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LonMaker resynchronization fails with: Attempt to assign a neuron ID that is already in use by another device. (Subsystem: LNS, #102)


Potential for Data Loss: The steps detailed in the resolution of this article may result in a loss of critical data if not performed properly. Before beginning these steps, make sure all important data is backed up in the event of data loss. If you are unsure or unfamiliar with any complex steps detailed in this article, please contact Product Support Services for assistance.


When doing a LonMaker resynchronization, the operation fails on a certain subsystem or when doing a commission on a controller in Lonmaker an error is displayed: Attempt to assign a neuron ID that is already in use by another device. (Subsystem: LNS, #102)


LonMaker 3.X


If re-commissioning or downloading and commissioning a controller in LonMaker fails or times out, this issue may crop up. LonMaker assigns the desired neuron ID to a temporary device while performing either of these commands, and if the operation fails, that temporary device will get stuck in the database with the same neuron ID as the controller the user was working on.

A successful resynchronization will bring this "phantom device" to light where it can be deleted, but if it is the resynch that is failing, the steps below detail how to remove a neuron ID from a device in the LNS database so it can be deleted.


  1. Try to do a resynch command in LonMaker to get the temporary device to show itself on the Visio drawing. If this works, then the temporary device will show up with a randomly generated alpha numeric name on the same page as the controller you were trying the commission or download.
  2. After the resynch completes, delete the device from the page and repeat the commission or download. If the resynch operation fails with: Attempt to assign a neuron ID that is already in use by another device. (Subsystem: LNS, #102), continue.
  3. Because the temporary device is in the LNS database, but not on the LonMaker Visio drawing, manual manipulation of the LNS database is required to remove this object. This is done with the LNS Object Browser.

    First, shut down LonMaker, then click START and chose RUN in Windows and type lnsobjectbrowser and click ok.

  4. The Startup Preferences are shown. Set the Client/Server Communication to Don’t change and the Local Network Access to Engineering Mode and then click Ok.

  5. After choosing settings in the Startup Preferences menu, the LNS Object Browser is displayed. Press F8 to take the object browser out of read only mode.

  6. Browse to the following: ObjectServer/Networks/Your_Network_Name/Systems/ Your_Network_Name/Subsystems/All/AppDevices. Note: Double-click to open each object.

  7. Within the APPDevices menu you will see the temporary device with the large alpha-numeric name. Double-click this device to get its properties in the right hand window.

  8. Double-click on the NeuronId line in the properties pane of this device and manually set the Neuron Id to 000000000000 (12 zeros) and click Ok.

  9. Exit out of the LNS Object Browser and re-open the LonMaker database. Perform another resynchronization of the database, and the suspect temporary device should now show up on the LonMaker drawing. Then, delete that device and re-attempt your work on the original controller.
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