Copyright © 2010 Future Technology Devices International Limited

1

Document Reference No.: FT_000117

USB TO RS485 SERIAL CONVERTER CABLE Datasheet

Version 1.4

Clearance No.: FTDI

#75

1 Description

The USB-RS485 cable is a USB to RS485 levels serial UART converter cable incorporating FTDI‟s

FT232RQ USB to serial UART interface IC device which handles all the USB signalling and protocols. The

cable provides a fast, simple way to connect devices with a RS485 interface to USB.

Each USB-RS485 cable contains a small internal electronic circuit board, utilising the FT232R, which is

encapsulated into the USB connector end of the cable. The FT232R datasheet, DS_FT232R, is available at

http://www.ftdichip.com. The integrated electronics also include the RS485 transceiver plus Tx and Rx

LEDs which give a visual indication of traffic on the cable (if transparent USB connector specified).

The other end of the cable is bare, tinned wire ended connections by default, but can be customised

using different connectors to support various applications.

The USB-RS485 cable is designed for use at the end of an RS485 network up to approximately 10m. For

longer networks or placement of the USB-RS485 cable in the middle of an RS485 network it is

recommended that the attached wire is cut to 20cm or less to ensure signal integrity

Cables are FCC, CE, RoHS compliant.

The cable is USB powered and USB 2.0 full speed compatible. Each cable is 1.8m long and supports a

data transfer rate up to 3 Mbaud. Each cable supports the FTDIChip-ID™, with a unique USB serial

number programmed into the FT232R. This feature can be used to create a security or password

protected file transfer access using the cable. Further information and examples on this feature are

available at http://www.ftdichip.com under FTDIChip-ID Projects.

The USB-RS485 cables require USB drivers, available free from http://www.ftdichip.com, which are

used to make the FT232R in the cable appear as a virtual COM port (VCP). This then allows the user to

communicate with the USB interface via a standard PC serial emulation port (for example TTY). Another

FTDI USB driver, the D2XX driver, can also be used with application software to directly access the

FT232R on the cable though a DLL. This is illustrated in the Figure 1.1

TTY

USB

USB_RS485

Virtual COM Port

Software application access to USB via D2XX

USB

TTY

Wire Ended

Customised connectors

Various Connector

Options

Wire Ended

Various Connector

Options

Customised connectors

Figure 1.1 Using the USB-RS485 Cable