Startech.com USB To Serial Adapter Cable With COM Retention ICUSB2321X User Manual

Content

StarTech.com USB to Serial Adapter Cable With COM Retention ICUSB2321X Manual

Introduction

The startech.com USB To Serial Adapter Cable With COM Retention ICUSB2321X adds one RS-232 serial port to a Windows computer through an available USB port. It is designed for connecting computers to legacy and industrial equipment that still uses a nine-pin serial interface, including network equipment, barcode scanners, laboratory instruments, point-of-sale systems, CNC controllers, and console-management devices.

This 30 cm USB-to-RS232 adapter uses a Texas Instruments TIUSB3410 chipset and supports data rates up to 230.4 Kbps. Its COM port retention feature helps preserve the assigned Windows COM port when the adapter is unplugged and reconnected, including when it is moved to another USB port. This can reduce reconfiguration time for software that depends on a fixed COM port number.

The adapter is a practical choice for technicians, system administrators, engineers, field-service professionals, and businesses maintaining equipment with legacy serial connectivity. Its integrated cable design keeps the USB-A plug and male DB9 connector together, making it easier to install in workstations and service kits.

Before installation, verify that the computer runs a supported Windows version and that the connected equipment requires RS-232 rather than RS-422, RS-485, or another serial standard. The adapter is intended for Windows systems and requires driver installation with administrator privileges.

Specifications and Key Features

Product: StarTech.com ICUSB2321X professional USB-to-serial adapter cable
Host interface: USB 2.0 Type-A male connector
Serial interface: One male DB9 RS-232 connector
Cable length: Approximately 30 cm (12 inches)
Chipset: Texas Instruments TIUSB3410
Maximum baud rate: Up to 230.4 Kbps
Data buffering: 32-byte FIFO with separate upstream and downstream buffers
COM port retention: Stores the assigned COM port so compatible software can continue using the same port after reconnection
Serial protocol: RS-232
Operating system support: Windows systems supported by the applicable hardware revision and driver package
Installation requirement: One available USB 1.1 or newer port and administrator privileges for driver installation
Typical applications: Serial console access, industrial equipment configuration, POS systems, instrumentation, scanners, and service tools

The adapter does not convert RS-232 into RS-485 or RS-422. Check the pinout and communication requirements of the target device before connection.

How to Set Up the ICUSB2321X USB-to-RS232 Adapter

Confirm that the computer uses a supported Windows operating system and that the target equipment requires an RS-232 connection.
Download the driver package applicable to the ICUSB2321X hardware revision from StarTech.com. Save the installer before connecting the adapter if the computer does not have internet access.
Run the driver installer with administrator privileges and follow the on-screen instructions. Restart Windows if the installer requests it.
Connect the adapter’s USB Type-A plug directly to the computer or to a powered USB hub.
Connect the male DB9 connector to the equipment’s compatible serial port. Tighten the connector screws without forcing them.
Open Windows Device Manager and expand Ports (COM & LPT). Identify the USB serial device and note its assigned COM number.
Configure the application with the equipment’s required baud rate, data bits, parity, stop bits, and flow-control settings. These values must match at both ends.
Open the serial connection and test communication using a suitable command, diagnostic screen, or vendor application.

Do not connect or disconnect the DB9 plug while equipment is powered unless its documentation permits hot-plugging. Avoid excessive cable tension, moisture, static discharge, and unsupported adapters or gender changers that may alter the pinout.

Troubleshooting the StarTech ICUSB2321X

Windows does not detect the adapter

Try another USB port, reconnect the cable, and check Device Manager for an unknown device or warning symbol. Reinstall the correct driver with administrator privileges and restart the computer.

The serial port appears but the application cannot connect

Confirm that the application is using the COM number shown in Device Manager. Close other programs that may be holding the port, then verify the baud rate, parity, data bits, stop bits, and flow-control settings.

Communication produces unreadable characters

Mismatched serial settings are the most common cause. Compare both devices’ configuration values and verify that the connected equipment uses RS-232 signaling and the correct DB9 pinout.

The COM number changed

Reconnect the adapter to the original USB port and check whether COM retention restores the previous assignment. If necessary, change the COM number through the device’s advanced port settings, ensuring that no other active device uses it.

Connection drops or times out

Use a direct USB connection, avoid loose extension cables, inspect the DB9 connector, and reduce the baud rate temporarily for testing. Keep the adapter away from severe electrical interference.

If the problem remains, record the Windows version, hardware revision, Device Manager message, COM number, serial settings, and target-device model before contacting StarTech.com technical support. Warranty service should be handled through the original seller or StarTech.com support process; retain proof of purchase and the product identification details.

Pros and Cons

Advantages

COM port retention: Helps software continue using a familiar COM number after reconnection.
Professional chipset: The TIUSB3410 and buffered data path support dependable serial communication for configuration and monitoring tasks.
Useful performance: The maximum 230.4 Kbps rate suits many console, automation, instrumentation, and service applications.
Compact design: The integrated 30 cm cable is convenient for laptop use, bench testing, and technician toolkits.
Broad application range: It can connect a Windows computer to compatible RS-232 equipment without an internal expansion card.

