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TUSB2046B Enumeration problem

STEVEN HEINTZ
Prodigy 20 points
Other Parts Discussed in Thread: TPS2041

We have the TUSB2046 controller in our design in front of an FTDI USB host controller.

Have noticed a strange quirk during initial enumeration though that I'd like some thoughts on....

Some USB devices are fast to respond during enumeration - and can always enumerate on any port.

Quite a few advanced USB devices (for example a particular microsoft usb mouse) can only enumerate if they are connected to port 2, 3, or 4 of the hub, and I have a quick responding device on an earlier port (i.e.; port 1)  On startup, the delay of enumerating the device on port 1 first seems to do the trick for the other devices

I've tried other brands of hubs, (wired in manually) and don't have this problem.  Our in-circuit design with the TI chip exhibits this behavior, as well as the TPS207x EVK board (that has an earlier version of the TUSB2046 chip - again wired in manually)

 

As long as I have a simple usb device on port 1 of the hub, I have no problem enumerating all types of devices on the other ports - but many of these devices can't come first in the chain.

Hope this makes sense....  Really frustrating though - Does it sound like a power-on/reset sequencing issue?

Thanks

Steve

 

 

  • 0
    Prodigy 20 points

    Found out one additional thing -

    When the TI HUB chip enumerates, it briefly sends the PWRON lines high momentarily - this causes the TPS2041 power mgt ICs to remove power from the connected devices briefly.

    Some devices (like the microsoft mouse) don't  have time to reboot and report in for the enumeration along with the hub.  I noticed when using the TPS207x EVK board on a Windows host, the windows machine doesn't hear from the mouse until a second enumeration request

    The embedded host chip isn't as gracious - (unfortunately)  it needs to enumerate the bus and collect all connected device information at once.   Overriding the TPS2041 power mgt ICs seems to resolve the problem for now - devices are always powered when plugged in, and can respond to enumeration requests immediately...

     

  • 0 in reply to STEVEN HEINTZ
    TI__Guru* 76130 points

    Hello Steven,

    Do you have the problem only on Port 1?

    Do you have your downstream devices permanently attached?

    Can you share your schematics?

    What is possible happening is that the reset timing for the TUSB2046 is too long and the downstream device is starting up before the hub, because of this, the downstream device is entering in suspend mode before the hub try to enumerate it. Try to lower the TUSB2046's reset duration within 1.5 to 2 ms.

     

    Regards.