[SOLVED] VTref is read as 0V in J-Link EDU

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  • [SOLVED] VTref is read as 0V in J-Link EDU

    Hello,

    we have bought a J-Link EDU and we are trying to use it with an iMX6SX.
    However, we cannot connect to the target because VTref is read as 0V.

    I have found this thread on the forum:
    forum.segger.com/index.php?pag…highlight=vtref#post12671


    Alex from Segger suggests to connect an external power supply to pins 1/4, so we did.
    We setup the bank power supply at 3.3V (as the target board), however JLink.exe still reports VTref as 0V.

    We are using the latest software release (6.30c). When we connected the J-Link for the first time, a firmware update was proposed. We installed it (v10). Hardware version is v10.10

    Can we do other tests?
  • Hello,

    Thank you for your inquiry.

    Alex from Segger suggests to connect an external power supply to pins 1/4, so we did.
    We setup the bank power supply at 3.3V (as the target board), however JLink.exe still reports VTref as 0V.

    Could you attach a picture of your connection setup that shows the J-Link interface to make sure the wiring was correct?
    Do you have any other eval board or target device to test against?
    Make sure you apply the voltage before checking VTref as VTref will only be displayed once initially on startup. If it was 0 V at the beginning and gets 3.3 V it will still show 0 V in the output.
    In this other thread Niklas says it is broken:

    If VTref still shows 0 V in J-Link commander after you provide 3.3 V to Pin 1 which you verified with a Multimeter then the J-Link is most likely defective.

    One more thing you could try is to try command "rconf" to reset the J-Link configuration.

    Did you buy the J-Link directly in our online shop or at a third party distributor?

    Best regards,
    Nino
    Please read the forum rules before posting.

    Keep in mind, this is *not* a support forum.
    Our engineers will try to answer your questions between their projects if possible but this can be delayed by longer periods of time.
    Should you be entitled to support you can contact us via our support system: segger.com/ticket/

    Or you can contact us via e-mail.
  • Hello Nino, thank you for your response.

    This is what I did after suspecting a bad connection to the target:
    photos.google.com/share/AF1Qip…tQ0pCUjRGQk9Fb1UxQmE4ZmdR


    the power supply is set at 3.3V
    from the power supply the brown wire goes to pin 1 in jlink (and to the red probe of the multimeter)
    from the power supply the gray wire goes to pin 4 in jlink (and to the black probe of the multimeter)
    (the USB cable is removed to take a better picture)

    Then I connected USB cable (without powering off the power supply, of course) and opened JLink.exe, which reports VTref=0V
    I tried rconf, nothing changed :(

    Can I try an older software release? Can I / should I rollback the firmware update?

    We have bough the device from Farnell. Having bought as University, it would be a big mess for our administration to manage the RMA/replacement.. I really hope to fix it without having go trough Farnell.
  • Hello,

    Thank you for providing the picture. It is more clear now.
    Currently you are supplying VTref to Pin 19 and GND to Pin 18.
    The interface description on our website and manual shows the pin out of the actual J-Link pin interface and not the cable out on the other end.
    segger.com/products/debug-prob…gy/interface-description/
    So connect your supply to the correct pin 1 and pin 4 and you should be good to go.
    For reference the blue line on the cable refers to the side pin 1 is at.
    To make sure you don't damage the J-Link with voltages from the target side we offer a variety of isolators as well: segger.com/products/debug-prob…ories/isolators/overview/

    Best regards,
    Nino
    Please read the forum rules before posting.

    Keep in mind, this is *not* a support forum.
    Our engineers will try to answer your questions between their projects if possible but this can be delayed by longer periods of time.
    Should you be entitled to support you can contact us via our support system: segger.com/ticket/

    Or you can contact us via e-mail.