Modern Edge Devices Bring Harmony to Disjointed Protocols

Summary

If TCP/IP won the “protocol wars” in the ‘90s, why are you still fighting protocol battles on the plant floor today? 

Because industrial networks were around long before the Internet. As far back as the 1960s, machines communicated via serial networks like RS-232, RS-485 and CAN bus—with specialized proprietary fieldbus protocols like Modbus, Profibus and DeviceNet. Even with TCP/IP on Ethernet, specialized protocols remained—Modbus now has a TCP/IP version, Profibus gave way to ProfiNET, DeviceNet to EtherNet/IP—even some new ones joined the protocol party.

After the industry demanded interoperability, OPC was born. Now we have OPC UA, a big step toward a unified architecture on OT networks.

Meanwhile on the IT side, using HTTP and HTTPS was common. It’s how web browsers—and most of the internet—works today.
 
MQTT Sparkplug came later. A recently named international standard, MQTT Sparkplus is built on efficient, secure and scalable publish/subscribe communications. This makes it a great fit for digital transformation projects and the industrial internet of things (IIoT).

I want to digitally transform, but my existing machines don’t support all these protocols. You’re not alone. Hundreds of billions of legacy industrial control systems are still in operation today. The adage, “If it ain’t broke, don’t fix it,” often delays digital transformation.
 

Modern edge devices save the day

So, should you put off digital transformation while waiting for existing systems to fail or spend a ton ripping and replacing your controls to support the latest protocols?

Thanks to modern edge devices—computing systems that process data locally at the source—you don’t have to make that choice.

Inexpensive devices using proven protocols are available now. They can either work with your existing PLC system or run in parallel to securely get your plant floor data where it’s needed—to your IT network, remote servers and even the cloud.

For example, many factories have long-standing equipment that relies on serial communications. Some new systems use serial protocols for reliability, simplicity and cost-effectiveness.

Thankfully, the latest edge devices include serial ports and software tools for RS-232, RS-485 and CAN Bus—everything from simple USB-to-serial interfaces through dedicated, configurable, multi-channel I/O modules.
You can achieve bidirectional serial communication in open programming platforms like Node-RED, JavaScript, Python, C++ and more. Or, if you prefer ladder diagrams and function blocks, use an IEC 61131-3 compliant PLC programming platform.
 
Alternatively, PLCs sold today all run Ethernet-based fieldbuses. They’re suited for coordinated motion-control applications where low latency and precise synchronization are paramount, but they may not fit for digital transformation.
 
Thankfully, you don’t have to rip out and replace your PLCs. Edge devices today have SCADA tools and programming platforms with native drivers for all the most popular protocols. Without disturbing existing systems, edge devices make it easy to convert data from a custom fieldbus into open protocols for digital transformation.
 
One of those open protocols is OPC-UA, which creates interoperability among PLC and I/O platforms. You’ll find options for both client and server functionality on the latest edge devices.
 
Native OPC UA servers expose I/O values from physical modules. SCADA-supported OPC UA servers provide southbound connectivity to fieldbuses and northbound connectivity to HMI dashboards and historians. And both clients and servers in IEC 61131-3 compliant PLC programming platforms provide endless interconnectivity options.
 

REST API and MQTT Sparkplug

REST application programming interfaces (APIs) are a common way to pass information across IT infrastructure. These APIs are a standard way to use HTTP or HTTPS messages to send and receive data in common formats like XML or JSON.
 
IT and programming professionals use tools like Swagger to understand, test and integrate with someone else's API by exploring documentation, trying out endpoints and generating client code for seamless integration. And yes, modern edge devices support this technology as well, enabling them to communicate using methods familiar to IT professionals.
 
As for MQTT Sparkplug, this technology for IIoT communications employs a publish/subscribe architecture. Originally designed for an industrial SCADA application, MQTT Sparkplug should be at the heart of any digital transformation project.
 
With MQTT’s Unified Namespace (UNS), you can model your data with context and create a plug-and-play architecture for all your machines. Your edge device gives you a single source of truth for your data (where it originates) and then securely publishes your data where it’s needed. The result is you can use the latest in machine learning, artificial intelligence, advanced analytics and anomaly detection.

Need to figure out where to begin? Start small. Prove ROI with a small investment. Find an edge device that’s commercially available off-the-shelf and speaks the protocols your plant runs today. Once you’ve proven it will work, it’s time to expand.

_{This piece was originally published in AUTOMATION 2024: 9th Annual Industrial Automation & Control Trends Report.}