What is RS-485?

RS 485 is used in most of today's PLCs (Programmable Logic Controllers) and can communicate with other industry standards such as USB... but what is it?

Knowing your tech, what it does, what it can operate with, and what it's best suited for is what this brief overview will assist you with. 

RS 485 Explained 

RS485 is a serial data interface system. It utilizes a variation of serial cables and adaptors. 

What it does is take data from one source, packages it, and then transfers it to another source. Think information between your printer, your computer tower, and your monitor.

This data is in a serial manner. Basically, something is sent and received, and then the receiver can send data to be received. The cycle goes back and forth until the entirety of the information is transferred. 

Now ramp that up about ten notches because RS485 can be full-duplex. Meaning it can handle things like multiple program buses, transmitters, and multiple serial ports all communicating data back and forth to your computer, all through its main serial cables.

This is like having four lines all sending data and then all receiving. Think of something like four assembly lines sending out robot parts, and then the receiver sends back information saying what it needs next, then the next package of parts comes through.

Compared to something like RS232, this is incredibly beneficial. Where RS232 handles one communication pair at a time, RS485 can handle up to 32. RS485 can also send information over distances of 4000 ft, where RS232 can reach about 3 ft max. 

Huge advantage.

RS485 Usage

Mind you, not everything has RS485 built in. Most common household systems like OEM or ODM CPU probably won't, so you'll have to do some manual modifications if you wish to use it. 

Lots of industrial equipment such as PLCs, TTLs devices, network hubs, multi-interface screens, and others utilize RS485 for the ability to send data faster.

For quick modifications and adaption, we'd recommend a USB to RS485 Adaptor. Because USB is so universal, adaptors like this save people from hardware headaches. Just note that a converter might be needed to transfer data from RS485 to a more readable standard like RS232. 

RS485 Performance

As already said, RS485 can send data up to 4000 ft, but at what speed?

A key thing to keep in mind is that the longer the cable, the slower the data. For shorter cables (under 50 meters) look for speeds of around 10/Mbits. 

A good measure established in a TI 485 Overview is the bps data signal rate times the cable length in meters should never go over 10^8.

This is an advantage over interfaces like RS232 where data is being transmitted around 9600 bps. 

Further Information

For the latest on RS 485, modifiers, adaptors, hubs and other tech such as USB 3.1 Gen 2, check out our blog. If you have a specific question pertaining to RS485 and how to integrate it into your company software or personal CPU, feel free to reach out and contact us.