USB – Universal Serial Bus is an industry standard that establishes specifications for cables and connectors and protocols for connection, communication and power supply between computers, peripherals and other computers.
USB was designed to standardize the connection of peripherals to personal computers, both to communicate with and to supply electric power. It has largely replaced interfaces such as serial ports and parallel ports and has become commonplace on a wide range of devices. Examples of peripherals that are connected via USB include computer keyboards and mice, video cameras, printers, portable media players, disk drives, and network adapters.
USB connectors have been increasingly replacing other types of charging cables of portable devices.
With the release of the original USB, the maximum data rate was 12Mbit/s. The original USB 1.0 specification, which was introduced in January 1996, defined data transfer rates of 1.5 Mbit/s “Low Speed” and 12 Mbit/s “Full Speed”.
Launching Year: January 1996
Cable length : 3m
Max power :2.5W
Maximum Current Rating:0.5A
Maximum voltage :5V
USB TYPE A 1.1:
These plugs and receptacles are officially referred to as Series A connectors and are the commonly seen, perfectly rectangular USB connectors.The introduction of USB 1.1 is what led to computers lacking a floppy drive and legacy ports, sometimes called “legacy-free PCs.”
USB TYPE B 1.1:
USB Type B: These plugs and receptacles are officially referred to as Series B connectors and are square except for rounding at the top. USB 1.1 Type B plugs are physically compatible with USB 2.0 and USB 3.0
USB 2.0 was released in April 2000, adding a higher maximum signaling rate of 480 Mbit/s (60 MB/s) named High Speed or High Bandwidth
Transfer rate : 480 Mbits/s
Maximum cable length: 5 meters
Maximum Voltage: 5 V
Maximum Power: 2.5 W
Maximum current rating : 0.5 A
USB 2.0 A
USB 2.0 B
Now Fitting these in small portable devices was a bit difficult so mini – micro versions. with the same performance and specification, but smaller size.
USB 3.0 has transmission speeds of up to 5 Gbit/s, about ten times faster than USB 2.0 (0.48 Gbit/s) even without considering that USB 3.0 is full-duplex whereas USB 2.0 is half-duplex. This gives USB 3.0 a potential total bidirectional bandwidth twenty times greater than USB 2.0.
Manufacturers distinguish USB 3.0 connectors from their USB 2.0 counterparts by using blue color for the Standard-A receptacles and plugs and by the initials SS.
Changes in specifications of USB 2.0 I.e.USB 3.0 made some improvement in
- Transfer Speed( SuperSpeed or SS, 5 Gbit/s )
- Increased bandwidth (Full-duplex )
- Power management (more defined )
- Improved Bus use ( NRDY ( no response; reject ) and ERDY ( accept)
- Support for rotating media
- Protocols same as USB 2.0
- Bulk protocol updated
- Stream protocol (new feature)
Launching Year: November 2010
Transfer speed:5 Gbits/s or 625 Mbits/s
Cable length :the USB 3.0 standard does not specify a maximum cable length, requiring only that all cables meet an electrical specification: for copper cabling with AWG 26 wires,
Maximum practical length: 3 meters (9.8 ft).
Max power :4.5W
Maximum Current Rating:0.9A or 900 mA
Maximum voltage :5V( same as usb 2.0)
(*NOTE : The available current for low-power (one unit load) SuperSpeed devices is 150 mA, an increase from the 100 mA defined in USB 2.0. For high-power SuperSpeed devices, the limit is six unit loads or 900 mA (4.5 W)—almost twice USB 2.0’s 500 mA.)
Width : 12 mm (A plug), 8 mm (B plug), 12.2 mm (Micro-A & Micro-B plugs)
Height : 4.5 mm (A plug), 10.44 mm (B plug), 1.8 mm (Micro-A & Micro-B plugs)
USB 3.0 Type A
A USB 3.0 Standard-A receptacle accepts either a USB 3.0 Standard-A plug or a USB 2.0 Standard-A plug. Conversely, it is possible to plug a USB 3.0 Standard-A plug into a USB 2.0 Standard-A receptacle. This is a principle of backward compatibility. The Standard-A is used for connecting to a computer port, at the host side.
USB 3.0 Type B
A USB 3.0 Standard-B receptacle accepts either a USB 3.0 Standard-B plug or a USB 2.0 Standard-B plug. Backward compatibility applies to connecting a USB 2.0 Standard-B plug into a USB 3.0 Standard-B receptacle. However, it is not possible to plug a USB 3.0 Standard-B plug into a USB 2.0 Standard-B receptacle, due to a physically larger connector. The Standard-B is used at the device side.
USB 3.0 Micro B
USB 3.0 also introduced a new Micro-B cable plug, which consists of a standard USB 1.x/2.0 Micro-B cable plug, with an additional 5-pin plug “stacked” inside it. That way, the USB 3.0 Micro-B host connector preserved its backward compatibility with the USB 1.x/2.0 Micro-B cable plugs, allowing devices with USB 3.0 Micro-B ports to run at USB 2.0 speeds on USB 2.0 Micro-B cables. However, it is not possible to plug a USB 3.0 Micro-B plug into a USB 2.0 Micro-B receptacle, due to a physically larger connector.
