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TUSB2077A hub configuration

Abraham Gogulamudi
Prodigy 40 points
Other Parts Discussed in Thread: TUSB2077A, TPS2042

Hi,

We are using TUSB2077A hub in freescaele iMX27 based system with windows CE 6.0.

In our design USB host1 of the processor is connected to TUSB1105RGTR which in turn is expanded through the hub TUSB2077A hub.

We are facing a problem with USB device connected to this. When we connect a BUS powered device it gets detected during boot up and works fine. But if we connect a self powered device it is not getting detected in the bootup. We have to disconnect and reconnect the device in order for it to get detected.

Kindly help us in fixing this issue.

 

 

  • 0
    TI__Guru* 76130 points

    Hello Abraham,

     

    Can you check the following:

     

    1) Since you are configuring the hub as self powered and also you are connecting a self powered device, probably there is an over-current condition, can you check the status of the ~OVRCUR  and ~PWRON signals when you connect the self powered device?

     

    2)  In your schematic, the TPS2042 has a 10K pull up on the ~OC# pins, in addition you are placing a 15 K series resistors in the ~OVRCUR inputs of the hub, this condition would probably cause the ~OVRCUR hub's inputs are not seeing a valid "1" .

     

    3) Does the fault happens with any self powered device?  Have you tried with more of  one different device?  (Just to make sure is not a downstream device issue)

     

    Regards.

  • 0 in reply to Elias Villegas M.
    TI__Guru* 76130 points

    Abraham,

     

    Please see another recommendation from a TI colleague:

     

    There could be a power up timing issue.

    Since the device you are attached is self powered device, per usb specification, a device will enter into suspend mode after 3 ms of bus inactivity. So probably the device is entering into suspend mode while the hub is just at  the powering up sequence, once the TUSB2077 is enumerated it doesn't "see" the suspended device.

     

    Julie,  thanks for the support.

  • 0 in reply to Elias Villegas M.
    Prodigy 40 points

    Hi Julie,

    Thanks for support.

    I have following observation.

    1. When we connect Self - powered device to TUSB2077 Hub.

    Observation 1: Host able get device descriptors of TUSB2077Hub, but Host unable to get Port status of TUSB2077 Hub.

    Observation2: if Disconnect and Reconnect Device to Host, Host able get device descriptors of  Device Connected and load related Drivers.

    2. When we connect bus- powered device to TUSB2077 Hub.

    Observation : Host able get device descriptors of TUSB2077Hub and Port status of TUSB2077 Hub.

     

    Kindly help us in fixing this issue.

    Thanks and Regards,

    Abraham Lincoln G

     

     

  • 0 in reply to Abraham Gogulamudi
    TI__Guru* 76130 points

    Hello Abraham,

     

    You need to ensure the TUSB2077 is powering up before the downstream device.

    The TUSB2077 requires a 1.5 to 2 ms long  reset pulse, plus the register initialization, and per USB specification, the hub is required to respond to the host within 10ms after power up.

    Can you measure the TUSB2077's reset pulse duration in order to know if you can reduce it to the minimum?

    Also, you can add a power-on delay circuit to the downstream device.

     

    Regards.