How to set JLink to never power the board

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    • How to set JLink to never power the board

      Is there a way to pre-set / force JLink to never power or try power the board? I don't know if this make sense though, tbh ..

      Basically, if my board is powered externally or from another USB source, I wouldn't want JLink to power it. What I see is, if I unplug power , say to reset whole system, JLink is supplying some power, and I have to unplug it to fully power down the board.
      But I'm not sure if it's expected behaviour - is it sensing no power and then supplying it .. ?

      I have tried to set power off permanently, by using the JLinkExe command shell , perm power off. But that doens't seem to persist , as on next GDBServer start it does, seems, put power back.
    • Hello,

      Thank you for your inquiry.
      Try "power off perm". This is usually the default J-Link is shipped with. Just make sure to not do a power on at some point again and the power supply pin will stay low.

      Best regards,
      Nino
      Please read the forum rules before posting: Forum Rules

      Keep in mind, this is not a support forum. Its main purpose is user to user interaction.
      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.
    • Hi Nino,

      That is what I have tried originally. It doesnt' seem to work with this unit - JLink EDU.

      I have the more expensive J-Trace, and I can see it is 'smart' enough to sense accurately when the board is powered (I observe it reacts with the led very quick every time i turn on/off the board).

      My J-Trace is too good for this board though ...
    • I get 0.589V when just plugging the Cortex plug into the board, the J-Link EDU, with no external power on.

      If I power the board then, connect JLinkExe, set power off perm, and then turn off power supply, I get a constant reading 1.867V on the board, coming from J-Link.
      And then quitting from JLink , "q", seems to put it back around 0.9V ....

      Is that normal? I think not.

      With my J-Trace, it's ~ 0.0..V to start, and back to 0 with off.

      So J-Link EDU is probably to cheap, and leaks current into the board .. ?

      The post was edited 1 time, last by v01d ().

    • Hello,

      this should not be the case.
      When the voltage should be 0, when "power off perm" was called. It should not even reach close to 0.9V.

      Does this also happen, when no board is connected to the J-Link and you measure the voltage of the J-Link Pin?

      Best regards,
      Fabian
      Please read the forum rules before posting: Forum Rules

      Keep in mind, this is not a support forum. Its main purpose is user to user interaction.
      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.
    • SEGGER - Fabian wrote:

      Hello,

      this should not be the case.
      When the voltage should be 0, when "power off perm" was called. It should not even reach close to 0.9V.

      Does this also happen, when no board is connected to the J-Link and you measure the voltage of the J-Link Pin?

      Best regards,
      Fabian

      Tested now, I read ~1.3+ V on J-Link pins after doing "power off perm", with no devboard connected ...
      Tried re-plugging it USB, same thing.
    • I realized I had a Segger USB J-Link Isolator lying around..

      So with J-Link EDU connected through the isolator, I 've brought it down to < 30 mV. Now my devboard stays off when I turn power off at least.

      The J-Link EDU seems is a little dodge, not worth the price _if_ you need isolator with it:
      At my Mouser
      - J-Link EDU: approx $20
      - Segger USB isolator: approx $300 !! (whaaat?) and not in stock anyway .

      Next cheapest non-Segger isolator is approx $50.

      The post was edited 1 time, last by v01d ().

    • Hi,

      Could you clarify which isolator you are currently using?
      Does the same behavior occur when using another target board?
      Could you measure the voltage of the J-Link's 5V-pin when power off perm is used?
      Do you get the same Voltage reading there?
      Could you provide us with your J-Link EDU's serial number for reference?

      In which context did you use the J-Link EDU?
      Is it for private or educational use?
      Could you elaborate?

      Best regards,
      Fabian
      Please read the forum rules before posting: Forum Rules

      Keep in mind, this is not a support forum. Its main purpose is user to user interaction.
      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.
    • Hi,


      Could you clarify which isolator you are currently using?
      USB Isolator -> segger.com/products/debug-prob…tors/j-link-usb-isolator/


      Does the same behavior occur when using another target board?
      Yes, I have purchased identical other / copy board. Also, have you not seen my above post, where you asked me to measure on pins with no board connected .. ?


      Could you measure the voltage of the J-Link's 5V-pin when power off perm is used?
      Have you not seen my above post ? Nov 8th 2019, Please see above.


      Do you get the same Voltage reading there?

      Ok, now I'm unsure about which pin you asking : I used pin 1 (red ribbon) & ground.


      Could you provide us with your J-Link EDU's serial number for reference?
      Yes, I can. Please provide your email where I can send it. As this is private info which can uniquely identify me, I do not wish to share it on my public posts.



      In which context did you use the J-Link EDU?

      I see where you think you going, but it will be denied :) . I'm using this specific J-Link EDU for educational purposes, as I'm enrolled into a student program.
      If your license management dept would like my info on that, please provide email where I can send it - but appropriate contact. (I'm ready to email them my course in-progress registration).

      I also have a couple of J-Link EDU now: the original I'm having issue with, as reported here - J-Link EDU mini (tiny un-sealed/unboxed one), and J-Link EDU , white box, not tested yet even by me.
      Can I get as many as I want.. ? Or do I have to be enrolled in separate course for each ... :D :D :D.


      Could you elaborate?

      Oh yes, I can with pleasure. As mentioned above, those are for educational use. The board used - for education / course. Hope that is elaborate enough.

      In Addition (means, I also have .. ) I own a J-Trace Pro Cortex, which is not restricted to Education only use. (And in fact, was purchased by my company). But, on that, I could have filed support through ticketing system...I guess.

      I hope these answers on your questions you had about licensing and my intended and actual use case, with licensing concerns, have been sufficiently answered by me here. On the thread about me having J-Link leaking current.

      Please do not hesitate to request serial numbers by email to appropriate Segger department!

      Best regards
    • Hi,
      Thank you for confirmation.

      From your description it is highly likely that your EDU was damaged from the USB side.
      This could have multiple reasons (e.g. resistors burned, faulty USB power supply).
      In that case the J-Link would need to be replaced.
      For sanity reasons could you try the same Setup with your J-Trace Pro?
      Do you see the same behavior there?

      Regarding your security concern:
      I can assure you, that we did not link the SN of any J-Link to any of our customers personal information at any openly accessible platform.
      If someone buys a J-Link from a 3rd party supplier, we do not even have the information on who bought it.
      So if there is a way to link SN to your personal information, you would be the person who made it so.

      If you have any concern about sharing this information here, please feel free to send me the SN via PM.

      Best regards,
      Fabian
      Please read the forum rules before posting: Forum Rules

      Keep in mind, this is not a support forum. Its main purpose is user to user interaction.
      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.
    • Hey Fabian,

      SEGGER - Fabian wrote:

      For sanity reasons could you try the same Setup with your J-Trace Pro?
      If you see above - I did already, see post from Oct 31st 2019 on this thread. I will re-check.

      I will re-try with my J-Link EDU too, not mini, haven't had chance yet.

      I can assure you, that we did not link the SN of any J-Link to any of our customers personal information at any openly accessible platform.
      Yea but your distributors , whom I buy most, may. In any event, I can PM you / email you/Segger. No issues .

      Please do not yet close this thread. I may take few days to reply due to travel.

      The post was edited 1 time, last by v01d ().