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DM8168 2.x: usb host overcurrent

Massimo
Expert 6475 points

Hi,

Can the ARM be notified in case of over current on VBUS when the device is configured as USB host? In example if there is a short-cut on the cable.

After an over current event, how can we “restore” the 5V supply?
Can we restore it under software control, or do we need to reset the device?

Maybe it's spec'ed in the TRM but I'm not able to find where.


Thanks, best regards

Massimo

  • 0
    TI__Expert 5475 points

    Hi,

    The USB 5.0 Power is sourced external to the device. All the device core does, in relation to the power control is, enable/disable a signal based on the role the controller assumes. If the controller assumes a Role of a Device, it will drive USB_DRVVBUS low. If the controller assumes the role of a Host, it will drive USB_DRVVBUS High.

    Since all of our devices are Self Powered and since all of our devices USB2.0 controller is an OTG controller, we hardly use the power on the VBUS. We only use it to enable the 1.5KOhm resistor in device mode. Other than that the also voltage comparators within the PHY tap into the the VBUS monitor the voltage level.

    If there is a short on the cable or any kind of other issue, that needs to be addresseed external to the device.

    Best regards, Zegeye

  • 0 in reply to Zegeye Alemu
    TI__Expert 7885 points

    Massimo

    In host mode, the usb hub driver on linux kernel can detect the over current condition. When over current device is connected to HUB, the hub can detect the overcurrent condition on a particular port and send the message to hub driver through interrupt transfer. The HUB driver will disable the particular HUB port and rest of the devices connected other port will continue to work. But if over current condition occurs on root port, then there is no recovery, remove the over-current device from the host and connect the good device.

    Regards

    Ravi B