RS485 is a standard for use in serial communications systems. Electrical signaling is balanced, and multipoint systems are supported. This communication standard is used in a wide range of computer and automation systems. RS-485 is used as the physical layer underlying many standard and proprietary automation protocols used to implement Industrial Control Systems, including the most common versions of Modbus and Profibus, also used in building automation as the simple bus wiring and long cable length is ideal for joining remote devices. It may be used to control video surveillance systems or to interconnect security control panels and devices such as access control card readers.
In this article I will show how to build simple and reliable USB to RS485 adapter with galvanic isolation and ESD protection.
Take a look at the second version of this adapter.