USB Technology: An Overview
Universal serial bus, or USB, is a type of technology that allows electronic devices to connect to a computer. This high-speed serial bus makes transferring data and power between devices easy. USB was first introduced in 1996 by a group of American companies, including IBM, Intel, and Microsoft. They aimed to create a simpler way to connect hardware to personal computers.
Before USB, PCs had different ports for devices like serial, parallel, mouse and keyboard, and game ports. USB replaced these interfaces with a standard port that can now support various devices, such as keyboards, mice, cameras, printers, scanners, flash drives, smartphones, and game consoles.
USB Versions and Speeds
USB has evolved over the years to offer faster speeds and more functionalities. Each version of USB has a different maximum signaling rate, which determines how fast data can be transferred between devices. The table below summarizes the main versions of USB and their speeds.
USB versions are backward-compatible, which means that devices and cables that support older versions can work with newer ones but at lower speeds. For example, a USB 3.0 device can work with a USB 2.0 port but only operates at USB 2.0 speed.
USB Connectors and Cables
USB connectors are the physical interfaces that connect devices using USB technology. There are three main types of USB connectors: A, B, and C. The A type is the host connector, usually found on PCs and laptops. The B type is the peripheral connector, which is usually found on devices that need to be connected to a host. The C type is the newest and most versatile connector, which can be used for hosts and peripherals.
Some cables have special features or functions that enhance the performance or compatibility of USB devices. For example, some cables have active electronics that boost the signal strength or extend the cable length. Some cables have adapters that allow different connector types to be used together. Some cables have switches that allow data or power to be toggled on or off.
USB-C is a new type of USB connector with many benefits over the older USB-A and USB-B connectors. Some of the benefits are:
Reversibility: USB-C connectors can be plugged in either way, so you don’t have to worry about the orientation of the cable or the port. This makes it easier and faster to connect devices. (This is not always true with some cables!)
Versatility: USB-C connectors can support various protocols and functions, such as data transfer, power delivery, video output, audio input/output, and more. This means you can use one cable and one port for multiple purposes, reducing the need for adapters and dongles.
Speed: USB-C connectors can support the latest USB standards, such as USB4 v2.0, which can offer up to 40 Gbit/s of data transfer rate. This is much faster than the previous USB standards, such as USB 2.0 (480 Mbit/s) or USB 3.0 (5 Gbit/s).
Power: USB-C connectors can support USB power delivery (USB-PD), a specification that allows devices to negotiate the optimal voltage and current levels for charging or powering each other. USB-PD can deliver up to 240 watts of power over a single cable, enough to charge laptops, monitors, and other high-power devices.
USB-C is becoming the standard for charging and transferring data among various devices, such as laptops, phones, tablets, cameras, game consoles, and more. It is also compatible with standards such as Thunderbolt and DisplayPort, offering even more features and performance. USB-C is a technology that simplifies and improves the connection of devices by using a standard and compact connector that can support various exciting new features.
USB Cable Lengths
The length of a USB cable should depend on the USB generation it supports and the performance and power delivery you need. The table below summarizes the main versions of USB and their recommended cable lengths.
As you can see, the newer versions of USB have shorter cable lengths because they offer faster speeds and more power, which require higher quality and lower resistance cables. Longer cables can cause signal degradation, data loss, and reduced power delivery, which can affect the performance and functionality of your devices.
Therefore, use the shortest cable possible for your devices and check the specifications of the devices and cables before using them. If you need to extend your cable connection, you can use active cables or USB hubs to boost the signal strength or provide additional power. However, you should also be aware of these solutions' limitations and compatibility issues.
There are several ways to extend a USB cable beyond the recommended maximum length. Depending on the USB generation and the distance you need, you can use one of the following methods:
USB extension cable: This simple and cheap solution allows you to connect your existing USB cable to another cable with a male and a female port. However, this method can only extend the cable by a few meters, and it can cause signal degradation and data loss if the total length exceeds the limit.
USB extender: This device converts the USB signal into an Ethernet signal and back, using an Ethernet cable to bridge the distance. This method can extend the cable by up to 50 meters, depending on the length of the Ethernet cable. However, this method may require external power and additional drivers.
USB over IP converter: This device connects your USB device to a network, allowing you to access it from any other device on the same network. This method can extend the cable by any distance as long as the network is available. However, this method may introduce latency and security risks.
USB Hubs and Tiers
When setting up a USB connection, it’s important to remember that there are limitations to how many tiers can be used. The USB standard allows for a maximum of 7 tiers, also known as levels or hubs, which determine the hierarchy of devices in the setup.
When a USB device is connected, two tiers are created — one for the USB device and the other for the host controller, such as a PC or a laptop. Every time the connection passes through a hub, additional tiers are established. The addition of each hub chip results in an extra tier.
Hub configurations are not always limited to standard 1 to 2, 1 to 3, or 1 to 4 configurations. Hubs can sometimes be established in unexpected locations, such as when extending a cable beyond the USB standard or duplicating ports. It may not always be obvious when a hub is being used, and as a result, one may need to realize when a new tier is formed.
When the number of tiers in a USB setup exceeds 7, the host controller (typically a laptop or PC) will not recognize the device and will not enumerate.
For more information about USB Tiers, please review the following:
USB Power Delivery
USB power delivery (USB-PD) is a specification that extends the power delivery capabilities of USB technology. It allows devices to negotiate the optimal voltage and current levels for charging or powering each other. USB-PD can deliver up to 240 watts of power over a single cable, enough to charge laptops, monitors, and other high-power devices.
USB-PD also lets devices switch roles between hosts and peripherals, depending on the power direction and data flow. For example, a smartphone can act as a host when connected to a flash drive but as a peripheral to a laptop. USB-PD also supports alternate modes, which allow devices to use other protocols, such as DisplayPort or Thunderbolt, over the same cable.
USB-PD requires USB Type-C connectors and cables supporting bidirectional power and data transfer. USB-PD also requires devices to have controllers that can communicate and negotiate the power delivery parameters.
USB Benefits and Challenges
USB technology has many benefits for users and manufacturers of electronic devices. Some of the main benefits are:
Simplicity: USB simplifies the connection of devices by using a standard interface and eliminating the need for multiple ports and cables.
Compatibility: USB is compatible with various devices and operating systems and supports backward compatibility with older versions.
Speed: USB offers fast data transfer rates that can meet the needs of different applications and devices.
Power: USB can power devices, reducing the need for separate power adapters or batteries.
Functionality: USB can support various functionalities and protocols, such as data storage, audio, video, networking, and charging.
However, USB technology also faces some challenges and limitations. Some of the main challenges are:
Complexity: USB has become more complex, with multiple versions, connectors, cables, and features. This can cause confusion and compatibility issues for users and manufacturers.
Security: USB can pose security risks for devices and data, as malicious software or hardware can be transferred or installed via USB ports or cables.
Interference: USB can interfere with other signals or devices, such as wireless networks or radio frequencies, due to its high-speed electrical pulses.
Durability: USB connectors and cables can wear out or break over time, due to frequent plugging and unplugging or bending and twisting.
USB technology is widely used and versatile, allowing users to connect various devices to computers. It has evolved over the years to offer faster speeds, more power, and more functionalities. However, it also has some challenges and limitations that must be addressed. As technology advances, USB will continue to adapt and improve to meet users’ and manufacturers’ changing needs and demands.
