OPC-UA Driver

Overview

Industrial data standard protocol based on OPC Unified Architecture (IEC 62541).

Item	Value
`opc_type`	`OPCUA`
Implementation class	`plantpulse.driver.protocol.opcua.OPCUA_34_Driver`
Library	Eclipse Milo (`milo-sdk-client`)
read	✅
write	❌ (Phase 3 / together with Sparkplug NCMD)
Security	Username/Password, Anonymous

Compatible with most OPC-UA servers, including Kepware, Matrikon, and Prosys.

OPC Registration Form

Field	Meaning	Example
`opc_agent_ip`	OPC-UA server IP	`192.168.0.40`
`opc_agent_port`	OPC-UA server TCP port	`49320` (Kepware default)
`timecycle`	Polling interval (ms)	`1000`
`options.servername`	Server name at the end of the endpoint	(leave blank for Kepware)
`options.username`	Authentication user	`kopens`
`options.password`	Authentication password	`***`
`options.discovery`	Whether to use the discovery endpoint	`false` (if true, endpoints are discovered automatically)

Format of the generated endpoint URL:

opc.tcp://<opc_agent_ip>:<opc_agent_port>/<servername>

If both username and password are present, UsernameProvider is used; otherwise AnonymousProvider is used.

Tag `plc_address` Format

Standard OPC-UA NodeId notation. Examples:

Notation	Meaning
`ns=2;s=Simulator.Sine1`	namespace 2, string identifier `Simulator.Sine1`
`ns=2;i=1234`	numeric identifier `1234`
`ns=3;g=09087e75-8e5e-499b-954f-f2a8624db28a`	GUID identifier
`ns=2;b=Mb=`	opaque (bytestring) identifier

For Kepware, the ns=2;s=<Channel>.<Device>.<Tag> format is typical.

`data_type` / `format` Mapping

The Value of the OPC-UA variable node is cast to String before being returned. data_type is used for casting by later stages (PLCValueFomula, Sparkplug publishing, etc.).

`data_type`	Behavior
`Float` / `Double`	Numeric value as-is
`Int` / `Integer` / `Int32` / `Short` / `Long`	Numeric value as-is
`Boolean` / `Bool`	`true`/`false` string
`String` / `Text`	UTF-8 string
`DateTime`	ISO string

format is not generally used with OPC-UA. If post-processing arithmetic is required, use fomula.

Common Errors and Fixes

Message / Symptom	Cause	Fix
`connection refused`	Server not running, port blocked	Verify communication with `telnet <ip> <port>`
`Bad_UserAccessDenied`	Wrong username/password, anonymous access not allowed	Register the user on the server side, or enable anonymous access
`Bad_SecurityChecksFailed`	Security policy mismatch	Check policies such as None / Basic256Sha256 on the server. Phase 1 prefers `MessageSecurityMode.None`
`endpointUrl` mismatch	`discovery=false` is set but the server returns a different hostname	Leave it as `discovery=true` or map it in the hosts file
Value is always 0 / null	NodeId typo, namespace number mismatch	Verify by reading the same NodeId with a client such as UA Expert

curl Registration Example

curl -X POST http://<edge-host>/api/v1/opc \
  -H "Content-Type: application/json" \
  -d '{
    "opc_id": "OPC_UA_Kepware",
    "opc_type": "OPCUA",
    "opc_name": "Kepware",
    "opc_agent_ip": "192.168.0.40",
    "opc_agent_port": "49320",
    "site_id": "SITE_00001",
    "auto_collect": true,
    "timecycle": 1000,
    "options": {
      "username": "kopens",
      "password": "***",
      "discovery": "false"
    },
    "tag_list": [
      {
        "tag_id": "OPC_UA_Kepware_TAG_00001",
        "tag_name": "Sine1",
        "plc_address": "ns=2;s=Simulator.Sine1",
        "data_type": "Float",
        "description": "Sine wave"
      },
      {
        "tag_id": "OPC_UA_Kepware_TAG_00002",
        "tag_name": "Random1",
        "plc_address": "ns=2;s=Simulator.Random1",
        "data_type": "Integer"
      }
    ]
  }'

Reading a value:

curl -s http://<edge-host>/api/v1/tag/OPC_UA_Kepware_TAG_00001/value | jq

Reference: Kepware Quick Setup Guide

Kepware Server → Project → add a channel (e.g., Simulator).
Add a device (e.g., Simulator) → model = 16 Bit Device.
Add tags → Sine1, type Float, scan rate 100ms, etc.
Enable port 49320 in Project Properties → OPC UA → Server Endpoint.
Enable Anonymous access or a user account.

→ Edge registration form:

Field	Value
opc_agent_ip	Kepware server IP
opc_agent_port	`49320`
options.servername	(blank)
options.username/password	The account created above
plc_address	`ns=2;s=Simulator.Simulator.Sine1`

Example Collection (by Data Type)

OPC-UA casts the variable node's value (Variant) to String before returning it. data_type is used for casting during post-processing (PLCValueFomula, Sparkplug DataTypeMapper). format is not generally used.

