USB stands for Universal Serial Bus according to ABBREVIATIONFINDER. It is a technology that has made it easier, faster and easier to connect different types of devices (digital cameras, external hard drives, flash drives, mice, keyboards, printers, card readers, etc.) to computers and mobile devices (such as tablets and smartphones), thus avoiding the use of a specific type of connector for each equipment.
In the following lines, you will see the main characteristics of this technology, you will know its connectors, you will know a little about its operation and you will understand the reasons that made USB to be “mandatory presence” in computers and in several other devices.
How did USB come about?
In the past, connecting devices to the computer was an unintuitive task, often worthy only of technicians or users with experience in the subject. To begin, faced with various types of cables and connectors, it was necessary to find out, almost by guesswork, on which computer port to connect the device in question.
When the installation was internal, the situation was worse, since the user had to open the computer and almost always set jumpers and / or IRQs . Just thinking about having to face a tangle of wires and connectors, many users gave up on the idea of adding a new item to their machine.
In the face of such situations, the industry understood the need to create a standard that would facilitate the connection of devices to the computer. So, in 1995, a number of companies – including Microsoft, Intel, NEC, IBM and Apple – formed a consortium to set a standard. Then came the USB Implementers Forum (USB-IF). Shortly thereafter, the first commercial specifications of what became known as Universal Serial Bus (USB) appeared.
In fact, the technology was already being worked on even before the consortium was defined as USB Implementers Forum. The first established versions date from 1994:
- USB 0.7: November 1994;
- USB 0.8: December 1994;
- USB 0.9: April 1995;
- USB 0.99: August 1995;
- USB 1.0: January 1996;
- USB 1.1: September 1998;
- USB 2.0: April 2000;
- USB 3.0: November 2008;
- USB 3.1: August 2013;
- USB 3.2: September 2017.
The first versions defined for large-scale commercial use were 1.1 and 2.0, which will be seen in more detail in this text.
Advantages of USB
One of the reasons that led to the creation of USB technology is the need to facilitate the interconnection of different devices, as you already know. Therefore, USB offers a number of advantages:
– Connection pattern: any USB compatible device uses defined connection patterns (see more in the topic on connectors), so it is not necessary to have a specific type of connector for each device;
– Plug and Play (something like ” Plug and Play “): almost all USB devices are designed to be connected to the computer and used right away. Only a few require the installation of specific drivers or software. However, even in these cases, the operating system normally recognizes the device’s connection;
– Power supply: most devices that use USB do not need to be connected to a power source, since the port itself is capable of providing electricity. Because of this, it ends up being very easy to find devices that have their battery recharged via USB, such as smartphones and tablets. The exception is for devices that consume more energy, such as printers and certain external hard drives;
– Connection of several devices at the same time: it is possible to connect up to 127 devices at the same time on a single USB port. This can be done, for example, through hubs , devices that use a single USB connection to offer more of them. It is worth noting that this mode of operation is not always feasible, since the data transmission speed is divided among all equipment;
– Wide compatibility: the USB standard is compatible with different platforms and operating systems. Windows, for example, has supported it since version 98. Operating systems like Linux, macOS and Android are also compatible.
– Hot-swappable : USB devices can be connected and disconnected at any time. On a computer, for example, there is no need to restart or turn it off to connect or disconnect the device;
– Cables up to 5 meters: USB cables can be up to 5 meters in size. This limit can be increased with the use of hubs or equipment capable of repeating the communication signals.
About USB operation
As already mentioned, the USB bus can be used to supply electricity to certain devices. To make this possible, USB cables have at least four internal wires: VBus (VCC), D +, D- and GND. The first is responsible for the electrical supply. The second and third are used for data transmission (the letter “D” comes from a date , given in English). The fourth, in turn, acts in the electrical control, serving as “ground wire”.
It is worth noting that, as stated in the previous topic, USB cables must be at most 5 meters long. This is necessary because, on larger cables, the data transmission time can exceed the limit of 1,500 nanoseconds. When this occurs, the information is considered lost.
Communication between devices connected via USB is done using a protocol. In it, the host , that is, the computer or the equipment that receives the connections, emits a signal to find the connected devices and establishes an address for each one, remembering that up to 127 devices can be addressed. Once communication is established, the host receives information about the type of connection the connected device uses. There are four possibilities:
– Bulk : this type is used by devices that handle large volumes of data, such as printers and scanners, for example. Bulk has error detection capabilities to guarantee the integrity of the information transmitted;
– Control : type used to transmit control parameters and device configuration;
– Interrupt : type used for devices that transfer little data, such as mice, keyboards and joysticks;
– Isochronous : this type is applied in continuous transmissions, where data is transferred at all times, which is why there are no error detection features, as this would delay communication. Devices such as speakers use this mode.
