Best Serial Port Cards AI pick
Chosen by an AI model from its trained knowledge, with its reasoning.
AI pick: Moxa CP-104EL-A
A low-profile PCIe RS-232 card with four ports, mature Windows and Linux drivers, and industrial-grade reliability for lab, POS and automation equipment.
Not for: Anyone who needs RS-422 or RS-485, or who only needs one port for a single legacy device and does not need industrial-grade hardware.
AI picks by need
For one port for a single legacy device
StarTech PEX1S953
A single-port PCIe RS-232 card using a 16C950 UART with a deep FIFO, enough for most legacy device connections.
Not for: Multi-device installations or RS-422/485 links.
For RS-422/485 industrial links
Brainboxes PX (line)
Brainboxes PX PCIe serial cards include RS-422/485 models with long driver support aimed at industrial users.
Not for: Simple RS-232 hookups where a basic card is enough.
What the AI looks for in Serial Port Cards
- Electrical standard
- Match RS-232, RS-422 or RS-485 to the device; they are not interchangeable Plugging the wrong standard in gives no communication and can damage line drivers.
- UART and FIFO
- Prefer 16C950-class or better UARTs with deep FIFOs for high baud rates Shallow FIFOs drop characters under load at high speeds.
- Port count and connector
- Check DB9 vs DB25 and whether multi-port cards use a fan-out cable Connector and cable type decide whether existing device cables plug in.
- Driver and OS support
- Confirm 64-bit Windows drivers and Linux kernel support for the chipset Industrial and lab software often runs on Linux or long-lived Windows builds.
- Card vs USB adapter
- Use an internal card for timing-sensitive or always-on links USB-serial adapters can add latency and can change COM port numbers after reconnecting.
Brands that matter
- Moxa: Industrial serial specialist with long driver support.
- StarTech: Accessible single and multi-port RS-232 cards.
- Brainboxes: Industrial serial cards including RS-422/485 models.
- Sunix: Serial cards often used in POS and industrial PCs.
- SIIG: Long-standing legacy I/O card maker.
What to avoid
- Unbranded cards that do not name the UART chipset.
- Using RS-232 cards for RS-485 devices without a proper converter.
- USB-serial adapters for timing-critical control equipment.
Questions
Can I set the COM port number?
Yes, on Windows you can usually reassign it in the port's advanced settings in Device Manager, which helps with software that expects COM1 or COM2.