Rs485 and Rs232 are serial communication standards that are very useful in the telecommunication industry. These two serial communicators have been around for a long time. In serial communication, there are several standards. Rs485 and Rs232 are some of these standards.
The serial communication standards are important aspects of the telecommunication industry. In this article, we will focus on Rs485 vs Rs232.
What does Serial Communication mean?
Serial communication is the process of sending data. It involves sending data sequentially over a computer bus or a communication channel. Serial communication is similar to Ethernet or the Universal Serial Bus (USB). Ethernet or USB is available in modern computers. Manufacturing industries connect their devices with the help of serial communication. Rs485 and Rs232 are good examples of serial communication.
In serial communication, you can only send data one bit at a time. This is different from parallel communication that sends several bits of information as a whole. Serial communication is useful for most computer networks. It is an ideal alternative where synchronization problems make parallel communication infeasible.
Serial communication is becoming more popular even at shorter distances. Over time, enhanced signal integrity in more recent serial technologies is better.
Companies prefer serial communication to Ethernet and USB. This is because these two are more complex. Also, serial communication can prevent the collision of data packets. This makes it a better option for linkage systems with many devices.
What is Rs485?
Rs485 also referred to as EIA-485 or TIA-485 is commonly used in technical applications. It is a serial communication standard that serves as a protocol for POS and telecom. Industries use Rs485 when they need to interconnect devices together for a system. This serial communication transmits data between a disk drive and a controller in computer systems.
Rs485 defines the electrical properties of the receivers and drivers for the communication protocol. This serial communication standard has been useful in several computer automation systems. This standard enables multiple devices on the same bus. In theater applications, RS485 is well-suited where devices are across a huge space.
Data transmits through two twisted wires in Rs485 standard. These wires are commonly called Twisted Pair Cable. These wires protect Rs485 against electrical noise. Therefore, Rs485 remains effective in noisy environments.
This serial communication with two wires enables half-duplex data transfer. This implies that data can transmit to and from devices in one direction at a time. While a 4-wire system enables data transmission to and from devices at the same time. This system allows full-duplex data transmission.
Rs485 features 32 receivers and 32 drivers. In this standard, one driver is always active at a time. The Rs485 standard makes use of differential receives and balanced transmit. Therefore, it can’t accept common-mode interference.
Rs485 is ideal when an application requires high-speed serial data communications. This standard offers high-speed data. Rs485 is defined by Electronic Industries Alliance and the Telecommunications Industry Association.
Features of Rs485
Rs485 is great for multi-point interconnection. This standard can save several signal lines. Rs485 can form a distributed system that enables about 32 receivers and 32 drivers in parallel connections.
- The voltage discrepancies between the two lines +2v~+6V is logic 1. The voltage discrepancies between -6V~-2V is logic “0.”
- The interface of Rs485 uses both a differential receiver and a balanced driver. This makes it a great anti-noise performance.
- The interface has a maximum transmission distance of 4000 feet. This is about 3000 meters.
- 10 Mbps is the highest data transmission rate of Rs485
Applications of Rs485
Most times, this serial communication standard is ideal for use in simple networks. It may be linked up in a 2 or 4 wire mode. Many automation and computer systems feature Rs485. It is useful in base stations, home appliances, and robotics. Rs485 is also available in commercial aircraft cabins for low-speed data communications. This is because of the minimal wiring required by Rs485.
With Rs485, you can build a multiple-point data communications network. This standard indicates that a system can use about 32 drivers with 32 receivers. With these features, 32 nodes can both receive and transmit. Using impedance receivers and automatic repeaters can help extend this further. This makes it possible to feature many nodes on a network.
Furthermore, Rs485 drivers can tolerate data collision issues and bus fault conditions. Rs485 is commonly used in factory floors and programmable logic controllers. This standard functions as the physical layer for several standards. It is also used in proprietary automation protocols to incorporate control systems.
For instance, Modbus makes use of Rs485 because of its allowance of many devices on a single network. Modbus is a well-known automation protocol. It allows the integration of several devices from various manufacturers into the main system.
The Rs485 standard also functions in performance venues to regulate lights and systems. It is also used for designing automation as the lengthy cable helps to join remote devices. Rs485 is incorporated to connect the security control panel to devices like access control card readers. This standard is ideal for high speeds and supports multiple devices in a system.
What is Rs232?
Rs232 is a serial communication standard that uses DCE and DTE signals. DCE means Data Communication Equipment while DTE means Data Terminal Equipment. Rs232 is the interface between DTE and DCE using serial binary data exchange. This standard is all about the serial data communication between DTE and DCE.
The computer is a good example of a DTE device. An example of a DCE is a modem. The DTE (computer) serially transmits the data to the DCE (modem). The computer sends binary data “11011101 to the modem. Then the modem transmits binary data “11010101” to the computer.
RS 232, also known as EIA/TIA-232, was developed in 1962. However, it keeps updating to meet the evolving demands of the serial communication industry. Rs232 is widely used despite the availability of Ethernet, USB, and Wi-fi. This is because Rs232 spreads over long distances. Also, it prevents electrical noise and is compatible across various manufacturers.
