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Power Delivery and Loopback test on USB port

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  • Power Delivery and Loopback test on USB port

    I have a USB board need to test the Power Delivery + loopback test on USB_Downstream_Port_0 and USB_Downstream_Port_1
    as diagram below

    Click image for larger version

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    I am planning to use PM 125 (PD) and PM065 (Loopback) to run the test. My question is how do I conncet from
    my test PC to the USB board and to the PM125 tester? How many PM 125 and PM065 do I need to test both USB ports.

    The connection with assumption that the test will fully automate with no cable swapping during test​.

    Thanks in advance for your help and suggestion.
    Last edited by p_pham; Apr-03-2024, 11:29 PM.

  • #2
    Can you give more details of the "USB board". It is a computer / PC? What type? What O/S? Or is it just a charger? If it is just a charger, then data loopback isn't possible as chargers don't do data transfer.

    Maybe some photos of the setup would help.

    The upstream / downstream differences in your diagram also aren't clear. Are you saying your USB ports are somehow uni-directional (i.e. not standard USB ports?)

    If you want full automation, can you write code?


    • #3
      Hi David,
      Thanks for geting back to me. I am try my best to answer your question

      It is a USB hub capable of both data (USB2 and USB3) and PD3.1. Hub can work with widows/linux

      It is a standard hub, so bidirectional

      Yes, we can write scripts in Python or using Labview to design



      • #4
        You would need a setup something like this using the USB PD Tester and loopback plugs.

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        I don't know if your hub is self powered or bus powered. The host machine should obviously support power delivery as well.
        The host machine would need to be running the monitoring software for the PD Tester (USBPDTest).
        And also running the USB3Test software for testing the data loopback function.

        There is also a programming API for both the PD Tester and the USB3 plugs. See the pages linked to above.


        • #5
          Thanks for the information. We will try it and let you know or may back with more questions.


          • #6
            Hi David,

            Thanks for your instructions and diagram. We are setting up our test system using your diagram and it is working fine for PD test. However, the tester unable to recognize the USB loopback (USB 3 loopback). Are there anything we need set on PD equipment or our tester? Does it matter if our USB port only support USB2 speed and we plug in USB3 loopback?


            • #7
              Our loopback plugs support both USB2 and USB3. So that should not be a problem.

              You do need to install the device driver on the Windows machine however. And you will probably also want the USB3Test software, from the same download page.

              Finally on the USB-PD tester there is an option to enable / disable the downstream loopback port from the on LCD screen menu. So check that as well.


              • #8
                Thank you for your quick response.


                • #9
                  Hi David,

                  We have driver installed and can run loopback when connect to the laptop.
                  However, when setup as diagram above, we can run power delivery. For the loopback, the LED on loopback is ON but show not connected,
                  I am not sure what setting should I make


                  • #10
                    Can you try the test without your hub, but with the PM125 device.