USB to RS485 Interface Converter

USB to RS485 Interface Converter

The USB-2-RS485 device is an USB to RS485 interface converter. It adds a standard 2-wire half-duplex RS485 bus interface to computers with USB interface.

The USB interface of the device is USB 2.0 and USB 1.1 compatible. The RS485 interface supports all common data rates up to 3Mbit/s. No additional power supply is required as the device is powered through the USB bus.

This device is supported by all major operating systems: Windows, Linux, Mac OS X and Android.

A virtual COM port driver is included, that is, the RS485 interface can be accessed as a standard serial COM port e.g. using any terminal program like HyperTerminal (supplied with all versions of Microsoft Windows).

2. USB TO RS485 INTERFACE HARDWARE

2.1 OVERVIEW

The device has two connectors. First connector is USB type B for connection to PC. Second connector is 8-pin connector for connection to RS485 bus.

Figure 1: overview

2.2 CONNECTORS

2.2.1 USB

The USB interface is a USB 2.0 full speed (12Mbit/s) device interface which is USB 2.0 and USB 1.1 compatible.

Table 1: USB type B connector, pin assignment

2.2.2 RS485

RJ45 connector is used to connect devices with a RS485 bus, as well as the power devices on the bus if necessary.

Table 2: RJ45 connector, pin assignment

If the another device which is connected to the RS485 bus has its own power supply, then use a wire 4, 5 and 6 only. The wires 1, 2 and 3 are used to power other devices connected to the RS485 bus. The supply voltage of these devices must be 5V.

The following figure shows the connection of devices to the RS485 bus.

Figure 2: devices connection

One terminator is built into device, and the other is placed at the end of the RS485 bus. Use the UTP cable to produce the RS485 bus. RS485 signal is transmitted over the twisted pair wires (blue white-blue).

2.3 TECHNICAL DATA

2.3.1 USB

• Connection to USB 1.1 or USB 2.0 hosts possible

• USB full speed device (12MBit/s)

• Bus powered (no extra power supply needed)

2.3.2 RS485

• Half duplex communication mode

• No loopback (receiver is switched off while transmitter is active)

• 120 Ω termination resistor

2.3.3 HOUSING

• Plastic housing

• Dimensions: 80 x 40 x 20 mm.

3. DRIVER INSTALATION

USB to RS485 device uses the FTDI chip drivers which can be obtained at: http://www.ftdichip.com/Drivers/D2XX.htm

After installing the FTDI drivers the device is registered as USB Serial Converter.

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