Limitations

Windows-focused compatibility: Users of macOS, ChromeOS, or Linux should select an adapter specifically supporting their operating system.
USB-A connection: Computers with only USB-C ports require a compatible USB-C adapter or hub.
Single serial port: Installations requiring several simultaneous RS-232 connections need a multi-port solution.
RS-232 only: It is not a replacement for RS-422, RS-485, Ethernet serial servers, or level-shifting interfaces.
Driver dependency: Administrator access and the correct driver are required before the adapter can be used.

The startech.com USB To Serial Adapter Cable With COM Retention ICUSB2321X is best suited to Windows users who need one dependable RS-232 port and stable COM-port assignment. Choose another product when native non-Windows support, multiple serial ports, USB-C connectivity, or RS-485 operation is required.

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Faqs

How do I set up the startech.com USB To Serial Adapter Cable With COM Retention ICUSB2321X for the first time?

Download the latest ICUSB2321X driver package from StarTech.com before connecting the adapter. Run the installer with administrator privileges, restart Windows if prompted, and then connect the adapter to an available USB port. Open Device Manager and confirm that a USB Serial Port appears under Ports (COM & LPT). Connect your RS-232 device with a suitable DB9 cable, then select the assigned COM port and matching serial settings in your terminal or control software.

Why is the startech.com USB To Serial Adapter Cable With COM Retention ICUSB2321X not appearing in Device Manager?

Try a different USB port, preferably one connected directly to the computer rather than through an unpowered hub. Disconnect the ICUSB2321X, uninstall any unknown USB or serial device entries, restart Windows, and reinstall the correct driver as an administrator. Check for a warning symbol in Device Manager and verify that the adapter is firmly connected. If it still does not appear, test it on another supported Windows computer to separate a driver issue from a hardware or USB problem.

How does COM port retention work on the ICUSB2321X USB to serial adapter?

COM port retention allows the startech.com USB To Serial Adapter Cable With COM Retention ICUSB2321X to remember its assigned COM port. After disconnecting and reconnecting the adapter, Windows can restore the same port assignment instead of creating a different number. This helps equipment-management, console, and automation software reconnect reliably. If the COM number changes, open Device Manager, review the port properties, and assign an available COM number that matches the application configuration.

Can I use the startech.com USB To Serial Adapter Cable With COM Retention ICUSB2321X with a modem, console cable, or industrial controller?

The ICUSB2321X provides one USB 2.0 connection to an RS-232 DB9 serial port, so it can work with compatible modems, console equipment, laboratory instruments, and industrial controllers that use standard RS-232 signaling. Confirm the device’s connector wiring, baud rate, parity, data bits, stop bits, and flow-control requirements first. It is not a universal USB-to-Ethernet or RS-485 converter, and a null-modem cable may be required for some equipment.

What should I do if the ICUSB2321X is detected but my serial device does not communicate?

First verify that the selected COM port belongs to the ICUSB2321X rather than another serial device. Compare the terminal software settings with the connected equipment, including baud rate, parity, data bits, stop bits, and hardware or software flow control. Confirm whether the connection requires a straight-through or null-modem cable, and check that the DB9 connector is fully secured. Close other programs that may already have the COM port open, then reconnect the adapter and retry.

How can I improve data-transfer reliability when using the startech.com USB To Serial Adapter Cable With COM Retention ICUSB2321X?

Use a short, good-quality USB connection and avoid loose extensions or unstable hubs. Keep the serial cable away from strong electrical interference, motors, and power cables when possible. Configure the exact communication settings required by the connected device rather than assuming default values. If data errors occur at a high transfer rate, test a lower baud rate and check cable length, grounding, and flow-control settings. Ensure only one application is accessing the COM port.

Does the startech.com USB To Serial Adapter Cable With COM Retention ICUSB2321X work with macOS, Linux, or ChromeOS?

The ICUSB2321X is intended for Windows systems, and StarTech identifies it as a Windows-only USB-to-serial adapter. Do not assume that macOS, Linux, or ChromeOS will provide a compatible driver. Before deployment, check the current operating-system support listed for the exact hardware revision and required driver. If the computer uses a newer Windows release, install the latest available driver and confirm compatibility, especially when replacing an older computer or migrating software.

How should I maintain and store the ICUSB2321X USB to RS-232 adapter cable?

Disconnect the ICUSB2321X by holding the connector rather than pulling the cable. Keep the USB and DB9 connectors clean, dry, and protected from dust, moisture, and excessive bending. Avoid placing heavy objects on the cable or sharply folding it near either connector. When not in use, store the adapter loosely coiled. If the connection becomes intermittent, inspect the cable and connectors for visible damage and replace the adapter if cleaning and reseating do not resolve the problem.