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TUSB2046B: TUSB2046B

Jim Wilcox
Prodigy 70 points
Part Number: TUSB2046B
Other Parts Discussed in Thread: TUSB2036

I have your TUSB2046B in a new design.  When I plug in the upstream port windows responds and it sounds like it might be working but upon checking the device manager in windows it reports
"A request for the USB device descriptor failed" unknown usb device.  I have had problems with this for 2 days now.  The suspend line goes low momentarily but then goes high again.  Does windows need special drivers installed?  I am running windows 8.  I see other people have had this same problem with no solution!  I have gone over all the posts and made sure my device is getting reset properly and all the pins are hi/low properly etc.  I have tried 1.5 pull up on both DP0 line and then on the DM0 line.  No luck.

I just discovered that when I set DP0 high thru a 1.5k resistor instead of DM0 that windows reports that device is working correctly!  But the suspend line toggles low for a few milliseconds and then goes high again when plugging in and unplugging the upstream port and the hub still does not work.

  • 0
    TI__Guru 60870 points
    Hi Jim,

    There should not be a pull-up on the DM line - this is for low speed devices only. For a full speed device or hub, the pull-up is on the DP line. Once the hub is enumerated, the host will often suspend it if there are no downstream devices attached. If the TUSB2036 is attached to a host with a pull-up on DP, are the descriptors for the hub loaded? Can you download usbview.exe from Microsoft and check which USB descriptors are loaded?

    Regards,
    JMMN
  • 0 in reply to JMMN
    Prodigy 70 points

    JMMN

    Hey thanks for your response!  I only tried a pullup on DM separately and then on DP separately.  With a pullup on DP only, windows reports that the device is working properly. In this case the hub never works although.  The suspend line goes low momentarily and then goes high.  The downstream port is not accessible even though plugged in the whole time? When I plug into the upstream port from the computer it sounds like it is working and the control panel sees it ok but the computer doesn't see the downstream port? If I plug my computer into where the downstream port goes and eliminate the hub that port works fine!  I will have to check with usbview.exe.

  • 0 in reply to Jim Wilcox
    TI__Guru 60870 points
    Ok, two things to check: VBUS on the downstream ports is 5V and that the 15K pulldowns are installed on the downstream ports.

    Thanks,
    JMMN
  • 0 in reply to JMMN
    Prodigy 70 points

    HUB SCH REVBBBBB.pdfThanks.  I do have those pulldowns.  And also I do indeed have a good 5V on VBUS.  Say I just tried to insert my schematic pdf file and it didn't work!

  • 0 in reply to Jim Wilcox
    TI__Guru 60870 points
    Hi Jim,

    The schematic did load, it looks like you have the overcurrent inputs grounded and they are active low. Can you disconnect them from ground?

    Regards,
    JMMN
  • 0 in reply to JMMN
    Prodigy 70 points

    Sorry I do have them pulled high.  In my original design I left them open without realizing there were no internal pull ups.  I had to use wires on the board to fix and when I sent you the schematic I quickly grounded them but I should have shown them pulled high to 3.3v.  The suspend line never goes low with those pulled low.

  • 0 in reply to Jim Wilcox
    TI__Guru 60870 points
    What happens on the downstream DM/DP lines when the hub enters suspend? Try downloading usbview and see if anything is getting reported as connected.

    Regards,
    JMMN
  • 0 in reply to JMMN
    TI__Guru 60870 points
    Hi Jim,

    Any update?

    Thanks,
    JMMN