MATLAB Function

Include MATLAB code in models that generate embeddable C code

Library:
Simulink / User-Defined Functions
HDL Coder / User-Defined Functions

Description

With a MATLAB Function block, you can write a MATLAB^® function for use in a Simulink^® model. The MATLAB function you create executes for simulation and generates code for a Simulink Coder™ target. If you are new to the Simulink and MATLAB products, see Implementing MATLAB Functions Using Blocks and Create Custom Functionality Using MATLAB Function Block for an overview.

Double-clicking the MATLAB Function block opens its editor, where you write the MATLAB function, as in this example:

To learn more about this editor, see MATLAB Function Block Editor.

You specify input and output data to the MATLAB Function block in the function header as arguments and return values. The argument and return values of the preceding example function correspond to the inputs and outputs of the block in the model:

You can also define data, input triggers, and function call outputs using the Ports and Data Manager, which you access from the MATLAB Function Block Editor by selecting Edit Data. See Ports and Data Manager.

The MATLAB Function block generates efficient embeddable code based on an analysis that determines the size, class, and complexity of each variable. This analysis imposes the following restrictions:

The first assignment to a variable defines its, size, class, and complexity.
See Best Practices for Defining Variables for C/C++ Code Generation.
You cannot reassign variable properties after the initial assignment except when using variable-size data or reusing variables in the code for different purposes.
See Reassignment of Variable Properties.

In addition to language restrictions, the MATLAB Function block supports a subset of the functions available in MATLAB. A list of supported functions is given in Functions and Objects Supported for C/C++ Code Generation. These functions include functions in common categories, such as:

Arithmetic operators like plus, minus, and power. For more information, see Array vs. Matrix Operations.
Matrix operations like size, and length
Advanced matrix operations like lu, inv, svd, and chol
Trigonometric functions like sin, cos, sinh, and cosh

Note

Although the code for this block attempts to produce exactly the same results as MATLAB, differences might occur due to rounding errors. These numerical differences, which might be a few eps initially, can magnify after repeated operations. Reliance on the behavior of nan is not recommended. Different C compilers can yield different results for the same computation.

Note

In the MATLAB Function block, the %#codegen directive is included to emphasize that the block’s MATLAB algorithm is always intended for code generation. The %#codegen directive, or the absence of it, does not change the error checking behavior in the context of the MATLAB Function block. For more information see Compilation Directive %#codegen.

To support visualization of data, the MATLAB Function block supports calls to MATLAB functions for simulation only. See Extrinsic Functions to understand some of the limitations of this capability, and how it integrates with code analysis for this block. If these function calls do not directly affect any of the Simulink inputs or outputs, the calls do not appear in Simulink Coder generated code.

From MATLAB Function blocks, you can also call functions defined in a Simulink Function block. You can call Stateflow^® functions with Export Chart Level Functions (Make Global) and Allow exported functions to be called by Simulink checked in the chart Properties dialog box.

In the Ports and Data Manager, you can declare a block input to be a Simulink parameter instead of a port. The MATLAB Function block also supports inheritance of types and size for inputs, outputs, and parameters. You can also specify these properties explicitly. See Type Function Arguments, Size Function Arguments, and Add Parameter Arguments for descriptions of variables that you use in MATLAB Function blocks.

Recursive calls are not allowed in MATLAB Function blocks.

By default, MATLAB Function blocks have direct feedthrough enabled. To disable it, in the Ports and Data Manager, clear the Allow direct feedthrough check box. Nondirect feedthrough semantics ensure that outputs rely only on the current state. Using nondirect feedthrough enables you to use MATLAB Function blocks in a feedback loop and prevent algebraic loops. For more information, see Use Nondirect Feedthrough in a MATLAB Function Block.

Ports

Input

expand all

`u` — Input argument `u`
scalar | vector | matrix

Input corresponding to the first input argument of the function inside the MATLAB Function block. If you rename the function argument in the editor, the block renames the port correspondingly.

Data types supported by MATLAB but not supported by Simulink may not be passed between the Simulink model and the function within the MATLAB Function block. These types may be used within the MATLAB Function block.

For more information on fixed-point support for this block, refer to Fixed-Point Data Types with MATLAB Function Block (Fixed-Point Designer) and MATLAB Function Block with Data Type Override (Fixed-Point Designer).

`n` — Input argument `n`
scalar | vector | matrix

nth input argument to the function in the MATLAB Function block. When you add the argument in the editor, the block adds the port correspondingly.

Output

expand all

`y` — Output argument
scalar | vector | matrix

First output argument of the function inside the MATLAB Function block. If you rename the function argument in the editor, the block renames the port correspondingly.

