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USB to RS485 Adapter

Model USB-485B

Category: USB to RS232 / RS485 / RS422 Adapters


The USB-485B is a bi-directional USB-powered RS485 to USB converter with built-in 120 ohm termination option, which makes a half-duplex RS485 available to a PC via the USB port. The USB-485B has a DB9 male connector on the RS485 port, and a USB type A female on the USB port. The adapter is powered from the USB port and no external power is needed. USB cable, terminal block, and drivers are included in the package. This converter operates from 300 to 1 mbps.

The USB-485B uses the latest FTDI chipset and is fully compatible with (32 /64 bits) versions of Windows 11, 10, 8.1, 8, 7, Vista, XP, and 98: Windows Server 2022, 2019, 2016, 2012 R2, 2012, 2008 R2, 2008, 2003 R2, 2003 Mac 10.3 â€" 10.15, and Linux.


  • Plug-and-Play (Hot-pluggable)
  • Adds One RS-485 Port Using One USB Port
  • Optional Terminal Block Included
  • Built-in Optional 120 Ohm Termination
  • USB 1.1 and 2.0 Compatible
  • Port Powered - No External Power Needed
  • Supports 300 baud to 1 mbps
  • 3 Feet (1m) Cable for Convenience
  • Transmit/Receive LED Indicators
  • Data Direction Auto-turnaround - No Flow Control Necessary
  • Internal 128/385 Byte TX/RX Buffers
  • No IRQs, IO, DMA Required. No IRQ Conflicts
  • Supports Remote Wakeup and Power Management
  • Easy to Install Included Drivers
  • Built-in 600W Surge and 15KV Static Protection
  • 5 Year Manufacturer's Warranty
  • RoHS 3, CE, FCC and REACH Certified
USB to RS485 Adapter
USB to RS485 Adapter
PRICE: $29.95


30 Day Money Back Guarantee!

5 Year Replacement Warranty!



Our internationally recognized ISO 9001:2015 Quality Management System (Cert. No. 743003912) with a scope of “Design, Sales, Distribution of Data Communication and IT Support Services“ was recognized and certified by TÜV Rheinland of North America known for its very demanding and stringent requirements. For more details see our Quality Policy.

STANDARDS: USB 2.0 and 1.1 Standards - RS-485 Standard
OPERATING SYSTEM: Windows 8.1 (32/64), Windows 8 (32/64), Windows 7 (32/64), Vista (32/64), Server 2012, Server 2008 R2, Server 2008, Server 2003, XP (32/64), 2000, 98Se, CE, Mac 8/9/X, Linux and Android
BAUD RATES: From 300 baud To 1 mbps
CONNECTOR TYPES: USB Side: Type A Female and RS-485 Side: DB9 Male or 3 Position Terminal Block
DISTANCE: USB Side: 10 ft (3m) and RS-485 Side: 4000 ft (1.2m)
LED INDICATIONS: RS-485: TX (Red) and RX (Green)
DRIVERS: FTDI drivers are included in package
POWER SOURCE: Port Powered From USB Port
STATIC PROTECTION: 15KV Electric Static Discharge (ESD) Protection
SURGE PROTECTION: 600W Surge Protection
WEIGHT: 2.7oz (76 grams)
DIMENSIONS: RS-485 Housing Without Terminal Block:
.98 X 1.43 X 0.72 in (50.2 X 36.2 X 18.2 mm)
RS-485 Housing With Terminal Block:
3.03 X 1.43 X 0.72 in (76.9 X 36.2 X 18.2 mm)
OPERATING TEMP.: 14ºF to 140ºF (-10ºC to 60ºC)
STORAGE TEMP.: -40ºF to 185ºF (-40ºC to 85ºC)
OPERATING HUMIDITY: 5% To 95% - No Condensation
PRODUCT SAFETY: CE, FCC and RoHS Conformance Certified
QUALITY MANAGEMENT: Manufactured and Distributed to ISO 9001:2015 QMS
RELIABILITY: Low Failure Rate - 99+% Reliability Since Inception
WARRANTY: 5 Year Replacement Warranty

RS485 Side DB9 Male or 3-way Terminal Block

Signal D- D+ GND
Pin # 1 2 5
Function D- D+ GND


The USB-485-B terminal block has an optional built-in 120 ohm termination. 120 ohm termination is an advanced feature typically used to reduce noise and signal reflections. It is recommended to use 120 Ohm termination if you are exceeding 600 feet in distance, 19.6K baud or in a noisy environment. The terminal blocks are shipped with 120 Ohm termination off but can be turned on using the convenient jumper setting located on the left bottom of the terminal block.

3 Position With 120 Ohm Off

3 Position With 120 Ohm On

Using two USB-485B units:

  1. Check that all connections comply with the connection diagrams.
  2. Perform a loop back test on two units:
    1. Connect the D+ to D+ and D- to D- on the USB-485B RS-485 ports.
    2. Connect the two USB connectors to the USB ports of the computers.
    3. Install the USB-485B FTDI driver on the computer per instructions provided.
    4. Running hyper terminal programs on both PCs, send ASCII characters to the USB-485B converter from one PC port, and check that the characters are received at the 2nd PC port. Repeat the test in the opposite direction. This tests that the transmit and receive functions of both USB-485B units are working properly.
    5. When there is constant RX data you should see the GREEN light blink. When there is constant TX data you should see the RED light blink.

Download FREE FULL VERSION AccessPort Advanced Serial Monitor, Simulation and Data Analysis Software Tool. This software tool is great for testing converters. Supports Windows 98/XP/VISTA/WIN 7/WIN 8/WIN 10.   DOWNLOAD SOFTWARE AND USER MANUAL

Below are some of the USB to RS485 Adapter applications.



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