Single Port USB 2.0 to RS-422 / RS-485 DB-9 Serial Adapter

RS-422 | RS-485 | 128 Bytes Receive | 256 Bytes Transmit | FTDI

  • Expand Your Serial Capabilities: The Mini Serial Adapter can be utilized through an existing USB Port to work with your legacy serial connections. It’s great for newer technologies with no serial port connections.
  • Safe Connections: Designed with a unique system load reduction feature, the USB to Serial Adapter also offers 15kV surge protection for connected devices.
  • Upstream: 1 USB port, Type B Female Connector
  • Downstream: 1 Male DB9, w/ nuts
  • RS-422 Signals: TxD-, TxD+, RxD+, RxD-, GND, RTS-, RTS+, CTS+, CTS-
  • RS-485 Signals: TxD-, TxD+, RxD+, RxD-, GND
  • Transmit Buffer: 256 Bytes
  • Receive Buffer: 128 Bytes


In stock

Volume Pricing

Units Price
1 - 4 $87.95
5 - 11 $85.31
12 - 24 $83.55
25 - 49 $81.79
50+ $79.16

Also available from:

Model No. USB-COMi



Industrial Single Port USB to RS422 / RS485 Adapter for connecting RS-422 and RS485 serial devices used in industrial environment to help expand or manage serial port availability. With RS-485 the data direction is controlled by the port, without further action from the software. Windows recognizes item as a Standard Com port, listed in Device Manager Section COM & LPT (Com Port number can be assigned in advanced settings)

The Single USB to RS422 Serial Port Adapter with the 128 byte FIFO allows high-speed communication, even in heavy loaded systems or systems without native COM port access, unique features reduce the system load. The serial port adapter also allows unusual speed settings like 500.000bps.

RS-422 & RS-485 Mode Block Configuration SW (DIP Switch) for Mode Setting

Operation Mode S1 S2 S3
RS-422 4 wire with Handshaking ON ON ON
RS-485 Full Duplex (4 wire) OFF ON ON
Half Duplex (2 wire)
– with Echo
Half Duplex (2 wire)
– without Echo


Hardware Specifications

  • Ports: One RS422/485 port
  • Connectors: one DB9 male
  • RS422/485 signals RS422 TxD+/-, RxD+/-,
  • RTS+/-, CTS+/-, GND
  • RS485 Data+/-, GND
  • Baud Rate: from 300bps up to 921.6Kbps supported
  • Transmit(TxD) and Receive(RxD) LEDS on unit for visual reference
  • Universal Serial Bus(USB) port offers easy plug and Play Operation

Data Signals Supported:

  • RS-422 data signals: TxD-, TxD+, RxD+, RxD-, GND, RTS-, RTS+, CTS+, CTS-
  • RS-485 4-wire data signals: TxD-, TxD+, RxD+, RxD-
  • RS-485 2-wire data signals: Data-, Data+

OS Support:

  • Windows 7, Windows 8, 8.1 and Windows 10
  • Linux and Mac OS 10.X

Ordering Information

  • Product Name USB-COM-I
  • Packing list USB-COM-I Adapter
  • USB cable 0,9m
  • CD, English Documentation
  • Bus-powered. No external power supply needed.

CoolGear 1 year Warranty

Package Contents:

  • RS422/485 Single port adapter
  • Manual
  • Driver CD
  • USB-COMi
  • 3ft USB A to B Cable


Product Specifications

Adapter Power

USB Bus Powered

Power Source

USB Connector

External Power Required


Country of Origin






Item Dimensions (L × W × H)

3.30 × 2.87 × 1.62 in.

Item Weight

0.181 lbs.


1 Serial Port

Material of Construction


USB Type

USB 2.0

Screw Lock Compatible


Serial Attributes
RS Signals

TxD-, TxD+, RxD+, RxD-, GND, TxD-, TxD+, RxD+, RxD-, GND, RTS-, RTS+, CTS+, CTS-

Serial Standards

RS422, RS485

Baud Rate

921.6K bps

FIFO Receive

128 bytes

FIFO Transmit

256 bytes

Data Bits

7, 8


None, Even, Odd, Mark, Space

Stop Bits

1, 2

Flow Control

Hardware (RTS, CTS), XON/XOFF

OS Support

Win 11, Linux, Mac OSX, Win 10, Win 7, Win 8

Operating Temperature

0°C to 55°C (32°F to 131°F)

Storage Temperature

-20 to 75°C (-4 to 167°F)


5% ~ 95% (non-condensing)

Product Information

1 year from date of purchase



LED Indicators


ESD Protection

15KV Surge Protection

Max Data Transfer Rate


Other Data

DB9 Male w/ Nuts

Chip Model

FT231XQ-R, MAX3089E


.65 lbs


4 × 4 × 2.5 in

UPC: 729440691448

DB9 RS-422 Pin-Outs

DB9 RS-232 Pin-Out Diagram
DB9 RS-232 Pin-Out Chart

DB9 RS-485 Half-Duplex Pin-Outs

DB9 RS-485 Pin-Out Diagram
DB9 RS-485 Pin-Out Chart

DB9 RS-485 Full-Duplex Pin-Outs

DB9 RS-232 Pin-Out Diagram
DB9 RS-232 Pin-Out Chart
win_icon_60px Windows FTDI Driver
Compatible with Windows XP, Vista, 7, & 8
Accessories & Replacement Parts

Accessories & Replacement Parts

The RS422/485 single port serial adapter has certain accessories that work with it. These accessories are what you can order if needed.

