• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 31 subscribers
  • Views 1134 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TI TUSB2077A

Leland Langston
Prodigy 80 points
Other Parts Discussed in Thread: TUSB2077A

I have implemented a self-powered USB hub using the above device.  When I connect the upstream port to a PC, the PC recognizes the hub.  When I plug a device (e.g., thumb drive) int a down stream port, the PC sees it and the files.  I can access the files on the thumb drive.  However, when I connect the upstream port to the PC ALL downstream ports are powered up within about 0.5 seconds, regardless of whether or not there is ANY USB device plugged into any port (i.e., even when no device is plugged into a down stream port>) It seems that the PC is telling all ports to power up.  I want the hub to apply power only to the ports that have a USB device plugged in (as do most hubs).  What must be done to make this so?

Leland

  • 0
    TI__Mastermind 18655 points

    Hello,

    Please, share your schematics.

    Regards,
    Joel

  • 0 in reply to Leland Langston
    TI__Mastermind 18655 points
    Hello Leland,

    Sorry for the delay in my reply, I missed the email.

    As you commented the port power is fully under the control of the host system. The TUSB2077A (or any other hub peripheral) can only respond to commands issued by the hosts system, which is a combination of the host controller and operating system.
    The USB host controls the port power of a USB hub using the SET PORT FEATURE (PORT POWER) and CLEAR PORT FEATURE (PORT POWER) commands, these commands cause the TUSB2077A to assert or dessert the PWRONz outputs. These commands are automatically by the USB driver loaded on the USB host. The power commands are sent during system power on / off, reboot, sleep and resume as needed. After enumerating the hub the host will remain all the downstream ports powered. Therefore, you will also be sent during overcurrent conditions. It is possible to generate these commands using another application, but it would likely require a custom USB driver to be used.

    Regards