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Original question:

TUSB8042: Using without EEPROM

TUSB8042: Overcurrent status

WST
Expert 1025 points

Part Number: TUSB8042

Is there a way for the driver to read the overcurrent status on any port without using the SMB interface? Does the HUB/driver report to the upstream controller the individual status of each of the 4 ports? I have the part connected in non-ganged mode, pin 42/GANGED is pulled low.

If I want to read the overcurrent status of an individual port, do I need to route the lines connected to the OVERCUR1-4Z pins to an external device?

  • 0
    TI__Guru 60870 points

    The TUSB8042 reports overcurrent events as required by the USB specification over USB protocol.  So if an overcurrent event occurs, the hub will notify the USB host immediately using an interrupt endpoint and typically the USB host will disable power to all the hub ports.  The TUSB8042 does not report overcurrent through its internal registers.  USB doesn't support silent failures so if the overcurrent occurs, the USB host should post a notice to the end user.

    Let me know if you have any further questions.

    JMMN

  • 0 in reply to JMMN
    Expert 1025 points

    Thank you for the quick response! I have already put in place individual over current limit ICs on the board, so having the HOST disable the power isn't necessary. I don't know the protocol enough to know if it reports individual port "overcurrent events" over the protocol so the user could be better informed which port is having problems. If not, then I would have to use an external method to report this so that the other ports could still be used if one shuts down. I do have an external 'or'ing' of the overcurrent status back to a controller SMARC pin that reports that an overcurrent event happened, so it is a backup to the USB-interrupt endpoint path.

  • +1 in reply to WST
    TI__Guru 60870 points

    On most operating systems, the USB host will typically report an generic overcurrent error and power off all the hub ports and typically require the hub to be disconnected and reconnected or reset before powering back on the ports. If the hub is in individual port power mode the hub will report which port is having the issue, but I have not seen that reflected in the operating system error window pop-ups.