PLC Programming - Advanced Object Oriented Programming (OOP)

Name: PLC Programming - Advanced Object Oriented Programming (OOP)
Rating: 4.6 (60 reviews)

Master CoDeSys OOP: Write Scalable PLC Code with Methods, Inheritance & Interfaces

Created byMarco Nucci

Last updated 4/2025

English

What you'll learn

Implement core CoDeSys OOP features like Methods, Properties, and Access Specifiers to create well-encapsulated Function Blocks.
Design and utilize Inheritance (EXTENDS, ABSTRACT, SUPER) and Interfaces (IMPLEMENTS) to build flexible, reusable, and maintainable Function Block hierarchies.
Apply Polymorphism using Interface variables (IF <> 0) and runtime checks (__QUERY...) to create decoupled and adaptable automation logic.
Safely and effectively use Pointers (POINTER TO) and References (REFERENCE TO) in CoDeSys, understanding critical validity checks.
Apply key OOP Design Patterns (State, Command, Observer) to solve common automation software challenges.
Evaluate when and how to appropriately apply OOP principles and patterns in PLC projects, avoiding common pitfalls like over-engineering.

Course content

8 sections • 36 lectures • 7h 8m total length

Introduction3:00
Course Contents5:10

Object-Oriented Programming In Automation12:59
Explore how object oriented programming for automation reorganizes PLC design around data and objects, using encapsulation, inheritance, polymorphism, and abstraction to enhance modularity, reusability, and maintenance in Codesys environments.
The Function Block (FB) as our Starting Point8:22
Explore object-oriented programming in automation through the IEC 61131-3 function block as the class, with interfaces, retained variables, and independent instances, plus Co-sysop enhancements.

Introduction to Methods11:25
Explore Codesys methods as a first object oriented feature for function blocks, enabling actions as methods with inputs, outputs, and access to parent block variables, improving readability and encapsulation.
Understanding Methods23:42
Access Specifiers11:08
Introduction to Properties8:49
Understanding Properties20:05
The THIS Pointer12:22
Exercise - Methods and Properties7:51
Exercise - Methods and Properties - Solution12:12

Introduction to Inheritance7:26
Explore how inheritance lets derived function blocks extend base blocks and inherit variables, inputs/outputs, and methods. This enables code reuse, easier maintenance, and sets the stage for polymorphism in PLC.
Understanding Inheritance11:25
Extend a base function block in Codesys by inheritance, adding an error property from status word bit four and a reset mechanism, then override methods to update drive data.
Overriding Methods, SUPER^ and ABSTRACT Function Blocks9:34
Master overriding base methods, using the super pointer to extend behavior, and design abstract function blocks and methods as blueprints for inheritance.
Overriding in Practice13:07
Inheritance Exercise - Introduction18:45
Explore inheritance by building a base function block for all grippers and extending it to pneumatic vacuum, clamp, and servo variants while maintaining the robots' shared movement logic.
Inheritance Exercise - Base Class14:08
Inheritance Exercise - Derived Classes22:59

Introduction to Interface11:08
Understanding Interfaces13:21
Polymorphism20:34
Understanding Polymorphism17:25
Interfaces Exercise - Introduction4:53
Explore interfaces and polymorphism to unify three robot programs into a single function block by using dependency injection to pass robot and gripper interfaces, enabling state-machine logic without code changes.
Interfaces Exercise - Solution18:49
Interfaces vs Inheritance9:09

Requirements

Solid understanding of fundamental PLC programming concepts (variables, data types, logic, control flow).
Practical experience programming PLCs using Structured Text (ST) within the CoDeSys V3 development environment (IDE navigation, creating basic POUs, downloading, going online/debugging).
Experience creating and using standard Function Blocks (FBs) in CoDeSys.
No prior Object-Oriented Programming (OOP) knowledge is required - We will build from your existing PLC programming foundation.

Description

Tired of wrestling with complex PLC code that's hard to maintain and reuse? Ready to move beyond basic Function Blocks and unlock the full potential of modern PLC programming?

