Stange problem when using two Jlink units

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    • Stange problem when using two Jlink units

      Hello,

      I have one Jlink Ultra and one Jlink Base Compact connected to my computer (via a USB hub). I used these Jlinks to debug two separate MCUs on my board. One instance of SES (7.30) is associated to the Jlink Ultra, and another separate instance of SES is associated with the Jlink Base.

      The problem that I'm seeing is this: The first time I connect to the board using any one of the two Jlinks my computer immediately goes haywire, screen goes black, the USB seems to get disconnected and then connected again (I can hear that ding from my Windows computer), the whole system seems to get hung up for like 3 seconds, and then comes back alive again. This only happens one time, subsequent operation using the debuggers works normally. But the whole thing repeats again the next time I reboot the computer.

      What could be causing this? Is this a known issue?

      Henry

    • Sounds strange... Is it possible that the USB hub, the J-Links are connected to, is not powered externally or its external power supply is broken?
      This would cause the hub and all J-Links connected to it to be fed from the USB cable that goes to your PC.
      Maybe it is just too much for that port and it cannot deliver sufficient current, so USB works unstable then?
      I still not see why it should affect your screen in any way but it would explain the "ding" which indicates USB detach + reattach/re-enumeration of the USB devices.
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    • Thanks for your reply Alex.

      I did some more testing, I moved one Jlink connection to one of the USB port on the computer and let the other Jlink connected to the USB hub, this time it works without any issues! So you may be right about the current being insufficient. It didn't occur to me previously that this might be the root cause since the 'disruption' occurs only one time, at the beginning.

      Henry