Design Models for Generated Embedded Code Deployment

When using Embedded Coder^® to generate code for an embedded system architecture, it is important to design your Simulink^® models with code generation in mind from the very beginning of the design process. Think about relevant design factors and issues such as:

Application Algorithms and Run-Time Environments

Use Simulink to design models that represent application algorithms and run-time environments from which you intend to generate deployable code. Depending on your application, you might deploy code to an execution environment that consists of a combination of:

Execution Environment Components	Choices
Hardware	Development computer Rapid-prototyping board Microprocessor Microcontroller FPGA ASIC
Cores	Single Multiple
Operating system	General-purpose Real-time None (bare metal)
Scheduling	Single-tasking Multitasking Interrupt driven Concurrency Provided by operating system Generated from model
Application algorithm code	Generated from model External code

As you design models to generate C or C++ code for rapid prototyping or production deployment, keep in mind the execution environment. Generate code that meets implementation requirements and avoids potential design rework. As the preceding table reflects, the execution environment for code that you generate can range from relatively simple to complex. For example, a simple case is code that you generate from a single, single-tasking model that runs on a single-core microprocessor. A complex case is code that generate from a model partitioned to run as a distributed system on a multicore microprocessor and an FPGA.

Software Execution Framework for Generated Code

Part of an application execution environment is the software execution framework that is responsible for scheduling and running the generated code. That software can preexist, as in the case of an operating system and its scheduler, or you can code the software manually. The level of complexity varies depending on which of the following modeling and code generation scenarios applies:

Generate code from a single top model, which represents the algorithms intended to run in the execution environment.
Generate code from a model, which represents part of an overall algorithm. You can mix the generated code with code written manually and code generated from other sources or releases of MathWorks^® products.

Single Top Model

For a single top model, the software execution framework is responsible for running generated code the same way that Simulink simulates the model. Functions in the generated code are highly coordinated and optimized because Simulink is aware of dependencies. The framework interfaces with code generated for the top model only. Code generated for a top model handles interfacing with code for referenced Model blocks.

Consider the following example, where a single top model is mapped to tasks that run on a single-core CPU.

For this system, you map model clock rates to tasks that run on the hardware. You can choose for Simulink to map the rates implicitly or you can map them explicitly in your model. You can model latency effects resulting from how you map rates in a model to single-tasking or multitasking execution environments. Simulink schedules the tasks properly based on rates in the model and data dependencies between tasks. The code generator implements the same dependencies in the code that it generates. The software execution framework invokes generated entry-point functions at rates based on system timers and interrupts. The generated code executes in the same manner that Simulink simulates the model, and contains code dedicated to communicating data between functions running at different rates.

Multiple Top-Level Models

When you generate code from multiple top models separately and mix that code with code acquired in other ways, the execution environment of the application takes on more software execution framework responsibility. For this modeling scenario, you generate code for standalone, atomic reusable components.

With this scenario, Simulink is not aware of model dependencies. Functions in code generated from the different models are minimally coordinated and optimized. For example, the models might share generated utility functions. Potential optimizations that cross model boundaries are not possible. You must design the software execution framework taking into account dependencies between units of code, including execution order. For an application that requires concurrent execution across multiple cores, you must consider data latency effects across the cores.

The code generator helps you address software execution framework challenges, such as sharing global data and avoiding identifier conflicts. The code generated for a each model handles the interfacing for referenced Model blocks.

Map Embedded System Architecture to Simulink Modeling Environment

When mapping an embedded system architecture to the Simulink modeling environment, think about the model design.

Modeling Algorithms	Given initial state and input, a set of tasks or instructions that efficiently produce the results that you want.
Modeling Interfaces	Mechanisms that enable algorithm components to communicate and exchange information across component boundaries.
Modeling Systems	Collection of algorithm components that achieve a higher-level, domain-specific goal or result. Components often share resources.
Modeling Run-Time Environments	Framework that handles scheduling of system algorithm resources and execution.

Consider the following questions regarding an embedded system architecture with corresponding modeling capabilities and links to related information. Use the information as a guide for mapping your architecture details to the Simulink modeling environment. Designing a model architecture with your specific embedded system architecture in mind can help you avoid rework and future conversion and maintenance costs.

