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TUSB8041: Manufactured Design TIDA-00288 but Computer Won't Recognize it

Justin Kern
Prodigy 40 points

Part Number: TUSB8041

Hello,

I have manufactured design TIDA-00288, but it isn't fully operational. After plugging it into a computer, I have taken a multimeter to check the 5v, 3v3 and 1v1 rails and they all look good, but the computer isn't detecting it as a USB hub. This design uses the TUSB8041, so this is the center of my focus. One anomaly I have found is that Pin 50, GRSTz, has about 3.3V on it. I have confirmed it isn't shorted to the 3v3 rail, so I'm not sure where it's coming from since it is connected only to a capacitor and then to ground.

I have made 3 minor modifications to the TIDA-00288 design. First, I only needed 3 downstream ports, so the fourth one is not being used. Second, I changed the downstream ports from the USB 3.0 A connector to USB 2.0 Micro. This has left the TX and RX pairs unused, so I am only using the D+/- for data from the downstream ports to the TUSB8041. I have left the TX and RX pairs connected to the upstream port, because this connector was left unchanged. Third, I added 4 low power LEDs to the 5v rail. They draw 0.4mW each, which Art Mecina of TI had confirmed would be safe to add (Thanks again, Art!).

  • 0
    TI__Guru 60870 points

    Hi Justin,

    GRSTz has an internal pullup, so it should be 3.3V after the reset completes.  Can you confirm that there is not a pulldown on SMBUSz?  Does the clock start?  What is the voltage on USB.VBUS and USB_R1 when it is connected to the host?

    Regards,

    JMMN

  • 0 in reply to JMMN
    Prodigy 40 points

    Thanks for your response!

    Correct, there is no pulldown on SMBUSz, I have it as a floating pin.

    USB.VBUS is 0.536V

    USB_R1 is 0.470V

    I don't have an oscope readily available and the fluke 87 only goes up to about 400KHz; is there another way to check if the clock is started?

    Thanks!

    -Justin

  • 0 in reply to Justin Kern
    TI__Guru 60870 points

    Hi Justin,

    Ok, more debug ideas:

    Can you confirm the thermal pad of the hub has a good ground connection?  It is the main ground for the hub and the hub can malfunction if it isn't connected.  Is there a bulk cap on the GRSTz line, no external pullup, so the hub gets a reset at power on?  What's your host OS?  If it is Microsoft can you download usbview.exe to see what is on the USB?  Or if you are running Linux, send the USBMON debug log?  Can you probe the upstream USB lines of the hub (DP and DM) that are connected to the host and see if DP is high (3V).

    Regards,

    JMMN

  • 0 in reply to JMMN
    Prodigy 40 points

    Hey JMMN,

    Thank you so much again for your input! Embarrassingly, when I replaced the cap on GRSTz, it seems I put too much solder on, and grounded GRSTz. After fixing this, I have it up and running at full capacity with no issues. Again, I sincerely appreciate your efforts. I had never heard of USB Device Viewer before, and I'm thankful you turned me to it! It will be helpful for my future USB projects.

    It's always something absurdly simple that gets ya-

    Justin

  • 0 in reply to Justin Kern
    TI__Guru 60870 points

    Great!  Glad it was something easy to fix!