What Is USB (Universal Serial Bus) 1

Meaning of USB


USB is the acronym for Universal Serial Bus. It is a technology that has become more and more simple, easy and fast the connection of several types of devices (digital cameras, External hard drives, USB sticks, mice, keyboards, printers, scanners, card reader, etc.) to the computer and the mobile devices, thereby avoiding the use of a specific type of connector for each device.

In the following lines, you will see the main characteristics of this technology, know your connectors, you’ll know a little bit about your operation and understand the reasons which led the USB to be “presence compulsory” in computers and various other devices.

The emergence of the USB standard

In the past, connecting devices to the computer was a little task intuitive, often worthy only of technical or users with experience in the subject. To begin with, before the various types of cables and connectors, it was necessary to find out, almost for divination, in which port of the computer to connect the the device in question.

When the installation was internal, the situation was worse, since the user had open the computer and almost always configure the jumpers and/or IRQs. Only in the thought of having to face a tangle of wires and connectors, many users gave up the idea of adding a new item to the your machine.

In the face of situations of this type, the industry understood the need create a standard that would facilitate the connection of your devices to the computer. Thus, in 1995, a number of companies — among them Microsoft, Intel, NEC, IBM and Apple formed a consortium to establish a default. Came then the USB Implementers Forum. A short time later, the first specifications commercial of what became known as the Universal Serial Bus (USB) emerged.

In fact, the technology is already being worked on even before the definition of consortium as the USB Implementers Forum. The earliest versions established dating back to 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.

The first versions defined for commercial use on a large scale were the 1.1 and the 2.0, which will be seen with 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 devices varied, as you already know. Thus, the USB provides a serial advantages:

– Standard connection: any device compatible with USB uses defined standards connection (see more on the topic about connectors), so it is not necessary to have a type of connector specific 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 immediately. Only a few require the installation drivers or specific software. However, even in these cases, the operating system typically recognizes the connection of the device;

– Electrical power: most of the devices that use USB does not need to be connected to a source of energy, already that the own port is able to provide electricity. As a result, ends up being very easy to find devices that have their battery recharged via USB, such as smartphones and tablets. The exception is devices that consume the amount of 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 a single USB port. This can be done, for example, by means of hubs, devices that use a single USB connection to offer a greater number of them. It is worth stressing that not always this mode operation is feasible, since the data transmission speed it is divided between all the equipment;

– Wide compatibility: the USB standard is compatible with several platforms and operating systems. The Windows, for example, the supports since version 98. Operating systems such as Linux, macOS and Android are also compatible. Currently, it is possible to find USB ports on many other devices, such as televisions, communication systems of cars and even equipment sound, as shown in the photo below:

– Hot-swappable: USB devices can be connected and disconnected at any time. In a computer, for example, not it is necessary to restart it or turn it off to connect or disconnect the device;

– Cables of up to 5 metres: USB cables can be up to 5 metres of size. This limit can be increased with the use of hubs or equipment able to repeat the signals of communication.


On the functioning of the USB

As already informed, the USB bus can be used to provide electrical power to certain devices. For this to be possible, the USB cables come with at least four internal wires: VBus (VCC), D+, GND. The first is the responsible for feeding electrical. The second and the third are used in the transmission data (the letter “D” comes from the date, given in English). The room, in turn, acts on the electrical control,serving as a “ground wire”.

Worth mentioning that, as stated in the previous topic, the USB cables must have a maximum of 5 metres in length. This is necessary because, in cables larger, the transmission time of the data can exceed the limit of 1,500 nanoseconds. When this occurs, the information it is considered lost.

The communication between devices connected via USB is made by means of a protocol. In it, the host, that is, the computer or the equipment that receives the connections, emits a signal to find the attached devices and establishes an address for each of them, remembering that up to 127 devicescan be addressed. Once established the communication, the host receives the information about the type of connection that the connected device uses. There are four possibilities:

Bulk: this type is used for devices that deal with large volumes of data, such as printers and scanners, for example. The Bulk features of error detection to ensure the integrity of the transmitted information;

Control: type used for transmission of parameters control and configuration of the device;

Interrupt: used for devices that transfer only a few, such as mice, keyboards and joysticks;

Isochronous: this type is applied in transmissions continuous, where the data are transferred all the time, the reason why there is no detection capabilities of errors, since this atrasaria communication. Devices as speakers use this mode.


USB 1.1

As occurs with other technologies, the USB standard passes periodically for revisions in their specifications to meet the current market needs. The first version of USB that became the default was 1.1.

This version, released in September 1998, contains almost all the features explained in the previous topic, however, your speed of transmission data is not very high: on slower connections, the transmission rate is up to 1.5 Mb/s (Low-Speed), that is, of about 190 KB per second. In turn, in the connections faster, this value is up to 12 Mb/s (Full-Speed), about 1.5 MB per second.

At the time of the release of USB 1.1, these rates do not were necessarily low, once served to the great majority of the devices. However, to the extent that the use of the USB grew, it was noted that it also increased the need for higher rates in the the transfer of data. Devices such as scanners and cameras digital went to work with resolutions more high, resulting in a greater volume of information.

Given this scenario and the emergence of technologies “competing”, in particular, the FireWire (or IEEE 1394), the consortium responsible for the USB if seen thank you the place on the market a review of the technology. It arose then, in April 2000, the USB 2.0 (Hi-Speed), which is a standard widely used until today.


USB 2.0

The USB 2.0 has come to the market offering speeds of up to 480 Mb/s, equivalent rate about 60 MB per second. The pattern of connection continues being the same as the previous version. In addition, the USB 2.0 it is fully compatible with devices that work with the USB 1.1. However, in these cases, the speed of the transfer data is the latter.

