Industrial Modbus RTU to 4G LTE MQTT Gateway Using WIS901-GE

## Introduction

In modern industrial automation and smart manufacturing, trillions of edge sensors and legacy machines still communicate via the traditional **Modbus-RTU (RS485)** protocol. However, bridging these field devices to modern cloud analytics platforms often faces challenges like harsh environments, lack of wired internet, and unstable connections.

This project demonstrates how to build a highly reliable, industrial-grade IIoT data acquisition system using the "WIS901-GE General 4G Industrial Gateway of WISEWISH ". We will poll data from a standard Modbus-RTU sensor and securely transmit it to an MQTT broker over a 4G LTE cellular network, verifying the results instantly using the MQTTX desktop client.

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## Why WIS901-GE?

For industrial deployments, consumer-grade routers or DIY microcontrollers fail under extreme conditions. The WIS901-GE stands out due to its:

* **Industrial-Grade Reliability:** Supports wide voltage input (9-36V) and works flawlessly in harsh environments.

* **Flexible Serial Connectivity:** Built-in RS485/RS232 configurable interface, perfect for Modbus devices.

* **Network Redundancy (Link Backup):** Supports seamless switching between wired WAN and 4G cellular networks to ensure 24/7 uptime.

* **Security First:** Certified with EN18031 cybersecurity regulations, featuring robust firewall policies.

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## Hardware Setup & Architecture

The architecture is straightforward but robust:

1. **The Sensor:** A Modbus-RTU sensor (e.g., Temperature/Humidity or Energy Meter) connected via RS485.

2. **The Gateway:** WIS901-GE acting as the central intelligence, powered via a 9-36V DC terminal block.

3. **The Uplink:** A 4G SIM card inserted into the WIS901-GE to provide cellular backhaul.

4. **The Client:** MQTTX software on a PC to subscribe and monitor the data streams.

### Wiring Connection:

* **Sensor A+ (TX+)** ---> **WIS901-GE RS485 A**

* **Sensor B- (RX-)** ---> **WIS901-GE RS485 B**

* **Sensor VCC/GND** ---> Power Supply (WIS901-GE handles wide 9-36V)

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## Step-by-Step Configuration

### Step 1: Network & 4G Initialization

Insert the 4G SIM card into the WIS901-GE slot. Power on the device and log into the web management gateway (Default IP: `192.168.10.1`).

Under the **Network / Cellular** settings, configure the APN parameters provided by your telecom carrier. Ensure the 4G signal indicator light on the hardware turns stable.

### Step 2: Modbus RTU (RS485) Serial Configuration

Navigate to the Serial/Industrial service tab in the WIS901-GE web GUI. Match the serial parameters with your sensor:

* **Baud Rate:** 9600 (typical)

* **Data Bits:** 8

* **Parity:** None

* **Stop Bits:** 1

### Step 3: MQTT Data Forwarding Setup (Using MQTTX)

To test and verify the data transmission without building a complex cloud platform, we can use **MQTTX**, a cross-platform elegant MQTT 5.0 desktop client.

1. **Configure a Public MQTT Broker:** In the WIS901-GE web GUI, navigate to the MQTT configuration page. Set the remote server to a free public MQTT broker:

* **Broker Address:** `broker.emqx.io` (or `broker.hivemq.com`)

* **Port:** `1883`

* **Client ID:** `WIS901_Gateway_Test`

2. **Define the Topic & Payload:** Map your Modbus register data into a structured JSON format. Set the publish topic to: `wis901/industrial/data`.

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## 📊 Verification & Results

Now, open the **MQTTX** app on your computer to subscribe and catch the live data coming from the field gateway over the 4G network:

1. Click **"New Connection"** in MQTTX.

2. Enter the same host (`broker.emqx.io`) and port (`1883`), then click **Connect**.

3. Click **"New Subscription"** and type the topic we defined in the gateway: `wis901/industrial/data`.

As shown in the client dashboard, the WIS901-GE successfully reads the serial Modbus data periodically and pushes the telemetry data in clean JSON format over the 4G LTE network:

```json

{

"device_id": "WIS901_001",

"status": "online",

"temperature": 26.5,

"humidity": 45.2,

"timestamp": 1718520000

}

This proves that the WIS901-GE functions perfectly as an independent edge gateway, capable of delivering raw industrial sensor data securely to any standard MQTT client or backend system.