Universal Serial Bus

The Universal Serial Bus (BUS) (in English: Universal Serial Bus), better known by the acronym USB, is a communications bus that follows a standard that defines the cables, connectors, and protocols used on a bus to connect, communicate, and provide power between computers, peripherals, and electronic devices.

Its development started from a group of companies in the sector that sought to unify the way to connect peripherals to their equipment, which at that time were not very compatible with each other, among which were Intel, Microsoft, IBM, Compaq, DEC, NEC and Nortel. The first full 1.0 specification was published in 1996, but in 1998 with the 1.1 specification it began to be widely used.

USB is used as a standard for connecting peripherals such as: keyboards, mice, USB flash drives, joysticks, scanners, digital cameras, web cameras, mobile phones, multimedia players, printers, multifunction printers, data acquisition systems, modems, network cards, sound cards, TV tuner cards, external DVD burners, external hard drives and external floppy drives. Its success has been total, having displaced connectors such as the serial port, parallel port, game port, Apple Desktop Bus or PS/2 to niche markets or to the consideration of obsolete devices to be removed from computers, or to use adapters, although many of them can be replaced by USB devices that implement those connectors.

Review

USB was designed to economize and standardize the connection of peripherals.

It was developed in the mid-1990s; and in 1996, the Universal Serial Bus Implementers Forum (USB Implementers Forum, USB-IF) released the unpopular first "USB 1.0" specification, until in 1998 it released the USB 1.1 specification.

As of 2004, approximately 6 billion devices are on the global market, and around 2 billion are sold each year.

Use

USB's field of application now extends to any electronic or component device, from cars (modern car radios are becoming media players with a USB or iPod connector) to Blu-ray Disc players or modern toys like Pleo. Variations have been implemented for industrial and even military use. But where its influence is most noticeable is in smartphones (Europe has created a standard that all smartphones, tablets, PDAs and game consoles must come with a microUSB charger), where it has replaced proprietary connectors almost entirely.

Some devices require minimal power, so multiple devices can be connected without the need for extra power supplies. For this, there are hubs (called USB hubs) that include power supplies to provide power to the devices connected to them, but some devices consume so much power that they need their own power supply. Hubs with a power supply can provide power to other devices without removing power from the rest of the connection (within limits).

In the case of hard drives, as of May 2020 USB became a standard as a native connection, the connection being only 3.0. There are even external boxes and cradles that implement eSATA and USB connectors, even USB 3.0. These and the mixed USB/FireWire have driven SCSI and parallel port connections out of the market for external drives.

Previous versions

The USB standard evolved through several versions before its official release in 1996:

• USB 0.7: launched in November 1994.
• USB 0.8: launched in December 1994.
• USB 0.9: launched in April 1995.
• USB 0.99: launched in August 1996.
• USB 1.0 Release Candidate: launched in November 1996.

Transmission speeds

USB devices are classified into six types based on their data transfer speeds:

• Low speed (1.0): Transfer rate up to 1.5 Mbit/s (188 kB/s). Used mostly by human interface devices (Human Interface Device, in English) such as keyboards, mice (mouse), web cameras, etc.
• Full speed (1.1): Transfer rate of up to 12 Mbit/s (1.5 MB/s) according to this standard, but it is said in independent sources that the measurements should be performed again. This was the fastest before USB 2.0 specification. These devices divide the bandwidth of the USB connection between them, based on a LIFO impedance algorithm.

Logo of USB 2.0

• High speed (2.0): Transfer rate up to 480 Mbit/s (60 MB/s), but with a maximum practical real rate of 280 Mbit/s (35 MB/s). The USB 2.0 cable has four lines, a pair for data, and another pair of power supply.

USB 3.0 Logo

• Superhigh speed (3.0): It has a transfer rate of up to 4.8 Gbit/s (600 MB/s). The speed of the bus is ten times faster than that of USB 2.0, because they have included 5 additional contacts, disposing the initially proposed fiber optic connector, and is compatible with the above standards. In October 2009, the Taiwanese company ASUS launched the first base plate that included USB 3.0 ports, after which many others have followed it and is now increasingly seen on new base plates and laptops, living together with USB 2.0.
• Superhigh speed + (3.1): SuperSpeed+ doubles the maximum data transfer speed to 10 Gbit/s (1.25 GB/s).
• Superhigh speed + (3.2): SuperSpeed+ doubles the maximum data transfer rate to 20 Gbit/s (2.5 GB/s).

