We make use of USB ports very frequently in our daily life for transferring photos from digital camera, for transferring files from smartphone to computer or vice-versa. Even, you have also heard a term ‘Serial port’. But, we don’t know exactly what USB port and Serial ports are? So, here are some information about these ports.
What is USB Port and Serial Ports in Computers?
A Serial port is an asynchronous port on the computer used to connect devices serially to the computer. It is a serial communication interface through which port is capable of transmitting one bit at a time. The serial port is found at the back of the computer and it is a part of motherboard. Serial port is used for connecting various hardwares like mouse, modem, network, printer, etc,.
Since, serial port can transmit only a bit at a time, it takes a lot of time to complete its task. So, to overcome its limitations USB is introduced which is faster and therefore serial ports are now rarely used as compared to how often they have been used in the past.
USB is an abbreviated form of Universal Serial Bus. A USB is a standard cable connection interface between personal computers and electronic devices of consumer. USB allows the USB devices to be connected to each other and transfer digital data over the cable. It can also supply electric power to the device that needs it like your mobile phone. USB is very user- friendly. There is no need to turn off the computer for installing the device. USB has the rate of data transfer 12 Mbps for disk-drives and 1.5Mbps for devices that need less bandwidth. Many computers have additional USB ports located on the front along with two standard USB ports at the back.
How USB and Serial ports are different?
Any computer that we buy today comes with one or more USB connectors. These USB connectors enables the connection of mice, printers, scanners, joystick and many more devices to the computer quickly and easily. The installation of device driver is also very fast and easy because the operating system supports USB. When you insert the plug of a USB device into USB port it causes the operating system to immediately search for a profile of the device in its driver. If the operating system cannot find appropriate driver then it is needed to be installed. It is installed only once, and next time the computer will able to find the driver od the device next time . Once, identification of device is done, data is transferred from the computer to device or vice-versa at maximum rate. Data can also be sent to printers via USB, and entire files can be transferred to and from hard drives and other storage devices.
Serial port takes a byte of data and transmits all the 8 bits of a byte, one bit at a time. So, Serial port requires only one wire to transmit the 8 bits one by one. Before transmitting each byte of a data, serial port sends a start bit, which is 0. After each byte of a data, it sends a stop bit to indicate that that the byte is complete. Serial ports depends on special controller chip, UART (Universal Asynchronous Receiver/ Transmitter). The UART takes the output parallely of the computer’s system bus and transforms it into a form that can be transmitted through serial port. Most UART chips have a built-in buffer from 16 to 64 kilobytes, in order to function faster. When buffer is processing data going out to the serial port, it enables the chip to cache data coming in from system bus. Serial ports are also known as communication (COM) ports. They are bi-directional i.e., it allows each device to receive as well as transmit data. Serial devices have different pins to transmit and receive data. If we use same pins then it would limit the communication such that information could only travel in one direction at a time. Using different pins enables communication such that information can travel in both the direction at a time.
How USB and Serial ports are different?
The differences between USB and Serial ports are given below:
|USB Ports||Serial Ports|
|USB port has the rate of data transfer 12Mbps for disk drives and 1.5Mbps for the devices that needs less bandwidth.||Serial port is capable of transmitting only 1 bit at a time with rate of data transfer of about 57kbps.|
|In many computers, additional USB port is found on the front along with two standard USB ports at the back.||Serial port is found at the back of the computer and it is a part of motherboard.|
|USB port transmit data very fast. So, it is now commonly used by the people.||Serial port transmit data at a very slow rate. So, serial ports are now rarely used.|
|USB devices can be used across multiple platforms. It works on Windows, Mac and can be used with other operating systems too.||Serial Ports are a part of the motherboards abd its functionality is depend on its OS drivers but it is not so easy to operate as USB Port|
|There is no need to turn off the computer for installing the devices. You can simply plug in and do your work.||In case of Serial port, it causes problems in installing the devices if computer is not turned off.|
|USB ports are user-friendly. Now OTP is supporting Android with USB pen drive.||Serial ports are not user-friendly as compare to USB Ports .|
Reference Book for Port Programming
There are some good reference books for port programming given below:
- The Windows Serial Port Programming Handbook
Publisher – Auerbach publication
This book explains the principles and methods of developing serial port interfaces using multiple languages. The serial interface programming allows to develop interfaces and apply them in real-world applications.
- Serial Port Complete: Programming and circuits for RS-232 and RS-485 with disk
Publisher – Lakeview Research
This book covers everything from basic electrical and physical parameters, cables and basic architecture to programming for PCs. It contains everything about the serial ports and network project.
- Serial Port Complete: COM ports, USB Virtual COM Ports for embedded systems.
Publisher – Lakeview Research, U.S.
PC COM Ports, USB ports, ports in embedded system are all illustrated in this book. It includes some topics like- upgrading RS-232 designs to USB or wireless networks and creating serial networks of embedded systems and PCs.
Enjoy Learning …….
This Article was originally submitted by Ms. Prachi Sinha pursuing B.Tech in Electronics & Communication.