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TUSB8042A: How to get started sending USB commands via a USB host

Max Kross2
Prodigy 50 points
Part Number: TUSB8042A

Hi! 

When going through the data sheet we noticed this line, 

"An individually port power controlled hub switches power on or off to each downstream port as requested by the
USB host."

Does this mean that via USB commands, individual USB ports can be enabled/disabled while the hub is powered on?

If so, what materials could we look at to get started in implementing this?

Thanks,

Max

  • 0
    TI__Guru 60870 points

    Hi Max,

    So yes the hub is pretty much a "dumb" device in that it will respond to whatever USB commands are sent from the host.   The port power commands are usually all handled by the default USB drivers.  TI doesn't have any resources on how to create an app or utility to manually send these commands.

    Regards,

    JMMN

  • 0 in reply to JMMN
    Prodigy 50 points

    Hi JMMN,

    Is there a documented way to toggle port power while the device is running using other protocols?

    Thanks,

    Max

  • 0 in reply to Max Kross2
    Guru 317450 points

    You have to send a ClearPortFeature(PORT_POWER) message to the hub. Whether this is possible, and how to do this, depends on the operating system you're using. (And it's likely that the OS does not expect this and will not properly disconnect the driver.)

    In practice, this feature is used only by the OS itself as part of overall power management.

  • +1 in reply to Max Kross2
    TI__Guru 60870 points

    Hi Max,

    We do not have any documentation on how to toggle port power by USB command and doing so unexpectedly may cause bus resets to occur that could impact other USB device operation.

    Regards,

    JMMN