J-Link no USB enumeration

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Max. 10 J-Links enumerate

When connecting multiple J-Links to USB 3.0 ports + hubs, it can happen that Windows only enumerates up to 10 J-Links and then throw enumeration errors. Depending on the USB setup, it may also be only 8 or 9 J-Links that are enumerated. This is not a problem in the J-Link USB driver, but a limitation of the USB 3.0 controller, as the error message indicates:

24JLinks USB30 Error.jpg

Sample setup with error

The following shows a sample setup which produces such an error

24JLinks USB30.png

Sample setup workarounds

The following shows different sample setups which workaround the problem and let Windows enumerate all J-Links.

Workaround 1

Eliminate the first level USB 3.0 hub and connect the other hubs directly to the PC:

24JLinks USB30 WorkAround1.png

Workaround 2

Use a USB 2.0 hub instead of the first level USB 3.0 hub:

24JLinks USB2.png

Connection lost on firmware update

J-Link USB Isolator in between

When issuing a firmware update and having J-Link connected to the PC via a J-Link USB Isolator, on some specific models it can happen that communication is lost on firmware update. This is due to a bootloader problem in these devices that unfortunately cannot be fixed via a firmware update. For these J-Links, firmware updates should be applied with no USB Isolator in between. After the firmware update has been successfully performed, the USB Isolator can be used again.

Affected J-Links:

  • J-Link PRO V4
  • J-Link ULTRA+ V4