SimulinkHow-ToBeginner · 4 min read

How to Use Embedded MATLAB Function Block in Simulink

Use the Embedded MATLAB Function block in Simulink to write custom MATLAB code that runs inside your model. Double-click the block to open the editor, write your MATLAB function, and connect inputs and outputs to use it in your simulation.

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Syntax

The Embedded MATLAB Function block lets you write a MATLAB function with this basic syntax inside the block editor:

function y = fcn(u)
%#codegen
% Your code here
end

Here, u is the input to the function, and y is the output. The %#codegen directive tells Simulink to generate efficient code from your MATLAB code.

matlab

function y = fcn(u)
%#codegen
% Example: square the input
    y = u^2;
end

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Example

This example shows how to use the Embedded MATLAB Function block to square an input signal.

1. Drag the Embedded MATLAB Function block into your Simulink model.
2. Double-click the block to open the editor.
3. Replace the code with the example below.
4. Connect an input source (like a Constant block) and an output sink (like a Display block).
5. Run the simulation to see the squared output.

matlab

function y = fcn(u)
%#codegen
    y = u^2;
end

Output

If input u = 3, output y = 9

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Common Pitfalls

Not using %#codegen: This directive is required for code generation and efficient simulation.
Unsupported MATLAB functions: Only a subset of MATLAB functions are supported inside the block. Check documentation for supported functions.
Incorrect input/output sizes: Make sure input and output sizes match your function definition.
Using workspace variables: Avoid using variables from the MATLAB workspace; define all variables inside the function.

matlab

Wrong:
function y = fcn(u)
    y = sin(u) + workspaceVar;
end

Right:
function y = fcn(u)
%#codegen
    y = sin(u) + 1; % Use constants or inputs only
end

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Quick Reference

Feature	Description
Block Name	Embedded MATLAB Function
Function Syntax	function y = fcn(u)
Codegen Directive	%#codegen
Input	Defined as function input argument
Output	Defined as function output argument
Supported Functions	Subset of MATLAB functions for code generation
Common Use	Custom algorithms inside Simulink models

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Key Takeaways

Use the Embedded MATLAB Function block to write custom MATLAB code inside Simulink models.

Always include %#codegen for code generation compatibility.

Check that your MATLAB code uses supported functions and matches input/output sizes.

Avoid using workspace variables; define all variables inside the function.

Test your function with simple inputs to verify correct behavior before complex use.