Collect OPC UA Data with N3uron

Last updated: 2026-11-03

Introduction

This tutorial continues Install N3uron. Use the OpcUaClient module on a reComputer RK Series device to connect to N3uron's public DataSim server, import simulated photovoltaic-site variables as Tags, and view their values in WebUI. No additional PLC or sensor is required.

N3uron DataSim OPC UA Server
opc.tcp://datasim.n3uron.com:4840
             |
             | OPC UA over TCP
             v
reComputer RK Series (N3uron)
     OpcUaClient / DataSim
             |
             v
       N3uron Tags
             |
             v
     Data -> Realtime

Prerequisites

For another RK model, confirm its Linux architecture and N3uron requirements using the installation tutorial before proceeding.

Step 1: Check the device and N3uron service

Run the following commands in a terminal or SSH session on the RK device:

cat /etc/os-release
uname -m
hostname -I
sudo systemctl status n3uron --no-pager

For ARM64 Linux, uname -m typically prints aarch64. Note the device's LAN IP address. The N3uron service should report active (running).

If the service is installed but stopped, start it:

sudo systemctl start n3uron

If N3uron is not installed, complete Install N3uron first.

Step 2: Open N3uron WebUI

Open the following address in the client computer's browser:

http://<RK_DEVICE_IP>:8003

Replace <RK_DEVICE_IP> with the RK device's IP address. The default HTTPS port is 8443 when HTTPS is configured.

Log in with the administrator account configured during installation. The navigation panel includes Data, System, and User.

Step 3: Create the OPC UA Client module

1. Go to System → Config → Modules.
2. Open the Modules menu and select New Module.
3. Set the name to OpcUaClient.
4. Set Module type to OpcUaClient, then click Save.

The screenshot shows the type menu before the selection is applied. Select the highlighted OpcUaClient entry instead of retaining ModbusServer. The module name alone does not determine its type.

Expand the saved module in Explorer. It should contain Certificates, OPC Browser, and Logger.

Step 4: Configure the DataSim client

Select OpcUaClient, open the Model panel menu, and choose New Client. Name the client DataSim.

Configure the following connection settings. The public endpoint and demo account are also documented in the Seeed N3uron example.

Click Save and allow the module to connect. If the server uses the same discovery and endpoint URL, use the endpoint address in both fields; see N3uron's client configuration documentation.

Step 5: Browse OPC UA nodes

Expand System → Config → Modules → OpcUaClient and select OPC Browser. Choose DataSim from the Client drop-down list.

Click Rebrowse if needed. Once browsing succeeds, the server's top-level nodes appear.

Expand the following path:

Objects
└── PVSIM
    └── BLUELAKE
        └── PVG001
            └── WST
                ├── HEIGHT_SUN
                ├── HUMIDITY
                ├── POA_IRRADIANCE
                ├── PRESSURE
                ├── TEMPERATURE_2M
                └── WIND_SPEED_10M

The server can also expose forecast variables and other branches. The account name sunn3rgy is not necessarily a folder name; follow the current node tree.

Step 6: Import variables as Tags

Use four variables from the WST branch:

1. In OPC Browser, expand Objects → PVSIM → BLUELAKE → PVG001 → WST.
2. Drag HUMIDITY into the Model panel's root folder /.
3. Repeat for POA_IRRADIANCE, TEMPERATURE_2M, and WIND_SPEED_10M.
4. Confirm that all four Tags appear in the Model tree. Save any pending changes.
5. If you inspect a Tag's source settings, Source → Enabled should be Yes, with its source module referencing OpcUaClient.

Step 7: Check real-time values

Go to Data → Realtime in the navigation panel. Some versions label this page Real Time. Select / in Tag groups to view the four Tags, including their Value, Quality, and Timestamp.

The RK3576 example shows the following sample readings:

These are sample readings, not fixed expected values. Good indicates a usable reading at the displayed time. Watch the value and timestamp of a changing variable across several refresh cycles to confirm updates. A value of 0 alone does not indicate a connection problem.

The four Tags are now available in N3uron for further processing, MQTT publishing, or WebVision dashboards.

Troubleshooting

Check service status and recent logs:

sudo systemctl status n3uron --no-pager
sudo journalctl -u n3uron -n 80 --no-pager

For a TCP connectivity check:

python3 - <<'PY'
import socket
host, port = 'datasim.n3uron.com', 4840
try:
    with socket.create_connection((host, port), timeout=8):
        print('TCP 4840 reachable')
except Exception as exc:
    print('Connection failed:', exc)
PY

A successful TCP connection alone does not verify OPC UA authentication. Check client diagnostics and values in Data → Realtime as well.