Abu Zar Mishwani
USB, short for Universal Serial Bus, serves as a set of standards that outline the requirements for cables, ports, and communication protocols.
These standards facilitate straightforward and widely recognized connections between a central device (host) and external peripherals.
This article will explain what USB is, its types, importance, and more.
What is USB?
USB, also known as the universal serial bus, revolutionized the way peripheral devices connect to computers. Prior to USB, computers typically featured limited serial connections and parallel ports, along with dedicated ports for keyboards, mice, and sometimes joysticks.
In the mid-1990s, several American companies, including IBM, Intel, and Microsoft, collaborated to establish the USB standard.
This initiative aimed to simplify the connection of computer peripherals. The USB port introduced a uniform approach for connecting diverse devices, offering significant speed advantages compared to alternative methods.
Initially, the adoption of USB technology faced challenges:
- Computer manufacturers hesitated to integrate USB ports into their systems until USB-compatible peripherals became widely available.
- Peripheral device manufacturers hesitated to promote USB products until USB ports became standard on newer computers.
- Operating systems had limited support for USB technology when it was first introduced, which slowed down its initial acceptance.
The launch of Apple Inc.‘s first iMac model in 1998 marked a significant milestone. This pioneering machine, which exclusively featured USB connections, was a game-changer.
Its popularity and positive reception compelled other manufacturers to adopt the USB standard, driving widespread technology acceptance.
Since then, USB has become the go-to interface for various peripheral devices, ranging from printers and scanners to keyboards.
Moreover, the widespread adoption of USB paved the way for the emergence of innovative technologies, such as portable memory sticks commonly known as USB storage.
These advancements, inspired by the acceptance of the USB standard, gradually replaced outdated storage methods like floppy discs.
Today, USB design is governed by the USB Implementers Forum (USB-IF), which comprises entities that advocate and advance USB technology.
The USB-IF endorses USB, oversees the standardization process, and enforces compliance through its program.
How Does USB (Universal Serial Bus) Work?
A computer’s “bus” is a network of cables that facilitates data transfer between internal components or between a computer and its external devices.
This concept draws a metaphorical comparison to an electronic busbar, which distributes electricity across large, energy-intensive locations like factories or data centers.
Before USB, each peripheral device typically required its own specialized port for connection to a computer.
As the variety and number of peripheral devices increased over time, a need arose for a standardized approach to facilitating data exchange between the primary host (computer) and various devices.
This necessity ultimately spurred the development of USB, providing a universal solution for connecting a wide range of peripherals to computers.
When a peripheral device is connected to a host computer via USB, the host machine will automatically recognize the type of device and install the necessary driver to enable its functionality.
USB facilitates data transmission between two devices by breaking the data into smaller units called “packets.”
Each packet contains a predetermined amount of bytes, which are digital information units.
These packets may include information such as the source and destination of the data, as well as any detected anomalies.
The operation of a USB can be divided into several components:
1. Bulk Data Transfer
This mode is utilized by devices like printers or scanners to transmit large volumes of data. It’s typically a low-priority process and isn’t time-critical. However, delays may occur if the host machine handles numerous USB devices simultaneously.
2. Small Packet Transmission for Critical Connections
Peripheral devices such as keyboards and mice employ this method to send small amounts of crucial data. These transmissions are occasional but essential. The remote device initiates requests and waits for the host to inquire about the specific data needed. If the initial request fails, the requests are retried. Additionally, the USB system notifies about changes in the device’s status.
3. Control Packet Transfers for USB Management
This type of data transmission is used to configure and manage USB devices. The host sends a request to the device, followed by data transmission. Control transfers also facilitate status checks. Only one control request can be processed at a time.
4. Real-time, Uninterrupted Data Transfer in Isochronous Mode
Isochronous transfer is utilized for real-time data like audio and video. Errors may occur during transmission, but the process continues without pausing to resend packets.
