USB to Null Modem Serial Adapter Cable 6.6ft - Reliable RS232 COM

In this review the StarTech 6.6ft/2m USB to Null Modem Serial Adapter is evaluated for technicians and hobbyists who need a dependable way to add an RS-232 port to a modern computer. The bottom line: it is a practical cable for resolving DCE/DTE mismatches and maintaining COM port assignments, with useful diagnostics from activity LEDs and solid build quality that make it worth considering for legacy equipment connections.

Key Features

• Null modem function: Lets a computer act as the opposite end of a serial link to resolve DCE/DTE conflicts without extra cross-wired adapters.
• Interchangeable screws and nuts: Ships with pre-installed DB9 screws and separate DB9 nuts so the adapter secures cleanly to a wider variety of serial devices or cables.
• Real-time LEDs: Transmit, Receive and USB LEDs provide immediate feedback on port activity and enumeration for easier troubleshooting.
• Robust protection: One-piece molded TPE housing with Level-4 ESD protection and copper shielding reduces failures from electrostatic discharge and interference.
• Broad OS support: Drivers auto-install on modern Windows, macOS, ChromeOS and Linux systems and COM retention helps the port remain consistent across reconnects.
• Performance-oriented chipset: FTDI FT232R chipset supports up to 921.6Kbps and ample FIFO buffers for reliable serial data flow.

Who It's For

The adapter is best for IT professionals, lab technicians and makers who still rely on legacy RS-232 peripherals such as industrial controllers, measurement equipment or point-of-sale hardware and need a simple USB-A to DB9 solution that preserves COM assignment and avoids wiring headaches. The durable housing and ESD protection suit workshop and field use.

It is less appropriate for users who need a compact dongle for occasional hobby use where absolute portability matters, or for installations requiring fully shielded industrial cable assemblies longer than 2 m. Also, users who require proprietary serial driver bundles beyond standard FTDI support should verify compatibility first.

Pros & Cons

Pros

• Secure mounting options with both slotted thumbscrews and installable DB9 nuts for compatibility.
• Activity and USB LEDs simplify diagnostics when troubleshooting serial links.
• FTDI chipset, good FIFO sizes and 921.6Kbps max speed provide dependable data throughput.
• Strong build quality with TPE housing, copper shielding and Level-4 ESD protection increases reliability.

Cons

• At 6.6 ft (2 m) the cable is not the most compact choice for purely portable applications.
• Users with unusual legacy systems should confirm driver compatibility, although common OSes are supported.

Specifications

Cable length	6.6 ft (2 m)
Connector type	USB-A to DB9 (female) null modem
Chipset	FTDI FT232R
Maximum baud rate	921.6 Kbps
FIFO buffers	128 byte RX / 256 byte TX
ESD protection	Level-4 (15kV air / 8kV contact)
Operating temperature	-40C to 80C

Our Verdict

The StarTech 6.6 ft USB to Null Modem Serial Adapter is a solid, mid-length cable for anyone needing a reliable RS-232 port on modern computers. With FTDI chipset performance, COM retention, activity LEDs and interchangeable mounting hardware, it solves common serial connectivity problems without extra adapters and represents good value for workshop and professional use.

Frequently Asked Questions

Will this work with my Windows or macOS computer?
Yes; drivers auto-install on Windows 7 and later and macOS 10.15 and later, and it is also compatible with ChromeOS and Linux.

Can I secure the adapter to different serial cables?
Yes; it ships with pre-installed DB9 screws and included DB9 nuts so you can use either thumbscrews or nuts for compatibility.

Does it resolve DCE/DTE wiring issues?
Yes; the built-in null modem functionality removes the need for cross-wired adapters to fix DCE/DTE conflicts.