Models USOPTL4 and USPTL4 are USB to one port RS-422/485 converters. Supporting 2-wire RS-485 or 4-wire RS-422/485 communications, these devices are great for applications requiring long range or multi-drop capabilities. Both models use pluggable terminal blocks on the RS-422/485 side. Two LEDs indicate data transmit or receive. Model USOPTL4 includes circuitry with 2000 Volts isolation protection against ground loops and voltage spikes. Both products draw power from the USB port so no power supply is required.
Simply install the drivers supplied on CD ROM and plug the converter into an available USB port on your computer or USB hub. The device show ups as an additional COM port in the Windows Device Manager, and is compatible with Windows applications.
Universal Serial Bus (USB) has become the connectivity workhorse of today’s PCs, replacing classic serial ports. But many commercial and industrial devices still use RS-422/485 interfaces. To connect these devices to modern PCs you need robust and reliable conversion solutions. USB ports are becoming more common on commercial and industrial equipment such as point-of-sale peripherals, medical devices, scientific instrumentation, laboratory equipment and other devices or in environments where surges, spikes and ground loops are likely to occur.
RS-485 Control
No special software is required to control the RS-485 receiver or transmit line driver. The driver is automatically enabled during each byte transmitted in RS-485 mode. The transmitter is always enabled in RS-422 mode. The receiver is tri-stated during each byte transmitted in the echo-off mode. The receiver is always enabled in the echo-on mode. There are 4.7k Ohm pull-up/pull-down resistors on the RDA and RDB lines. A termination resistor may be added to R16 if needed. See B&B’s RS-422/ RS-485 Application Note (available on our website) for more information on termination and DC biasing of an RS-485 network.
