As technology advances, the need to integrate old serial devices into modern Ethernet networks becomes more common. Serial devices, which often use RS-232, RS-432 or RS-485 communication standards, can still be essential for various applications, from industrial automation to medical equipment. However, these devices are not designed for IP-based Ethernet networks which operate using protocols such as IEEE802.3, IP/TCP, DHCP, and FTTP. Therefore, special converters are required to facilitate the seamless transfer of data between different systems and devices.
Understanding the Network Basics
Before we get started, it’s essential to understand the key concepts involved:
Serial Communication
Serial communication sends data one bit at a time in the form of binary pulses (1/0) over a single channel. It’s widely used for its simplicity, cost-effectiveness and ability to transmit data over longer distances with fewer wires. It can be used to connect sensors and actuators in automated systems or to connect devices such as GPS units, modems and some types of computer peripherals.
Common standards and protocols in serial communication include:
- RS-232: RS-232 is strictly point-to-point (one transmitter and one receiver) and uses single-ended signaling. It can transmit data typically up to 50 feet (15 meters) at lower speeds (19.2Kbps). The maximum data rate can reach up to 115.2Kbps with reduced distances. Voltage levels are defined as a range from ±3V to ±15V.
- RS-422: It is standard for balanced serial communication and commonly used in environments where data integrity over longer distances is crucial. By following the full-duplex mode, it can seamlessly transmit data up to 4000 feet at a baud rate of 10Mbps. RS-422 is designed for multi-drop applications where data can be transferred from one transmitter to up to 10 receivers on the bus.
- RS-485: RS-485 is an improvement over RS-422 and it can support up to 32 transmitters and 32 receivers on a single bus, making it ideal for multi-point communication. It’s typically used in building automation, industrial networks and data acquisition systems.
Ethernet Networks
Ethernet is a widely used technology for local area networks (LANs). It uses a more complex, packet-based communication method, allowing multiple network devices to communicate over a common infrastructure. Ethernet offers higher data rates and supports extensive network structures, making it ideal for modern applications.
Ethernet networks can use various types of cabling including twisted pair cables (like Cat5e, Cat6), coaxial cable, and fiber optics. Twisted pair cabling is the most common in modern Ethernet networks. Ethernet standards have evolved over time with various speeds available, such as 10Mbps, 100Mbps, 1Gbps and 10Gbps. Higher speeds like 25Gbps, 40Gbps, and 100Gbps are also available, primarily used in data centers and enterprise networks.
How to Convert Serial Data to Ethernet Signals?
Serial ports are commonly found on legacy devices such as printers, scanners, and industrial equipment, while Ethernet ports are found on modern networking devices such as routers, switches, and computers. To integrate these devices into the same system, a Serial-to-Ethernet converter, also known as a device server or terminal server, acts as a bridge between these two types of devices, allowing them to exchange data seamlessly.
What’s a Serial-to-Ethernet Converter?
Serial-to-Ethernet converters are a tool that enables communication between devices with serial ports and devices with Ethernet ports, translating serial data into Ethernet packets and vice versa. They typically have one or more serial ports and an RJ45 Ethernet port which connects to a LAN or the Internet. The converters offer various configuration options, including setting the IP address, subnet mask, and parameters (baud rate, parity, stop bits, etc.). Configuration can often be done through a web interface, serial console, or dedicated software.
How Does a Serial-to-Ethernet Server Work?
Its working principle is relatively simple yet incredibly powerful. Inside the server, the incoming serial data is converted into Ethernet packets. Its processor encapsulates the serial data into the payload of Ethernet frames, ensuring that the integrity of data is maintained. The encapsulated data is then sent over the Ethernet network to its destination, which could be a computer or a server located elsewhere on the network. Similarly, when data is received from the network, the server converts the Ethernet packets into serial data and sends it to the legacy device.
Operation Modes:
A serial-to-Ethernet server can operate in several modes, each designed to handle different types of network communication. Here are the primary operation modes:
- Transparent Mode: Data sent to the serial port is directly forwarded to the Ethernet network without modification, and vice versa.
- Virtual COM Port: Software on a computer can create a virtual COM port that maps to the remote serial device, making it appear as though the serial device is directly connected to the computer.
- TCP/UDP Server/Client Mode: The converter can be set to operate as a server or client for TCP/UDP communications, allowing flexibility in network setup.
7 Steps to Add Serial Devices to a LAN
Adding serial devices to an Ethernet network involves several steps to ensure proper configuration and communication between the devices and the network. Here is a step-by-step guide to achieve this:
Step 1: Select the Right Serial-to-Ethernet Converter
Determine the type of serial devices (RS-232, RS-422, RS-485) and the number of ports needed. You should assess the compatibility of the server with your existing devices and network infrastructure. Ensure that the server supports the protocols and standards used in your network. Key features to consider include:
- Number of serial ports: Single-port or multi-port options are available.
- Supported serial standards: Ensure compatibility with your devices (RS-232, RS-422, RS-485).
- Ethernet connectivity: Ensure the device supports your network’s standards (10/100/1000 Mbps).
- Power supply: Check if it needs an external power source or can be powered over Ethernet (PoE).
- Environmental ratings: Industrial-grade converters are more robust and can handle harsh conditions.
Step 2: Physically Connect the Devices
Use appropriate serial cables to connect your serial devices to the serial ports on the converter. Then, use an Ethernet cable to connect the converter’s Ethernet port to your local area network (LAN). Plug in the power adapter of the serial-to-Ethernet converter or use PoE if supported. Moreover, ensure that the connected serial devices are powered on and operational.
Step 3: Configure Network Settings
Connect to the converter’s configuration interface, typically via a web browser by entering the device’s default IP address, or using a dedicated configuration software provided by the manufacturer. Assign a static IP address to the converter or configure it to obtain an IP address via DHCP, depending on your network setup. Set the subnet mask, gateway, and DNS servers as needed.
Step 4: Configure Serial Port Settings
Configure the serial port settings to match the parameters of the connected serial devices (baud rate, parity, data bits, stop bits, and flow control). Choose the appropriate operation mode (Transparent, TCP/UDP Server, TCP/UDP Client, Virtual COM Port, Paired Mode) based on your application requirements.
Step 5: Configure Security Settings
Enable user authentication to restrict access to the converter’s configuration interface. If supported, you can also enable encryption protocols such as SSL/TLS to secure data transmission over the network. In the next step, configure any necessary firewall settings to allow communication between the converter and the networked devices.
Step 6: Install Virtual COM Port Software (Optional)
Download and install virtual COM port software provided by the converter manufacturer on the computer that needs to communicate with the serial devices. Map the virtual COM ports to the remote serial ports of the converter, ensuring they appear as local COM ports on the computer.
Step 7: Test the Connection
Use network diagnostic tools to ensure the converter is reachable over the network (e.g., ping the converter’s IP address). Send and receive data between the serial devices and the networked computer/application to ensure proper communication. It’s highly recommended to periodically check for and apply firmware updates to the converter to maintain security and functionality.
Applications
- Industrial Automation: Connecting PLCs, HMIs, and sensors into a SCADA system over Ethernet.
- Building Automation: Integrating HVAC systems, lighting controls, security systems, and access control devices into a BMS.
- Point-of-Sale (POS) Systems: Connecting serial-based POS terminals, barcode scanners, receipt printers, and cash registers to a network.
- Agriculture: Connecting irrigation control systems, climate control systems in greenhouses, and livestock monitoring equipment.
- Retail and Warehousing: Integrating barcode scanners, inventory management systems, and automated storage and retrieval systems (ASRS).
