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TUSB2077A: USB Hub Detection Issue

Sanket Patadiya
Prodigy 20 points
Part Number: TUSB2077A


Hi TI Team,

I am SANKET PATADIYA from VOLANSYS TECHNOLOGIES. 

In one of our project we are using the TUSB2077APT USB Hub Controller IC. We are driving 1 upstream port and 4 downstream ports using the IC.

Issue details:

When we plug in the upstream port to the PC the COMM port generates on the device manager of PC but it gets refreshed on and on.

When i checked the Pin 42 (PORTDIS) it fluctuates between 0 to 3V3. 

Basically, we are facing issue in COMM port detection.

Find the sch attached below for your refrence.

Please suggest a suitable solution.

Thanks & Regards,

  • 0
    TI__Guru 60870 points

    Hello Sanket,

    The downstream ports are missing the caps / series resistors / 15K pulldowns, see Figure 9 in the datasheet.  The absence of 15K pulldowns is likely impacting device connection.  The caps / series resistors should be added but would have less impact on functionality.

    Regards,

    JMMN

  • 0 in reply to JMMN
    Prodigy 20 points

    Hi JMMN,

    Thanks for your quick response.

    Actually, We have already applied the 15k Pulldowns, Series Resistors and Caps on downstream ports.

    Please find the attached photo of the USB Termination Schematic.

    While debugging my observations are as below:

    - Pin 1,40,41,42 : SUSPND, HUBCFG, PORTPWR, PORTDIS respectively  are fluctuating between 0 to 3V3.

    Can you please help us to identify probably which part of sch is making these pins fluctuate?

    Thanks & Regards,

  • 0 in reply to Sanket Patadiya
    TI__Guru 60870 points

    It appears that the USB host is resetting USB for some reason.  Can you provide any debug output from the host?  What operating system is being used?

    Regards,

    JMMN