Knowledge base

Modbus Set Register

ModbusSetRegisterAction sets one holding register value on a direct ModbusThing. Use it for fixed setpoints, neutral output commands, PWM or servo values, motor speed, brightness, valve targets, and controller modes.

// How it works

Write one target value to a direct device register

The action updates the local target register value in ModbusThing. The background write loop sends the register block when the target differs from the last read holding-register state.

SET

Fixed setpoint

Write known values such as 1500, 0, or a mode number.

STOP

Neutral command

Create explicit actions such as Stop motor, Center servo, or Reset output.

EVT

Automation

Bind detection or operator events to register changes without writing custom code.

// Reference

Configuration parameters

Parameter	Required	Description	Default
Title	Yes	Display name of the action.	None
Modbus	Yes	Target direct ModbusThing.	None
Index	Yes	Zero-based index in the ModbusThing writable holding-register buffer.	None
Value	Yes	Integer value written to the target register.	1500

// Operations

Operational notes

IDX

Index must exist

The configured index must exist in the direct device writable buffer. Ensure the ModbusThing count covers it.

DEF

Use startup defaults

Configure defaultRegisterValue as the neutral startup state, then use this action for deliberate changes.

SAFE

Test setpoints safely

Validate values with unloaded or disconnected hardware before using them for physical motion or power outputs.

// Next steps