The USB signals are transmitted in a twisted pair cable with a characteristic impedance of 90 Ω ± 15%, whose wires are called D+ and D-. These, together, use a differential signal in half duplex, that is, they the 2 wires are used for both transmit and receive, but not simultaneously. USB 3.0 uses a second pair of wires, also with a differential signal, to carry out full duplex communication, thus allowing bidirectional communication simultaneously. The reason for differential mode communication is simple, it reduces the effect of electromagnetic noise on long links. D+ and D- work together and are not independent connections. The signal transmission levels vary from 0 to 0.3 V for lows (zeros) and from 2.8 to 3.6 V for highs (ones) in versions 1.0 and 1.1, and by ±400 mV in high speed (2.0). In early versions, the data cables (D+ and D-) are not grounded, but in high-speed mode you have a 45 Ω termination to ground or a 90 Ω differential to match the cable impedance. This port only supports the connection of low consumption devices, that is, they have a maximum consumption of 100 mA for each port; however, in case a device that allows 4 ports per USB output (max 4 port extensions) is connected, then USB power will be allocated in units of 100mA up to a maximum of 500mA per port. With the first manufacturing of a PC with USB 3.0 in 2009, we now have 1A (one amp) per port, giving 5W (five watts) instead of 0.5A (500mA, 2.5W) as maximum.

Speed comparison

Mini USB fans

Connections of external devices

• Firewire 400: 400 Mb/s (50 MB/s)
• Firewire 800: 800 Mb/s (100 MB/s)
• Firewire s1600: 1.6 Gb/s (200 MB/s)
• Firewire s3200: 3.2 Gb/s (400 MB/s)
• USB 1.0: 1.6 Mb/s (200 KB/s)
• USB 1.1: 12 Mb/s (1.5 MB/s)
• USB 2.0: 480 Mb/s (60 MB/s) Maximum practical actual rate of 280 Mb/s (35 MB/s)
• USB 3.1 Gen 1: 4.8 Gb/s (600 MB/s)
• USB 3.1 Gen 2: 10 Gb/s (1.2 GB/s)

High Speed External Device Connections

• e-SATA: 2.4 Gb/s (300 MB/s)
• USB 3.0: 4.8 Gb/s (600 MB/s)
• USB 3.1 Gen 2: 10 Gb/s (1.2 GB/s)
• Thunderbolt: 10 Gb/s (1.2 GB/s)
• Thunderbolt 2: 20 Gb/s (2.5 GB/s)
• Thunderbolt 3: 40 Gb/s (5 GB/s)

Connections for expansion cards

• PCI Express 1.x (x1): 250 MB/s
• PCI Express 2.0 (x1): 500 MB/s
• PCI Express 3.0 (x1): 1 GB/s
• PCI Express 1.x (x8): 2 GB/s
• PCI Express 2.0 (x8): 4 GB/s
• PCI Express 3.0 (x8): 8 GB/s
• PCI Express 1.x (x16): 4 GB/s
• PCI Express 2.0 (x16): 8 GB/s
• PCI Express 3.0 (x16): 16 GB/s

Internal storage connections

• ATA: 100 MB/s (UltraDMA 5)
• PATA: 133 MB/s (UltraDMA 6)
• SATA I: 1.5 Gb/s (187.5 MB/s)
• SATA II: 3 Gb/s (375 MB/s)
• SATA III: 6 Gb/s (750 MB/s)
• SATA 3.2: 16 Gb/s (2 GB/s)

USB 3.0

USB 3.0 Features

Unlike USB 2.0, this technology (USB 3.0 Super Speed) is almost ten times faster, going from 480 Mbit/s to 5 Gbit/s, about 600 MB/s. It also has support for external HD devices, which increases its performance. Another feature of this port is its "intelligence rule": devices that are plugged in and fall into disuse after a while immediately go into a low-power state.

Main differences between ports:
At the same time, the intensity of the current increases from 500 to 900 milliamps, which is used to supply a mobile phone or a portable audiovisual player in less time.
On the other hand, it increases the speed of data transmission, since instead of working with three lines, it does so with five. In this way, two lines are used to send, another two to receive, and a fifth is in charge of supplying the current. Thus, the traffic is bidirectional (Full-duplex).