`n` — Output argument `n`
scalar | vector | matrix

nth output argument from the function inside the MATLAB Function block. When you add the argument in the editor, the block adds the port correspondingly.

Model Examples

Radar Tracking Using MATLAB Function Block

Use an extended Kalman filter with the MATLAB® Function block in Simulink® to estimate an aircraft's position from radar measurements. The filter implementation is found in the MATLAB Function block, the contents of which are stored in the Simulink model itself.

Open Model

Spiral Galaxy Formation Simulation Using MATLAB Function Blocks

This model was inspired by the classic paper "Galactic Bridges and Tails" (Toomre & Toomre 1972). The original paper explained how disc shaped galaxies could develop spiral arms. Two disc shape galaxies originally are far apart. They then fly by each other and almost collide. Once the galaxies are close enough, mutual gravitational forces cause spiral arms to form.

Open Script

Block Characteristics

Data Types	`Boolean^[a]` \| `bus^[a]` \| `double^[a]` \| `enumerated^[a]` \| `fixed point^[a]` \| `integer^[a]` \| `single^[a]` \| `string^[a]`
Direct Feedthrough	`no`
Multidimensional Signals	`limited^[a]`
Variable-Size Signals	`limited^[a]`
Zero-Crossing Detection	`no`
^[a] Actual data type or capability support depends on block implementation.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Actual data type or capability support depends on block implementation.

HDL Code Generation
Generate Verilog and VHDL code for FPGA and ASIC designs using HDL Coder™.

HDL Coder™ provides additional configuration options that affect HDL implementation and synthesized logic. Actual data type or capability support depends on block implementation. For best practices of using the MATLAB Function block, see:

HDL Architecture

MATLAB Function (Default)

This is the default architecture for MATLAB Function blocks with fixed-point data types. When you use this architecture, you can use speed and area optimizations for blocks that surround the MATLAB Function block. The code inside the MATLAB Function block is not optimized.

MATLAB Datapath

This is the default architecture for MATLAB Function blocks with floating-point data types. When you use this architecture, the code generator treats the MATLAB Function block like a regular Subsystem block. By enabling this architecture for fixed-point types, you can use speed and area optimizations for blocks inside the MATLAB Function block and across the MATLAB Function block with other Simulink blocks.

This capability enables you to specify additional properties for the MATLAB Function block that you would specify for a Subsystem such as ClockRatePipelining and FlattenHierarchy.

HDL Block Properties

AdaptivePipelining	Automatic pipeline insertion based on the synthesis tool, target frequency, and multiplier word-lengths. The default is `inherit`. To specify this property, set Architecture to `MATLAB Datapath`. See also AdaptivePipelining (HDL Coder).
BalanceDelays	Detects introduction of new delays along one path and inserts matching delays on the other paths. The default is `inherit`. To specify this property, set Architecture to `MATLAB Datapath`. See also BalanceDelays (HDL Coder).
ClockRatePipelining	Insert pipeline registers at a faster clock rate instead of the slower data rate. The default is `inherit`. To specify this property, set Architecture to `MATLAB Datapath`. See also ClockRatePipelining (HDL Coder).
ConstMultiplierOptimization	Canonical signed digit (CSD) or factored CSD optimization. The default is `none`. See also ConstMultiplierOptimization (HDL Coder).
ConstrainedOutputPipeline	Number of registers to place at the outputs by moving existing delays within your design. Distributed pipelining does not redistribute these registers. The default is `0`. For more details, see ConstrainedOutputPipeline (HDL Coder).
DistributedPipelining	Pipeline register distribution, or register retiming. The default is `off`. See also DistributedPipelining (HDL Coder).
DSPStyle	Synthesis attributes for multiplier mapping. The default is `none`. To specify this property, set Architecture to `MATLAB Datapath`. See also DSPStyle (HDL Coder).
FlattenHierarchy	Remove subsystem hierarchy from generated HDL code. The default is `inherit`. To specify this property, set Architecture to `MATLAB Datapath`. See also FlattenHierarchy (HDL Coder).
InputPipeline	Number of input pipeline stages to insert in the generated code. Distributed pipelining and constrained output pipelining can move these registers. The default is `0`. For more details, see InputPipeline (HDL Coder).
InstantiateFunctions	Generate a VHDL^® `entity` or Verilog^® `module` for each function. The default is `off`. See also InstantiateFunctions (HDL Coder).
LoopOptimization	Unroll, stream, or do not optimize loops. The default is `none`. If you set Architecture to `MATLAB Datapath`, you can only unroll loops. If you want to use loop streaming with the `MATLAB Datapath` architecture, you can use the streaming optimization by specifying a StreamingFactor. See also LoopOptimization (HDL Coder).
MapPersistentVarsToRAM	Map persistent arrays to RAM. The default is `off`. See also MapPersistentVarsToRAM (HDL Coder).
OutputPipeline	Number of output pipeline stages to insert in the generated code. Distributed pipelining and constrained output pipelining can move these registers. The default is `0`. For more details, see OutputPipeline (HDL Coder).
ResetType	Suppress reset logic generation. The default is `default`, which generates reset logic. See also ResetType (HDL Coder).
SharingFactor	Number of functionally equivalent resources to map to a single shared resource. The default is 0. See also Resource Sharing (HDL Coder).
StreamingFactor	Number of parallel data paths, or vectors, that are time multiplexed to transform into serial, scalar data paths. The default is 0, which implements fully parallel data paths. To specify this property, set Architecture to `MATLAB Datapath`. See also Streaming (HDL Coder).
VariablesToPipeline	Warning `VariablesToPipeline` is not recommended. Use `coder.hdl.pipeline` (HDL Coder) instead. Insert a pipeline register at the output of the specified variable or variables. Specify the list of variables as a character vector, with spaces separating the variables. To specify this property, set Architecture to `MATLAB Function`.

