rOpen62541

rOpen62541 is an open-source B4R library wrapper for the industrial open62541 OPC UA protocol stack, specifically optimized for the ESP32-S3 Dual-Core architecture. It provides thread-safe cross-core communication, dynamic string-node creation with a flat hierarchy, and type-agnostic runtime write diagnostics.

• Server-Only Architecture: This library is dedicated exclusively to acting as an OPC UA Server data provider; it does not include client connection parsing capabilities.
• Proof of Concept & Learning Project: This framework was explicitly developed as a personal educational project to learn the foundational basics of OPC UA by creating a custom standalone hardware device from scratch.
• No Professional Intent: There is absolutely no intention for this codebase to be deployed in mission-critical environments, production facilities, or professional commercial installations.

Note: For a detailed breakdown of the underlying dual-core task design and memory synchronization layers, see the Developer Notes.

rOpen62541 uses a simple, flat node hierarchy.

All application nodes are added directly below the root object:

Objects (ns=0;i=85)
└── Factory_Floor (ns=1;s=Factory_Floor)
    ├── Temperature
    ├── Humidity
    ├── Pump1_Status
    ├── Pump1_Speed
    ├── Valve1_Status
    ├── Production_Count
    └── Trigger

Folders and additional hierarchical levels are not supported by the current B4R wrapper. This is an intentional design choice to keep the B4R API simple and to minimize RAM usage and processing overhead on ESP32-class microcontrollers.

For applications requiring a logical structure, prefix naming can be used to organize nodes while retaining the flat hierarchy. This is similar to the tag-naming approach commonly used in industrial automation systems:

Factory_Floor
├── Tank1_Temperature
├── Tank1_Level
├── Tank1_Pressure
├── Pump1_Status
├── Pump1_Speed
├── Pump2_Status
└── Pump2_Speed

For example:

OPCUAServer.AddFloatNode("Tank1_Temperature", "Tank 1 Temperature", 22.5)
OPCUAServer.AddFloatNode("Tank1_Level", "Tank 1 Level", 75.0)
OPCUAServer.AddBooleanNode("Pump1_Status", "Pump 1 Status", False)

This approach provides a simple and predictable OPC UA address space while keeping the wrapper lightweight and well suited for embedded ESP32 applications.

• Supported Hardware: Optimized for Espressif ESP32-S3 high-memory microcontrollers (specifically the N16R8 format featuring 16MB Flash and 8MB PSRAM).
• Network Layer: Requires standard embedded network lwIP socket frameworks to be initialized on boot.

This server implementation complies strictly with core industrial data-modeling specs and has been successfully verified across multiple desktop, terminal, and automation client ecosystems:

• Node-RED - Fully interoperable using the standard node-red-contrib-opcua flow palette node module.
• opcua-commander - Validated using the interactive, keyboard-driven terminal curses explorer (TUI).
• B4J (Native Client) - Integration with OPC UA Client library for B4J.
• B4J with PyBridge - Working via Python-backend socket communication routing bridges PyBridge framework.
• Node.js OPC UA Stack — Working via simple TypeScript client example.

Download the repository from GitHub.

• Copy the src sub-folder rOpen62541 into your B4R Additional Libraries folder, keeping the folder structure fully intact.
• Copy the src file rOpen62541.xml into your B4R Additional Libraries folder. Note: B4R installation instructions in case not installed.

The repository includes complete, ready-to-run environment folders tracking specific implementation patterns:

• Go to the Project Examples Index — Explore runnable source code frameworks for Environment Simulation, Method Callbacks, Peripheral I/O Mapping, and System Node ID lookups.

For detailed tutorials, API blueprints, and environment configurations, please visit our centralized documentation hub:

• Go to the Project Documentation Hub — Complete step-by-step guides covering Callbacks, Node IDs, Developer Notes, Functions, and Troubleshooting.

• rOpen62541 Library * MIT License as stated in the LICENSE file provided with rOpen62541.
• Open62541 Library * Mozilla Public License v2.0 as stated in the LICENSE file provided with open62541.

• Developers, maintainers, and open-source contributors of the official open62541 architecture framework, providing an industrial-grade embedded C implementation of OPC UA.
• Developer of the open62541-121-esp32 repository, which served as the foundation for this B4R wrapper.
• Anywhere Software for the B4X suite of RAD development tools.
• Developer of the B4J library SS_OPCUAClient.
• AI for engineering collaboration.

Disclaimer

• All product names, logos, protocols, and brands are property of their respective owners.
• This B4R library is an independent open-source wrapper tracking standard open62541 architectures.
  • It is neither officially endorsed nor maintained by the primary open62541 project core maintainers.
• This codebase represents a strict standalone proof-of-concept / learning exercise and is explicitly not intended for professional, commercial, or critical industrial application.
• This wrapper, its cross-core FreeRTOS mutex mappings, and its data type interceptor routines were designed and polished with the specialized interactive assistance of an AI engineering collaborator, achieving optimal compatibility with the B4R pre-compiler stack.