At the end of 2009, manufacturers such as Asus or Gigabyte presented motherboards with this new revision of the bus. Version 3.0 of this universal connector is 10 times faster than the previous one. Those who have a keyboard or a mouse of the previous version will not have compatibility problems, since the system will recognize it instantly, although they will not be able to benefit from the new advances of this usb port.

At the Consumer Electronics Show (CES), which took place in Las Vegas, United States, several devices that come with the new connector were presented. Both Western Digital and Seagate announced external drives equipped with USB 3.0, while Asus, Fujitsu and HP announced that they will have portable models with this port.

Main differences between USB 2.0 and 3.0 The main appreciable difference is the data transfer speed, which is much higher than the USB 3.0 standard. Support for HD formats is almost non-existent in USB 2.0, but is widely supported by USB 3.0. USB 3.0 devices can be plugged into USB 2.0 connectors and vice versa, if it is type A. If it is type B or micro-B, USB 2.0 devices can be plugged into USB 3.0 connectors, but not the other way around.

USB 3.1 with reversible Type-C connectors

USB-C connector structure

In August 2014, the USB-IF, an organization made up of companies such as Intel, Microsoft, HP and Apple among many others and which decides on the USB standard, published the specification of the new USB connector, also known as &# 34;Type C", which implements a new type of reversible connector both in ends and in position. This type of connector, in addition to offering convenience due to its reversible design, offers a speed of up to 10 Gbit/s of performance while 2A on 5V can be drawn, and optionally, also 5A on 12V (60W) or 20V (100W). This is the reason why MacBook, since its 2016 models, can be powered simply through its USB connection also based on the new USB 3.1 specification.

This type of connector is intended to be the successor to all the previous ones (Type A and B), which will become obsolete when the new one is implemented in all types of mobile and desktop devices.

The USB 3.1 specification identifies two different transfer rates: the USB 3.1 Gen 1 4.8 Gbps specification and the USB 3.1 Gen 2 10 Gbps specification. This causes a change in the nomenclature of the specifications, being able to use the terms USB 3.0 and USB 3.1 Gen 1 (known as SuperSpeed USB) as synonyms. The USB 3.1 specification is renamed USB 3.1 Gen 2, known as SuperSpeed USB 10 Gbps or SuperSpeed+.

The USB 3.1 standard is backwards compatible with USB 3.0 and USB 2.0. This means that a USB 3.1 device connected to a USB 2.0 device will transfer data at a speed of USB 2.0 up to a maximum of 480 Mbit/s. Also, it will be necessary to take into account the USB version of the cable that allows this maximum data transfer, you can have two devices with USB 3.1 but if you use a USB 2.0 cable, the transfer is limited to that standard.

The USB Type-C specification brings a new reversible connector for USB 3.1 devices. The Type-C connector will be used on both host and guest devices, thus replacing multiple Type-A and Type-B connectors and cables with a future-proof standard similar to Lightning from Apple and Thunderbolt. The 24-pin dual-sided connector provides 4 power/ground pairs, two differential pairs for the USB 2.0 data bus (although only one pair is implemented on the Type-C cable), four pairs for the high-speed data bus, two "use sideband" and two configuration pins for wire orientation detection, dedicated biphase mark code (BMC) configuration data channel, and V_CONN +5V power for live wires. Type-A and Type-B cables/adapters will be required for legacy devices in order to connect to Type-C hosts, however adapters/cables with a Type-C receptacle are not allowed.

USB Type C cable from a MacBook Air.

Full-featured USB 3.1 Type-C cables are electronically marked active cables and contain a chip with an identification function based on the Vendor-Defined Message and Data (VDM) configuration channel of the specification & #34;USB Power Delivery 2.0". USB 3.1 Type-C devices also support 1.5 A and 3.0 supply currents via the 5 V bus voltage, in addition to the baseline 900 mA; devices can either negotiate a USB power boost via the configuration line, or can optionally support the full "Power Delivery" using both the BMC-coded configuration line and the legacy BFSK-coded VBUS line.

Alternate mode dedicates some of the physical wires in the Type-C cable for direct device-to-host transmission of a large number of alternate data protocols. The four high-speed lanes, two sideband pins, and—for port, detachable device, and permanent cable applications only—two USB 2.0 plugs and one configuration pin can be used for alternate mode transmission. The modes are configured by VDM through the configuration channel. As of December 2014, Alt Mode implementations include DisplayPort 1.3 and MHL 3.0; other serial protocols such as PCI Express and Base-T Ethernet are possible.

