An independent hardware developer spent a year taking a CNC-machined aluminum compact case from drawings to small-batch production: teaching himself 3D design, coordinating overseas machine shops, handling tolerances and quality control, writing assembly instructions, building a website to sell it — and finally winding the project down because of a personal relocation. The detail worth remembering from his retrospective: what repeatedly drained the project's time was not performance design, but a power button wired with reversed polarity, mounting holes that didn't match between the 250W and 500W power supplies, and international shipping rates that had to be configured country by country — all problems of "connections and supporting infrastructure."

Projects on the factory floor follow a similar rhythm: choosing an industrial computer is only the first step. Once the machine has to land in a workshop, two things it cannot handle on its own surface immediately: how to bring legacy field devices online, and how to get data out of a site with no fiber. These two gaps are filled by the serial device server and the industrial router, respectively.

1. Access: Putting Legacy Serial Devices on the Network

Meters, PLCs, and variable frequency drives in a workshop mostly still speak RS485/RS232. The serial ports built into an industrial computer usually number only two or three; when devices are scattered across different distribution cabinets, port count becomes the ceiling.

The USR-TCP232-410s is a dual-port serial device server: one RS485 channel plus one RS232 channel can work simultaneously, performing bidirectional Modbus RTU to Modbus TCP conversion with support for multi-master polling. Data can be reported via MQTT, with SSL/TLS encryption and two-way certificate authentication. It can also handle edge acquisition on its own: parsing and computing collected data locally, reporting it in JSON format, and taking some of the load off the host computer. Operating temperature spans -40 to 85°C, the housing is metal, and the 9~36V DC wide-range power input suits demanding environments inside cabinets.

2. Uplink: Getting the Field onto the Cloud

On sites with no fiber and no on-site IT, 4G is often the only realistic uplink. The industrial router USR-G806w is built on a Qualcomm platform, with 3 Ethernet ports (configurable as 1 WAN + 2 LAN or 3 LAN), enhanced WiFi, and dual 5dBi antennas. VPN support covers OpenVPN, IPSec, PPTP, L2TP, and GRE; as an OpenVPN client it can connect to three servers at once, it can also act as a server, and .ovpn configuration files import with one click.

Its backup mechanisms suit unattended sites: 4G, wired, and WiFi serve as mutual backups for internet access — when one link drops, it switches over automatically. Device offline events, weak signal, and data overage all trigger real-time alerts via email and SMS. Dual hardware and software watchdogs, operation from -20 to 70°C, and full surge and ESD protection round it out.

3. Compute: The Brain on Site

The industrial computer USR-EG628 is the computing core of this setup: RK3562J quad-core Cortex-A53 at 2.0GHz, shipping with Ubuntu, Node-RED preinstalled, and Docker supported. Interfaces include 2× RS485, 1× RS232, 1× CAN, and dual Ethernet ports.

This layer handles acquisition, protocol conversion, and local interlocked control. When the network drops, the production line keeps running — decisions like tripping on limit violations are made locally; once the network recovers, buffered data is re-uploaded. Programs written in C/C++ and packaged in Docker become standard deliverables that migrate directly to another unit of the same model.

4. One Complete Data Path

Take workshop energy monitoring as an example:

RS485 meters in the distribution cabinet → TCP232-410s converts to Modbus TCP → Ethernet into a LAN port on the G806w → EG628 pulls data from the internal network, computes locally, and triggers interlocks on limit violations → G806w reports to the cloud platform or MES over 4G/VPN.

Each of the three devices owns one segment: the 410s handles device access, the EG628 handles compute and control, and the G806w handles the outbound link. If any link in the chain breaks, on-site control keeps running.

5. Three Things to Confirm Before Selecting

• Serial port count: plan for 1.5× the actual requirement, and extend the rest with a serial device server rather than filling every port on the industrial computer to save one device;
• Uplink: find out first whether the site has fiber and how the 4G coverage is, then decide which link the router leads with and whether multi-link backup is needed;
• Certification checklist: when equipment ships overseas with a project, certifications must be verified in advance. Both the EG628 and G806w carry CE, FCC, RCM, and other certifications, and the 410s carries CE, FCC, and RCM — the case project at the beginning was ultimately stalled by exactly this link: international delivery.

Selection is the same story: the spec sheet sets the floor, the connection plan decides the delivery. If the site details are already on the table — the device list, the distribution cabinet layout, whether fiber exists, what the 4G signal looks like — send them over and let's work out the division of labor among these three devices together. It beats staring at spec sheets alone.