Complex Data Support

This block supports code generation for complex signals.

See also Complex Data Type Support (HDL Coder).

Tunable Parameter Support

HDL Coder supports both tunable and non-tunable parameters with the following data types:

Scalar
Vector
Complex
Structure
Enumeration

For details, see Generate DUT Ports for Tunable Parameters (HDL Coder) and .Design Guidelines for the MATLAB Function Block (HDL Coder)

Restrictions

If the block contains a System object™, block inputs cannot have non-discrete (constant or Inf) sample time.
HDL Coder does not support a MATLAB Function that contains the same variable as the input and output of the function. For example, this MATLAB code is not supported.
```
function y = myFun(y)
%#codegen

y = 3 * y;
```

For the MATLAB language subset supported for HDL code generation from a MATLAB Function block, see Supported MATLAB Data Types, Operators, and Control Flow Statements (HDL Coder).

PLC Code Generation
Generate Structured Text code using Simulink® PLC Coder™.

Fixed-Point Conversion
Design and simulate fixed-point systems using Fixed-Point Designer™.

Actual data type or capability support depends on block implementation.

Documentation

MATLAB Function

Description

Ports

Input

`u` — Input argument `u`
scalar | vector | matrix

`n` — Input argument `n`
scalar | vector | matrix

Output

`y` — Output argument
scalar | vector | matrix

`n` — Output argument `n`
scalar | vector | matrix

Model Examples

Radar Tracking Using MATLAB Function Block

Spiral Galaxy Formation Simulation Using MATLAB Function Blocks

Block Characteristics

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

HDL Code Generation
Generate Verilog and VHDL code for FPGA and ASIC designs using HDL Coder™.

PLC Code Generation
Generate Structured Text code using Simulink® PLC Coder™.

Fixed-Point Conversion
Design and simulate fixed-point systems using Fixed-Point Designer™.

See Also

Topics

Simulink Documentation

Support

Documentation

MATLAB Function

Description

Ports

Input

u — Input argument u scalar | vector | matrix

n — Input argument n scalar | vector | matrix

Output

y — Output argument scalar | vector | matrix

n — Output argument n scalar | vector | matrix

Model Examples

Radar Tracking Using MATLAB Function Block

Spiral Galaxy Formation Simulation Using MATLAB Function Blocks

Block Characteristics

Extended Capabilities

C/C++ Code Generation Generate C and C++ code using Simulink® Coder™.

HDL Code Generation Generate Verilog and VHDL code for FPGA and ASIC designs using HDL Coder™.

PLC Code Generation Generate Structured Text code using Simulink® PLC Coder™.

Fixed-Point Conversion Design and simulate fixed-point systems using Fixed-Point Designer™.

See Also

Topics

Simulink Documentation

Support

`u` — Input argument `u`
scalar | vector | matrix

`n` — Input argument `n`
scalar | vector | matrix

`y` — Output argument
scalar | vector | matrix

`n` — Output argument `n`
scalar | vector | matrix

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

HDL Code Generation
Generate Verilog and VHDL code for FPGA and ASIC designs using HDL Coder™.

PLC Code Generation
Generate Structured Text code using Simulink® PLC Coder™.

Fixed-Point Conversion
Design and simulate fixed-point systems using Fixed-Point Designer™.