This comprehensive course is your guide to mastering Advanced Object-Oriented Programming (OOP) techniques specifically within the CoDeSys V3 environment (IEC 61131-3). Designed for experienced PLC programmers familiar with Structured Text (ST) and standard Function Blocks, this course bridges the gap between traditional methods and powerful OOP principles.

This course is designed for experienced PLC programmers comfortable with Structured Text (ST) and standard Function Blocks. If you are new to PLC programming or need a stronger foundation in structured programming concepts before tackling advanced OOP, I highly recommend checking out my other courses first: "PLC Programming - Learn the Basics with CoDeSys" for beginners, and "PLC Programming - Structured Programming and Design Patterns" for intermediate concepts.

We'll start by understanding why OOP matters in automation, addressing common concerns and demonstrating its benefits for managing complexity. Then, we dive deep into the practical application of CoDeSys OOP features:

Enhance your Function Blocks: Learn to create cleaner, more intuitive code using Methods, Properties, and control visibility with Access Specifiers. Understand the crucial role of the THIS pointer.
Master Memory Management: Gain confidence using Pointers (POINTER TO, ADR, ^) and References (REFERENCE TO, REF=), learning their syntax, applications, and essential safety checks (<> 0, __ISVALIDREF) vital for reliable PLC code.
Build Reusable Hierarchies: Explore Inheritance (EXTENDS) to create specialized FBs based on common code. Learn to Override methods, leverage the SUPER pointer, and utilize ABSTRACT classes to define robust templates.
Achieve True Flexibility: Discover Interfaces (INTERFACE, IMPLEMENTS) to define capability contracts and unlock Polymorphism. Learn how to write decoupled code that interacts with diverse objects uniformly using Interface Variables and runtime checks (__QUERY...).
Apply Practical Knowledge: Learn OOP Design Patterns adapted for automation (State, Command, Observer, adapted Factory), master Debugging techniques specific to OOP structures in CoDeSys, and understand crucial Best Practices – including when not to use OOP and how to refactor legacy code using the Wrapper pattern.

Throughout the course, we use practical examples rooted in automation scenarios (like controlling drives) and provide exercises to solidify your understanding.

Throughout the course, we use practical examples rooted in automation scenarios (like controlling drives) and provide exercises to solidify your understanding. To ensure compatibility with the provided exercise projects, it is advised that students install CoDeSys Development System V3.5 SP19 Patch 5.

By the end of this course, you won't just know about OOP; you'll be able to confidently design, implement, and maintain complex, scalable, reusable, and highly maintainable PLC applications using advanced OOP techniques in CoDeSys V3.

Enroll today and elevate your PLC programming skills to the next level

Who this course is for:

PLC Programmers and Automation Engineers currently working with CoDeSys V3 based systems (e.g., Beckhoff, Wago, Schneider Electric, Festo, Bosch Rexroth, etc.).
Developers experienced with IEC 61131-3 languages (especially Structured Text) and standard Function Blocks.
Engineers facing challenges with complex code, code reuse, or maintainability in large PLC projects.
Programmers wanting to leverage modern software engineering practices within the PLC environment.
Those seeking a deep, practical understanding of Methods, Properties, Inheritance, Interfaces, and Polymorphism in CoDeSys.

PLC Programming - Advanced Object Oriented Programming (OOP)

What you'll learn

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Course content

Introduction to the Course2 lectures • 8min

Introduction to Object Oriented Programming2 lectures • 21min

Introduction to Object Oriented Programming - Methods and Properties8 lectures • 1hr 48min

Pointers and References - Foundation for Flexibility4 lectures • 48min

Inheritance - Building Hierarchies ("IS-A" Relationship)7 lectures • 1hr 37min

Interfaces & Polymorphism - Flexible Contracts ("Can-Do" Relationship)7 lectures • 1hr 35min

Effective OOP Application & Best Practices.5 lectures • 48min

Bonus Section1 lecture • 3min

Requirements

Description

Who this course is for: