StarTech 21050-PC-SERIAL-LP 2-Port Low Profile PCIe RS-232 Serial Card

Overview

The StarTech 21050-PC-SERIAL-LP is a dual-port RS-232 serial expansion card designed for systems integrators and IT architects who need to reconnect legacy DB-9 serial devices to modern PCs that no longer ship with native COM ports. Built around the ASIx AX99100 chipset and riding a PCIe 2.0 x1 slot, this card delivers two independent RS-232 channels at up to 921.6 Kbps per port — fast enough for virtually any serial-driven device in a security or automation stack. The low-profile form factor (6.7 cm × 6.6 cm × 1.8 cm, 54 g) means it fits compact rack servers and small-form-factor workstations where a standard-height card simply won't clear the chassis.

If you're integrating access control panels, serial-over-IP bridges, legacy PTZ controllers, or industrial sensors that still speak RS-232, the PCIe serial expansion card category has a narrow field of genuinely reliable options — this is one of them. The 21050-PC-SERIAL-LP (often searched as 21050 PC SERIAL LP) ships with Windows and Linux driver support, making it usable on both enterprise workstations and embedded Linux-based appliances.

Key Features

• Two Independent RS-232 DB-9 Ports: Each port operates independently at up to 921.6 Kbps — more than adequate for serial console access, PTZ camera controllers, or barcode scanner integration. Having two ports on a single card means one slot handles two devices, preserving other PCIe slots for higher-bandwidth needs.
• PCIe 2.0 x1 Interface: Seats in any PCIe x1, x4, x8, or x16 slot (PCIe is backward and forward compatible in physical length), so it fits the widest possible range of server and workstation motherboards without slot competition.
• ASIx AX99100 Chipset: A proven multi-protocol UART chipset with broad OS driver coverage. On Windows and Linux systems, driver installation is straightforward and the card enumerates as standard COM ports — no custom middleware required for most applications.
• 256-Byte FIFO per Port: The 256-byte hardware FIFO buffers incoming and outgoing data, reducing the risk of data loss under high CPU load — important on shared server platforms where interrupt latency isn't always predictable.
• Hardware and Software Flow Control: Supports both RTS/CTS hardware flow control and XON/XOFF software flow control. This matters when connecting devices that use different handshaking methods; you're not locked into one approach.
• Full Parity Support (Even, Odd, None, Space, Mark): All five parity modes are supported, along with 5/6/7/8/9 data bit configurations. Legacy industrial and security devices often use non-standard serial framing — this card handles all of it without workarounds.
• Low-Profile Card Format: At 6.7 cm × 6.6 cm and 54 g, this card fits 1U rack servers and SFF workstations that only accept low-profile PCIe cards. This is the spec that disqualifies most competing full-height cards from compact builds.
• Per-Port Activity LEDs: Two activity LEDs provide instant visual confirmation that serial traffic is flowing — useful during commissioning to verify a device is communicating before diving into software diagnostics.
• Operating Temperature 0°C to 55°C: Covers standard data center and office environments. For deployments in unconditioned spaces (warehouses, exterior enclosures), confirm ambient temps stay within this range — the card is not rated for industrial temperature extremes.
• Windows and Linux Compatibility: Broad OS support means this card works in enterprise Windows Server environments, Ubuntu-based VMS appliances, and embedded Linux NVR platforms alike — no OS-specific procurement needed.

Integration and Compatibility

The 21050-PC-SERIAL-LP integrates directly with any application that addresses standard Windows COM ports or Linux /dev/ttyS (or /dev/ttyUSB-style) serial nodes. This includes access control panel management software, serial PTZ camera controllers in VMS platforms, industrial SCADA systems, and serial console management for network equipment. The PCIe 2.0 x1 electrical interface is compatible with PCIe 1.x and 3.x slots — slot generation mismatch does not prevent functionality at RS-232 baud rates.