In March 2015, Apple launched a new MacBook model that was thinner than the MacBook Air and equipped with a USB Type-C connector. On the other hand, Google announced this type of connector for upcoming Android tablets and phones.

USB 3.2

This standard was released on July 26, 2017, and was published in September of that year. The main novelty it brought was the possibility of taking advantage of two 5 or 10 Gbps tracks to reach maximum transfer speeds of up to 20 Gbps on devices with USB-C (USB Type C) connectors. [1]

USB4

USB 4 was officially announced in March 2019, and published on August 29 of that year by the USB Implementers Forum. Their primary motivation was increasing bandwidth (allowing up to 40 Gbit/s), converging the USB-C ecosystem, and minimizing confusion for the end user. The specification is compatible/based on Thunderbolt 3, as well as backward compatible with USB 3.2 and USB 2.0.

In 2020 it was announced that this standard would be compatible with DisplayPort 2.0 and would support resolutions higher than 8K, such as 16K (15360 x 8460) at 60Hz and 30bpp 4:4:4 HDR with DSC. [2]

USB On-The-Go

USB On-The-Go, often abbreviated as USB OTG, is a specification that enables USB devices such as digital audio players, mobile phones or tablets to act as servers, making it possible to connect USB sticks and hard drives, mice or keyboards, among other components.

Physical characteristics

Compatibility and Connectors

The USB standard specifies relatively wide mechanical tolerances for its connectors, attempting to maximize compatibility between connectors manufactured by the company, a goal that has been achieved. The USB standard, unlike other standards, also defines sizes for the area around a device's connector, to prevent blocking of an adjacent port by the device in question.

The USB 1.0, 1.1, and 2.0 specifications define two types of connectors for connecting devices to the server: A and B. However, the mechanical layer has changed for some connectors. For example, the IBM UltraPort is a private USB connector located at the top of the LCD of IBM laptop computers. It uses a different mechanical connector, while maintaining the characteristic USB signals and protocols. Other manufacturers of small items have also developed their small connection means, and a wide variety of them have appeared, some of poor quality.

A USB extension called "USB On The Go" (on the fly) allows a port to act as a server or as a device; this is determined by which side of the cable is connected to the appliance. Even after the cable is connected and the drives are communicating, the 2 drives can "switch roles" under the control of a program. This facility is specifically designed for devices like PDAs, where the USB link could connect to a PC as a device, and connect to a keyboard or mouse as a server. The "USB-On-The-Go" he has also designed 3 small connectors, the mini-A and the mini-B, so this should stop the proliferation of miniaturized input connectors.

Type A and B connectors

The classic USB specification includes several sizes and types of connectors that are compatible with different specifications:

• the larger "standard" for example on USB memory devices.
• the size "mini" (especially for the end of connector B, as in many digital cameras)
• the "micro" size, in its USB 1.1/2.0 and USB 3.0 variants (for example, in most smartphones)
• the "On-The-Go USB interface" scheme, in mini and micro sizes.

Unlike other data cables (Ethernet, HDMI, etc), each end of a USB cable uses a different type of connector; one of type A or type B. This type of design was chosen to avoid electrical overloads and not damage the equipment, since only the type A female presents the electrical charge.

A and B Type Pinout

Pin layout of the “mini” and “micro” types

USB Mass Storage

USB implements connections to storage devices using a set of standards called USB mass storage device class (abbreviated as "MSC" or "UMS").. This was initially designed for optical and magnetic drives, but now also supports a wide variety of devices, particularly USB drives.

Wireless USB

Wireless USB (usually abbreviated W-USB or WUSB) is a high-bandwidth wireless radio communication protocol that combines the ease of use of USB with the versatility of wireless networking. It uses the Ultra-WideBand platform developed by the WiMedia Alliance as its radio base, which can achieve transmission rates of up to 480 Mbit/s (same as USB 2.0) at ranges of three meters and 110 Mbit/s at ranges of ten meters and operates in the frequency ranges from 3.1 to 10.6 GHz. As of 2018, the transition is in full swing and there are still not many devices that incorporate this protocol, both clients and hosts. While this process lasts, using the appropriate adapters and/or cables, a WUSB device can be converted into a USB device and vice versa.

List of peripherals that can be connected to a USB and USB OTG port

The USB port is a standard that allows the transfer of information to or from another peripheral. This list details the peripherals that can be connected to a USB port. In alphabetical order.