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Getting started

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Use this page to make your first MELSEC SLMP read from Node-RED. Start with one simple TCP flow, then move to arrays, strings, UDP, routing, or broader verification.

Prerequisites

Requirement Value
Node-RED 3.0 or later
PLC MELSEC PLC reachable from your Node-RED host
First TCP target 192.168.250.100:1025
Starting PLC profile melsec:iq-r

Install

  1. Open the Node-RED editor.
  2. Open Manage palette.
  3. Open the Install tab.
  4. Search for @fa_yoshinobu/node-red-contrib-plc-comm-slmp.
  5. Install the package.
  6. Restart Node-RED if your environment requires it.

Create a connection node

Create or open a slmp-connection config node and set these fields:

slmp-connection field Example value Description
Host 192.168.250.100 PLC IP address or host name.
Port 1025 TCP port for the first example.
Transport TCP Use TCP for the first run.
PLC profile melsec:iq-r Required canonical PLC profile.

Leave the route fields at their defaults unless your PLC network needs a different target.

Import the basic flow

  1. Open the Node-RED import dialog.
  2. Import examples/flows/slmp-basic-read-write.json.
  3. Open its slmp-connection node.
  4. Confirm Host is 192.168.250.100.
  5. Confirm Port is 1025.
  6. Confirm Transport is TCP.
  7. Confirm the PLC profile is melsec:iq-r.
  8. Deploy.
  9. Trigger the read inject node.
  10. Open the debug sidebar and verify msg.payload.

In object output mode, a successful read looks like this shape:

{
  "D300": 123
}

The value depends on your PLC memory.

Read your first value

To build the first read manually, add an slmp-read node and set:

slmp-read field Example value Description
Connection Your slmp-connection node Shared PLC connection.
Source Literal text The address list is entered in the editor.
Addresses D300 First safe word register to read.
Output Object payload Returns an object keyed by address.
Metadata Full msg.slmp Includes connection and target metadata.
Errors Throw Lets Node-RED route runtime errors normally.

Trigger the node with any message. A successful response sets msg.payload.D300 to the current value.

Confirm success

  1. The flow deploys without editor validation errors.
  2. The slmp-connection node has PLC profile melsec:iq-r.
  3. The read inject node produces a debug message.
  4. msg.payload contains a D300 key.
  5. The connection status does not stay red after repeated reads.

If it does not work

Symptom Check
The read returns nothing or errors immediately PLC profile on slmp-connection must be set. It is required, and there is no runtime default.
The first flow feels too busy Import slmp-basic-read-write.json first, not slmp-device-matrix.json.
Address validation fails on the first run Start with D300. Do not test with G or HG on the first run.
TCP does not connect Confirm the PLC is reachable at 192.168.250.100:1025 from the Node-RED host.
UDP is your target Move to the UDP example after TCP works, and set the UDP port to 1035.

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