For security integrators pairing this card with a network video recorder or VMS server that requires serial PTZ control, verify that the VMS assigns COM port numbers predictably after reboot — some Windows Server configurations reassign COM port numbers after driver reinstall, which can break PTZ mappings. A quick registry COM port assignment fix resolves this, but plan for it during commissioning.

If you need more than two serial ports on a single card, review the broader StarTech serial and I/O expansion line for 4-port and 8-port PCIe variants. The 21050-PC-SERIAL-LP is specifically the right pick when two ports are sufficient and low-profile height is a hard constraint.

Frequently Asked Questions

Q: What PCIe slot does the 21050-PC-SERIAL-LP require?

A: The card uses a PCIe x1 connector and is electrically compatible with PCIe 2.0. Because PCIe is physically backward-compatible, it will also seat in x4, x8, or x16 slots. It will not fit PCI (non-Express) slots.

Q: Does the 21050-PC-SERIAL-LP work in a standard-height chassis, or only low-profile?

A: The card ships as a low-profile form factor (6.6 cm tall). Check whether a full-height bracket is included in the package — if not and you need full-height installation, a compatible bracket may need to be sourced separately.

Q: What is the maximum baud rate supported?

A: Each port supports up to 921.6 Kbps independently. This is well above the 115.2 Kbps standard maximum and covers virtually all RS-232 devices, including high-speed serial console and PTZ controller applications.

Q: What operating systems are supported?

A: The 21050-PC-SERIAL-LP is compatible with Windows and Linux. Specific version support should be confirmed against StarTech's current driver release notes, as OS version compatibility expands with driver updates.

Q: What is the warranty on the 21050-PC-SERIAL-LP?

A: StarTech provides a 2-year hardware warranty on this product.

Q: Will this card work with serial PTZ camera controllers in a VMS environment?

A: Yes. The card enumerates as standard COM ports on Windows and as serial device nodes on Linux, which is exactly what VMS platforms use to address serial PTZ controllers. Confirm your VMS documentation for COM port assignment requirements during initial configuration.

Eden Phillips

The spec I always point integrators to first on the 21050-PC-SERIAL-LP is the 256-byte hardware FIFO. On a busy VMS server handling camera streams and storage writes simultaneously, CPU interrupt response to serial events is not guaranteed to be instant — and without a deep enough FIFO, you lose bytes. At 921.6 Kbps with a 256-byte buffer, you have a meaningful margin before data loss becomes a real risk, which is why this card holds up in shared server environments where a cheaper single-byte FIFO card would cause intermittent serial communication errors that are genuinely painful to diagnose.

Technical Highlights:

• 921.6 Kbps Max Baud Rate: Eight times the standard 115.2 Kbps ceiling — ensures headroom for any RS-232 device you're likely to connect now or in the future, with no throughput bottleneck at the card level.
• ASIx AX99100 Chipset: Broad driver coverage across current Windows Server and Linux kernel versions; enumerates as native COM ports without requiring custom middleware or virtual COM port layers.
• Low-Profile PCB (6.7 × 6.6 × 1.8 cm, 54 g): Fits 1U rack servers with half-height PCIe slots — the physical constraint that eliminates most full-height alternatives from compact appliance builds.

Deployment Considerations:

• On Windows Server deployments, lock COM port numbers in Device Manager after initial driver installation — PCIe serial cards can be reassigned after driver updates, which breaks any VMS or access control software that references a hardcoded COM port number.
• Operating temperature is rated 0°C to 55°C. If this card is going into a dense 1U server in a poorly ventilated rack, verify that internal chassis temperatures at the card slot stay within that envelope under full load — the card itself is compact and passive-cooled.

This card is the right fit for a VMS workstation or compact rack server that needs to drive one or two serial PTZ controllers or communicate with a legacy access control panel — particularly where the chassis enforces a low-profile PCIe height restriction and you need a card that enumerates cleanly on Linux without patching kernel modules.