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Best Serial Port Cards (2026 Guide)

Selections were based on user rating and review volume, protocol and form-factor coverage (RS232/485/422, PCIe/ISA/DIN-rail), and notable hardware features such as UART type and Ethernet/PoE support

This page collects top-rated serial port cards and converters for connecting RS-232/485/422 devices to PCs or Ethernet networks, selected for strong user ratings and review volume. Picks prioritize compatibility (PCIe, ISA, DIN-rail, PoE-capable modules), proven UART chips, and clear protocol support to help match hardware to legacy and industrial use cases

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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    MOXA CP-118U-I 8-Port PCI Serial Board

    MOXA CP-118U-I 8-Port PCI Serial Board

    Moxa • ★ 2.8/5 • Premium

    8-port universal PCI serial board supporting RS-232/422/485 with embedded ESD and optical isolation protection. Provides multi-port serial connectivity for industrial or embedded systems. Customer insight: mixed sentiment: none

    • 8-port universal PCI compatibility
    • multi-protocol serial support
    • protective electrical isolation features
    Check current price on Amazon →

Buying Guide

Confirm interface and form factor

Choose between PCIe, ISA, PCI or DIN-rail/inline modules depending on your host system and available expansion slots or mounting requirements

Match serial standards and port counts

Verify support for RS232, RS485, or RS422 and the number of ports you need; converters often handle multiple standards while expansion cards are typically RS232-focused

Check UART and buffering

Look for reliable UARTs (e.g., 16650-class) and adequate FIFO buffering to reduce CPU load and improve data integrity on high-throughput or multiport setups

Consider network and power features

For device servers, prioritize Ethernet support and features like PoE or DTU modes when integrating serial devices over LAN or remote links

Assess driver and OS support

Confirm vendor drivers and compatibility with your OS — especially for legacy ISA systems or specific industrial protocols — to avoid integration headaches