In scenarios where data fidelity isn’t critical, such as transmitting non-essential audio parts in a VoIP call, it’s preferable to omit these components rather than risk audio glitches caused by packet resending.
As the number of connected devices increases, the host computer tracks the bandwidth requested by all isochronous and interrupt devices.
Collectively, these devices may utilize up to 90% of the available bandwidth. For standard USB, the available bandwidth is typically 480 megabits per second, while with USB 3.0, it increases to 4.8 gigabits per second.
Once the total bandwidth allocated to isochronous and interrupt devices reaches 90%, the host computer prohibits access to additional isochronous or interrupt devices.
Any remaining bandwidth, which is always a minimum of 10%, is then utilized by control packets and bulk transfer packets. Beyond this threshold, simultaneous data transfer from multiple USB connections is not possible.
How Do USB Cables Work?
The USB port is a standardized interface for connecting cables to PCs and consumer electronics devices. Users can connect to this port via a specialized USB cable wire.
One cable end connects to the host device, while the other connects to the peripheral. Depending on the USB type, the cable’s two ends may or may not be symmetrical.
USB cables are capable of transmitting both power and information. To achieve this dual functionality, USB cables typically consist of two types of wires.
One set of wires is dedicated to transporting electrical current facilitating power transmission, while the other is responsible for carrying data signals between connected devices.
In a conventional USB 2.0 connection, there are four metal strips. The two outermost strips serve as the positive and negative terminals for the power supply, while the two center strips are designated for data transmission.
However, additional data-carrying strips are included with the latest USB 3.0 connection to increase data transmission rates. Four extra signaling lines are added, enabling USB 3.0 to achieve more speed compared to USB 2.0.
Features of USB
Key features of USB include:
1. Hot Swapping
Hot swapping is a key feature of USB technology. It allows devices to be removed or replaced without a system restart or interruption.
In older systems, such as those with traditional ports, installing or uninstalling a device often requires rebooting the PC.
This was done partly to prevent damage from electrostatic discharge (ESD), an unintended electrical current that can harm sensitive electronic components.
However, with USB, this inconvenience is eliminated. Hot swapping in USB is fault-tolerant, meaning it can continue to operate even in the event of hardware failure.
2. Direct Current Transfer
Another notable aspect of USB technology is its direct current (DC) utilization. Many devices are powered by a DC through a USB power connection without engaging in data communication.
Examples of such devices include USB speakers, small refrigerators, keyboard lamps, and various USB-based chargers for electronic devices.
3. Multiple Contact Points
All USB connections contain at least four contacts for power, ground, and two data wires (D+ and D-). USB 3.0 connectors and newer versions have five contacts. The USB connection is designed to transmit 5 volts at a maximum current of 500mA.
It is important to note that USB connectors can only be inserted in one direction. While it is possible to forcibly insert them incorrectly, doing so may cause damage to the device.
4. Shielding and Protection
The USB connection features insulation, including a metal casing separate from the circuit.
This insulation is essential for preserving the integrity of the signal, especially in electrically congested environments.
Additionally, all USB cables are encased in plastic at the connection end to protect the cable and maintain the integrity of the electrical connection.
Types of USB
USB can be categorized based on four generations of development or the type of cable connections they use. First, let’s discuss the four versions of USB that have evolved.
1. The Inception of USB
Before USBs, computer systems relied on serial and parallel ports for connecting external devices, as previously mentioned.
Recognizing the limitations of these ports and the need for a more versatile solution, several prominent computer manufacturers, including Intel, Microsoft, and Apple, collaborated to develop a universal connectivity standard.
This collaboration resulted in the creation of the first generation of USB technology, which aimed to seamlessly connect multiple external devices to a PC without needing a system reboot.
This significant development took place in the 1990s, marking the inception of USB technology.
2. USB 2.0
In 2000, USB 2.0 emerged as the dominant standard for connectivity. The most notable improvement over USB 1.1 was the significant increase in transfer speed.