Modeling Algorithms

Architecture Considerations	Modeling Considerations	Related Information
What is the system domain?	Product prerequisites (based on domains of components)	Blocks and Products Supported for Code Generation Simulink Control Design Signal Processing Signal Generation, Manipulation, and Analysis (DSP System Toolbox)
Does the system involve physical domains, such as mechanical, electrical, or hydraulic domains?	Physical systems	Physical Modeling Basic Principles of Modeling Physical Networks (Simscape) Essential Physical Modeling Techniques (Simscape)
What aspects of your algorithm can you represent with blocks provided by MathWorks products? What blocks do you need to create?	Block usage, creation, and customization	Blocks and Products Supported for Code Generation External Code Integration
Does the architecture include state machine components?	Event-driven system	Model Reactive Systems in Stateflow (Stateflow)
Is there a need to standardize code that the code generator produces from multiple models?	Custom code definitions for data and functions	Define Storage Classes, Memory Sections, and Function Templates for Software Architecture Embedded Coder Dictionary

Modeling Interfaces

Architecture Considerations	Modeling Considerations	Related Information
What data must you represent in the generated code? How do you need to represent input and output—data type, dimension, complexity? Do the algorithms use floating-point or fixed-point arithmetic? How will the data change?	Data representation	Define Interfaces of Model Components Data Representation and Access Modeling Patterns for C Code Fixed-Point Designer
Where and how is data pulled into the system and pulled within the system?	Input	Comparison of Signal Loading Techniques
Where and how is data pushed within the system and out of the system? What external triggers are required?	Output	View Data in the Simulation Data Inspector Organize Parameter Data into a Structure by Using Struct Storage Class
What functions do you need to define for each component? What is the prototype for each entry-point function?	Functions and function calls	Configure C Code Generation for Model Entry-Point Functions Control Generation of C++ Class Interfaces
Can you benefit from setting up default code generation configurations for categories of data and functions?	Data and function configuration	Configure Default C Code Generation for Categories of Data Elements and Functions Code Mappings Editor
Do you need to export functions that are invoked by controlling logic that is outside the model?	Function export	Export-Function Models Overview Generate Component Source Code for Export to External Code Base
Does the system monitor signals or log data (for example, for calibration)?	C API and ASAP2 data exchange interfaces	Exchange Data Between Generated and External Code Using C API Export ASAP2 File for Data Measurement and Calibration
Do you need to replace code generated for functions or operators, for example, to optimize the code for specific hardware?	Code replacement	What Is Code Replacement? What Is Code Replacement Customization?
Do you need to control the placement of data or functions in memory?	Memory sections	Control Data and Function Placement in Memory by Inserting Pragmas
Is there a requirement for elaboration and future considerations?	Elaboration and future considerations	Define Interfaces of Model Components

Modeling Systems

Architecture Considerations	Modeling Considerations	Related Information
What is the scope of the system? Controller? External environment or plant? Test harness? How is the system partitioned into algorithm components (chunks of logic)? Which components can you represent in Simulink? Can you design components for reuse? What is the motivation for reuse (for example, division of labor or plug-n-play)?	Componentization	Define Interfaces of Model Components Component-Based Modeling Guidelines Compare Capabilities of Model Components Create a Custom Library Export-Function Models Overview Integrate Basic Algorithms Using MATLAB Function Block Control Generation of Functions for Subsystems Generate Code for Model Reference Hierarchy Code Generation of Stateflow Blocks
Do aspects of the system require unit testing? Is a team of people collaborating on the project? Do you need to protect intellectual property?	Model referencing	Model Reference Basics Compare Capabilities of Model Components Generate Code for Model Reference Hierarchy Generate Code from Atomic Subcharts
Are you modeling a client-server architecture?	Simulink Function and Caller blocks	Client-Server Architecture Simulink Functions Overview
Is relevant legacy or custom code available?	External code integration	External Code Integration
Can you apply a reference architecture or reference components?	Model and project templates	Create a Template from a Model Create a New Project Using Templates
Do you need to export functions that are invoked by controlling logic that is outside a model?	Export-function models	Export-Function Models Overview
Is there a need to package the source code for a component as a shared object library to simplify distribution or sharing?	Shared object libraries (dynamic link libraries)	Package Generated Code as Shared Libraries
Can you reuse functions?	Function reuse	Generate Reusable Code from Library Subsystems Shared Across Models Generate Reusable Code from Library Subsystems Shared Across Models Generate Reentrant Code from Top Models Generate Reentrant Code from Subsystems
Do components need to share access to global data? Within the system, do state changes occur? In each case, how does the result get communicated? Are there identifier (naming) issues to consider?	Shared data	Local and Global Data Stores Standard Data Structures in the Generated Code Storage Classes for Parameters and Signals Used in Model Blocks Code Generation of Constant Parameters Data Stores in Generated Code Customize Generated Identifier Naming Rules
Do you need to control placement of data or functions in memory?	Memory sections	Control Data and Function Placement in Memory by Inserting Pragmas
Are you required to apply the AUTOSAR standard? If yes, what aspects of the architecture involve AUTOSAR?	AUTOSAR	AUTOSAR Blockset
Does your system need to meet other standards or guidelines?	Standards and guidelines	Support for Standards and Guidelines

