Modbus API

Developer documentation

This section is intended for developers only.

Modbus register map

All registers are 16-bit holding registers. Separate registers are used for reading and writing.

Example: - To read the status of a light on CH2, use holding register 1002 - To write/change the status, use holding register 2

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Channel mapping

Channel type	Direction	Modbus register	Value
Binary inputs	Read	CH# + 1000	0 = off, 1 = on
Inputs	Read	CH# + 1000	0 = off, 1 = minimum value, 100 = maximum value
Binary outputs	Write	CH#	0 = off, 1 = on
Binary outputs	Read	CH# + 1000	0 = off, 1 = on
Dimmer outputs	Write	CH#	0 = off, 1 = minimum value, 100 = maximum value
Dimmer outputs	Read	CH# + 1000	0 = off, 1 = minimum value, 100 = maximum value
Blind/shutter outputs	Write position	CH#	0 = minimum value, 100 = maximum value
Blind/shutter outputs	Write action	CH# + 1	0 = open blind, 1 = close blind
Blind/shutter outputs	Read position	CH# + 1000	0 = minimum value, 100 = maximum value

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Notes

• CH# refers to the numeric channel index (e.g., CH2 → 2)
• Reading always uses the + 1000 register offset
• Writing uses the base register number (CH#), except blind/shutter actions which use CH# + 1