Debugging using multiple J-Link adapters

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  • Debugging using multiple J-Link adapters

    I'd like to debug multiple processors, similar to the multi-core debugging method described at, except that my processors are not on the same JTAG chain. Therefore, I'd like to use two J-Link adapters, one connected between my IAR EWARM C-Spy debugger and target system 1, and the other connected between J-Flash and target system 2.

    However, it doesn't appear that the two J-Link adaptors can be distinguished on the USB. They both appear to be "Device 0"

    {J-Flash: Options|Project Settings ...|General|Connection to J-Link


    IAR: Project|Options|Debugger|J-Link/J-Trace|Connection|Communication}

    For example, selecting "Device 1" in J-Flash when I have two J-Link adapters connected to my PC produces an error when I try to "Target|Connect" to my target system 2. The error message is "Can not connect to J-Link via USB. Failed to connect". Connecting to my target system 2 is possible when I select "Device 0" and either a) have one J-Link connected to my PC or b) the J-Link connected to target system 2 is the first J-Link enumerated on the USB.

    Is there a way to debug using multiple J-Link adapters? I'm using the J-Link.sys driver that came with my IAR tool chain (IAR v4.42A).


  • Hello dean,

    The steps needed to use multiple J-Links with one PC are described in the J-Link / J-Trace user guide in chapter 4.4 "Connecting multiple J-Links / J-Traces to your PC".
    However you will need a V5 J-Link for this to work!

    These are the steps you need to do in short:
    1. Connect the J-Link you wish to be the second one (do not connect the first J-Link at the same time)
    2. Start JLink.exe
    3. Type: usbaddr = 1
      This will make your J-Link the second J-Link device. First one has the number 0 as every shipped J-Link has.
    4. Unplug and re-plug your second J-Link. Your system should recognize a new USB device.
      The driver can be found in your J-Link installation folder, it is named "JLink1.sys"
    To after that you can plug in both J-Links at once, they should both enumerate correctly. To use your second J-Link with JLink.exe start JLink.exe and type the command: usb 1
    When choosing the second J-Link in IAR EWARM it should now work correctly.