Introduction

Serial communication is a common method of transmitting information sequentially or bit by bit between a computer and peripheral device.  Several digital types of equipment, such as RS-232 and RS-485, are useful in supporting serial communications. Chen & Zhang (2015) defines RS-232 as single-ended a standard that increases communication distance in low serial communications with low speed.  According to Osisiogu (2015), RS-232 is a form of serial communication that transmits data that defines the signals that connect data terminal equipment (DTE) like computer terminal data circuit-terminating equipment (DCE) like the modem. The RS-232 is mainly applied in computer serial ports.  However, Osisiogu (2015) states that RS-485 is a standard serial communication method that defines the electrical of receivers or drivers used in digital multipoint systems that are balanced.  Equally, according to Grofu & Cercel (2014), RS-485 is the only serial communication interface with the capacity to internetwork with any transmitters and receivers in a similar network.

According to Chen & Zhang (2015), RS-232 used unbalanced transmission, and it has limited communication distance; thus, it enables local communication between devices. The transmission of data is low and the line used has an approximated maximum length of 20m (Alicke et al.,2000). The shorter distance and vulnerability to network jamming makes it difficult for RS-232 to send messages continuously. The highest of nodes in RS-232 is one, and it unidirectional. Conversely, in RS-485, the transmission is balanced, and it has more connection points, which allow the transmission of data for a longer distance. According to Xunwen et al. (2010), it allows data transmission at the rate of 35mbs and more, and lines lengths or distances of 1200 m. Thus, RS-585 is common in controlling and monitoring systems. It can continuously send timed messages and receive messages at any time from the host computer. Besides, the maximum number of nodes is 32, and it is bi-directional.

Furthermore, Alicke et al. (2000) point out that at the driver output, the RS-232 has a higher signal amplitude of more or less than 5 V to 15 V. The triggering of the receiver occurs when it senses the electrical input is less than -3 V or more than 3 V (Alicke et al., 2000). The maximum signal slope is 30 V/μS.  According to Tanghe (2011), RS-232, regarding ground levels, its signals are driven on a single wire, and thus, its line of operation is simplex or full-duplex. The wire has two serial pins; the transmitter and the receiver.  In contrast, the RS-485 requires the drivers to have a minimum output voltage of 1.5 V with 32 unit loads of approximately 12KΩ (Alicke et al., 2000). The bus voltage levels vary from -7 V to 12 V, and the receivers may be sensitive to determine the bus’s state (Xunwen et al., 2010). Tanghe (2011) also reveals that RS-485 has one or more pairs of wires or differential configuration.  The line of operation for RS-485 is a full-duplex.

According to Osisiogu (2015), RS-232 is used to connect data storage, modems, mice, uninterruptible power supplies, and printers. Besides, Alicke et al. (2000) point out that RS-232 plays a role in defining the interface’s physical layer, the appropriate connectors such as 25-pin D-type, and the protocols. On the contrary, Osisiogu (2015) also states that RS485 is used in a wide range of automation systems and computers.  It plays a significant role in enabling low-speed communications in commercial aircraft because it requires minimal wiring, which decreases the weight within the aircraft (Osisiogu, 2015).). Additionally, Alicke et al. (2000) point out that the differential transmission form of RS-485 enables it to resist corruption by electrical noise. It is also resistant against potential shifts between nodes in the ground. Thus, the interface is useful in areas that require reduced noise emissions. The RS-485 can also thrive in harsh surroundings or the environment, and it can also resist electromagnetic interference caused by welding equipment and motors (Osisiogu, 2015).

Therefore, RS-485 is the best interface for use in serial communication. Its differential signaling capability enables it to transmit data for longer distances than RS-232.  It is also immune to noise, making it a suitable option in environments that require less noise or are susceptible to excess noise. Thus, it can be used in places like process control plants and factories. Its emissions are low-radiated and less harmful. Xunwen et al. (2010) reveal that the anti-jamming and distance communication properties of RS-485 have made it a potential option for full-duplex communication, which involves the simultaneous transmission and reception of information between end-devices.  The authors reveal that experiences have been carried out that show the interface can be reliably used for full-duplex communication (Xunwen et al., 2010). The interface also enhances power saving because it can operate with a voltage of three. The interface also has a short response time between the sender and the software being used, and the communication tie is also shorter than that of RS-232 (Chen & Zhang, 2015). However, the RS-485 requires unique types of cables to operate, which may be expensive to acquire.

References

Alicke, F., Bartholdy, F., Blozis, S., Dehemelt, F., Forstner, P., Holland, N. and Huchzermier, J., 2000. Comparing Bus Solutions. Application Report, Texas Instruments, SLLA067, 67.

Chen, Z., and Zhang, W., 2015, July. DSP Serial Communication Application Design. In International Conference on Logistics Engineering, Management and Computer Science (LEMCS 2015). Atlantis Press.

Grove, F., and Cercel, C., 2014. RS485 COMMUNICATION SYSTEM. Annals Constantin Brancusi’University of Targu-Jiu. Engineering Series, (3).

Osisiogu, U., 2015. A Seminar Paper on Serial Communication in Arduino. NNAMDI Azikiwe UNIVERSITY, AWKA. https://www.academia.edu/13190556/A_Seminar_Paper_on_Serial_Communication_in_Arduino

Tanghe, S.,2011, Multiprotocol Transceivers Combine RS485 and RS232 in a Single Device to Simplify and Shrink Applications that Use Both Standards.

Xunwen, S., Shaoping, W., Dongmei, Z. and Zhu, Q., 2010, January. RS-485 serial port pseudo-full-duplex communication research and application. In 2010 Prognostics and System Health Management Conference (pp. 1-5). IEEE.