1 Description
The USB-RS485-PCB is a USB to RS485 level serial UART converter PCB incorporating FTDI‟s FT232RQ
USB to Serial UART interface IC device which handles all the USB signalling and protocols. The PCB
provides a fast, simple way to connect devices with a RS485 interface to USB.
Each USB-RS485-PCB contains a small internal electronic circuit board, utilising the FT232R plus a USB
type-A connector. The FT232R datasheet, DS_FT232R, is available at http://www.ftdichip.com. The
integrated electronics also include an RS485 transceiver plus Tx and Rx LEDs which give a visual
indication of UART traffic.
The PCB is USB powered and USB 2.0 full speed compatible. Each PCB supports a data transfer rate up to
3 Mbaud and 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
PCB. Further information and examples on this feature are available at http://www.ftdichip.com under
FTDIChip-ID Projects.
The USB-RS485-PCB requires USB drivers, available free from http://www.ftdichip.com, which are
used to make the FT232R on the PCB 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 PCB though a DLL. This is illustrated in the Figure 1.1.
2 Typical Applications USB to Serial RS485 Level Converter. Upgrading Legacy Peripherals to USB. Interface Microcontroller UART or I/O to USB. Interface FPGA / PLD to USB.
USB Instrumentation PC interface. USB Industrial Control. USB password protected file transfers.
2.2 Features USB-RS485-PCB provides a USB to RS485 Serial UART interface. Entire USB protocol handled by the electronics on the PCB. EIA/TIA-485 interface with low power requirements. UART interface support for 7 or 8 data bits, 1 or 2 stop bits and odd / even / mark / space / no parity. Data transfer rates up from 300 baud to 3 Mbaud. Internal EEPROM with user writeable area. FTDI‟s royalty-free VCP allow for communication as a standard emulated COM port and D2XX „direct‟ drivers provide DLL application programming interface. Support for FT232R FTDIChip-ID™ feature for improved security. PCB is USB Powered – no external supply required. X-On / X-Off software handshaking Low USB bandwidth consumption. UHCI / OHCI / EHCI host controller compatible. USB 2.0 Full Speed compatible. -40°C to +85°C operating temperature range. RoHS compliant ESD Protection for RS-485 I/O‟s
±15kV Human Body Model (HBM)
±15kV EN61000-4-2 Air Gap Discharge
±8kV EN61000-4-2 Contact Discharge