CANopen Nodes

Communicate with CANopen PLCs, motor drives, and sensors over CAN bus from inside your pipelines. MaestroHub provides three CANopen connector nodes (SDO Read, SDO Write, and NMT Command) backed by a shared connection profile. For event-driven TPDO subscriptions, see the CANopen Trigger node.

Configuration Quick Reference

Field	What you choose	Details
Parameters	Connection, Function, Function Parameters, Timeout Override	Select the CANopen connection profile, choose a function from that connection, configure function parameters with expression support, and optionally override the timeout.
Settings	Description, Timeout (seconds), Retry on Timeout, Retry on Fail, On Error	Node description, maximum execution time, retry behavior on timeout or failure, and error handling strategy. All execution settings default to pipeline-level values.

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CANopen SDO Read Node

CANopen SDO Read Node

Read a single Object Dictionary entry over SDO. The node issues a real SDO upload against the remote node and decodes the response bytes locally according to the configured data type.

Supported Function Types:

Function Name	Purpose	Common Use Cases
SDO Read (canopen.sdo.read)	Read an OD entry by (index, sub-index)	Statuswords, identity objects, vendor-specific configuration

Node Configuration

Parameter	Type	Required	Description
Connection	Selection	Yes	CANopen connection profile to use
Function	Selection	Yes	SDO Read function from the selected connection
Function Parameters	Dynamic	Varies	Auto-populated from the function schema (index, subIndex, dataType). See your CANopen connection functions for full parameter details.
Timeout Override	Number (seconds)	No	Override the default function timeout

All function parameters support expression syntax ({{ expression }}) for dynamic values from the pipeline context.

Input

The node receives the output of the previous node as input. Input data can be referenced in function parameter expressions using $input.

Output Structure

On success the node produces:

{
  "success": true,
  "functionId": "<function-id>",
  "data": {
    "index": "0x1000",
    "subIndex": 0,
    "dataType": "uint32",
    "value": 401
  },
  "durationMs": 12,
  "timestamp": "2026-05-20T08:30:00Z"
}

Field	Type	Description
success	boolean	true when the SDO upload completed without an abort
functionId	string	ID of the executed function
data.index	string	OD index of the entry read, formatted as 0xNNNN
data.subIndex	number	OD sub-index of the entry read
data.dataType	string	Data type used to decode the response (see Data Types)
data.value	any	The decoded value. Type matches dataType: bool returns a boolean, uint16 a number, string a string, etc.
durationMs	number	Execution time in milliseconds
timestamp	string	ISO 8601 / RFC 3339 UTC timestamp

On an SDO abort, success is false, error contains the abort message (e.g. SDO abort 0x06020000: object does not exist in the object dictionary), and the per-call metadata includes the raw abortCode. See SDO Abort Codes for the table.

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CANopen SDO Write Node

CANopen SDO Write Node

Write a value to an Object Dictionary entry via SDO. The connector encodes the value to the wire width implied by the data type, then issues a real SDO download.

Supported Function Types:

Function Name	Purpose	Common Use Cases
SDO Write (canopen.sdo.write)	Write an OD entry by (index, sub-index)	Setpoints, controlwords, mode changes, recipe parameters

Node Configuration

Parameter	Type	Required	Description
Connection	Selection	Yes	CANopen connection profile to use
Function	Selection	Yes	SDO Write function from the selected connection
Function Parameters	Dynamic	Varies	Auto-populated from the function schema (index, subIndex, dataType, value). The value field supports ((paramName)) templates; see your CANopen connection functions.
Timeout Override	Number (seconds)	No	Override the default function timeout

All function parameters support expression syntax ({{ expression }}) for dynamic values. Use expressions like {{ $input.payload.target }} to feed dynamic values into the value parameter.

Input

The node receives the output of the previous node as input.

Output Structure

{
  "success": true,
  "functionId": "<function-id>",
  "data": {
    "index": "0x6040",
    "subIndex": 0,
    "dataType": "uint16",
    "value": 15
  },
  "durationMs": 14,
  "timestamp": "2026-05-20T08:30:00Z"
}

Field	Type	Description
data.index	string	OD index of the written entry, formatted as 0xNNNN
data.subIndex	number	OD sub-index of the written entry
data.dataType	string	Data type used to encode the value
data.value	any	Echo of the value that was written (after parameter substitution and type coercion)

On an SDO abort, success is false and error contains the abort message; see SDO Abort Codes.

Safety First

Always implement validation and safety checks before writing to industrial equipment. CANopen Controlwords and target setpoints can put a motor, valve, or actuator into motion immediately. Use a Condition node upstream to bound the value, or gate the write behind an explicit operator action.

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CANopen NMT Command Node

CANopen NMT Command Node

Send a Network Management command to drive a CANopen node through its CiA 301 state machine. Pass nodeId=0 to broadcast to every node on the bus.

Supported Function Types:

Function Name	Purpose	Common Use Cases
NMT Command (canopen.nmt.command)	Send an NMT command to one or all nodes	Drive startup, controlled shutdown, hung-node recovery

Node Configuration

Parameter	Type	Required	Description
Connection	Selection	Yes	CANopen connection profile to use
Function	Selection	Yes	NMT Command function from the selected connection
Function Parameters	Dynamic	Varies	Auto-populated from the function schema (command, nodeId). See NMT Commands.
Timeout Override	Number (seconds)	No	Override the default function timeout

Input

The node receives the output of the previous node as input.

Output Structure

{
  "success": true,
  "functionId": "<function-id>",
  "data": {
    "command": "start",
    "nodeId": 16
  },
  "durationMs": 3,
  "timestamp": "2026-05-20T08:30:00Z"
}

Field	Type	Description
data.command	string	The NMT command that was sent (start, stop, preOperational, resetNode, resetCommunication)
data.nodeId	number	The target node ID. 0 indicates a broadcast to every node on the bus.

Broadcast warning

Setting Target Node ID to 0 broadcasts the command to every node on the CAN segment. A broadcast resetNode will hard-reset every device on the bus simultaneously. Use with care on shared segments.

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Settings Tab

All three CANopen node types share the same Settings tab:

Setting	Type	Default	Description
Description	Text	-	Optional description displayed on the node
Timeout (seconds)	Number	Pipeline default	Maximum time the node may run before timing out
Retry on Timeout	Toggle	Pipeline default	Automatically retry the node if it times out
Retry on Fail	Toggle	Pipeline default	Automatically retry the node if it fails
On Error	Selection	Pipeline default	Error strategy: stop the pipeline, continue to the next node, or follow the error output path

When left at their defaults, these settings inherit from the pipeline-level execution configuration.