This occurs because the USB tries to communicate at the speed of 480 Mb/s. If this fails, will then try to work at the speed of 12 Mb/s. finally, if unsuccessful, will attempt to communicate at the rate of 1.5 Mb/s. As to the possibility of a device USB 2.0 to work on connections USB 1.1, it can happen, but depending on, essentially, the manufacturer and the device.

One aspect that is interesting to point out in relation USB 2.0 is that its launch has also brought a novelty, which served to make the technology even more popular: from version 2.0, manufacturers were able to adopt the standard in its products without the requirement to deal with royalty, that is, without have to pay a license to use the technology.

The release of USB 2.0 also brought another advantage: the default FireWire has been standardized primarily for working with applications that involve video and audio, taking Apple as the largest supporter. Thus, it is quite practical to connect a video camera for that environment. As the speed of the USB 2.0 surpasses the speed of the first implementations of the FireWire (with speed of up to 400 Mb/s), the standard also became a viable option for applications of the media, which has increased its range of utilities.

The developers of the standard FireWire were not stopped and cast a specifications new (FireWire 800, which works to 800 Mb/s). In addition, the need for increasing speeds data transmission is still a reality. On this account, the USB still being reviewed. This work gave space to the USB 3.0 and, more recently, to USB 3.1.

USB 3.0 and USB 3.1

The specifications of the USB 3.0 (SuperSpeed) were set at the end of 2008, however, the first products compatible with the new standard began to reach out to the consumers in the second half of 2010.

In August 2013, the specifications for USB 3.1 were finished. Both versions are quite similar, but the USB 3.1 takes advantage of the USB 3.0 for being up to two times faster.

Here are the main features of the USB 3.0 and USB 3.1:

– Bi-directional transmission of data: in version 2.0 (and earlier), the USB standard allows data to trafeguem device A to B and from device B to A, but each one in turn. In the standard 3.0, the sending and receiving of data between two devices it can happen at the same time;

– Higher speed: the speed of data transmission it is up to 4.8 Gb/s (gigabits per second), equivalent to approximately 600 MB per second, a value that is absurdly higher than the 480 Mb/s-default USB 2.0. In USB 3.1, this limit increases to 10 Gb/s;

– The electrical power more powerful: the standard USB 3.0 can provide more power: 900 milliamps against 500 milliamps of USB 2.0;

– Backward compatibility: connections, USB 3.0 can support USB 1.1 devices and USB 2.0.

Types of connectors

The USB technology has various types of connectors, the connector To the more well-known, being present in the overwhelming majority of the computers compatible with the technology, in addition to power be found in other devices, such as TVs and home theaters.

Since the main goal the USB standard is to facilitate the connection of various devices to the computer, usually the cables of these devices are of the type The in a tip, and some of the other types in another, and the second the tip also have some proprietary format, that is, a specific manufacturer.

In the following images, the connectors (male) are on the left side, while their respective fittings (female connectors) are on the right side:


It is the most common type, being present in the majority of of today’s computers. It is also the most used type for the data storage devices known as “USB sticks”:


The most recent standard — the completion of their specifications happened in August 2014. THE USB-C is compact (has the 8.4 mm wide by 2.6 mm thick) and reversible, or can be docked to any side.

The USB-C has been developed especially to work with USB connections 3.1, although it can also work with the previous specifications and with other technologies.

Learn more about the USB-C in this text.


Used in devices of small size having a reduced size, as compact digital cameras and MP3-players. In fact, the Mini USB is called USB Mini-B, since there is a format virtually unusable called USB Mini-A. Here are the connectors on Mini-USB:


USB Micro-A: format the new, smaller than the Mini-USB oriented devices thick-thin, such as on smartphones and tablets. Despite this, it is little used;

USB Micro-B: similar to format Micro-A, however, its fit is slightly different. Compared to Micro-A, Micro-B is much more common:

Worth mentioning that connectors female Micro-can be called Micro-B to be compatible with male connectors on both the types.

As informed at the start of the topic, there are manufacturers that use USB connectors owners. The cable below is used in a MP3-player from Sony, is an example:

Connectors owners tend to not be well accepted by they have high cost in relation to market standards and because they are more difficult to find.

The colors of the connectors

Manufacturers are not necessarily required to following this scheme, but there is a standardization of color in USB connectors so that users can know more easily the speed of each port.

USB ports 1.0 and 1.1 (practically not more manufactured) are usually color-coded white. USB 2.0 connectors tend to be black, although some manufacturers also use white.

USB ports 3.0 and 3.1, in turn, have the color blue. Is can still find doors in the colors yellow and red indicate that a device can be reloaded there even when the the computer is in sleep mode or powered off, but connected to a a source of energy.

The trident, symbol of the universal USB

The symbol of the USB ports is, since version 1.0 a representation inspired by the trident of Neptune, one of the the gods of Greek mythology. You certainly already saw this drawing.

No one knows for sure the reason for this choice, but unofficial information indicate that the”exchange” of each tip of the trident a different way — circle, triangle and square — it was made like that to to say that the USB is a standard that supports various types of devices.


With the popularization of communication technologies wireless, such as Bluetooth and Wi-Fi, there are those who question the future of the USB, once the trend is that all the devices start to communicate without the use cables.

However, the emergence of more advanced versions of the USB, as the specifications 3.1 along with the USB connector-C, suggests that the connections physical will complement each time to the wireless options. A type should not replace the another one so soon. The USB technology will probably have a lot “time life”, therefore.

What Is USB (Universal Serial Bus) 1