This standard involves two communication types. These are parallel and serial. Rs232 interprets important timings of signal and the points of the connectors. Rs232 is a method of data transfer across a single wire. It is a standard that defines data transmission between two devices. This standard uses a few wires. Also, it incorporates a serial transfer method in which bytes of data are output onto a single wire.
Data transmission occurs in one direction for every wire. Therefore, you need two wires for bi-directional communication. Rs232 can transmit a byte of data over a serial cable featuring between 3 to 22 signals.
How does RS232 Work?
You can understand the way RS232 works through the protocol format. This communication protocol transfers data in a single direction. There is no clock for synchronizing the receiver and transmitter in this standard. A start bit accompanied by 7-bit binary data initiates the data format.
The transmission of data starts by sending a Start bit ‘0’. After this, there are 7 bits of ASCII data. For the receiver’s approval, the party bit appends this data. The information from the transmitter should be compatible with the receiver. A stop bit halts the transmission and the binary ‘1’ represents it. Generally, you can send 1 or 2 stop bits.
The Rs232 incorporates a process called “handshaking.”. Handshaking involves interchanging data signals between the receiver and the sender. These signals create a communication connection between the receiver and sender. RS232 features two types of handshaking; software and hardware handshaking.
Maintaining good communication between the receiver and sender helps to avoid data loss. The buffer helps to achieve this. It enables both the receiver and sender to store data until it is processed by each other at various speeds. The buffer acts as a temporary storage location.
The hardware handshaking enables the flow and control of data reception and transmission. This handshaking type incorporates control signals like DTR, CTS, RTS, and DSR. The software handshaking makes use of two ASCII characters for start-stop communication. This handshaking uses XOFF/XON characters to regulate serial communication. It uses 3 wires which are signal GND, RXD, and TXD.
Electrical Features of RS232
These refer to the specifications of RS232 in terms of voltage levels and more.
RS232 uses the TTL-specific GND and 5V logic levels. Here, logic “1” falls within the range of -15 volts to -3 volts. Logic “0” is within the range of +3 volts and +15 volts. This means that logic “0” is high voltage while logic “1” is low voltage. An undetermined logic state refers to voltages within the range of -3V and +3V.
This refers to the resistance between the wires DCE and DTE. The line impedance of Rs232 should be from 3Ω to 7Ω. In the Rs232 standard, there are two different cable lengths. The authentic RS232 shows that the maximum cable length should be 15 meters.
This defines how the signal level changes. In the RS232 standard, the greatest slew rate is about 30V/ µs. The slew rate of Rs232 helps to reduce cross-talk with other signals.
The baud rate is the number of binary bits transmitted every second. RS232 standard supports baud rates within the range of 110 to 230400. The baud rate will determine the speed at which the transmitter will send the data to the receiver.
Applications of Rs232
Rs232 is widely used in several applications. They include:
- Demodulator applications
- Handheld equipment
- Modems and printers
- Barcode scanners and POS terminals
- Teletypewriter devices
- CNC controllers
- PC COM port interfacing
Rs485 vs Rs232 – Comparing the Two Standards
Rs485 and Rs232 are both serial communication standards. However, these standards work differently. Here, we will look at the differences between these standards.
Data transmission speed
Rs232 can function at a very short distance. It is also applicable in applications with low data speed requirements. The transmission speed of this standard is 1Mb/s, which is about 15M. On the other hand, RS485 features a transmission speed of about 10Mb/s, which is about 15M. At a maximum distance of 1200M, this standard can only transmit data at 100Kb/s.
Rs485 is widely used in automation and computer systems. This standard is ideal for transmitting data between a disk drive and controller. Also, Rs485 is well-suited for low-speed data communications. Meanwhile, Rs232 is specifically designed to interconnect a modem with a terminal. This standard is ideal for laboratory automating surveying.
For Rs485, the maximum distance is about 1200 meters. This is longer than that of Rs232 which is 15 meters. However, in Rs232, you can extend the length with an exchange with slower data rates. Rs485 is ideal in applications that need to operate at a distance from the transmitter.
Numbers of receivers and transmitters
The serial interface of Rs232 helps to connect only two devices. The Rs485 interface can link up about 32 devices to a transmitter. Also, it is important to know that Rs485 and Rs232 aren’t fixed. Most times, newer equipment makes use of a USB interface. To make various kinds of equipment work together will require conversion. So, there has to be a conversion from USB to these standards or these standards to USB. You may also need Rs485 to Rs232 or vice versa.
Prevention of ground potential and electrical noise
Rs485 serial standard functions on a different voltage system. This enables Rs485 to feature a higher noise immunity level. Also, the differential voltage system enables Rs485 to feature lower voltage use.
Meanwhile, RS232 functions on a system that operates when there are minimal differences in ground potential. However, RS232 is very weak and enables data corruption in a noisy environment.
Rs232 and Rs485 are great serial communication standards. However, these two standards have different functions. In this article, we have compared Rs485 vs Rs232. Both Rs485 and Rs232 are widely used in computer systems and robotics. These standards have their disadvantages and advantages. However, you can choose any of them based on the project’s requirements.