USB RS485 Adapter
USB-485-1 $37.95 In stock

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The USB-485-1 is a port-powered, bi-directional, integrated USB to RS485 converter / adapter that can be used to convert any standard full-duplex USB port into a two-wire balanced half-duplex RS485 port and vice versa. The unit can be used to communicate with one loop of up to 256 units of RS485 devices and it comes with a built-in selectable 120-Ohm terminator for system reliability and easy installation (see Application Note). This USB to RS485 converter is powered from the USB port and it supports data auto-sensing & self-adjusting, therefore, no baud rate setting is required. And with the data direction auto-turnaround technology, no external power or flow control is required for RS485 communications. The USB to RS485 adapter uses the latest FTDI chipset and is fully compatible with Windows 8/7/Vista/XP/Server2008/ Server2003/2000/98 (32-bit), Windows 8/7/Vista/XP/ Server2008/Server2003 (64-bit), Win CE, Mac, and Linux.

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.


PRODUCT PHOTOS (usb to rs485 converter / adapter)

USB RS485 Adapter
USB RS485 Converter
USB to RS485


  • Adds one RS-485 port to your USB port.
  • Communicate with one loop of up to 256 units of RS485 devices.
  • 300 to 3M Baud operation (auto-sensing and self-adjusting).
  • Built-in selectable 120Ω end-of-line terminator for system reliability and easy installation.
  • Built-in 15kV ESD static and circuit protection.
  • Data direction auto-turnaround, no flow control is required.
  • Supports Windows 8/7/Vista/XP/Server2008/Server2003/2000/98 (32-bit), Windows 87/Vista/XP/Server2008/Server2003 (64-bit), Win CE, Mac, and Linux.
  • Supports remote wakeup and power management.
  • Plug and play (hot-pluggable, data format auto-sensing and self-adjusting).
  • Port-powered, no external power required.
  • No IRQs required, no IRQ conflicts.
  • Surface Mount Technology manufactured to RoHS and ISO-9001 standards.
  • Safety: Strictly certified by world-class lab SGS / TUV (Cert No. E1/2013/90010C; E1/2013/90011C).
  • 5-year manufacturer's warranty.


Part Number: USB-485-1
Compatibility: USB 2.0 (backward compatible) and EIA/TIA RS-485 standards
Power Source: From USB port
Current Consumption: Less than 60mA
Baud Rates: 300 to 3M bps (Auto-sensing & Self-adjusting)
Distances: USB side: 10ft (3m); RS-485 side: Depending on the power from USB port, will transmit up to 4000ft (1.2km) at 19,200bps
Connectors: USB Side: Type A Female; RS-485 Side: DB-9 Male / 5-Way Terminal Block
Maximum number of drops: 256
End of Line Terminator: 120Ω (Built-in, selectable)
Dimensions (H x W x D): 0.8 x 1.3 x 3.6 in (20 x 32 x 92mm) (excluding cable)
Cable Length: 3.3 ft (1 m)
Weight: 3.8 oz (108 g)
Operating Temperature: 32ºF to 104ºF (0ºC to 40ºC)
Operating Humidity: Up to 90% RH (no condensation)


USB Side

USB Connector

USB Type A Connector (view from front)

RS485 Side

DB-9 Male: 1 3 5 6 7
Function B- A+ GND Tie to turn ON the 120Ω end-of-line terminator
Terminal Block: A+ B- GND 120
Function RS485+ RS485- GND Tie to turn ON the 120Ω end-of-line terminator

Note: The USB RS485 Converter comes with a 5-way terminal block (RS485 side) for easy wire connections. However, you may choose not to use the terminal block provided and simply follow the above table for pin assignments.

RS232 to RS485 converter - DB9 and Terminal Block pinouts
DB-9 Male / Terminal Block (view from front)



USB to RS485 converter - RS485 bus 120 Ohm end-of-line terminator Jumper settings

Important: Turn ON Jumper 120 (120 Ohm End-Of-Line Terminator) at both ends of the RS-485 bus when the data rate is over 19.2kbps or the distance is over 660ft (200m).


USB to RS485 Conveter - Connection



1) Driver installation

USB RS485 Adapter - USB driver installation

Make sure that the USB-RS485 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 to rs485 converter loopback
  • Connect two numbers of the USB-485-1 converters to your PC’s USB ports and connect A+ to A+, B- to B- on the RS485 terminal blocks (as shown above).
  • Run two instances of the 232Analyzer FREE version software on your computer.
  • Select "ASCII" for both the Send and Receive data formats. Then send command and/or string such as "CommFront" from one COM port. You should receive an echo of the command/string sent ("CommFront") on the other COM port. 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.

RS232 RS485 Converter - Loopback test by using CommFront 232Anlayzer software
Screenshot 1: Send commands from 1st instance of the 232Analyzer software

RS232 to RS485 Converter - Loopback test by using CommFront 232Analyzer software
Screenshot 2: Receive commands from 2nd instance of the 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