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AM335x USB overcurrent input

Jonas Antunes23
Prodigy 95 points

Other Parts Discussed in Thread: TPS2051

Hi All,

I am making a board based on BeagleBone Black that needs two USB host ports.

The USB1 is ready to use.

The USB0 I had to change to be host (I made changes on Device Tree Blob - am335x-bone-common.dtsi).

For tests purposes the USB0_VBUS was fixed at 5V and the USB0 is working very well as host.

Like USB1, the VBUS for USB0 wilI be supplied for a power switch control based on TPS2051.

The TPS will use the USB0_DRVVBUS enable signal and the output USB0_OCn signals a overcurrent condition.

So, I want to know which GPIO could be the input of this USB0_OCn and if there are changes to do on device driver and/or device tree.

For the USB1 port, the USB1_OCn is connected to GPIO1_26 and I didn't see specifics references about this input on device tree files.

Best regards,

Jonas

  • 0
    TI__Guru 63605 points

    I'm not able to answer any software related questions, but can provide some additional information about how the USB controller is able to detect an over-current condition.

    The USB controller is able to detect an over-current condition because the PHY measures the voltage applied to VBUS.  The PHY uses an internal signal to tell the controller VBUS has dropped below a valid level.  If the TPS2051 output drops below the VBUS valid threshold (4.4v max) while DRVVBUS is still active, the PHY assumes this voltage drop has occurred because the power source is current limited due to an over-current condition. Therefore, you may not need to connect the TPS2051 OCn output to a GPIO.

    Regards,
    Paul

  • 0 in reply to peaves
    Prodigy 95 points

    Hi Paul,

    In fact my OS (Debian 8, kernel 4.4.14) doesn't react when the OCn is activated.

    Only when I reduced the VBUS (around 3.9V) the device driver reported VBUS_ERROR and the PHY turned off the TPS2051 by DRVVBUS line.

    Just for convenience I'll reserve on my project a GPIO for OCn from the new TPS2051. May be that the device driver or my application can use it on future.

    Thanks a lot for your reply.

    Best regards,

    Jonas