The Embedded OPC UA Automation Kit Documentation turns a ESP32-C3 Microcontroller into a fully featured OPC UA server. Out of the box, the kit provides an OPC UA server on port 4840 with full Namespace Zero and the OPC UA Device Integration (DI) and Encryption.

Nine GPIO pins are controllable via OPC UA, supporting digital input, digital output, PWM and ADC modes. Each pin's mode is switchable at runtime through a typed GpioMode enumeration. A Blink method lets you toggle the onboard LED for a configurable duration.

Live monitoring variables expose the current WiFi status, IP address, SSID and free heap memory, all readable by any OPC UA client and shown simultaneously on the integrated 0.42-inch OLED display. The device object follows the DI companion specification with Manufacturer, Model, SerialNumber, HardwareRevision, SoftwareRevision and more, making it instantly recognizable in any OPC UA client. All of this runs within roughly 95 kB of free RAM on a chip that costs a few euros- enabled by the o6\Embedded Extension.

The board connects via USB-C, which also serves as the built-in USB-JTAG interface for flashing and serial monitoring — no external programmer is needed. A 0.42-inch SSD1306 OLED display with a resolution of 72 by 40 pixels is connected over I²C on GPIO 5 (SDA) and GPIO 6 (SCL), showing the current endpoint URL, OPC UA memory usage and free RAM at a glance. The onboard LED on GPIO 8 is used by the Blink method for visual device identification. The board is powered directly over USB and creates its own WiFi network on first boot.

Flashing takes under a minute and requires only Python and a USB-C cable. The provided Kit Software Download here provides all you need. The binary files and a shell script for flashing. The file bootloader.bin is the ESP-IDF second-stage bootloader that initializes the chip hardware. The file partitions.bin defines the flash layout — an NVS partition for WiFi credentials, a PHY calibration partition, and a factory application partition. The file firmware.bin is the actual o6\Embedded application containing the OPC UA server, the ROM nodestore with Namespace Zero and the DI companion specification, the GPIO and WiFi logic, the OLED driver and the encrypted endpoint. The flash-script ties it all together: it first erases the NVS partition to clear any previously stored WiFi credentials, then writes all three binaries to their correct flash offsets in a single esptool call.

The ESP32-C3 kit is a reference implementation, but the underlying architecture of o6\Embedded is not tied to any specific chip. The key design principle is the placement of OPC UA nodes in ROM or flash memory. The entire Namespace Zero, the DI companion specification, and application-specific nodes are compiled into a compact binary that is memory-mapped at runtime with zero-copy access. This ROM nodestore approach works on virtually any embedded platform that can map a region of flash into the address space — which covers the vast majority of microcontrollers and embedded systems on the market today, from small Cortex-M devices to larger application processors running Linux or RTOS.

Because the node definitions live in ROM, the runtime RAM footprint drops dramatically. The OPC UA server only needs memory for sessions, subscriptions, and dynamic state — not for the thousands of nodes that make up a full information model. This makes it feasible to run a standards-compliant OPC UA server with encryption on hardware that costs just a few euros.

The open62541 OPC UA stack at the core of o6\Embedded already supports FreeRTOS, Zephyr, bare-metal and POSIX environments. Porting to a new platform is primarily a matter of providing a network interface and a flash mapping for the ROM nodestore binary. Use the contact form below to get more details about porting to your target platform, access to the source code examples, and the ROM nodestore generation toolchain.