A common mismatch on factory floors and in equipment rooms: the PC has computing power to spare, but the field devices "speak serial." PLC, variable frequency drives, power meters, and temperature sensors—a fair share of them still offer nothing but RS-232 or RS-485. Ordinary commercial PC and many compact builds ship with only USB and Ethernet, and the gap shows up the moment installation begins.

The experience of an independent hardware designer illustrates the point. He spent a year building a CNC-machined aluminum compact computer, from learning CAD and working with overseas machine shops to handling tolerances, quality control, logistics, and packaging instructions. The entire project was about solving details, not performance. Teams building equipment face something similar: what consumes project time is rarely compute selection—it is interface planning, wiring, and on-site commissioning. Serial connectivity sits at the front of that list.

Option 1: Choose an Edge Industrial Computer with Built-in Serial Ports

Take the USR-EG628:  RK3562J quad-core Cortex-A53 at up to 2.0GHz, running Linux Ubuntu, with 2× RS485, 1× RS232, 1× CAN, 2× Ethernet, and 2× USB. It supports 4G/5G, WiFi, and Ethernet with network backup, ships with Node-RED pre-installed, and supports Docker. For most serial data acquisition scenarios, one device covers computing, networking, and device access at once.

For wiring, three rules cover most of it:

• RS485 uses two wires, A and B, in a daisy-chain (bus) topology—no star branches;

• The 120Ω termination resistor goes only at the two ends of the bus, nowhere in between;

• Baud rate, parity, and slave address must match the device side; on a Modbus RTU bus, every address must be unique.

Option 2: When Serial Ports Run Short, Select by Bus Plan

A single RS485 bus is specified for 32 nodes, but real installations need headroom. Energy storage, solar, and metering scenarios often involve dozens of meters; planning roughly a dozen per bus keeps polling cycles under control.

In these cases, a multi-serial model is the straightforward answer:

• USR-EG828-EMS: 8× RS485, 2× CAN, 16× DI, 16× DO, 4× Ethernet, built for energy storage and microgrid monitoring. It reports to management platforms via MQTT and spreads multiple buses across separate serial ports;

• USR-EC500(X86 architecture): i5-7200U, 8 serial ports, 5 Ethernet ports. Serial ports map directly to COM ports in Windows. If the line already runs legacy Windows software, this path requires no program changes.

Option 3: Retrofitting an Existing PC—Two Routes

USB-to-RS485 convertersare the first idea that comes to mind, and the source of the most field problems: most lack isolation, pick up interference once cables get long, and leave a cluster of dongles behind the chassis that makes troubleshooting painful. Fine for temporary debugging, not recommended for long-term deployment.

External serial device serversconvert serial devices to Ethernet before they reach the PC—stable, but the cabinet gains a power supply, extra cabling, and additional failure points. For a permanent production line, switching directly to an edge industrial computer with built-in serial ports often costs less overall.

Getting the Software Layer Running

Using the Node-RED pre-installed on the EG628:

• Open the Node-RED editor in a browser;
• Add a Modbus node and enter the serial parameters (baud rate, slave address);
• Fill in the register address from the device manual, and read a single temperature value first to verify the link;
• Publish data to a platform via an MQTT node, or write local rules for interlocking control.

The entire acquisition chain runs without writing code. When custom algorithms are needed, the system opens SSH and supports C/C++, Python, and Docker. The EG628 also supports PLC programming, so it can act as an edge controller rather than just a data gateway.

Field Commissioning Checklist

When serial communication fails, the cause is almost always one of the following:

• Wiring order: A/B swapped is the most common fault—check this first;

• Common ground: RS485 is differential, but a large ground potential difference between devices still requires a signal ground connection;

• Cable routing: separate conduits for power and signal lines, keep away from interference sources like variable frequency drives, use shielded twisted pair over long distances, and ground the shield at one end only;

• Parameters: then check baud rate and parity, and finally slave address conflicts.

What Else to Confirm at Selection

Wide operating temperature range, power input range, isolation protection, and certifications (the EG628 carries CE, FCC, RoHS, RCM, 3C, among others). These parameters determine whether the device survives on the shop floor long-term—far more important than clock speed.

Connecting RS-232/RS-485 devices is not a hard problem; it is a checklist: compute, interfaces, software, wiring—confirmed in order. An edge industrial computer with the right interfaces arrives on site, gets wired, configured, and verified. "Plug in and it works" is not luck; it is the result of finishing that checklist during selection.