RS-485/Ethernet Interface Converter

The RS-485/Ethernet Interface Converter (IC) is designed to unify devices of various types into a single Modbus network.

Data transmission between devices uses the standard ModbusTCP protocol (from the Ethernet side) and ModbusRTU (from the RS-485 side). Support for these protocols by many SCADA packages expands the possibilities for building production automation systems. The result is a very simple and efficient way to connect various devices to a PC or PLC on an Ethernet network.
The converter supports up to 10 TCP sockets. This means that up to 10 devices on the Ethernet network can simultaneously exchange information with the converter.

The ModBus RS-485/Ethernet Interface Converter has the capability to branch the RS-485 network (ModbusRTU) into several smaller segments, each connected via a separate RS-485/Ethernet IC, uniting them into one Ethernet network. This way, significantly more devices can be connected. With Internet connection access, remote control and monitoring of connected equipment from anywhere with Internet access become possible.
This converter connected to the Ethernet network provides much higher throughput than standalone RS-485 networks, which in turn increases the polling frequency of device parameters.

Device configuration is done through a web interface accessible using any standard web browser, such as Internet Explorer.
Each Modbus TCP/RTU converter has a unique Ethernet IP address, which must be specified on the PC or PLC during system setup.

RS-485/Ethernet Interface Converter — Modbus TCP/RTU

The PI RS-485/Ethernet connects equipment with an RS-485 interface and Modbus RTU protocol to an Ethernet network. It allows a PC, PLC, or SCADA system to exchange data with serial devices over a local network without laying a separate RS-485 line to the workstation.

The device receives a request via Ethernet, forwards it to a device on the RS-485 network, and returns the received response to the network client. This enables existing Modbus RTU devices to be integrated into dispatching and data collection systems, as well as allows linking remote RS-485 segments via network infrastructure.

Communication Modes

In firmware version 1.1.0, the data format from the Ethernet side is selected through the web interface:

• Modbus TCP — requests with MBAP header are converted to Modbus RTU frames for transmission over RS-485. This is the default mode.
• Modbus RTU over TCP — RTU frame along with CRC is transmitted over the network connection. This mode is intended for systems operating with this exchange format.

On the RS-485 side, the device exchanges Modbus RTU frames. If the remote server's IP address is not set, the converter waits for incoming TCP connections on the configured port. If the server is configured, the device initiates connection to its IP address and port.

Settings and Features

The built-in web interface allows configuring MAC address, static IP address, mask, gateway, and network port. Obtaining an address via DHCP is also available; if none is obtained, the saved static configuration is used. The device responds to ping, which helps check network availability.

For RS-485, baud rate, parity, and number of stop bits are configurable. Supported are 8 data bits; speeds of 1200, 2400, 4800, 9600, 19200, 38400, 57600, 78800, and 115200 bps; parity options none, even, or odd; 1, 1.5, or 2 stop bits.

Changing parameters and password requires the current device password. After saving, the web interface reports success or error; successfully saved parameters apply after reboot. Configuration is stored in Flash memory and is not lost when powered off. Factory reset is available using the device button.

Main characteristics

• Ethernet: one RJ-45 port, 10BASE-T/100BASE-T.
• Serial interface: one two-wire RS-485 line.
• Protocols: Modbus TCP or Modbus RTU over TCP from Ethernet side; Modbus RTU from RS-485 side.
• Network configuration: static address or DHCP.
• Factory network settings: Modbus TCP, IP address 192.168.0.10, port 502.
• Firmware version described: 1.1.0.

For remote access, it is recommended to use a secure network or VPN: the device's web interface operates via HTTP without encryption.