Performance of open62541 OPC UA servers on embedded hardware

Paper at IEEE INDIN 2025

Adaept Engineering shows that there is another way. At this year's IEEE International Conference on Industrial Informatics (INDIN 2025) in Kunming, China, we presented the paper “Comparative Evaluation of open62541 OPC UA Servers on Embedded Devices.” In it, we describe how an OPC UA server can be implemented with the open62541 stack on three widely used embedded platforms and what actual performance can be achieved.

The experimental setup

An STM32H757 (Cortex-M4/M7), an Espressif ESP32-ROVER-E (Xtensa LX6), and a Raspberry Pi 4 (Cortex-A72) were used for the study. Open62541 ran on each platform. Zephyr was used as the operating system for the microcontrollers to enable platform-specific hardware abstractions. The server responded to read accesses to a simple data model. To generate practical load, it was first queried by a single client, then by up to 100 clients simultaneously via 1Gbit Ethernet. The measurement campaign recorded the response times (RTT) depending on the number of clients.

Surprising findings

Even a first glance at the measurement results shows the enormous potential of microcontrollers as fully-fledged, secure data nodes in the Industrial IoT. At a rate of 1000 requests per second from a client, the STM32H7 delivers a response within one millisecond. If the request period is increased to 5 milliseconds, i.e., 200 requests per second, each response is delivered within approximately one millisecond, regardless of the number of clients (1 to 5).

For comparison, the OPC UA server was tested on an ESP32. If a client queries the server 200 times per second, the response time is 5 milliseconds. As a result, it was demonstrated that the ESP32 can serve up to four clients, each with 200 queries per second, without buffer overflows.

‍

The Raspberry Pi 4 is the most powerful platform with the most complex operating system in the test setup. Up to 50 clients were able to interact with the server at a rate of 1,000 requests per second each. Here, too, the ratio of clients to response time scales as expected: 100 clients can be processed at 500 requests per second, and so on.

Why microcontroller with OPC UA are still rare

The paper makes it clear that the technical hurdles are real, but by no means insurmountable. However, developers often shy away from the perceived overhead of the OPC UA standard: security layers, expandable data space, and services such as discovery, history, and subscription seem cumbersome when only a few megabytes of heap memory are available. Added to this are the high demands on timing and interoperability, which many embedded teams without specialized domain knowledge are unwilling to tackle.

{{callout}}

Adaept Engineering closes the gap

In Kunming, we not only presented measurement values, but also held a tutorial on how to integrate open62541 into embedded platforms. This significantly shortens the path from concept to a running, standards-compliant OPC UA node based on a microcontroller. Those who already work with STM32 H7 or ESP microcontrollers can integrate a standards-compliant server in just a few days with our expertise.

‍

‍