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RS232 Versus RS485: Which Is Better, RS232, or RS485?

The comparison of RS232 versus RS485 is not new. Hence, it’s an old contest that has been around for a while now. And it’s because RS232 and RS485 are one of the first serial interfaces.

Nonetheless, engineers still use them today. Plus, they come in handy for measurement and control devices. Also, these interfaces are one of the easiest-to-use and cheapest.

But that’s not all.

Most engineers find it hard to understand the difference. As a result, there’s a lot of confusion. But it shouldn’t be, especially if you’re a PCB engineer.

That’s why we created this article to clear the air. Also, we want new engineers to spot the difference between the interfaces with ease.

So, if you’re ready to find out about these interfaces, keep reading.

1. What Is RS232 Used For?

RS232, in telecommunications, stands for Recommended Standard 232. Hence, RS232 first came into existence in 1960. Also, the founders invented it for conveying data via serial communication.

Besides, that’s not all.

Officially, the interface helps to define signals linking a DTE and a DCE. Thus, in this case, a DTE represents data terminal equipment. And the DCE stands for data circuit-terminating equipment. Also, another name for a DCE is data communication equipment. Thus, an excellent example where such linking happens is in a modem.

Source – Wikipedia

The RS232 also defines a standard for certain factors. Hence, it establishes the timing of signals, electrical features, and the meaning of signals.

Plus, there’s more.

RS232 defines the pinout of connectors and their physical scope.

The most recent version of this interface is TIA-232-F. Also, it first existed in 1997. This current version interfaces between DCE and DTE. Plus, it employs serial binary data interchange.

Today, we see the RS232 standard in PC serial ports. In short, you can find most of it in industrial communication devices.

Also, at some point, the RS232 was a standard feature for most computers. Then, you’d see their application in serial ports. Plus, PC makers used the RS232 for connections. So, they weren’t for only modems.

Beyond that, some PC makers used them for PC mice, printers, etc. In short, you could even see them in PC power supplies. Generally, computer producers used them in peripheral devices.

History of RS232 (How It All Started)

The Electronic Industries Association first introduced RS232 in 1960. So, that year, the body made RS232 a “recommended standard.”

Also, the very first DTEs were teletypewriters. And back then, they were electromechanical. Furthermore, the pioneer DCEs were modems. So, when electronic terminals were in vogue, they designed them to be teletypewriters. Plus, they were all RS232 compliant.

But that’s not all.

Back then, the designers that used the RS232 standard termed it “strange.” Why? It’s because the interface didn’t foresee the need for some devices. Thus, an excellent example of the devices are printers, POS terminals, etc.

Also, the interface faced common bottlenecks. Hence, these bottlenecks frustrated a lot of designers back then. So, what were these bottlenecks in particular? For example, they had a non-standard pin installation of circuits on connectors. Or even misplaced or incorrect control signals.

As if that wasn’t enough, there was a lack of adherence to the standards. So, this issue gave birth to breakout boxes. Also, test equipment, patch boxes, etc. thrived at this time.

Thus, their goal was to help engineers connect unequal equipment. Fortunately, these new devices helped in salvaging the issues.

In brief, the general digression from the standard was to help engineers do one thing. And it was to drive signals at a lower voltage.

Source – Wikipedia

The Scope of the RS232 Standard

The RS232 standard got enacted in 1969 by EIA. Hence, it has four standard rules, which are:

1. First, the Interface mechanical features, pin identification. Besides, they are pluggable connectors.

2. Second, there are standard subsets of interface circuits. Plus, they are for specific telecom applications.

3. Third, it supports every circuit in the interface connector.

4. Finally, there are electrical signal features. And they are timing, signaling rate, slew-rate of signals.

So, here’s the kicker.

The standard doesn’t define a few elements. So, these elements are character codes like EBCDIC, ASCII, etc. And it doesn’t show the error finding protocols. Also, there are undefined elements like character framing and conveying order of bits.

2. What Is RS485 Interface?

Also known as TIA-485(-A), RS485 is a standard. So, it defines the electrical features of receivers and drivers. Plus, it’s useful in serial communication systems.

Furthermore, it has an electric signaling that supports two systems. Hence, these particular systems are multipoint and balanced.

An RS458 three-wire connection

Source – Wikipedia

Also, TIA and EIA are the bodies responsible for the existence of the standard. Plus, engineers use it because it works well in two situations. Firstly, the standard functions well over long distances. Second, it works perfectly in electrically noisy areas.

But that’s not all.

Multiple receivers work well with the RS485 interface. And it’s because they get connected in a multidrop bus and linear network.

Hence, these features make RS485 perfect for industrial control systems.

Also, RS485 works well for affordable local networks. Hence, engineers use similar differential signaling over RS422 (a twisted pair).

But here’s the kicker.

RS485 interface uses three-stage logic. Plus, it allows individual transmitters to get deactivated. So, this logic system enables RS485 to use linear bus topologies. And it works with ONLY two wires.

Also, the equipment found in a set of RS485 wires is nodes. Plus, some engineers know the nodes, devices, or stations of the RS485.

In short, the ideal arrangement for the nodes is point-to-point. Plus, these nodes(multidropped) can be a line or bus. Therefore, the nodes aren’t stars or rings. Hence, star and ring topologies aren’t ideal. And it’s because it has signal reflections. Also, it has extreme termination impedances.

3. What’s the Difference Between RS232 and RS485?

Now, we have gotten to the big question. So, what exactly makes RS232 different from RS485?

We’re going to make it easy for you to find out. Hence, we’ll start with the key features.

3.1 RS485 vs. RS232: Key Features

3.2 The Major Differences Between RS232 and RS485

They are as follows:

3.2.1 Maximum Range of Operation

The max range of operation for RS232 is 50 feet. Besides, the length is extendable with low data rates. And it’s 4000feet for RS485.

