Please Note: This lab can be accomplished either through the Arduino Create web environment or by downloading open62541, an open source OPC-UA libary and compiling it and your application locally on the Up2 board. If you use the Arduino Create environment then it is not necessary to download and install the open62541 library on the Up2 board. You can skip to the next step via the link at the bottom of this document.
This lab will guide you through the implementation of a simple OPC UA application to illustrate client-server communications. Both ends will run locally:
- Server: upon request reads and returns the date and time from the local clock
- Client: reads a timestamp from the server and prints it
OPC is the interoperability standard for the secure and reliable exchange of data in the industrial automation space and in other industries. It is platform independent and ensures the seamless flow of information among devices from multiple vendors. The OPC Foundation is responsible for the development and maintenance of this standard.
The OPC standard is a series of specifications developed by industry vendors, end-users and software developers. These specifications define the interface between Clients and Servers, as well as Servers and Servers, including access to real-time data, monitoring of alarms and events, access to historical data and other applications.
When the standard was first released in 1996, its purpose was to abstract PLC specific protocols (such as Modbus, Profibus, etc.) into a standardized interface allowing HMI/SCADA systems to interface with a “middle-man” who would convert generic-OPC read/write requests into device-specific requests and vice-versa. As a result, an entire cottage industry of products emerged allowing end-users to implement systems using best-of-breed products all seamlessly interacting via OPC.
Initially, the OPC standard was restricted to the Windows operating system. As such, the acronym OPC was borne from OLE (object linking and embedding) for Process Control. These specifications, which are now known as OPC Classic, have enjoyed widespread adoption across multiple industries, including manufacturing, building automation, oil and gas, renewable energy and utilities, among others.
With the introduction of service-oriented architectures in manufacturing systems came new challenges in security and data modeling. The OPC Foundation developed the OPC UA specifications to address these needs and at the same time provided a feature-rich technology open-platform architecture that was future-proof, scalable and extensible. Today the acronym OPC stands for Open Platform Communications.
These are just some of the reasons why so many members and other technology organizations (collaborations) are turning to OPC UA for their interoperability platform
See What is OPC?
We are going to use an open source OPC UA stack: open62541
open62541 can be compiled to generate a single header and source code file, than can then be integrated in your project. This is enabled by the option in the subsequent steps:
UA_ENABLE_AMALGAMATIONLAB_DIR is a shell environmental variable that should be set to the directory that you are creating your labs in. For example, $HOME/labs.
export LAB_DIR=$HOME/labsFollow the next steps to generate the open62541 header and code:
mkdir -p ${LAB_DIR}
cd ${LAB_DIR}
git clone https://github.com/open62541/open62541.git
cd open62541
mkdir build
cd build
sudo apt install cmake
cmake .. -DUA_ENABLE_AMALGAMATION:BOOL=ON
makeYou should be able to see the open62541.c and open62541.h files now. Copy both to your working directory in order to include and link them.
cd ${LAB_DIR}
mkdir opcua-lab
cd opcua-lab
cp ${LAB_DIR}/open62541/build/open62541.c ${LAB_DIR}/opcua-lab/