MATLAB: How to create a custom mask dialog for the Simulink block that interacts with the MATLAB base workspace variables

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I would like to create a mask dialog where I can enter a variable name in one field, and have another field update with that variable's current value according to my base workspace. I would also like to be able to edit the value associated with the variable in the mask dialog, and have it change the actual value of the variable in the base workspace.

Is this behavior possible with Simulink mask dialogs? This would save me time from switching back and forth between my Simulink model and base MATLAB workspace when adjusting variables.

Best Answer

Yes, this behavior is possible. See the attached example, "read_write_mask_value.slx".

First, the proper mask fields needs to be created in the "Parameters & Dialog" tab of the Mask Editor. For each variable, you will need two parameters - one for the variable name, and one for the variable value. The attached example demonstrates this for two variables: Gain, and Delay.

To pull the value from the variable stored in the workspace, write a mask callback for the parameter that holds the variable name (not the variable value). To access the callback code for a parameter, click the pencil in the "Dialog" section of the "Property Editor" in the "Parameters & Dialog" tab of the Mask Editor. In the attached example, this callback code is in "g1_var" and "d1_var". The callback code evalutes the variable name entered in the "g1_var" mask parameter, and sets the "g1_val" mask parameter to that value.

To apply a changed value back to the associated variable in the base MATLAB workspace, write a mask callback for the parameter that holds the variable value (not the variable name). In the attached example, this callback code is in "g1_val" and "d1_val". The callback code reads the value entered in the "g1_val", and assigns it to the variable in the base workspace with the name matching "g1_var".

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In R2019b, the behavior of "setVariable" is modified such that it overrides only model variables (as opposed to MATLAB variables).

I attached a simpler model ("SimpleVars_R2019b.slx") to help illustrate this. This model has two "From Workspace" blocks, one set to "a" and one set to "evalin('base', 'b')".

If you call "findVars" on this model, only "a" is considered to be a model variable, even though both output their timeseries when run:

>> vars = Simulink.findVars('SimpleVars_R2019b')
vars = 
    VariableUsage with properties:
            Name: 'a'
          Source: 'base workspace'
      SourceType: 'base workspace'
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The R2019b behavior provides stricter control of overrides and achieves parity with other Simulink tools. You will need to update the model to use variables which are recognized by Simulink.

Please update the "From Workspace" block variable parameter from "evalin('base', 'y_coordinate')" to just "y_coordinate". Then save the model and run the test file again.

You should observe that "setVariable" updates all of the variables now.

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In the Simulink model put a MATLAB Function block.

Double click on it to open the function in MATLAB Editor, and add additional parameters, e.g. "param1" to the function signature. Then in Editor tab under Simulink subtab click on "Edit Data" in order to open the Ports and Data Manager. Click on the new parameter, and in the General tab change the scope to be "Parameter", and click on "Apply" to save this

Then back in Simulink right click Mask > Create Mask, open "Parameters & Dialog" tab. On the left pane it shows "Controls", choose "Edit" control and drag it to "Dialog box" in the middle pane.

Change the name of this control to be the name of the parameter, e.g. "param1". Then set the default value and prompt, e.g. 1 and "Parameter 1". Click on "OK" at the bottom of the window to save this mask.

Now if you double click on the Function block, it will allow to change the default value for the parameter used in the block. You can go back to the source code of the block by clicking the arrow at the bottom left corner, should you wish to make further changes to the function itself.

For more information on adding parameter arguments, please see the documentation page in https://www.mathworks.com/help/simulink/ug/parameter-arguments-in-matlab-function-block-functions.html.

An example "function_block_parameters.slx" has been attached to this answer and the screenshot of the model is shown below.

Best Answer

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