What Is Modbus
Modbus is a serial communication protocol developed by Modicon in 1979. It was designed for industrial programmable logic controllers and has since become the most widely deployed industrial protocol worldwide — estimated to be installed on hundreds of millions of devices.
Modbus defines a master/slave (or client/server) communication model. A master device (such as an IIoT monitoring platform) sends requests to slave devices (such as a PLC or energy meter), which respond with data. The protocol is simple, reliable, and well-supported across virtually all industrial device manufacturers.
Modbus is used to monitor:
- Programmable Logic Controllers (PLCs) controlling industrial processes
- Variable Frequency Drives (VFDs) managing motor speed and energy consumption
- Energy meters measuring electrical consumption at the circuit or equipment level
- Temperature and pressure transmitters in process industries
- Flow meters and level sensors
- Remote Terminal Units (RTUs) in utility and infrastructure environments
- Solar inverters and battery management systems in renewable energy
- UPS systems and power distribution units in data centers
Modbus Protocol Variants
| Variant | Transport | Typical Use |
|---|---|---|
| Modbus TCP | Ethernet / TCP-IP | Modern devices with Ethernet ports, IP-connected systems |
| Modbus RTU | RS-232 or RS-485 serial | Legacy devices, field instruments, serial bus networks |
| Modbus ASCII | RS-232 or RS-485 serial | Less common; used where human-readable framing is needed |
Modbus TCP is the dominant variant in new installations and modern equipment. Modbus RTU remains common in legacy environments and in field-level devices that predate Ethernet connectivity. The underlying data model (register map, function codes, data types) is consistent across variants — only the transport layer differs.
Modbus Register Types
Modbus devices expose data through registers. Mango by Radix IoT can read and (where configured by the device manufacturer) write to any standard Modbus register type:
| Register Type | Data Type | Typical Use |
|---|---|---|
| Coils (0xxxx) | Boolean (read/write) | Output relay states, digital control outputs |
| Discrete Inputs (1xxxx) | Boolean (read only) | Digital input states, contact closures |
| Input Registers (3xxxx) | 16-bit integer (read only) | Measured values: temperature, pressure, flow |
| Holding Registers (4xxxx) | 16-bit integer (read/write) | Setpoints, configuration, measured values |
Mango by Radix IoT supports standard Modbus data type conversions including 16-bit unsigned, 16-bit signed, 32-bit integer (two-register combinations), 32-bit float, and 64-bit values where the device supports them.
Industries That Use Modbus
Manufacturing
Modbus is embedded in PLCs from every major manufacturer (Siemens, Rockwell, Mitsubishi, Schneider Electric, and others). Industrial plants use Modbus for process monitoring, equipment status, production counters, and alarm conditions.
Energy and Utilities
Electric, water, and gas utilities use Modbus-enabled RTUs and meters extensively. Energy meters report real-time consumption, demand, power factor, and power quality data over Modbus. Water utility pump stations commonly report flow, pressure, and level data via Modbus RTU.
Renewable Energy
Solar inverters, wind turbine controllers, battery energy storage systems, and weather stations commonly use Modbus TCP for data communication. Mango by Radix IoT aggregates generation, storage, and environmental data from Modbus-connected renewable energy assets.
Data Centers
UPS systems and power distribution units (PDUs) in data centers frequently expose load, battery, input/output voltage, and alarm data via Modbus. Mango by Radix IoT connects to this equipment directly, providing power infrastructure visibility alongside BACnet cooling data.
Commercial Buildings
Energy submetering equipment, variable frequency drives for HVAC fans and pumps, and some building automation devices expose data via Modbus. Mango by Radix IoT connects to these alongside BACnet building systems for complete facility monitoring.
How Mango by Radix IoT Implements Modbus
All protocol drivers, including the Modbus driver, are included in a standard Mango by Radix IoT installation and covered by the license. There are no separate driver purchases, per-protocol licenses, or add-on fees. Mango by Radix IoT includes native Modbus TCP and Modbus RTU drivers.
Connection Configuration
For Modbus TCP: Mango by Radix IoT connects directly to the device IP address and port (default 502). For Modbus RTU: Mango by Radix IoT connects to a local or remote serial port (RS-232 or RS-485) or via a serial-to-Ethernet converter.
Register Mapping
Mango by Radix IoT allows operators to define data points by specifying register address, register type, data type, unit conversion, and scaling. Device-specific register maps (published by device manufacturers) are used to identify what each register contains.
Polling Configuration
Mango by Radix IoT polls Modbus devices at configurable intervals — from sub-second polling for fast-changing process values to minute-level polling for slowly changing environmental data. Polling groups allow different polling rates for different register sets on the same device.
Retrofitting Legacy Devices
A Modbus RTU device from 1995 communicates exactly the same way as one installed in 2025. Mango by Radix IoT connects to this equipment directly without hardware modification, making Modbus monitoring practical for retrofitting legacy industrial environments.
Use Cases: Modbus + Mango by Radix IoT
Industrial Energy Management
Manufacturing plants install Modbus energy meters at production lines, HVAC systems, and compressed air systems. Mango by Radix IoT aggregates sub-meter consumption data, identifies energy waste at the equipment level, and provides trend analysis for energy management programs.
Renewable Energy Site Monitoring
Solar farms connect Modbus TCP-enabled string inverters, combiner boxes, and weather stations to Mango by Radix IoT. Real-time generation data, equipment alarms, and weather-normalized performance metrics are available from a single platform.
Water Utility SCADA
Remote pump stations report flow, pressure, level, and run-time data to Mango by Radix IoT via Modbus RTU. Alarm conditions — low level, high pressure, pump failure — trigger notifications to on-call operations staff.
Data Center Power Monitoring
UPS systems report load percentage, battery state-of-charge, estimated run time, bypass status, and fault conditions via Modbus. Mango by Radix IoT integrates this power infrastructure data alongside BACnet cooling data for comprehensive data center visibility.