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Overview

This article shows you how to publish tag data collected by E2C Trinity to an external MQTT broker. You will create a Tag Group, configure an MQTT Cloud Service, add a publish rule, and verify the data using MQTTX.

Stage 1 — Southbound Collection: E2C Trinity reads data from your industrial devices (PLC, sensor, meter, etc.) using protocols like Modbus TCP, OPC UA, or BACnet, and stores the values as internal "Tags."

Stage 2 — Northbound MQTT Publish (this guide): E2C Trinity connects to your MQTT broker as a client, packages the collected tags into JSON payloads, and publishes them to configured topics.

Stage 3 — Cloud Consumption: Your cloud platform (AWS IoT, Azure IoT Hub, or a custom application) subscribes to the MQTT topics and processes the data.

Note: E2C Trinity also supports Sparkplug B (an industrial IoT specification built on MQTT 3.1.1) and HTTP for cloud data forwarding. These are covered in separate articles.

Core Concepts & Glossary

If you are already familiar with MQTT, feel free to skip this section.

Example Configuration Used in This Guide

To make it easier to follow, all steps in this guide use the same example values:

Before You Start

Before beginning the configuration, make sure you have:

• An E2C Trinity gateway with live tag data already being collected from your industrial devices.
• A running MQTT broker accessible from the gateway — either a cloud service (AWS IoT, Azure IoT Hub, EMQX Cloud) or a local broker (EMQX, Mosquitto).

Security Notice: Public MQTT brokers (such as broker.emqx.io) should only be used for testing with non-sensitive data. Do not publish production, customer, credential, or personally identifiable data to a public broker. Always use TLS when sending data over the public internet.

• An MQTT client tool for testing: MQTTX (desktop app, recommended) or mosquitto_sub (command-line).
• The following information from your MQTT administrator:
  • Broker address and port
  • Username and password (if authentication is required)
  • TLS certificates (if encryption is required)

Step-by-Step Configuration

Important: The screenshots use E2C Factory as an example. The workflow is also applicable to E2C Field, although some menu names or interface details may differ depending on the software version.

Workflow Overview

Skip ahead: If you already have a Tag Group with live tags, jump to Step 3.

Step 1: Verify Live Tag Data

Purpose: MQTT only forwards data that already exists as live tags. Before configuring anything, confirm that your data collection is working.

1. In the E2C Trinity web interface, navigate to Data Collection in the left sidebar.
2. Verify that your device is listed and shows a green status icon.
3. Confirm that the Latest Value column shows real-time data and the Update Time is current.

If you do not see live data, complete the device and tag configuration first. Refer to the relevant protocol guide (e.g., "How to Configure Modbus TCP Data Collection in E2C Factory") on the Robustel Support Center.

Step 2: Create a Tag Group

Purpose: E2C Trinity publishes data to MQTT by Tag Group — not by individual tags. You must create at least one Tag Group before configuring message publishing. Think of a Tag Group as a "folder" that bundles related tags for batch transmission.

2.1 Create the Group

1. Navigate to Data to Cloud > Tag Group.
2. Click + Create Group.

3. In the Add Group pop-up window, configure:

4. Click Save and Configure Tag to assign tags immediately (recommended), or click Save to add tags later.

2.2 Add Tags to the Group

1. The Add Tag window shows all available tags from your configured devices on the left.
2. Select the tags you want to include and click > to move them to the group. Use ALL to move all tags at once.

3. Click Close when done. Your Tag Group is ready.

Note: You can always add or remove tags later by selecting the group and using the Add and Batch Delete buttons.

Step 3: Create an MQTT Cloud Service

Purpose: Create a connection in E2C Trinity that defines the target MQTT broker and how to connect to it.

3.1 Basic Connection Settings

1. Navigate to Data to Cloud > Cloud Service.

2. Click + Create Cloud Service. Enter a Cloud Service Name (e.g., MES_MQTT) and select MQTT as the Cloud Service Type. Click Save.

3. Fill in the Basic Settings:

3.2 Save and Test Connection

Critical Step: After completing the configuration, you must save and verify the connection.

1. Click the Save button at the top-right corner.
2. Click the Test Connection button. The Cloud Service Status indicator shows whether the connection is successful.

• A green status with "Connected" means the gateway has successfully connected to the MQTT broker.
• If the status shows Disconnected, refer to the Troubleshooting section.

Important: Gateway Time Synchronization

MQTT connections — especially TLS connections — rely on accurate timestamps. If the gateway's system clock is incorrect, the connection may fail.

To check and synchronize the gateway's time:

1. In the gateway's Web GUI (RobustOS Pro), go to Services > NTP.
2. Use the NTP tab to configure NTP servers (e.g., pool.ntp.org).
3. Use the Status tab to verify the System Time. If the Last Update Time shows "Not Updated," click Sync to manually synchronize.