Looking at them at the same time
In January 2013 the USB group announced plans to update USB 3.0 to 10 Gbit/s (1250 MB/s).The group ended up creating a new USB specification, USB 3.1, which was released on 31 July 2013, replacing the USB 3.0 standard. The USB 3.1 specification takes over the existing USB 3.0’s SuperSpeed USB transfer rate, also referred to as USB 3.1 Gen 1, and introduces a faster transfer rate called SuperSpeed USB 10 Gbps, referred to as USB 3.1 Gen 2, putting it on par with a single first-generation Thunderbolt channel.
The USB 3.1 standard is backward compatible with USB 3.0 and USB 2.0. It defines the following transfer modes:
USB 3.1 Gen 1 – SuperSpeed, 5 Gbit/s data signaling rate over 1 lane using 8b/10b encoding (effective 500 MB/s); the same as USB 3.0
USB 3.1 Gen 2 – SuperSpeed+, new 10 Gbit/s data rate over 1 lane using 128b/132b encoding (effective 1212 MB/s)
LAUNCH DATE : 31 JULY 2013
Transfer speed: 10 Gbits/s or 1250 Mbits/s
Cable length : The USB 3.1 standard does not specify a maximum cable length, requiring only that all cables meet an electrical specification: for copper cabling with AWG 26 wires,
Maximum practical length: 3 meters (9.8 ft).
Max power :4.5W
Maximum Current Rating:0.9A or 900 mA
Maximum voltage :5 V (same as USB 2.0)
This rebranding of USB 3.0 as “USB 3.1 Gen 1” has allowed manufacturers to advertise products with transfer rates of only 5 Gbit/s as “USB 3.1,” omitting the generation
Not much was changed in the design, just the power of the USB change and Data transfer speed improved.
But now these are ports are directional so a reversible USB type was developed.
On 25 July 2017, a press release from the USB 3.0 Promoter Group detailed a pending update to the USB Type-C specification, defining the doubling of bandwidth for existing USB-C cables. Under the USB 3.2 specification, released 22 September 2017, existing SuperSpeed certified USB-C 3.1 Gen 1 cables will be able to operate at 10 Gbit/s (up from 5 Gbit/s), and SuperSpeed+ certified USB-C 3.1 Gen 2 cables will be able to operate at 20 Gbit/s (up from 10 Gbit/s).
The increase in bandwidth is a result of multi-lane operation over existing wires that were intended for the flip-flop capabilities of the USB-C connector.
The USB 3.2 standard is backward compatible with USB 3.1/3.0 and USB 2.0. It defines the following transfer modes:
- USB 3.2 Gen 1×1 – SuperSpeed, 5 gigabits per second (Gbit/s) data signaling rate over 1 lane using 8b/10b encoding (effective 500 MB/s) , the same as USB 3.1 Gen 1 and USB 3.0.
- USB 3.2 Gen 2×1 – SuperSpeed+, 10 gigabits per second (Gbit/s) data rate over 1 lane using 128b/132b encoding (effective 1,212 MB/s), the same as USB 3.1 Gen 2.
- USB 3.2 Gen 1×2 – SuperSpeed+, new 10 gigabits per second (Gbit/s) data rate over 2 lanes using 8b/10b encoding (effective 1 GB/s).
- USB 3.2 Gen 2×2 – SuperSpeed+, new 20 gigabits per second (Gbit/s) data rate over 2 lanes using 128b/132b encoding (effective 2,424 MB/s).
USB Type C Thunderbolt
Thunderbolt is the brand name of a hardware interface developed by Intel (in collaboration with Apple) that allows the connection of external peripherals to a computer. Thunderbolt 1 and 2 use the same connector as Mini DisplayPort (MDP), whereas Thunderbolt 3 re-uses the USB-C connector from USB. It was initially developed and marketed under the name Light Peak, and first sold as part of an end-user product on 24 February 2011.
Thunderbolt combines PCI Express (PCIe) and DisplayPort (DP) into two serial signals, and additionally provides DC power, all in one cable.
Thunderbolt can be implemented on PCIe graphics cards, which have access to DisplayPort data and PCIe connectivity, or on the motherboard of new computers with the onboard graphics card, such as the MacBook Air.
Thunderbolt was commercially introduced on Apple’s 2011 MacBook Pro, using the same Apple-developed connector as Mini DisplayPort, which is electrically identical to DisplayPort but uses a smaller, non-locking connector.
Apple stated in February 2011 that the port was based on Mini DisplayPort, not USB. As the system was described, Intel’s solution to the display connection problem became clear: Thunderbolt controllers multiplex data from existing DP systems with data from the PCIe port into a single cable. Older displays that using DP 1.1a or earlier must be located at the end of a Thunderbolt device chain, but native displays can be anywhere along the line. Thunderbolt devices can go anywhere on the chain. In that respect, Thunderbolt shares a relationship with the older ACCESS bus system, which used the display connector to support a low-speed bus.