Modeling Run-Time Environments

Architecture Considerations	Modeling Considerations	Related Information
What level of control over run-time interfacing does your application require? How much of your system can you represent in a model?	Runtime interfacing	Execution of Code Generated from a Model See Modeling Interfaces.
Is the system partitioned into concurrent components to maximize parallelism? Which components?	Concurrency	Multicore Processor Targets
Are components driven by an external clock? What clock rates do system components use? Do components use a single rate or multiple rates?	Clocks and clock rates	Define Interfaces of Model Components
Are components in the system driven by clocks? What clock rates do system components use? Do components use a single rate or multiple rates? What are the priorities of system tasks and functions?	Time-based scheduling	Absolute and Elapsed Time Computation Time-Based Scheduling
Are components in the system driven by events (interrupts)? What are the priorities of system tasks and functions?	Event-based scheduling	Absolute and Elapsed Time Computation Event-Based Scheduling Model Reactive Systems in Stateflow (Stateflow)
Does the system need to handle initialization, reset, or terminate events?	Initialization, reset, termination	Using Initialize, Reset, and Terminate Functions Generate Code That Responds to Initialize, Reset, and Terminate Events
Is the system a single-tasking or multitasking system? Are components required to execute in real time? What are the execution order dependencies (sequencing) between components? What are the time constraints for task and function execution?	Task execution	Execution of Code Generated from a Model Modeling for Single-Tasking Execution Modeling for Multitasking Execution
If you know the processing platform, what is it? Will the system run on a single-core or multicore processor? Is the system a distributed system? Is the processing platform hybrid or heterogeneous? Does the architecture employ symmetric or asymmetric multiprocessing? If asymmetric, how is the platform software partitioned across CPUs?	Processing platforms	Multicore Processor Targets
Do you want to generate and run a standalone executable that does not require an external real-time kernel or operating system? Is a real-time operation system (RTOS) required? If yes, what RTOS?	Kernel, operating system	Deploy Generated Standalone Executable Programs To Target Hardware Deploy Generated Component Software to Application Target Platforms

Model Templates for Code Generation

Embedded Coder provides a set of built-in templates to use as a starting point to create models for common application designs. Use the templates to create models that are preconfigured to generate code for embedded system applications.

Template	Description
Code Generation System	Basic model consisting of an Inport block and Output block.
Exported functions	Model for generating code from function-call subsystems. You can export each function-call subsystem separately by right-clicking a subsystem, selecting C/C++ Code > Export Functions, and clicking Build.
Fixed-step, multirate	Fixed-step model that uses multiple rates and consists of Inport blocks, an Outport block, and a Sum block. The model is configured to use a fixed-step discrete solver and to use two rates with model configuration parameter Periodic sample time constraint set to `Unconstrained` and parameter Treat each discrete rate as a separate task selected. Simulink inserts a Rate Transition block to handle the two sample rates.
Fixed-step, single rate	Fixed-step model that uses a single rate and consists of Inport blocks, an Outport block, and a Sum block. The model is configured to use a fixed-step discrete solver.

To create a model from a template:

On the MATLAB^® home tab, click Simulink.
In the Simulink start page, expand Embedded Coder.
Hover over a template and click Create Model. A new model that uses the template contents and settings appears in the Simulink Editor window.

For more information, for example to create and use a template as a reference design, see Create a Template from a Model.

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