Best Serial Port Cards (2026 Guide)
We selected products based on high user ratings, review volume, diverse form factors (PCIe, ISA, DIN-rail, Ethernet), and coverage of RS-232/422/485 functionality
The Verdict
- Best Overall: HF2211 Serial Port Server: RS232/485/422 to Ethernet DTU — Best for networked serial access: converts RS-232/485/422 to Ethernet for remote device integration
- Best Value: 2-Port ISA Serial/Parallel Expansion Card — Best legacy PC expansion: two-port ISA card that adds serial and parallel ports for older systems
- Best Premium: MOXA CP-118U-I 8-Port PCI Serial Board — Best high-density industrial board: eight-port PCI serial card designed for heavy-duty multiport deployments
This roundup covers top-rated serial port cards and converters used to add RS-232/422/485 ports or convert serial to Ethernet for industrial and legacy-device connectivity. Picks were chosen from high-rating listings with substantial review volume and varied form factors like PCIe, ISA, DIN-rail, and Ethernet device-servers
Top Picks
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1
Best Overall HF2211 Serial Port Server: RS232/485/422 to Ethernet DTU
Best for networked serial access: converts RS-232/485/422 to Ethernet for remote device integration
HF2211 converts RS232/485/422 serial interfaces to Ethernet for networked devices. Enables remote access and Ethernet DTU networking with multiple certifications for safety and compliance
- multi-interface serial support
- Ethernet DTU capability
- compliance certifications
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2
Best Value 2-Port ISA Serial/Parallel Expansion Card
Best legacy PC expansion: two-port ISA card that adds serial and parallel ports for older systems
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
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3
USR-DR301 DIN-Rail RS232 to Ethernet Converter
Best DIN-rail Ethernet converter: compact RS-232 to Ethernet device-server for industrial racks
DIN-rail RS232 to Ethernet device server with compact size. Enables remote serial access via Ethernet/Websocket. Customer note hints ease of use
- DIN-rail mounted
- RS232 to Ethernet
- Websocket capable
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4
RS232/485/422 to RJ45 Ethernet module with POE
Best PoE serial module: combines RS-232/485/422 to RJ45 Ethernet with power-over-Ethernet capability
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
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5
StarTech 4 Port RS232 PCIe Serial Card with 16650 UART
Best PCIe multiport balance: four RS-232 ports with 16650 UART support for reliable multi-device connections
Four RS232 ports with high-speed data transfer, featuring 16650 UART and 256-byte FIFO. Includes 4x 30cm IDC to DB9 cables. Suitable for PCI Express systems
- four high speed rs232 ports
- 16650 uart performance
- includes serial cables
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6
BLACK BOX IC820A RS-232 to RS-422/485 Bidirectional Converter
Best for robust signal conversion: bidirectional RS-232 to RS-422/485 converter for mixed-protocol setups
RS-232 to RS-422/485 bidirectional converter for serial connections. Useful for integrating legacy serial devices with multi-protocol interfaces. Customer sentiment notes solid value and quality
- RS-232 to RS-422/485 compatibility
- bidirectional data flow
- premium build quality
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7
Best Premium MOXA CP-118U-I 8-Port PCI Serial Board
Best high-density industrial board: eight-port PCI serial card designed for heavy-duty multiport deployments
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