost is small enough to allow us to use original TUSB320, if possible, and then revisit this later.

  • 0 in reply to Evan Shultz
    TI__Mastermind 30450 points

    Hi Evan,

    I see, unfortunately without the software I do not know what it would do. Perhaps some function controlling the MODE_SELECT register in I2C could simulate Try.SNK/SRC functionality.

    As this is not a supported use case, I cannot guarantee this will work.

    Best,

    Shane