What is USB 1.1?
As with other technologies, the USB standard periodically undergoes revisions to its specifications to meet current market needs. The first version of USB that became standard was 1.1.
This version, launched in September 1998, contains practically all the features explained in the previous topic, however, its data transmission speed is not very high: in the slowest connections, the transmission rate is up to 1.5 Mb / s (Low-Speed), that is, about 190 KB per second. In turn, in the fastest connections, this value is up to 12 Mb / s (Full-Speed), about 1.5 MB per second.
At the time of the USB 1.1 launch, these rates were not necessarily low, as they served the vast majority of devices. However, as USB usage grew, it was noted that the need for higher data transfer rates also increased. Devices such as scanners and digital cameras started to work with higher resolutions, resulting in a greater volume of information.
Faced with this scenario and the emergence of “competing” technologies, in particular FireWire (or IEEE 1394) , the consortium responsible for USB was forced to place a technology review on the market. Then, in April 2000, USB 2.0 (Hi-Speed) emerged , which is a widely used standard today.
What is USB 2.0?
USB 2.0 arrived on the market offering speeds of up to 480 Mb / s, a rate equivalent to about 60 MB per second. The connection pattern remains the same as the previous version. In addition, USB 2.0 is fully compatible with devices that work with USB 1.1. However, in such cases, the data transfer speed is the latter.
This is because USB tries to communicate at 480 Mb / s. If not, you will then try to work at 12 Mb / s. Finally, if it is not successful, it will try to communicate at a rate of 1.5 Mb / s. As for the possibility of a USB 2.0 device working on USB 1.1 connections, this can happen, but depending, essentially, on the manufacturer and the device.
One aspect that is interesting to highlight in relation to USB 2.0 is that its launch also brought a novelty that served to make the technology even more popular: as of version 2.0, manufacturers were able to adopt the standard in their products without the obligation to deal with royalties , that is, without having to pay technology usage licenses.
The launch of USB 2.0 also brought another advantage: the FireWire standard was standardized mainly to work with applications that involve video and audio, with Apple as the biggest supporter. Thus, it is quite practical to connect a video camera by this means. As the speed of USB 2.0 exceeds the speed of the first FireWire implementations (with speeds up to 400 Mb / s), the standard has also become a viable option for media applications, which has increased its range of utilities.
The developers of the FireWire standard did not stand still and released new specifications (FireWire 800, which works at 800 Mb / s). In addition, the need for increasing data transmission speeds is still a reality. As a result, USB continues to be revised. This work gave way to USB 3.0 and later to USB 3.1 and USB 3.2.
USB 3.0, USB 3.1 and USB 3.2
The specifications for USB 3.0 (SuperSpeed) were defined in late 2008, however, the first products compatible with the new standard began to reach consumers in the second half of 2010.
In August 2013, USB 3.1 specifications were finalized. Both versions are very similar, but USB 3.1 takes advantage over USB 3.0 as it is up to twice as fast.
In September 2017, it was time for the USB 3.2 specifications to be ready. The three versions are very similar to each other, with the greatest difference being the data transfer capacity of each one.
Here are the main features of USB 3.0, USB 3.1 and USB 3.2:
– Bidirectional data transmission: in version 2.0 (and earlier), the USB standard allows data to travel from device A to B and device B to A, but each in turn. In standard 3.0 and above, sending and receiving data between two devices can happen at the same time;
– Higher speed: the data transmission speed is up to 5 Gb / s (gigabits per second), equivalent to about 600 MB per second, an absurdly higher value than the 480 Mb / s of the USB 2.0 standard. In USB 3.1, this limit increases to 10 Gb / s (double). In USB 3.2, the speed can reach 20 Gb / s (yes, twice as much again).
– More powerful electrical supply: USB 3.0, USB 3.1 and USB 3.2 standards have a specification called USB Power Delivery (USB-PD) that works with 100 watts and, thus, allows the power of devices that consume more energy;
– Backward compatibility: USB 3.0, USB 3.1 and USB 3.2 connections can support USB 1.1 and USB 2.0 devices.
USB4 (or USB 4): up to 40 Gb / s
If USB 3.2 is already very fast with its 20 Gb / s, the fourth generation of USB promises to go even further: USB4 (or USB 4) can allow data transfer at up to 40 Gb / s!
This will be possible because, in a way, USB4 was designed to be based on Thunderbolt 3 . It makes sense: this technology also works with up to 40 Gb / s and, instead of its own connector, it uses USB-C ports. So why not combine both technologies in one?
That’s the plan here. In addition to 40 Gb / s, USB4 can be implemented at speeds of 10 Gb / s and 20 Gb / s (depends on each device), as well as providing up to 100 watts for electrical power.