Modbus Sources

Novant supports native integration with Modbus devices, allowing you to read and write data points from building systems using the Modbus TCP protocol. This guide explains how to configure Modbus sources, define device connection parameters, and map register addresses for use in your projects.

Sources

Novant supports the following Modbus types:

Modbus TCP devices
Modus devices routed through a Modus IP gateway

The address format for Modus sources is:

<ip>:<port>/<unit_id>

Where:

ip is the IPv4 address of the Modbus device or gateway
port is the Modbus TCP port (typically 502)
unit_id is the Modbus Unit ID (slave address)

Examples:

10.0.0.5:502/1
10.0.0.6:5502/3

Points

The address format for Modbus points is:

<point_type> "." <register_type> "." <start_address> [ "." <data_type> ]

Examples:

bv.co.0
bv.di.5
ai.in.100.int32
av.hr.200.float64

Point Type

The point_type identifies the logical point behavior (read-only, write-only, or read/write) and value type.

Prefix	Point Type
`bi`	Read-only binary input
`bo`	Write-only Binary output
`bv`	Read/write binary value
`ai`	Read-only analog input
`ao`	Write-only analog output
`av`	Read/write analog value

Register Type

The register_type specifies which Modbus register space is accessed.

Prefix	Register Type
`co`	Discrete binary output coils
`di`	Discrete binary input coils
`in`	Analog input registers
`hr`	Analog output holding registers

Register Addressing

The start_address is a zero-based register index with no padding.

Depending on the selected data_type, multiple contiguous registers may be read starting at the specified address.

Data Types

For ai, ao, and av point kinds, a data_type is required to define how raw Modbus registers are interpreted.

Type	Description
`int16`	One register wide 16-bit signed integer
`int32`	Two register wide 32-bit signed integer
`int64`	Four register wide 64-bit signed integer
`uint16`	One register wide 16-bit unsigned integer
`uint32`	Two register wide 32-bit unsigned integer
`float32`	Two register wide IEEE 754 32-bit float
`float64`	Four register wide IEEE 754 64-bit float