Getting Started with Flow (Node-RED)
You can access the built-in Node-RED environment on the gateway through the /ui/flow menu.
Node-RED is a low-code tool for creating data flows by connecting blocks (nodes) via drag-and-drop. It allows you to read and write tag values from the gateway, interface with external systems via MQTT/HTTP, and design automations such as alarms, logging, and formulas.
Node-RED 4.1.10 + Node.js 20 (both installed globally within the image). During the first boot of the container, userDir.seed
(node_modules + PlantPulse Edge / node-red-contrib-opcua nodes) are
automatically copied to /data1/pp-data/node-userdir/ (user flows are preserved from the second boot onward).
User flows remain intact even after an image upgrade. The flow tab will be empty — example flows are imported from documentation rather than being included in the image (Example Flows for Import).
PlantPulse dedicated nodes (pp-tag-value-read / pp-tag-value-write / pp-opc-* / pp-tag-list)
are connected to node/conf/plantpulse-edge-nodes/ of the image via absolute path symlinks — the entrypoint guarantees this at every boot (preventing issues where symlinks from the old native version, which used relative paths, would break in containers).
Complete up to 자주 하는 작업 → 새 PLC 연결 추가 / 태그 등록 and start from a state where one or more tags are being collected in real-time. Node-RED uses those tag values as input.
1. Access
Connect to the gateway in your browser and go to Flow (Node-RED) in the left menu or navigate directly to http://<gateway>/ui/flow.
2. Screen Layout
| No. | Area | Description |
|---|---|---|
| ① | Left Palette | List of available nodes. Grouped by category; the PlantPulse Edge category contains gateway-specific nodes (pp-tag-value-read · pp-tag-value-write · pp-opc-* · pp-tag-list) |
| ② | Flow Tabs | Organize flows into multiple sheets. Create a new tab with + |
| ③ | Center Workspace | Drag and drop nodes here and connect them with wires |
| ④ | Right Sidebar | info shows help for the selected node, and debug shows output logs for debug nodes |
| ⑤ | Top-right Deploy | Click this to apply changes to the gateway |
3. Basic Operations — Useful Shortcuts
| Action | Method |
|---|---|
| Add Node | Drag from palette to workspace |
| Configure Node | Double-click node → Edit in right panel → Done |
| Connect Nodes (Wire) | Drag from the output port (right) of a node to the input port (left) of another node |
| Break Wire | Click to select the wire, then Delete |
| Multiple Selection | Drag to select an area with Shift, or add selection with Ctrl/Cmd + 클릭 |
| Copy / Paste | Ctrl/Cmd + C / Ctrl/Cmd + V |
| Search | Ctrl/Cmd + F — Search for node names in the palette |
| Import Flow | Menu → Import → Paste JSON (you can import Example Flows for Import as is) |
Even if you add, delete, or modify nodes, the gateway will not recognize the changes until you click Deploy. A red dot (●) on a node indicates "unsaved changes."
4. Basic Structure of a Message (msg)
Data flowing between nodes is always a JavaScript object called msg. The most frequently used fields are:
| Field | Meaning |
|---|---|
msg.payload | Payload (primary data). Can be number, string, object, or buffer |
msg.topic | Topic (classification label). Frequently used in MQTT, Switch, Join, etc. |
msg.timestamp | Timestamp (filled manually when needed) |
msg._msgid | Unique ID automatically assigned by Node-RED — for tracking |
Most nodes operate using only msg.payload.
5. Edge Nodes — Overview (Gateway Exclusive)
Among the nodes registered by the gateway in the PlantPulse Edge category of the palette (7 in total), first look at the two that center on input and output. These are the input/output for almost all IIoT flows.
| Icon | Node | English Name | Action | Called REST |
|---|---|---|---|---|
| ⬇ | Read Tag Value (pp-tag-read) | read tag value | Get the current value of a tag (from cache or direct PLC read) | GET /api/v1/tag/{tagId}/value |
| ⬆ | Write Tag Value (pp-tag-write) | write tag value | Write a value to a tag (reflected immediately in PLC) | POST /api/v1/tag/{tagId}/value |
inject (1s) ──▶ 태그값 읽기 ──▶ 처리 (function/switch/...) ──▶ 태그값 쓰기 / mqtt out / debug / file ...
How to find nodes — Enter read tag or PlantPulse in the palette search box → Filters only the corresponding nodes. They are colored in light pastel blue.
| Frequently Left Blank in Node Settings | How to Fill Dynamically |
|---|---|
| Tag ID | Specified dynamically via msg.tag_id = 'TAG_...' during the flow (reuse one node for multiple tags) |
| Value (Write Node) | Filled during the flow via msg.value or msg.payload |
Thoroughly verify using an external simulator or test tags before applying writes to actual equipment. Write permissions should only be granted to tags agreed upon with the operations team.
For detailed fields, I/O, and all protocol support tables → Edge Category (Read/Write Tag)
6. First Flow — Hello World
Goal: Read a tag every 5 seconds and output it to the Debug sidebar.
- Drag the
injectnode from the palette → Double-click →Repeat: intervalevery 5 seconds→ Done - Drag the PlantPulse Edge → Read Tag Value node → Enter an actual tag (e.g.,
TAG_TEST_00042) in Tag ID → Done - Drag the
debugnode from the palette - Connect the three nodes via wires in the order of
inject → 태그값 읽기 → debug - Click Deploy in the top-right
- Open the debug tab in the right sidebar to verify the value is printed every 5 seconds
This pattern (Periodic Trigger → Read → Process) is the fundamental form of all IIoT flows.
7. Next Steps
Follow the left menu in order:
- Basic Node Usage — Functions of 14 nodes frequently used in IIoT
- Edge Nodes (Read/Write Tag) — Gateway-specific nodes (detailed version of the overview in Section 5)
- MQTT Nodes in Detail — Broker Setup / Pub / Sub / LWT / Birth
- OPC-UA Nodes in Detail — Endpoint / Item / Client / Subscribe / Browse
- Sparkplug B Nodes in Detail — Group / Edge / Birth-Death / TxRx
- IIoT Example Collection — 12 patterns frequently created in the field
- Example Flows for Import — 6 sets of complete flows to run immediately via paste
- Flow Troubleshooting — Common pitfalls
8. Learn More
- View all tags, values, and node IDs currently held by the gateway at a glance in the OPC UA Server (
/ui/opcua). → Using OPC UA Server - The REST API itself is covered in the
고급 / 통합 파트너용 → REST APIchapter. Node-RED'spp-tag-read/pp-tag-writeare thin wrappers for that API. - Node-RED Official Manual:
<https://nodered.org/docs/>