isolated usb rs232 rs422 rs485 converter
Model: USB-Serial-3  119.95 In stock order usb rs232 rs485 rs422 converters
Instant Volume Discounts
Qty: 10+ $107.96
Qty: 50+ $101.96
Other Qty: Ask

The USB-Serial-3 is a rugged, industrial-grade, optically-isolated USB to RS232/RS485/RS422 converter, which can be used to convert any standard USB port into a three-wire RS-232 port, a two-wire RS-485 port, or a four-wire RS-422/RS-485 port and vice versa. This industrial opto-isolated USB to RS232 / RS485 / RS422 converter uses the latest chipset from Silicon Labs and is fully compatible with Windows 8 / 7 / Vista / XP / Server2003 / 2000 (32-bit), Windows 8 / 7 / Vista (64-bit), Win CE (5.0, 6.0), Mac OSX, and Linux (2.6x, 2.4.36). It supports multi-drop RS485/RS422 networks and can be used to communicate with one loop of up to 128 units of RS485 or RS422 devices; when working with RS-485 signals, the CommFront’s auto-turnaround feature eliminates the need for flow control. This USB Serial Converter product operates within a temperature range of -40ºF to 185ºF (-40ºC to 85ºC), features 600W surge protection, 15kV static protection and 2500V opto-isolation circuitry, which effectively protect your USB devices from ground loops, noise problems, transient surges, remote lightning and spikes. The device comes with a built-in selectable 120-Ohm terminator for system reliability and easy installation. The unit is powered from the USB port and it features data format auto-sensing and self-adjusting; therefore, no DIP switch or jumper settings are required. And thanks to the professional and unique casing design, the product can be mounted directly on a wall, panel or DIN Rail, without a need of using any unsecured DIN-Rail or wall-mount brackets.

CommFront's USB converters were strictly certified by SGS and/or TUV (both are the Nationally Recognized Testing Laboratories [NRTLs] in North America (approved by OSHA) and the Notified Bodies in the European Union. CommFront's product quality is ensured by our ISO 9001:2008 (Cert No. SG12/04213) quality control system (strictly certified by SGS/UKAS), and we back our high-quality converter products with a 30-day risk-free money-back guarantee and a 5-year replacement warranty.



industrial usb rs422 rs485 rs232 converter
industrial usb serial converter
isolated usb rs232 rs422 rs485 converter
din rail usb to rs232 rs422 rs485 converter
usb serial converter
usb rs232 rs422 rs485 converter


  • Adds one RS-232, RS-485 or RS-422 port to your USB port.
  • USB port-powered, no external power required.
  • Industrial grade enclosed in a rugged, rustless ABS housing.
  • Supports multi-drop RS485/RS422 networks (up to 128 nodes).
  • 2500V optical isolation effectively protects USB devices from ground loops, transient surges, remote lightning and spikes.
  • 300 to 115.2K Baud operation (auto-sensing and self-adjusting).
  • Direct DIN-Rail (Rack) or Wall / Panel mounting.
  • Plug and play (hot-pluggable, data format auto-sensing and self-adjusting).
  • Data direction auto-turnaround, no flow control is required.
  • Built-in 120Ω end-of-line terminator for system reliability and easy installation.
  • Supports Windows 8/7/Vista/XP/Server2003/2000 (32-bit), Windows 8/7/Vista(64-bit), Win CE, Mac, and Linux.
  • Operating temperature: -40ºF to 185ºF (-40ºC to 85ºC).
  • Built-in 600W surge protection, 15kV static protection and circuit protection.
  • Surface Mount Technology manufactured to RoHS and ISO-9001 standards.
  • Safety: Strictly certified by TUV (Cert No. SG-CE-100004; SG-FCC-100001).
  • 5-year manufacturer's warranty.


Part Number: USB-Serial-3
Compatibility: USB 2.0 and EIA/TIA RS-232/485/422 standards
Power Source: From USB port
Current Consumption: Less than 200mA
Baud Rates: 300 to 115,200bps (auto-sensing & self-adjusting)
Optical Isolation: 2500Vrms (AC, 1 min)
Distances: USB: 10ft (3m); RS-232: 16ft (5m); RS-485/422: Depending on the power from USB port, will transmit up to 4000ft (1.2km) at 19,200bps
Connectors: USB: Type B male; RS-232/485/422: 10-Way Terminal Block
Accessories: 1x 5ft (1.6m) USB extension cord (Type B female to Type A female)
Maximum number of drops: RS-232: 1; RS-485/422: 128
End of Line Terminator: 120Ω (built-in, selectable)
Surge Protection: 600W
Static Protection (ESD): 15kV
Dimensions (H x W x D): 4.5 x 3.6 x 0.9 in (115 x 73 x 33 mm)
Weight: 4.2 oz (120 g) (with terminal block)
Operating Temperature: -40ºF to 185ºF (-40ºC to 85ºC)
Operating Humidity: Up to 90% RH (no condensation)


USB Side

USB Type B Male Connector

USB Type B Male Connector (view from front)

USB Connector
USB Type A Female Connector (view from front)

RS-232/485/422 Side

Pin TX+/A+ TX-/B- RX+ RX- J1 J2 J3 J4 GND TX RX
RS232 - - - - - - GND TX RX
RS485 485+ 485- - - - Tie to ON 120Ω GND - -
RS422 TX+ TX- RX+ RX- Tie to ON 120Ω - - GND - -

usb terminal block


Opto Isolated USB to RS232 converter

 Figure 1: USB to RS232 Connection

Opto Isolated USB to RS485 converter

 Figure 2: Master-Slave Multi-Drop Connections (RS485)


Opto Isolated USB to RS422 converter

 Figure 3: Master-Slave Multi-Drop Connections (RS422)


usb driver installation

Install drivers from the CD provided with the product (as shown above).

The latest drivers (chipset: Silicon Labs’ CP210x) are available at:


1) Driver installation

usb drivers device manager

Make sure that the USB-Serial-3 converter is connected to your USB port, and the driver is installed correctly (as shown above); otherwise, please reinstall the drivers.

2) Loopback Test

usb serial converter connection

  • Connect a USB-Serial-3 to your PC's COM port and connect TX+ to RX+, TX- to RX- (as shown above).
  • Run 232Analyzer FREE version software on your computer.
  • Select "ASCII" for both the Send and Receive data formats. Then send a command and/or string such as "CommFront" from the 232Analyzer software. You should receive an echo of the command/string sent ("CommFront"). By performing a simple loopback test like this, you can test both the transmitter and receiver of the converter. This is very helpful when you are in doubt about the performance of your converter.

usb serial converter - loopback test 2
Screenshot: Send/receive commands from 232Analyzer software.

232Analyzer is an advanced RS232 Serial Protocol Analyzer software that allows you to control, monitor and analyze serial port (RS232 / RS485 / RS422 / TTL, etc.) activities. Not just the data, it also allows you to monitor or change RS-232's line states: RTS, CTS, DTR, DSR, DCD, and RI.

The FREE version (no time limitation) can be downloaded from here.


RS-232: 3 easy steps to understand and control your RS232 devices
RS-485/RS422: Building a reliable RS485/RS422 network