USB 2.0 offered data transfer rates of up to 480 megabits per second, forty times faster than USB 1.1.
Moreover, USB 2.0 was backward and forward compatible, which could be used with USB 1.1 ports and devices and vice versa.
3. USB 3.0, 3.1, and 3.2
USB 3.0, also known as SuperSpeed USB, was the first USB version capable of efficiently transporting high-definition video.
It offered transfer speeds of 5 gigabits per second, significantly improving over previous versions.
However, unlike its successors, USB 3.0 didn’t achieve widespread acceptance similar to USB 1.0.
MacBooks and Chromebooks were among the early adopters of USB 3.1, introduced in 2014. USB 3.1 featured a maximum transmission rate of 10 gigabits per second.
USB 3.2 was launched three years later, doubling the transmission rate to 20 gigabits per second, making it twice as fast as USB 3.1.
Notably, only USB 3.1 and USB 3.2 are compatible with Type C connections. These ports are full-duplex, meaning data can be transmitted in both directions.
4. USB4
USB4, also called USB 4.0, is a standard introduced by the USB Implementers Forum (USB-IF) in version 1.0 in 2019.
The USB4 protocol is based on the Thunderbolt 3 standard, initially submitted by Intel Corporation to the USB-IF.
Its design allows for the dynamic utilization of a single high-speed connection with various end-device types.
This flexibility enables USB4 to execute each transfer according to the specific data or application type.
The initial products compatible with USB4 included Intel’s Tiger Lake processors, with more devices beginning to appear around the end of 2020. Despite this, USB4 connections have yet to become mainstream.
We can categorize USB types by considering the nature of the cable connection and physical design. Below are the main types to keep in mind, continuing from the previous list:
- Standard USB-A: This is the traditional rectangular-shaped USB connector found on most computers and chargers.
- USB-B: This connector is typically used for connecting peripheral devices such as printers and scanners. It has a squarish shape with slightly beveled corners.
- Micro USB: Commonly used in smartphones, tablets, and other portable devices, the micro USB connector is smaller and thinner than USB-A and USB-B connectors. It has a trapezoidal shape.
- Mini USB: This connector was popular in older devices like digital cameras and MP3 players. It’s smaller than USB-A and USB-B connectors but larger than micro USB connectors.
- USB-C: This is the latest standard, featuring a reversible and symmetrical design, which can be inserted into a port in any orientation. USB-C ports are increasingly common in modern devices due to their versatility and high data transfer rates.
Importance of USB Technology
USB is a fundamental technology in today’s digital landscape, playing a crucial role for individuals and businesses.
1. Simplifies Connectivity
USB’s unified interface eliminates the need for multiple connection types, offering scalability for various accessories. With most personal computers equipped with multiple USB ports, additional ports can be easily added through USB hubs.
2. Streamlines Space and Power
USB sockets are compact, reducing space requirements, and the USB interface doubles as a power source. Host devices can provide 5V DC power to peripherals, minimizing power supply complexities.
3. Driver-Free Configuration
USB peripherals require driver installation only once, with subsequent connections automatically initiating driver setup. This streamlined process ensures seamless integration with host devices.
4. Enhances Speed and Reliability
USB supports multiple speed settings, catering to diverse needs with speeds ranging from 1.5Mbit/s to 10Gbit/s. Additionally, USB protocols detect and correct data transmission errors, enhancing reliability.
5. Cost-Effective Solutions
USB’s widespread popularity and adaptable manufacturing process have made USB-supported products affordable. Components and cables are readily available at low costs, and USB peripherals consume minimal power during “suspend mode,” reducing overall expenditures.
Conclusion
Over the past two decades, USB has emerged as the preferred connectivity option for consumer devices, enjoying widespread acceptance.
Its versatility extends to various applications, from connecting PC peripherals for home use to expanding storage capacity for mobile devices.
Businesses can utilize USB technology to augment their storage needs and offer employees greater versatility.