RS485 converter-bringing about radical changes!
To enable personal computers to connect with RS485-compliant devices on industrial automation networks USB to RS485 converters are often used, such as factory floor automation, video surveillance cameras and door security card readers. The use of multiport repeaters allows construction of very large RS485 star topologies although the RS485 specification recommends a default topology based on ‘master-slave’ point-to-point or multi-drop configurations. To assist with monitoring and control tasks it’s into these kinds of networks that a variety of USB to RS485 converters can be deployed. RS232 TO RS485 is also being increasingly used.
To connect with a single RS485 interface the simplest converter allows a single USB interface. These converters support Windows, Mac and Linux device drivers although basic in functionality. There are usually few device or resource conflicts are meant by plug and play installation.
Two, four or more switch-selectable RS485 / RS422 interfaces and support point-to-point and point-to-multipoint configurations are available in multiport USB to RS485 converters. The converter is fully plug-and-play with automatic send data control and auto speed detection and no external power supply is required. With a choice of RS232, RS422 or (two-wire, half duplex) RS485 interfaces some multiport converters also come.
Allowing easier connection of cable or even individual wires many of these converters have a standard 9-pin D-Sub male connector and some also have an optional screw terminal board. Accessories such as gender-changers, DB-9 to DB-25 adapters and DB-9 to RJ-45 adapters many manufacturers also provide.
One area of concern is with Microsoft’s Vista and Windows 7 operating systems and low-cost USB to RS485 adapters as mentioned earlier in this article. In many cases for serial communications, the processor chip hardware simply does not meet the industry standard requirements and by the way in which these newer operating systems expect communications to be handled at the hardware level, this weakness has been exposed.
Interacting poorly with the specific combination of Windows 7/Vista, software update packs RS232 and RS485 peripherals in use on a particular system is another limitation is the supplied driver software itself. Showing up as computer freezes and COM-port connection problems, the end result is often low-level timing errors. A low-end processor chip may work fine on one computer but not on another computer with an almost identical hardware and software configuration which is the annoying aspect. It is a tedious and slow process to troubleshoot the resulting errors.
Using USB to RS422 converters is the solution to this problem that have been hardware and software-optimized to support Vista and Windows 7. When these converters are to be used in less forgiving industrial automation environments this is especially important. Thus this new advance in the technology has brought about a radical change.