The Challenge of Legacy and Modern Protocols
Legacy fieldbus protocols were built around point-to-point communication. This design still works well in applications where one device reliably exchanges data with another, but it shows its limitations when systems scale. Modern protocols like OPC UA or MQTT provide network-oriented approaches that can connect multiple devices, even across facilities.
Over time, device vendors have started adding new protocols to existing hardware to improve integration options. This opens the door for engineers to solve problems in ways that balance performance, compatibility, and scalability.
A Real-World Example: The Barcode Gateway Project
In 2024, our strategic distributor, HH Barnum, collaborated with our application support team to assist with what seemed like a routine request: integrate a Weintek HMI with a ProGlove barcode gateway. The gateway managed multiple barcode scanners and transmitted scanned data to an HMI, where the HMI would parse, re-transmit, and possibly perform other tasks with the data.
On the surface, this looked straightforward. Weintek HMIs already support a wide range of scanner connection methods:
- USB, RS-232, RS-485
- Communication Device Class (CDC)
- Point of Sale (POS) modes
The gateway data was easy enough to read. But then a new issue emerged, latency.
The Limitation of One-to-One Protocols
Our barcode drivers, like many built around legacy designs, assumed a one-to-one topology: one scanner, one HMI. But in this application, multiple scanners were transmitting data nearly simultaneously. Suddenly, the HMI risked missing barcodes, which meant the re-transmission system could fail.
We considered using the gateway’s TCP/IP interface to parse raw data, but questions remained about whether the HMI could process and forward the information fast enough. That’s when a better option surfaced.
Turning to MQTT for Reliability
With HH Barnum’s assistance in testing the ProGlove barcode gateway at their facility, it was brought to our attention that this device also supported MQTT, a modern publish/subscribe protocol designed for reliable, lightweight communication. Since Weintek HMIs can act not only as MQTT clients but also as brokers, the solution practically built itself:
- The gateway published scan data via MQTT.
- The HMI, functioning as a broker, received and parsed the data.
- Any messages arriving at the same time were stored in a queue, preventing data loss.
By shifting from a point-to-point protocol to MQTT, the system gained the flexibility and reliability needed to handle concurrent scans without compromise.
Customization for High Throughput
To further optimize performance, our engineers collaborated with HH Barnum to develop a custom script that automated message handling. This enabled a high output rate and ensured successful, timely delivery of all scan data. The result was a solution robust enough to be presented and ultimately adopted by the end user, with the help of our distribution partner, HH Barnum.
Why Multi-Protocol Support Matters
The success of this project was not related to one specific protocol. Instead, it was about having options and strong partner support. Because Weintek HMIs support both traditional and modern communication methods, our engineers were able to:
- Choose the right protocol based on the application’s requirements.
- Overcome the limitations of legacy point-to-point protocols.
- Deliver a solution that ensured both reliability and performance.
Key Takeaways:
- Supporting multiple protocols is essential for meeting strict application needs.
- The protocol chosen should always reflect the structure, processing speed, and feature requirements of the application.