Boolean

`data_type`	`plc_address` example	Notes
`Boolean`	`ns=2;s=Simulator.Boolean1`	Boolean tag in Kepware Simulator
`Boolean`	`ns=2;s=PLC.Status.Running`	Kepware Channel.Device.Tag
`Boolean`	`ns=2;i=1003`	numeric NodeId

16/32-bit Integers

`data_type`	`plc_address` example	Notes
`Integer`	`ns=2;s=Simulator.Random1`	Random integer simulation
`Integer`	`ns=2;s=Simulator.Counter1`	Counter
`Integer`	`ns=2;s=PLC.D100`	Kepware MELSEC channel exposure

64-bit Integers

`data_type`	`plc_address` example	Notes
`Long`	`ns=2;s=Simulator.LongCounter`	UInt64 / Int64 node
`Long`	`ns=2;s=PLC.Cycle.Total`	Cumulative counter

Floating Point

`data_type`	`plc_address` example	Notes
`Float`	`ns=2;s=Simulator.Sine1`	Sine wave simulation
`Float`	`ns=2;s=Simulator.Ramp1`	Ramp wave
`Double`	`ns=2;s=PLC.Pressure`	High-precision measurement

Strings

`data_type`	`plc_address` example	Notes
`String`	`ns=2;s=Simulator.User1.Name`	String node
`String`	`ns=2;s=PLC.Recipe.Active`	Recipe name

By NodeId Format

identifier type	`plc_address` example
String (`s=`)	`ns=2;s=Simulator.Sine1`
Numeric (`i=`)	`ns=2;i=1234`
GUID (`g=`)	`ns=3;g=09087e75-8e5e-499b-954f-f2a8624db28a`
Opaque (`b=`)	`ns=2;b=Mb=`

Using Formulas

Purpose	`data_type`	`fomula`	Notes
Unit conversion	`Float`	`${VALUE}*0.001`	g → kg, etc.
Zero-point correction	`Float`	`${VALUE}-${TAG_ZERO}`	Can reference other OPCUA tags
Type conversion	`Float`	`${VALUE}*1.0`	Force Integer → Float
Polynomial	`Float`	`${VALUE}${VALUE}0.0001`	Non-linear

Comprehensive curl Example (All Types)

curl -X POST http://<edge-host>/api/v1/opc \
  -H "Content-Type: application/json" \
  -d '{
    "opc_id": "OPC_UA_FULL",
    "opc_type": "OPCUA",
    "opc_name": "Kepware Full",
    "opc_agent_ip": "192.168.0.40",
    "opc_agent_port": "49320",
    "site_id": "SITE_00001",
    "auto_collect": true,
    "timecycle": 1000,
    "options": { "discovery": "false" },
    "tag_list": [
      {"tag_id":"OPC_UA_FULL_T01", "tag_name":"BoolTag",    "plc_address":"ns=2;s=Simulator.Boolean1",        "data_type":"Boolean"},
      {"tag_id":"OPC_UA_FULL_T02", "tag_name":"IntTag",     "plc_address":"ns=2;s=Simulator.Random1",         "data_type":"Integer"},
      {"tag_id":"OPC_UA_FULL_T03", "tag_name":"LongTag",    "plc_address":"ns=2;s=Simulator.LongCounter",     "data_type":"Long"},
      {"tag_id":"OPC_UA_FULL_T04", "tag_name":"FloatTag",   "plc_address":"ns=2;s=Simulator.Sine1",           "data_type":"Float"},
      {"tag_id":"OPC_UA_FULL_T05", "tag_name":"DoubleTag",  "plc_address":"ns=2;s=PLC.Pressure",              "data_type":"Double"},
      {"tag_id":"OPC_UA_FULL_T06", "tag_name":"StringTag",  "plc_address":"ns=2;s=Simulator.User1.Name",      "data_type":"String"},
      {"tag_id":"OPC_UA_FULL_T07", "tag_name":"NumIdTag",   "plc_address":"ns=2;i=1234",                       "data_type":"Integer"},
      {"tag_id":"OPC_UA_FULL_T08", "tag_name":"ScaledTag",  "plc_address":"ns=2;s=Simulator.Sine1",           "data_type":"Float", "fomula":"${VALUE}*100"}
    ]
  }'

Overview​

OPC Registration Form​

Tag plc_address Format​

data_type / format Mapping​

Common Errors and Fixes​

curl Registration Example​

Reference: Kepware Quick Setup Guide​

Example Collection (by Data Type)​

Boolean​

16/32-bit Integers​

64-bit Integers​

Floating Point​

Strings​

By NodeId Format​

Using Formulas​

Comprehensive curl Example (All Types)​