3.2.2 The Number of Receivers and Transmitters

RS232 is ideal for connecting two devices. But, RS485 connects 32 devices.

3.2.3 The Ground Reference Latent and Electrical Noise

RS232 is too fragile and allows data corruption. In contrast, RS485 accounts for no data corruption. And it’s because it has a more extended data transfer capacity.

3.2.4 Speed of Data

RS232 has a data speed of 1 Mbps up to 50 feet. But, RS485 transfers data at 10 Mbps at a max distance of 4,000 feet.

4. RS232 versus RS485: Advantages and Disadvantages

No doubt, when it comes to serial interfaces, the RS485 and RS232 are standard. But, the serial interfaces should be able to specify three things. The three things are timings, the transmission of logic levels, and data rates.

And like most devices, each of these protocols has its benefits and drawbacks.

RS232 Devices

Pros

1. The RS232 terminal is quite affordable.

2. The terminal supports a lot of compatible legacy devices. And it’s all thanks to the terminal’s simplicity. Plus, the RS232 is useful for point-to-point connection. An excellent example is a connection between DCE and DTE devices.

3. When it comes to long distances, RS232 supports about 50 feet. But, this distance applies to low baud rates. Also, the device has error connection capabilities.

4. RS232 has +/-5 Volts or higher. As a result, the device is immune to noise.

5. The adaptors or converters to convert RS232 to Ethernet/RS485/USB etc. are easy to find.

6. Its mode of operation is full-duplex.

Cons

1. The protocol has an unbalanced transmission.

2. RS232 works best for only system-to-system communications. So, it isn’t ideal for the chip to sensor device communications. Or even for chip-to-chip communications.

3. At long distances, the RS232 can only support lower speed. So, if you want a higher rate, you can only get it at short distances.

4. Usually, the RS232 device needs a separate transceiver chip. Consequently, it adds cost to the system.

5. The RS232 isn’t a good option for the single master-multiple slave setup. Instead, it applies to only the single-master and single-slave mode.

6. The power consumption of the RS232 tends to increase.

7. RS232 has low bandwidth.

RS485

Pros

1. At a distance of about 1200 meters, the RS485 supports a maximum transmission speed of 100Kbps. And this is a result of its differential signaling.

2. If the readers or controllers are communicating on the same data line, the response time is short.

3. When you compare RS485 to I2C protocol, its communication is faster.

4. The interface is resistant to noise. And it’s because of its differential signaling.

5. It has a balanced transmission line. As a result, RS435 supports multi-stations

6. It’s possible to connect so many devices to the RS485. For instance, you can connect 32 devices. And you can achieve this with an input resistance of 12kΩ.

7. With the RS485, you can inter-network multiple receivers in the same network. Transmitters aren’t left out as well.

Cons

1. With the RS485 interface, you can’t use ordinary cables. So, you have to opt for special cables.

2. The protocol can’t transfer a large amount of data at about 115.2 Kbps speed. And it’s because the device loses data at such a high rate. So, it’s ideal for transferring data at 56.2Kbps. But, it will take a longer time for the transfer.

3. It needs about four wires for its multidrop mode. And it’s unlike the RS232 that requires only two wires for its point-to-point method.

4. It isn’t easy to back up your system with the RS485.

5. You can only use a single node to transmit data at a time.

6. The protocol’s mode of transmission is half-duplex.

5. RS232 Versus RS485: Examples of Devices that Use RS232 and RS485

It’s time to dig into the devices that use each of the protocols. After all, you’re already familiar with the pros and cons of RS232 and RS485.

RS232 Devices

D-subminiature

Also known as D-sub, the device name comes from its shape. It has two or more parallel rows of sockets surrounding a D-shaped metal shield.

A male D9 connector

Source – Wikipedia

13W D Male connector

Source – Wikipedia

The metal shield ensures the correct orientation. And it provides mechanical support. Also, the guard may shield against electromagnetic interference. The connectors on this device have gender. The female connectors are the socket contacts. In contrast, the male connectors are the parts with pin contacts.

There are 4-40 jack screws on the panel mounted connectors. And they accept screws on the cable end connector cover. Also, the cable end connector cover helps to lock the connectors together.

PCI Express

PCI Express with RS23 port

Source – Wikipedia

This device communicates through a link. And the link refers to point-to-point communication. Besides, you can find this between two PCI Express ports. After all, it allows them to receive ordinary PCI requests. Also, the link could have one or more lanes.

If it has a single lane, it’s a low-speed peripheral. And a good example is an 802.11 Wi-Fi card. A graphics adapter is an example of a high-speed peripheral with 16-lane.

RS485 Devices

Grove

Source – Wikipedia

The grove is an easy-to-connect device. So, it allows for plug and play. Plus, you can even use it for your Arduino connect.

Industrial USB

Source – Seed

This USB comes with the original FT232RL inside. Also, it features some protection circuits. Examples of the protection circuits are TVS diode, lightning-proof, etc.

The small device is relatively easy to use. Plus, it allows for automatic transceiving. And it has fast safety functions, communication, and stability. So, it’s best for applications with high communication needs.

Closing Words

RS232 VS RS485: which is best for you? Well, it all depends on your project and needs.

So, if you want a simple solution for connecting two devices over a short distance, RS232 is ideal.

Besides, if you prefer a solution that involves having multiple receivers on your network, opt for the RS485.Which of the protocols do you plan to use? So, do you have questions about any of the devices? Feel free to reach us.

Hommer
Hi, I am Hommer, the founder of WellPCB. So far we have more than 4,000 customers worldwide. Any questions you can feel free to contact me. Thanks in advance.

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