[SOLVED] Problem with J-Link SWD Isolator

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  • [SOLVED] Problem with J-Link SWD Isolator

    Problem is I cannot connect to target when J-Link SWD Isolator is in between.

    I wanted to use the isolator to connect to the target TI CC32220SF board, in SWD mode. The SWD mode without isolator works.
    Why doesn't this work with the SWD isolator ... ?

    (Note: I do set "power on" to power the isolator itself first. in case you ask)

    Connection is:
    J-Link Edu <--> J-Link SWD Isolator <--> J-Link Cortex-M Adapter <--> Target

    The Segger products in this setup:
    segger.com/products/debug-probes/j-link/models/j-link-edu/
    segger.com/products/debug-prob…tors/j-link-swd-isolator/
    segger.com/products/debug-prob…s/9-pin-cortex-m-adapter/

    The setup without isolator in-between works
    J-Link Edu <--> J-Link Cortex-M Adapter <--> Target.

    What is wrong, why this original Segger isolator doesn't work with the other Segger original products?

  • Actually, the 2 SEGGER products (J-Link EDU and SWD Isolator) are working fine together. Dozens of customers use them.
    It is probably the target side that is a bit problematic here.
    Not sure what board you use but is the board designed to also allow drawing current on the VTref pin? (pin 1)
    This is needed as the SWD isolator uses VTref to adjust its target buffers for the correct HIGH levels but also uses this pin to supply power to these buffers.
    Maybe that's the problem here: The SWD Isolator cannot draw current from the target board to power its own target side.
    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.

  • I have a problem with J-Link SWD isolator too, when using production programming but for STM32 devices.
    The first time I program a board it is programmed succesfully, then the second fails.
    So what I see is alternating exactly one succeed and one failure.

    v01d: is it the same issue? I got in touch with support, but they were not abe to replicate this issue

  • SEGGER - Alex wrote:

    ...
    Not sure what board you use but is the board designed to also allow drawing current on the VTref pin? (pin 1)
    This is needed as the SWD isolator uses VTref to adjust its target buffers for the correct HIGH levels but also uses this pin to supply power to these buffers.
    Maybe that's the problem here: The SWD Isolator cannot draw current from the target board to power its own target side.
    Hey Alex,

    Could you help me out to check on it? The board is CC3220SF launchad. Quick start on the board don't think has details about drawing current on pin1. Schematic extract page attached, J8 is the connector. I see is VCC_BRD ->R32/1k->p1. Aaand I'm unsure on the answer :)

    Also, question:

    SEGGER - Alex wrote:

    ...The SWD Isolator cannot draw current from the target board to power its own target side....

    Does SWD need to power both of its sides - the J-Link/emulator side, AND it's own Target side ..? ( without powering the target, as target is powered externally .)
    Files

    The post was edited 2 times, last by v01d: more info ().

  • simone wrote:

    I have a problem with J-Link SWD isolator too, when using production programming but for STM32 devices.
    The first time I program a board it is programmed succesfully, then the second fails.
    So what I see is alternating exactly one succeed and one failure.

    v01d: is it the same issue? I got in touch with support, but they were not abe to replicate this issue
    Hello Simone,

    Issue is likely different : mine cannot connect at all, 0 / zero success on any attempt.

  • Hi,
    the reason why the J-Link is not able to connect to the target when using the J-Link SWD Isolator is, that the board is not able to provide the necessary amperage to supply the isolator.
    I added a section covering this in the article about this board in our Wiki:
    wiki.segger.com/CC3220_LaunchP…ith_JTAG-.2FSWD-Isolators

    Best regards,
    Fabian
    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.

  • SEGGER - Fabian wrote:

    I added a section covering this in the article about this board in our Wiki:
    wiki.segger.com/CC3220_LaunchP…ith_JTAG-.2FSWD-Isolators

    Hello,

    I double checked and no, your indicated solution on wiki doesn't seem to solve it for me.

    In my setup, I apply external 3.3V to the target, refer J22 - external supply. This can be separated from the emulator's side of the board, so that i has it's own supply - refer J19,J17 (VBAT, BRD), cross them to put target on separate supply from emulator side, or keep them as is to keep on same supply.

    Whichever way, I have no luck with Segger SWD Isolator.

    Please share then how on is supposed to connect it using the isolator

  • Hi,
    The external power supply has to be connected to the target side of the Isolator, not to the target supply pins.
    We updated the article and added a picture to it to prevent any misunderstanding.

    Does it work on your side, when you use a similar setup as described in the article?
    If not:
    Are both power LEDs of the Isolator turned on?
    Could you please provide us with a picture of your setup?

    Best regards,
    Fabian
    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.