USB 2.0 Cable for close connections Use this USB 2.0 cable to connect your desktop or laptop using a USB hub, printer, or scanner. Transfer…

Model# USB2-AB


In stock

6in 16in 1ft 2ft 3ft 4ft 5ft 6ft 10ft 15ft
This option is required
Black White
This option is required

Select options

RS232 Male to Female Serial Data Cable Complete your serial data connection with this 5ft. RS232 DB-9 Male to Female data cable for fast reliable…

Model# 9DBMF5FT


In stock

Add to cart


Product Documentation & Drivers

Need drawings, CAD files, or other compliance documentation? Click HERE

Serial F.A.Q.

Product F.A.Q.

View frequently asked product questions below. For all serial troubleshooting, visit this page.
Still need help? Reach out!

  • How do I clean and reinstall my FTDI drivers?
      1. Download the CDM Uninstaller HERE.
      2. Extract the zip file, or open the “CDMuninstallerGUI.exe” utility.
      3. Leave the ‘Vendor ID’ set to 0403 and ‘Product ID’ set to 6001.
      4. Click Add.
      5. Click Remove Devices.
      6. Download the corresponding driver for your operating system and follow on-screen prompts. Windows Driver | MacOS Driver

    Video tutorial here.

  • How can I change my device’s COM port?
      1. Click on Start and navigate to the Control Panel
      2. Locate and click on Device Manager
      3. Under “Ports (COM & LPT)” you will find your serial device titled “USB Serial Port” along with its current COM Port.
      4. Right click on “USB Serial Port” and click on Properties.
      5. Navigate to the “Port Settings” tab and click on “Advanced…”
      6. Once there, the “COM Port Number:” can be changed with a dropdown menu to select the port number.
      7. Click your desired port number (i.e. COM2) and click “OK”.
      8. Click “OK” once more.
      9. Your serial device is now assigned to your chosen COM Port.


  • How do I check to ensure the COM port is listed properly in Windows?
    To ensure your serial device is installed properly, complete the following:

    1. Press Windows Key + R to open the Device Manager. Once Run comes up, type “devmgmt.msc” into the text field and press Enter.
    2. Expand the section labeled, Ports (COM & LPT).
    3. You should now see a COM number in brackets to the right of each port. If the device is installed properly, no exclamation points or question marks should be present next to the device.
  • I have everything hooked up, but nothing is functioning correctly.
    To rule out potential issues, quickly test your individual components to ensure that they are working correctly individually, and are not the source of the problem:

    • Serial cables
    • Serial ports
    • Serial devices

    Test your components by:

    • Hook up the serial cable(s), serial port(s), and serial device(s) in a different setup to see if the issue stems from a particular component, or the setup as a whole.
    • Replace the serial cable, port, or device within your setup to further troubleshoot the issue’s origin.

    When testing cables:

    • Test each cable individually.
    • Use short cables when you are testing.

    When testing serial ports and devices:

    • Press the Windows key + R, in Run, type devmgmt.msc, and press Enter to open the Device Manager. You can then check to see if your device is listed under Ports (COM & LPT).
    • Ensure that the COM port number is the correct number for the serial device and that the software being used to connect the computer to the serial device uses the correct COM port number.
    • If the device is listed with an error, follow the instructions on the website to reinstall the drivers.
  • Serial communication is not functioning correctly, how can I tell if the problem caused by the adapter or my serial software application?
    Older serial communication applications make use of legacy hardware addresses, often incompatible with PCI, PCIe, and USB to Serial products. Contact the software provider to troubleshoot.
  • I am receiving an error when I try to install the drivers in Windows 8 64 bit.
    Driver Signature Enforcement in Windows 8 may need to be disabled in order to use various drivers. After disabling this feature, the driver will be allowed to install.

    Note: You are required to restart your computer after disabling the Driver Signature Enforcement. Save all open work on your computer.

    Disable driver signature enforcement:

    1. Press the Windows key + C.
    2. Click Settings > Change PC Settings.
    3. In the left pane, click General.
    4. In the right pane, under Advanced startup, click Restart now.

    When your system restarts:

    1. Click Troubleshoot > Advanced options > Startup Settings > Restart.
    2. Press 7.

    When your computer restarts, Driver Signature Enforcement will be disabled and you can install the drivers.

  • I am receiving an error when I try to install the drivers in Windows 10 64 bit.
    Driver Signature Enforcement in Windows 10 may need to be disabled in order to use various drivers. After disabling this feature, the driver will be allowed to install.

    Note: You are required to restart your computer after disabling the Driver Signature Enforcement. Save all open work on your computer.

    Disable Driver Signature Enforcement:

    1. Click the Windows icon in the taskbar.
    2. Click Power.
    3. Press and hold the Shift key and click Restart.

    After your computer restarts:

    1. Click Troubleshoot Advanced Options Startup Settings Restart.
    2. Press 7.

    When your computer restarts, Driver Signature Enforcement will be disabled and you can install the drivers.

  • Why did the software not install properly in macOS High Sierra (10.13) or later?
    High Sierra 10.13 and later versions of macOS enforce strict security policy revisions. In order for the device to operate, software packages like those used in this installation must be allowed in macOS Security and Privacy settings once the software is installed.

    Once the driver/software is installed, follow these steps to allow the software:

    1. Open System Preferences.
    2. Open Security & Privacy.
    3. Click the Allow button near the bottom of the General tab.

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