For detailed instructions, refer to the RobustOS Pro Software Manual on the Robustel Support Center.

Step 4: Add a Publish Rule

Purpose: Tell E2C Trinity which Tag Group to publish and under which MQTT topic.

1. After saving the MQTT Cloud Service, scroll down to Message Management. Make sure the Publish tab is selected.
2. Click Add.

3. In the Add Publish pop-up window, configure:

4. Click Save. After saving, E2C Trinity starts publishing data according to the Tag Group reporting settings.

Customizing the Payload Format: The Function Code panel allows you to write a JavaScript function to transform the data payload before publishing. If you leave the default return msg;, the data is published in E2C Trinity's standard JSON format. For advanced customization, click View Help in the right-side panel for the full API reference.

Step 5: Verify the Published Data

Purpose: Confirm that the MQTT broker is receiving data from E2C Trinity.

Using MQTTX (desktop app — recommended):

1. Open MQTTX and create a new connection to your broker (same address and port as in Step 3).
2. Click Connect, then + New Subscription, enter the topic (e.g., publish/machine), and click Confirm.
3. You should see JSON messages arriving at the configured reporting interval:

Each message follows this structure:

{
  "groupName": "Machine_Data",
  "groupTime": 1784633235145,
  "messageId": "66b517bf-192c-4522-b08a-7b5087964d96",
  "messageType": "normal",
  "payload": {
    "cycle_count": {
      "deviceName": "A_Packaging_Machine",
      "tag": "cycle_count",
      "time": 1784633234000,
      "value": "2780"
    }
  }
}

Note: The value field is shown as a string in this example. Verify the output format for your tag data type and software version — the encoding may vary depending on the tag type.

If you see real-time data in the MQTT client, your configuration is complete.

Troubleshooting

Where to Find Logs

• Debug Logs: In E2C Trinity, navigate to Debug Logs in the left sidebar.
• System Logs: In the gateway's management page (RobustOS Pro), go to Services > Syslog.

Advanced Topics

TLS Configuration

TLS (Transport Layer Security) encrypts the data between your gateway and the MQTT broker, preventing unauthorized access or tampering. When you enable TLS in the MQTT Cloud Service settings, you need to select an authentication method. Select the authentication method according to the requirements provided by your MQTT broker administrator — do not guess.

After selecting the method, paste the certificate contents into the corresponding fields and save the configuration.

Last Will Message (LWT)

A Last Will Message is a pre-defined message that the MQTT broker automatically publishes to a specified topic if the gateway disconnects unexpectedly — for example, due to a power failure or network outage. This allows your cloud platform or monitoring system to detect offline gateways.

To configure LWT, expand the Last Will Message section in the MQTT Cloud Service settings and specify:

• Topic — where the message is published (e.g., gateway/status)
• QoS — the delivery guarantee level
• Payload — the message content, typically a JSON string like {"status": "offline"}

Custom Payload Formatting

By default, E2C Trinity publishes tag data in its standard JSON format (see the example in Step 5). If your cloud platform expects a different JSON structure, you can use the Function Code panel in the Add Publish window to write a JavaScript function that transforms the payload before publishing.

The function receives a msg parameter containing the tag data. You can use Edge.ReadTags() to read additional tag values, perform calculations, filter data, or restructure the JSON output. Other APIs are available for advanced logic. Click View Help in the right-side panel for the full API reference.

Sparkplug B

Sparkplug B is an industrial IoT data exchange specification built on top of MQTT 3.1.1. It adds standardized topic structures (e.g., spBv1.0/{Group ID}/DDATA/{Edge Node ID}/{Device ID}), binary Protobuf payloads, and device lifecycle state management (birth/death certificates). It is commonly used in SCADA and industrial platforms that require self-describing, interoperable data models.

To use Sparkplug B, create a new Cloud Service and select Sparkplug B as the type instead of MQTT. In the current E2C Trinity implementation, Sparkplug B uses a fixed reporting model and does not expose user-defined Topic, Last Will Message, or Clean Session settings.

Cloud Platform Integration

The Standard MQTT configuration described in this guide can be used with MQTT 3.1/3.1.1-compatible brokers, provided that the broker's authentication, client ID, topic, and access-policy requirements are met. Guides for connecting E2C Trinity to specific cloud platforms and brokers — including AWS IoT Core, Azure IoT Hub, and EMQX — are planned for future release. For more E2C Trinity articles, visit the Robustel Knowledge Base.

Appendix

A. Related Articles

• How to Configure Modbus TCP Data Collection in E2C Factory
• How to Configure OPC UA Data Collection in E2C Factory
• How to Forward Data to BACnet/IP in E2C Factory
• E2C Factory Software Product User Manual
• E2C Field Software Product User Manual