--- title: "MATLAB troubleshooting" canonical: "https://help.vicon.com/space/Nexus217/350750814/MATLAB%20troubleshooting" format: markdown --- The following table lists possible issues you may encounter when modeling with MATLAB, helps you to understand why the issue may have occurred, and suggests the remedial actions to take, in the order to try them. | **Issue** | **Reason** | **Action** | | --- | --- | --- | | When you import a long trial into MATLAB, after some time, importing stops and the following error message is displayed: `Error using ViconNexus/GetDeviceChannelGlobal (line ####)` `Host application failed to respond to the information request.` | MATLAB cannot load device data if the number of device frames is too large. | Import the data using `GetDeviceChannelGlobalAtFrame` or `GetDeviceChannelGlobalForFrame` to get a subsection of the trial, repeat the process as necessary and append each data subsection at the end to join the data again. | | If your data is atypical (for example, if it includes gait that is not normal overground walking, or if it requires cropping) and you don't modify the script to your particular trial, this may result in blank outputs. | The scripts are designed for normal gait (that is, overground walking) such as the gait trials in the sample data that is provided. | To ensure the scripts work well with your particular data, copy them and modify them as required. | | Nexus error: When you click the **Run Script** button, Nexus becomes unresponsive for some time, and finally, the **Matlab** tab displays the following error: `Default Run Matlab Operation Host Application is not connected, unable to retrieve command list ` MATLAB error: `Default Run Matlab Operation Host Application is not connected, unable to retrieve command list` | MATLAB connects to Nexus over TCP/IP. If you disconnect your Ethernet cable and turn off wifi (ie, if you are working entirely offline), MATLAB and Nexus cannot connect. | Install the Microsoft Loopback Adapter. For instructions on how to do this, see [Install the Microsoft loopback adapter](https://vicon-help.atlassian.net/wiki/spaces/Nexus217/pages/350750824/Set+up+Python+for+use+with+Nexus#InstallLBAdapter). | | MATLAB error when constructing an instance of the ViconNexus object `vicon = ViconNexus();` ` Undefined function or variable 'ViconNexus'` | When you try to create an instance of the class object ViconNexus, MATLAB is unable to locate the definition for the class. This is generally an indication that the Search path in MATLAB has not been set to include a path to the NexusSDK or that the NexusSDK has not been installed | Ensure that the NexusSDK has been installed. The 32-bit version of the SDK should be installed for a 32bit installation of MATLAB; the 64-bit version of the SDK should be installed for a 64-bit installation of MATLAB. In MATLAB, ensure that the path to the NexusSDK has been added: 64-bit MATLAB NexusSDK path is: NexusInstallFolder*SDK\Win64\Matlab* 32-bit Matlab NexusSDK path is NexusInstallFolder*SDK\Win32\Matlab* Use the shortcut provided on the **Start** menu to set the MATLAB path. | | MATLAB error when constructing an instance of the ViconNexus object `vicon = ViconNexus(); ` ` Could not load file or assembly 'NexusSDKClientDotNET.dll' or one of its dependencies. The specified module could not be found.` | This can happen if the VC++ 64-bit runtimes did not get installed from the Nexus bootstrap installer *setup.exe* | Install the runtimes manually. Navigate to the folder where the installation files were unzipped run *vcredist_x64.exe* | | Generic type error message received in MATLAB after calling a function `result = vicon.function(); ` ` Error using ViconNexus/function (line 123) ` ` Error: Invalid Parameter Value` | | Look at the log in the Nexus **Matlab** tab as it may contain more detailed information on the error that has been generated. | | MATLAB error `Host application failed to respond to the information request.` | After MATLAB sends a command to Nexus, it waits for a specific amount of time for the reply to be received. If the reply is not received in that timeframe, this error is generated. Delays in processing can occur when Nexus is waiting for input from the user to proceed or it has become unresponsive. | Look at the log in the Nexus **Matlab** tab to see if an error has been generated. Often, commands will return a reply, but some commands, such as **OpenTrial** and **RunPipeline**, require that Nexus generates a notification of task completion. An error in these commands can cause the reply to be delayed or not be generated. Look at the log in the Nexus **Matlab** tab to see if the command was received by Nexus. If the log does not have an entry showing that the command was received then it is possible that something has happened to the connection between the applications. Restart Nexus. Make sure that Nexus is not displaying a user prompt, if it is, answer the prompt and retry the command. Restart Nexus. | | MATLAB error `Unable to Communicate with the host application.` | The function called failed to execute because the connection to Nexus has either been dropped or never established. | Make sure that Nexus is running and is responsive. If running from within MATLAB, remove the **ViconNexus** object from the workspace using the MATLAB **clear** command and re-create the object. Restart Nexus. Restart MATLAB. | | Nexus error MATLAB version is shown in the **Matlab** tab but a message states that MATLAB is not accessible. | This can happen if Nexus is able to determine that MATLAB is installed but it is unable to access the MATLAB automation server. | Run **matlab.exe** with the /register option to have MATLAB re-register its automation server components. | | When there are multiple versions of MATLAB installed, Nexus is running the wrong version of MATLAB | MATLAB registers COM components to provide access to its automation server, Nexus will use the currently registered components so the order of installation/uninstall/upgrade of different MATLAB versions can make a difference. | Run **matlab.exe** from the MATLAB version you wish to use with the /register option to have MATLAB re-register its automation server components. |