Intel announced they would release a developer kit in the second quarter of 2011, while manufacturers of hardware-development equipment have indicated they will add support for the testing and development of Thunderbolt devices. The developer kit is being provided only on request.
In June 2013, Intel announced that the next generation of Thunderbolt, based on the controller code-named “Falcon Ridge” (running at 20 Gbit/s), is officially named “Thunderbolt 2” and entered production in 2013.
The data-rate of 20 Gbit/s is made possible by joining the two existing 10 Gbit/s-channels, which does not change the maximum bandwidth, but makes using it more flexible.
The bandwidth of Thunderbolt 1 and Thunderbolt 2 are identical, and Thunderbolt 1 cabling is thus compatible with Thunderbolt 2 interfaces. At the logical level, Thunderbolt 2 enables channel aggregation, whereby the two previously separate 10 Gbit/s channels can be combined into a single logical 20 Gbit/s channel.
Thunderbolt 3 is a hardware interface developed by Intel. It shares USB-C connectors with USB and can require special “active” cables for maximum performance for cable lengths over 0.5 meters (1.5 feet). Compared to Thunderbolt 2, it doubles the bandwidth to 40 Gbit/s (5 GB/s), allowing up to 4-lane PCIe 3.0, 8-lane DisplayPort 1.2, and USB 3.1 10 Gbit/s.
Intel’s Thunderbolt 3 controller (codenamed Alpine Ridge, or the new Titan Ridge) halves power consumption and simultaneously drives two external 4K displays at 60 Hz (or a single external 4K display at 120 Hz, or a 5K display at 60 Hz when using Apple’s implementation for the late-2016 MacBook Pros) instead of just the single display previous controllers can drive.
Intel offers three varieties for each of the controllers:
- Double Port (DP) uses a PCIe 3.0 ×4 link to provide two Thunderbolt 3 ports (DSL6540, JHL6540, JHL7540)
- Single Port (SP) uses a PCIe 3.0 ×4 link to provide one Thunderbolt 3 port (DSL6340, JHL6340, JHL7340)
- Low Power (LP) uses a PCIe 3.0 ×2 link to provide one Thunderbolt 3 port (JHL6240).
On 8 January 2018, Intel announced a product refresh (codenamed Titan Ridge) with “enhanced robustness” and support for DisplayPort 1.4. The new peripheral controller can now act as a USB sink (compatible with regular USB-C ports).
The USB4 specification was released on 29 August 2019 by USB Implementers Forum, based on the Thunderbolt 3 protocol specification.
It supports 40 Gbit/s (5 GB/s) throughput, is compatible with Thunderbolt 3, and backwards compatible with USB 3.2 and USB 2.0.
Thunderbolt 4 was announced at CES 2020 and the final specification was released in July 2020. The key differences between Thunderbolt 4 and Thunderbolt 3 are support for USB4 protocol and data rates, a minimum bandwidth requirement of 32 Gbps for PCIe link, support for dual 4K displays, and Intel VT-d-based direct memory access protection to prevent physical DMA attacks. The maximum bandwidth remains at 40 Gbps, the same as Thunderbolt 3 and four times faster than USB 3.2 Gen2x1.
Lightning is a proprietary computer bus and power connector created and designed by Apple Inc. Introduced on September 12, 2012, to replace its predecessor, the 30-pin dock connector, the Lightning connector is used to connect Apple mobile devices like iPhones, iPads, and iPods to host computers, external monitors, cameras, USB battery chargers, and other peripherals.
Using 8 pins instead of 30, Lightning is more dense than its predecessor.
On November 25, 2012, Apple acquired the “Lightning” trademark in Europe from Harley-Davidson. Apple was given a partial transfer of the Lightning trademark, suggesting that Harley-Davidson likely retained the right to use the name for motorcycle-related products. Apple is the sole proprietor of the trademark and copyrights for the designs and specifications of the Lightning connector.
The iPad Pro, released in 2015, features the first Lightning connector supporting USB 3.0 host. However, the only accessory that supports USB 3.0 is the new camera adapter. Normal USB-A – Lightning cables are still USB 2.0.
On October 30, 2018, Apple announced that their new range of iPad Pros will replace Lightning with USB-C.
Lightning is an 8-pin connector that carries a digital signal. Unlike the Apple 30 pin connector it replaces (and USB Type A or B connectors), the Lightning connector can be inserted either face up or face down.
Each pin on the reverse side of the connector is connected to its directly opposite twin on the other side. Part of the processor’s job is to route the power and data signals correctly whichever way up the connector is inserted. Official Lightning connectors contain an authentication chip that was intended to make it difficult for third-party manufacturers to produce compatible accessories without being approved by Apple .
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