USB to 4 RS232/422/485 Ports


  • Four-port serial communications adapter
  • Full-speed USB 2.0 device, USB 3.0 and 1.1 compatible
  • Supports field selectable RS-232, RS-422 or RS-485 protocols, per port
  • Includes type FT232BM UART with 384-byte receive/128-byte transmit FIFO buffers
  • Speeds up to 921.6kbps simultaneously
  • Power LED and individual port activity LEDs next to the USB and each COM connector
  • All required power drawn from USB port, no external power adapter required
  • Compact, low profile enclosure


  • OEM (board only) version with PC/104 mounting holes and PCB footprint for added flexibility in embedded applications
  • OEM board with 10-pin vertical male headers instead of DB9s
  • Extended operating temperature (-40°C to +85°C)
  • DIN rail mounting provision
  • RoHS Available. Please contact us for ordering information


  • Multiple POS peripherals
  • Barcode scanners
  • Scales
  • Date-entry terminals
  • Data acquisition and automation modules

This flexible serial communications adapter was designed for effective multipoint transmission in any one of three modes on each channel. These modes are RS232, RS422 and RS485 (EIA485) protocol.


The OEM (board only) version is perfect for a variety of embedded applications. What makes the OEM option unique is that its PCB size and mounting holes match the PC/104 form factor (without the bus connections). This allows our rugged USB to quad-serial port board to be added to any PCI-104 or PC/104 stack by connecting it to a simple USB port usually included on-board with embedded CPU form factors such as EBX, EPIC, and PC/104. This is especially important since many newer CPU chipsets do not support ISA and have plenty of USB ports. The USB-FLEXCOM4 OEM board can also be installed using standoffs inside other enclosures or systems.


Available accessories include a broad range of cable assemblies and screw terminal boards for quick and easy connectivity. The ADAP9 accessory provides a screw terminal connection to break out the RS-232/422/485 signals on the DB9M connector. Special order items such as conformal coating, custom software, and more, are also available.


The USB-FLEXCOM4 is plug-and-play which allows quick connect or disconnect whenever you need additional I/O on your USB port. The USB-FLEXCOM4 is supported for use in most USB supported operating systems and includes a free Linux and Windows XP -> 10, both 32 & 64 bit compatible software package. This package contains sample programs and source code in Visual Basic, Delphi, and Visual C++ for Windows. Also incorporated is a graphical setup program in Windows. Embedded OS support includes Windows Xpe, WES7, etc.

Available Reference Manuals

Available Software Downloads

Available Datasheets

Drivers and Downloads

Full list of available Downloads: Software Packages, Drivers, Manuals, and other documents

Custom Software

ACCES also offers Custom Software Services for our products. Our prices are unbelievably low, often as inexpensive as free! If you need something tweaked to support your needs, or an entire enterprise application developed from scratch, it is definitely worth your time to inquire with us, first.

Further information about available ACCES Software:

Redistributing Windows Drivers
A list of ACCES drivers and the files that compose them under different versions of Windows, so you can easily redistribute ACCES cards and drivers.

OEM Version

Communications Interface

  • Serial Ports: COM A through COM D via four male DB9 connectors
  • Character length: 5, 6, 7, or 8 bits
  • Parity: Even, odd or none
  • Stop Interval: 1, 1.5, or 2 bits
  • Serial Data Rates: Up to 921.6k for RS-422 and RS-485 modes, asynchronous RS-232 speeds up to 230.4kbps.
  • Receiver Input Sensitivity: +200 mV, differential input
  • Common Mode Rejection: +12V to -7V
  • Transmitter Output Drive: Up to 60 mA, with thermal shutdown
  • Bus Type USB 2.0 Full-Speed
  • USB Connector: Type B, high-retention
  • Embedded USB Connector 5-pin header, Molex part number 53047 Mating connector housing is Molex part number 51021 0500 -OEM VERSION


  • Operating Temperature: 0°C to +60°C (Optional 40°C to +85°C)
  • Storage temperature: -50°C to +120°C
  • Humidity: 5% to 95%, non-condensing
  • Power Required: 5VDC at approximately 110 mA (plus loads up to an additional 240 mA) from USB bus
  • Size: Board Dimension: 3.550 x 3.775 inches (PC/104 size & mounting)
  • Box Dimension: 4.00 x 4.00 x 1.25 inches

    Pinout Table
    DB-9 Male Pin for each of Ch A-DRS-232 Signals (Industry Standard)RS-485 Signals (2 Wire)RS-422 Signals (Also 4wire RS485)
    Ch x pin 1DCD RX-
    Ch x pin 2RXTX+/RX+TX+
    Ch x pin 3TXTX-/RX-TX-
    Ch x pin 4DTR  
    Ch x pin 5GndGndGnd
    Ch x pin 6DSR  
    Ch x pin 7RTS  
    Ch x pin 8CTS  
    Ch x pin 9RI RX+

    ModelPrice (USD)

    Ordering Guide
    USB-FLEXCOM4USB to four port RS-232/422/485 serial adapter
    USB-COM232-4AUSB to four port RS-232 only serial adapter
    ADAP9Screw terminal adapter (single DB9 female to 9 screw terminals) $19
    ADAP9-2Screw terminal adapter (dual DB9 female to 18 screw terminals) $25
    MP104-DINDIN-rail mounting provision $19
    CUSB-EMB-HDR30" USB 1x5 standard header to micro OEM cable $19
    CUSB-EMB-HDRM30" USB 1x5 metric header to micro OEM cable $19
    CUSB-EMB6" micro-fit to micro-fit embedded OEM cable $19
    USB-104-HUBRugged, industrial grade, 4-port high-speed USB 2.0 hub
    Options (call for pricing)
    -OEMBoard only model, no enclosure
    -FFast version (RS-232 up to 921.6kbps)
    -HDROEM board with 10-pin vertical male headers instead of DB9s
    -PExternal power components and AC/DC adapter
    -TExtended operating temperature (-40°C to +85°C)
    -CallCustom baud rates
    -RoHSRoHS compliant version
    Acquisition, Control, Communication: Engineering and Systems

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