Communication Interfaces

Before integrating a device, you need to understand which communication interface it supports and select a matching UCM or connection method.

Physical Communication Standards

Physical communication standards define how data is transmitted over the wires. Different standards require different hardware UCM models.

RS-232

RS-232 is a serial communication standard for point-to-point connections between two devices. It is common in industrial equipment, sensors, and laboratory instruments.

• UCM model: ENP-RS232
• Connection type: Point-to-point (one device per port)
• Typical use: Devices with DB-9 or terminal block serial connectors

RS-485

RS-485 is a serial communication standard that supports multi-drop connections — multiple devices can share the same bus.

• UCM model: ENP-RS485
• Connection type: Multi-drop bus (multiple devices on one bus)
• Typical use: Modbus RTU networks, industrial sensor chains

CAN

CAN (Controller Area Network) is a robust bus standard designed for real-time communication in automotive and industrial automation environments.

• UCM model: ENP-CAN
• Connection type: Multi-node bus
• Typical use: Fuel cells, battery management systems, automotive devices

Multi-Interface UCMs

The ENP-RS-CAN-USB M2 module supports both RS-232/RS-485 and CAN interfaces.

Communication Protocols

Protocols define the data format and communication rules on top of physical standards. The same protocol can sometimes run on different physical layers.

Modbus

Modbus is one of the most widely used protocols in industrial automation. It uses a client-server model where the UCM (client) requests data from the endpoint device (server).

Variant	Physical Layer	UCM	Connection URI Example
Modbus RTU	RS-232	ENP-RS232	port://rs232
Modbus RTU	RS-485	ENP-RS485	port://rs485
Modbus TCP	Ethernet/TCP	Virtual UCM	tcp://192.168.1.42:502

Modbus operates with registers — addressable data locations on the device. There are four register types:

• Coils (read/write, boolean)
• Discrete Inputs (read-only, boolean)
• Holding Registers (read/write, 16-bit)
• Input Registers (read-only, 16-bit)

See the Modbus Lua API reference for details on how to read and write Modbus registers.

CAN Protocol

CAN protocol uses message-based communication where each message has an identifier (ID) and a data payload. Unlike Modbus, CAN devices broadcast messages on the bus rather than responding to individual requests.

See the CAN Lua API reference for details on monitoring and sending CAN messages.

TCP/IP Protocols (Virtual UCM)

Virtual UCMs running on an Enapter Gateway can integrate devices over TCP/IP without a physical communication standard. Supported protocols include:

• HTTP — RESTful APIs and web-based device interfaces (Lua API)
• OPC UA — Industrial standard for machine-to-machine communication (Lua API)
• SNMP — Network management protocol (Lua API)

Matching Your Device

To select the right UCM, check your device's communication interface specification (usually found in the device manual or datasheet):

1. Identify the physical interface — look for RS-232, RS-485, CAN, or Ethernet connectors on the device.
2. Identify the protocol — check if the device supports Modbus RTU, Modbus TCP, CAN, HTTP API, etc.
3. Select the UCM — pick a hardware UCM matching the physical interface, or use a virtual UCM, which supports both physical interfaces (depending on the Enapter Gateway model) and TCP/IP protocols.

Browse a library of open-source, ready-to-use integrations to check if your device is already supported.