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Best Serial Port Cards Under $100 (2026)

We ranked products by a composite value score using interface versatility (RS232/422/485), build/form factor suitability, UART/buffering specs, management features, and price under $100

This roundup covers serial port cards and converters priced under $100, selected for strong value, functional versatility, and relevant connectivity features for industrial and embedded applications. Picks were chosen by scoring each unit on interface support (RS232/422/485), form factor (PCIe, ISA, DIN-rail, module), firmware/tooling, and overall value-to-feature ratio

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

Match card or converter protocol support (RS232, RS422, RS485) to your device requirements to avoid level-shifting or adapter needs

Consider form factor and mounting

Select PCIe or ISA expansion cards for PCs, or DIN-rail and module-style device servers for industrial racks and field installations

Check UART and buffering

Look for cards with hardware UARTs (e.g., 16650-class) or adequate FIFO buffering to reduce CPU load and improve throughput for multi-port use

Network-enabled converters vs. direct ports

Ethernet device servers (serial-to-Ethernet/DTU) provide remote access and PoE options, while native PCIe/ISA cards give direct local serial ports

Evaluate software and management tools

Prioritize devices with well-documented configuration utilities, protocol modes, and firmware updates for reliable integration in mixed environments