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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 ComponentsChoices
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 AlgorithmsGiven initial state and input, a set of tasks or instructions that efficiently produce the results that you want.
Modeling InterfacesMechanisms that enable algorithm components to communicate and exchange information across component boundaries.
Modeling SystemsCollection of algorithm components that achieve a higher-level, domain-specific goal or result. Components often share resources.
Modeling Run-Time EnvironmentsFramework 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 ConsiderationsModeling ConsiderationsRelated Information
What is the system domain?Product prerequisites (based on domains of components)
Does the system involve physical domains, such as mechanical, electrical, or hydraulic domains?Physical systems
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
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

Modeling Interfaces

Architecture ConsiderationsModeling ConsiderationsRelated 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
Where and how is data pulled into the system and pulled within the system?Input
  • Where and how is data pushed within the system and out of the system?

  • What external triggers are required?

Output
  • What functions do you need to define for each component?

  • What is the prototype for each entry-point function?

Functions and function calls
Can you benefit from setting up default code generation configurations for categories of data and functions?Data and function configuration
Do you need to export functions that are invoked by controlling logic that is outside the model?Function export
Does the system monitor signals or log data (for example, for calibration)?C API and ASAP2 data exchange interfaces
Do you need to replace code generated for functions or operators, for example, to optimize the code for specific hardware?Code replacement
Do you need to control the placement of data or functions in memory?Memory sections
Is there a requirement for elaboration and future considerations?Elaboration and future considerations

Modeling Systems

Architecture ConsiderationsModeling ConsiderationsRelated 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
  • 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
Are you modeling a client-server architecture?Simulink Function and Caller blocks
Is relevant legacy or custom code available?External code integrationExternal Code Integration
Can you apply a reference architecture or reference components?Model and project templates
Do you need to export functions that are invoked by controlling logic that is outside a model?Export-function modelsExport-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
  • 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
Do you need to control placement of data or functions in memory?Memory sections
Are you required to apply the AUTOSAR standard? If yes, what aspects of the architecture involve AUTOSAR?AUTOSARAUTOSAR Blockset
Does your system need to meet other standards or guidelines?Standards and guidelinesSupport for Standards and Guidelines

Modeling Run-Time Environments

Architecture ConsiderationsModeling ConsiderationsRelated 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
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
  • Are components in the system driven by events (interrupts)?

  • What are the priorities of system tasks and functions?

Event-based scheduling
Does the system need to handle initialization, reset, or terminate events?Initialization, reset, termination
  • 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
  • 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 platformsMulticore 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

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.

TemplateDescription
Code Generation SystemBasic model consisting of an Inport block and Output block.
Exported functionsModel 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, multirateFixed-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 rateFixed-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:

  1. On the MATLAB® home tab, click Simulink.

  2. In the Simulink start page, expand Embedded Coder.

  3. 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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