Modbus Nodes

Modbus is the most widely deployed protocol in industrial automation. MaestroHub supports all three variants: TCP, RTU, and ASCII so you can communicate with PLCs, sensors, meters, and supervisory systems from a single node set.

Configuration Quick Reference

Field	What you choose	Details
Parameters	Connection, Function, Function Parameters optional Timeout Override, Debug Mode	Choose the shared Modbus connection profile (credentials, transport method, retry settings) and its saved function, then fill in the parameters specified within the function. Inputs accept literal values or Maestro expressions that are validated at save time and resolved during each execution.
Settings	Retry on Fail, On Error, Notes, Display Note In Pipeline	Configure pipeline-level behavior: retry strategy, whether errors stop or continue, and operator notes that can surface on the canvas for quick context.

Parameters inherit validation from the stored function, while node-level settings apply Maestro pipeline controls such as retries and inline documentation.

Modbus Read Node

Modbus Read Node

Read data from PLCs, sensors, meters, and industrial devices.

Supported Function Types:

Function Name	Purpose	Common Use Cases
Read Coils (0x01)	Read digital outputs	Motor status, valve positions
Read Discrete Inputs (0x02)	Read digital inputs	Limit switches, sensors
Read Holding Registers (0x03)	Read holding registers	Setpoints, configuration
Read Input Registers (0x04)	Read input registers	Temperature, pressure, flow
Read FIFO Queue (0x18)	Read FIFO queue	Event logs, alarm history

Modbus Write Node

Modbus Write Node

Write control values, setpoints, and configuration to devices.

Supported Function Types:

Function Name	Purpose	Common Use Cases
Write Single Coil (0x05)	Write single digital output	Start/stop motor
Write Single Register (0x06)	Write single register	Update setpoint
Write Multiple Coils (0x0F)	Write multiple digital outputs	Batch control
Write Multiple Registers (0x10)	Write multiple registers	Configuration update
Write Masked Register (0x16)	Masked register write	Bit manipulation
Read/Write Multiple Registers (0x17)	Atomic read+write	Synchronized operations

Safety First

Always implement validation and safety checks before writing to industrial equipment. Consider adding condition nodes to verify values are within safe ranges.

Modbus Read Group Node

The Modbus Read Group node is an advanced connector node that allows you to execute multiple Modbus read operations efficiently within a single node. It provides powerful grouping capabilities and the Read All feature for comprehensive data collection.

Configuration

Connection and Functions

The Read Group node supports adding multiple function references, where each reference can either:

• Target a specific function from the connection
• Use Read All to execute all read functions associated with a connection

Read All Feature

The Read All toggle changes the behavior of a function reference:

Mode	Description	Use Case
Specific Function (default)	Execute a single named function	Selective data collection from specific registers
Read All	Execute all read functions from the connection	Complete device data snapshot, monitoring dashboards

How to Enable Read All

1. Add a function reference in the Modbus Read Group node
2. Toggle the Read All switch for that reference
3. Optionally provide a Group Key (defaults to connection ID if not specified)

Read All toggle enabled - executes all read functions from the selected connection

When Read All is enabled:

• The function selector is hidden (not needed)
• All read functions (Read Coils, Read Discrete Inputs, Read Holding Registers, Read Input Registers) from the selected connection are executed
• Results are grouped under the specified group key or connection ID

Output Structure

{
  "connectionId_or_groupKey": {
    "function1_name": { /* function result */ },
    "function2_name": { /* function result */ },
    "function3_name": { /* function result */ }
  }
}

Parameters

Parameter	Description	Options
Execution Mode	How functions are executed	parallel (default), sequential
Continue on Error	Whether to continue if a function fails	true, false (default)
Functions	List of function references	Array of connection/function pairs

Example Use Cases

Complete Device Snapshot

Use Read All when you need to collect all data points from a device for:
- Historical logging
- Complete device state export
- Dashboard population
- Diagnostic data collection

Selective Data Collection

Use specific functions when you need:
- Targeted data from specific registers
- Optimized performance (fewer operations)
- Precise control over what data is collected

Mixed Approach

Combine both modes in a single Read Group node:
- Read All from Connection A (complete data)
- Specific functions from Connection B (targeted data)

Execution Modes

Parallel Execution (Default)

• All functions execute concurrently
• Faster total execution time
• Best for independent read operations
• Use when functions access different address ranges

Sequential Execution

• Functions execute one after another
• More predictable timing
• Better for devices with limited concurrent request handling
• Use when device performance is a concern

Error Handling

Continue on Error = false (Default)

• Node fails if any function fails
• Ensures data consistency
• Best for critical operations where partial data is not acceptable

Continue on Error = true

• Node continues even if individual functions fail
• Failed functions return error in their result
• Best for monitoring scenarios where partial data is valuable
• Successful function results are still available in output

Best Practices

When to Use Read All

• Initial device commissioning and exploration
• Complete device state backups
• Dashboard views requiring all device data
• Diagnostic and troubleshooting scenarios

When to Use Specific Functions

• Production pipelines with known data requirements
• Performance-sensitive operations
• Selective data forwarding to specific systems
• When only a subset of device data is needed

Performance Considerations

• Read All executes all defined functions, which may impact performance on large function sets
• Consider using parallel execution mode for Read All to optimize speed
• Monitor device capabilities - some devices may have limits on concurrent requests
• Use Continue on Error strategically based on data criticality

Naming Conventions

• Use descriptive Group Keys when using Read All with multiple connections
• Group Keys help organize output data in complex pipelines
• Default connection ID grouping works well for simple scenarios