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    #1

    USB data lines

    I have this Asus X541UA mobo in which both the USB2 and 3 ports don't work (aren't recognized in BIOS or in Win10). The 5V is there, but one of the data lines reads low (.2V in diode mode, where the others are .6V) for both connectors. According to the BV, these traces go to what I believe is an ESD chip, but it is not present, and the traces are hardwired, then go direct to the CPU. I don't have a scope to look for activity on the data lines.

    I guess since this is direct to CPU, there really isn't much I can do. Does that seem right? Other than that, it works great, and the USB C still works fine.
    Last edited by brew99; 05-23-2019, 11:08 AM.
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    #2
    Re: USB data lines

    Hmm.... If you take the cpu out, do you still see the voltage drop you are talking about? Also, does it's resistance change if you switch the polarity of the test leads around? I would expect some line conditioning or such..

    --Edit--
    OH! I'm sorry, this is a laptop board. ahah Right.. so taking the processor out of circuit is a bit harder. :'D I am curious about that polarity change though. I will have to look at that boardview later too. I'm sure it's as you said, but it just seems like such a crap design to not have things like line conditioners between the processor and the usb output.

    It could be that you are shorting to another layer of the board through something like a via point.. If there are test points for the pins that the processor uses for usb, maybe check the resistance between the data pin for usb and then the test point. If you see something odd it may be a messed up via point or something..
    Last edited by Retro-Hipster; 05-23-2019, 12:44 PM.


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      #3
      Re: USB data lines

      "According to the BV, these traces go to what I believe is an ESD chip, but it is not present, and the traces are hardwired, then go direct to the CPU."

      Which ESD chip is that on the boardview D5201,L5233/SLN5213
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        #4
        Re: USB data lines

        Originally posted by SMDFlea View Post
        "According to the BV, these traces go to what I believe is an ESD chip, but it is not present, and the traces are hardwired, then go direct to the CPU."

        Which ESD chip is that on the boardview D5201,L5233/SLN5213
        Not sure if you are asking me for the actual chip ID #s or if you are just wondering if I'm talking about the chip reference.

        Yes, I'm referring to the D5201 and D5203, which are both not populated (on this board, but are on another board I have (@work now so will get later)). Pins run from USB connector to pins 3 and 4 of this chip, then via SLN5213(or L5233) which is a zero ohm 4 lead resistor pack. It seems to be both of the "P" signals that measure low.

        I've given it to my son for now, and he can use the USB C, but I was just curious if I was missing something simple as it's the first I've looked into a USB issue. I have a few of these boards, and they all seem to have various states of those components populated or not. I don't know the history of any of the boards
        Attached Files
        Last edited by brew99; 05-23-2019, 02:12 PM.

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          #5
          Re: USB data lines

          Here is a pic of the mobo with the area circled in red for both USB2 and 3. USB3 doesn't even have the 0ohm resistor pack, but has a hard trace between pads
          Attached Files
          Last edited by brew99; 05-23-2019, 09:41 PM.

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            #6
            Re: USB data lines

            Do any recognise a keyboard or flash drive, have you tried legacy boot and looked at I/O Interface Security usb options in bios .
            Last edited by SMDFlea; 05-24-2019, 01:43 AM.
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              #7
              Re: USB data lines

              I have not tried a keyboard, but did try a flash drive. The flash drive LED lights up solid, but no sign of blinking LED as if it was reading/writing to it. The same flash drive works in another machine, so I know that it's ok.

              I've got 2 other non-working mobo of the same model, so don't know if the USB acts the same or not, but they do measure about 0.6V in diode mode, which is what I believe it should be (this one measures about 0.2V on the "P" data lines).

              I've played around in the BIOS also, and don't see anything which should limit it from being seen. Even checked out YT on this model and made sure I was setting things so it could boot from USB.


              Just funny how there seems to be no protection for the CPU on these data lines on these boards.

              Anyhow, thanks for the suggestions...I'll live with it as is (atleast the USB C works)
              Last edited by brew99; 05-24-2019, 09:22 AM.

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                #8
                Re: USB data lines

                Just a little update: I decided to try a USB 3.0 stick in the USB3 port, and it worked. Seems that just the USB2 devices aren't recognized, and have to do with that one D+ line that appears to be lower resistance than normal.

                So long story short, the one USB3 port is still usable, but only with a USB3 device

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