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Best Serial Port Cards Under $200 (2026)

We selected products under $200 and scored them by value using feature set (interfaces, form factor, UART), average user ratings, and relative price-to-functionality

This roundup covers serial port expansion and conversion hardware priced under $200, focused on devices that add RS-232/422/485 ports or convert serial to Ethernet for industrial and legacy-equipment use. Selections were ranked by a value score that factors device features (UART type, protocol support, DIN-rail or PCIe form factor), customer ratings, and price-to-feature balance

Top Picks

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    2-Port ISA Serial/Parallel Expansion Card

    2-Port ISA Serial/Parallel Expansion Card

    MOUDOAUER • ★ 3.7/5 • Budget

    Retro ISA interface card with 2 RS232 ports (COM1/COM2) and a 5V powered PCI-like adapter. Works in vintage systems with ISA slots; supports DB15 and pin header COM2. Customer says it works with printers

    • two RS232 ports
    • DB15 and pin header interfaces
    • requires only 5V power
    Check current price on Amazon →
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    RS232/485/422 to RJ45 Ethernet module with POE

    RS232/485/422 to RJ45 Ethernet module with POE

    waveshare • ★ 3.5/5 • Budget

    Industrial data gateway converting serial protocols to TCP/IP, supporting multi-function serial server and gateways. Useful for data acquisition and monitoring. Customer note: reliability is good, though documentation quality and setup ease are mixed

    • POE capable Ethernet module
    • bi-directional transparent transmission
    • serial to TCP/IP with multiple gateway features
    Check current price on Amazon →
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Buying Guide

Choose the right interface

Confirm whether you need RS-232, RS-485, RS-422 or a combination; many adapters and servers support multiple standards but native support ensures compatibility with legacy equipment

Match form factor to your installation

Select PCIe cards for desktops, ISA for older systems, or DIN-rail and Ethernet device servers for industrial racks and field deployments

Check UART and buffering

Look for cards with higher-quality UARTs (e.g., 16650-class) or built-in buffering to reduce CPU load and improve throughput on multi-port setups

Prefer Ethernet or PoE when networked

Serial-to-Ethernet converters and PoE-capable modules simplify remote access and power for field devices compared with direct serial cabling

Verify driver and OS support

Ensure the manufacturer provides drivers or firmware compatible with your operating system and that device servers offer configurable TCP/UDP or virtual COM modes