Processing Modbus Sensor Data at the Edge Using Node-RED on a Robustel IoT Gateway

I can't tell you how many times I've seen engineers get stuck on the same problem: they have a factory floor full of valuable sensors speaking Modbus, but all that data is trapped. Getting those raw, cryptic register values into a modern dashboard or cloud platform can feel like a complex coding project. But what if it didn't have to be?

What if you could visually drag-and-drop a few blocks to create a powerful data processing pipeline right at the edge? That's the magic of using Node-RED on a powerful Industrial IoT Edge Gateway . It transforms the gateway into a low-code, highly flexible Node-RED Modbus Gateway. In this guide, we’re not just going to talk theory; we're going to walk you through the exact steps to build this solution using a Robustel EG5120.

Before we can build our data flow, we need to make sure our industrial IoT edge gateway, the Robustel EG5120 , is ready. The power of this device comes from RobustOS Pro, its Debian-based OS, which allows us to easily install the software we need.

1. Access the EG5120 Web Interface: Log in to your gateway's management page (default IP: 192.168.0.1).

2. Navigate to the APP Center: Go to System -> APP Center.

3. Install the "MING" Stack: You will need to install the ming-ig application package, which includes support for InfluxDB and Grafana, and the node-red-app package. You can upload and install these

.deb or .rpk files directly from this interface.

4. Install the Extend Image (Insider Tip): This is a step many people miss. To get the full functionality and dependencies for these applications, you often need to first install an

extend-image patch for Debian. After installing this, it's a good practice to restore to factory default to ensure all new settings are applied correctly.

Once these are installed, you will see a new

Development tab in the main menu, giving you access to Node-RED, Data Storage (InfluxDB), and Data Visualization (Grafana).

Now for the fun part. We will build the flow that reads, processes, and stores our sensor data.

(Note: This section's structure is preserved for easy screenshot insertion.)

To accelerate development, you can start by importing a pre-built workflow.

1.  Navigate to Development -> Node RED -> Basic -> Flows List.
2. Click   Choose File to upload a pre-made Node-RED flow JSON file (for example, a workflow designed for the Robustel S6000U sensor ).
3.  Click the  upload icon, and then click the checkmark to activate the flow.

1. On the same page, under Basic Settings, ensure Enable Node-RED is on, activate flow and click Open Editor. This will open the Node-RED visual programming canvas in a new tab.
2. You will see the imported flow, which typically consists of several connected nodes.

Let's look at the key nodes in a typical Node-RED Modbus Gateway flow:

• Modbus Read Node: This is the starting point. It's configured with the sensor's Modbus slave ID, the register address you want to read, and the polling interval (e.g., every 1 second).
•  Function Node (Post-Processing): This node contains a small piece of JavaScript code. It takes the raw data from the Modbus node, which might be a cryptic array of numbers, and transforms it into a clean, human-readable JSON object (e.g.,{"temperature": 25.7, "humidity": 30}).
•  Debug Node: This is your best friend for troubleshooting. I can't stress this enough. By connecting a debug node to the output of any other node, you can see the exact data passing through the flow in the debug sidebar on the right. Always check your data here before sending it to a database.
•  InfluxDB Out Node: This is the final step. This node is configured to connect to your local InfluxDB database. It takes the clean JSON object and writes it into the database as a new time-stamped data point.

Once you click the Deploy button in the top right, your flow is live! You should see data appearing in the debug sidebar every second, confirming that your

Modbus data collection is successful.

Briefly, navigate to Development -> Data Storage in the EG5120's interface. Here, you can configure crucial settings for your InfluxDB database, such as setting a

Retention Time (e.g., 720 hours) to automatically delete old data and manage storage space.

You have just built a complete, industrial-grade data processing pipeline at the edge, all with minimal coding. By using a Node-RED Modbus Gateway like the Robustel EG5120, you've transformed the complex task of industrial data acquisition into a simple, visual workflow. This approach not only dramatically accelerates development but also empowers you to create highly customized and efficient IIoT applications.

What's next? Now that your data is flowing into InfluxDB, the next logical step is to visualize it. You can explore our guide on Creating Real-Time Dashboards for Your IoT Data with InfluxDB and Grafana .