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USB hardware
The initial versions of the USB standard specified connectors that were easy to use and that would have high life spans; revisions of the standard added smaller connectors useful for compact portable devices. Higher-speed development of the USB standard gave rise to another family of connectors to permit additional data links. All versions of USB specify cable properties. Version 3.x cables, marketed as SuperSpeed, added a data link; namely, in 2008, USB 3.0 added a full-duplex lane (two twisted pairs of wires for one differential signal of serial data per direction), and in 2014, the USB-C specification added a second full-duplex lane.
USB has always included some capability of providing power to peripheral devices, but the amount of power that can be provided has increased over time. The modern specifications are called USB Power Delivery (USB-PD) and allow up to 240 watts. Initially USB 1.0/2.0 provided up to 2.5 W, USB 3.0 provided up to 4.5 W, and subsequent Battery Charging (BC) specifications provided power up to 7.5 W. The modern Power Delivery specifications began with USB PD 1.0 in 2012, providing for power delivery up to 60 watts; PD 2.0 version 1.2 in 2013, along with USB 3.1, up to 100 W; and USB PD 3.1 in 2021 raised the maximum to 240 W. USB has been selected as the charging format for many mobile phones and other peripherial devices and hubs, reducing the proliferation of proprietary chargers. Since USB 3.1 USB-PD is part of the USB standard. The latest PD versions can easily also provide power to laptops.
A standard USB-C cable is specified for 60 watts and at least of USB 2.0 data capability.
In 2019, USB4, now exclusively based on USB-C, added connection-oriented video and audio interfacing abilities (DisplayPort) and compatibility to Thunderbolt 3+.
Unlike other data buses (such as Ethernet), USB connections are directed; a host device has downstream-facing ports (DFP) that connect to the upstream-facing port (UFP) of hubs or peripheral devices. USB implements a tiered star-like network topology.
Only downstream-facing ports originally provided power by default; this topology was chosen to easily prevent electrical overloads and damaged equipment.
Every legacy USB cable has two distinct ends with mechanically distinct plugs, one Type-A plug (connecting to a downstream-facing port of a host or hub) and one Type-B plug (connecting to the upstream-facing port of a hub or peripheral device). Each format has a plug and receptacle defined for each of the A and B ends. A USB cable, by definition, has a plug on each end. With one exception (Type-A to Type-A plugs) every cable had one Type-A plug and one Type-B plug. With the release of Type‑C came transitional cables: a Type‑C plug at one end and a Type-A or a Type-B plug at the other. These transitional cables are still directional, and in such a cable the Type‑C plug is electrically marked as either A or B as appropriate to complement the opposite connector. The modern standard is a cable with a Type-C plug on each end; these cables are non-directional, leaving it to the connected devices to negotiate their respective roles. All legacy receptacles are either Type-A or Type-B except the Micro‑AB and (deprecated) Mini‑AB receptacles. Such an Type-AB receptacle accepts both Type-A and Type-B plugs, and a device with such a receptacle takes the DFP (host, hub DFP) or UFP (peripheral device, hub UFP) role according to the type of plug attached.
There are three sizes of legacy USB connectors: The original Standard, the Mini connectors, which were the first attempt to accommodate handheld mobile equipment (now mostly deprecated), and Micro, all of which were superseded in 2014 by Type‑C, which is required for operation modes with two lanes (USB 3.2 1×2 (10 Gbit/s), USB 3.2 2×2 (20 Gbit/s), or any USB4 modes) and allows power up to 240 watts in either direction.
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USB hardware AI simulator
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USB hardware
The initial versions of the USB standard specified connectors that were easy to use and that would have high life spans; revisions of the standard added smaller connectors useful for compact portable devices. Higher-speed development of the USB standard gave rise to another family of connectors to permit additional data links. All versions of USB specify cable properties. Version 3.x cables, marketed as SuperSpeed, added a data link; namely, in 2008, USB 3.0 added a full-duplex lane (two twisted pairs of wires for one differential signal of serial data per direction), and in 2014, the USB-C specification added a second full-duplex lane.
USB has always included some capability of providing power to peripheral devices, but the amount of power that can be provided has increased over time. The modern specifications are called USB Power Delivery (USB-PD) and allow up to 240 watts. Initially USB 1.0/2.0 provided up to 2.5 W, USB 3.0 provided up to 4.5 W, and subsequent Battery Charging (BC) specifications provided power up to 7.5 W. The modern Power Delivery specifications began with USB PD 1.0 in 2012, providing for power delivery up to 60 watts; PD 2.0 version 1.2 in 2013, along with USB 3.1, up to 100 W; and USB PD 3.1 in 2021 raised the maximum to 240 W. USB has been selected as the charging format for many mobile phones and other peripherial devices and hubs, reducing the proliferation of proprietary chargers. Since USB 3.1 USB-PD is part of the USB standard. The latest PD versions can easily also provide power to laptops.
A standard USB-C cable is specified for 60 watts and at least of USB 2.0 data capability.
In 2019, USB4, now exclusively based on USB-C, added connection-oriented video and audio interfacing abilities (DisplayPort) and compatibility to Thunderbolt 3+.
Unlike other data buses (such as Ethernet), USB connections are directed; a host device has downstream-facing ports (DFP) that connect to the upstream-facing port (UFP) of hubs or peripheral devices. USB implements a tiered star-like network topology.
Only downstream-facing ports originally provided power by default; this topology was chosen to easily prevent electrical overloads and damaged equipment.
Every legacy USB cable has two distinct ends with mechanically distinct plugs, one Type-A plug (connecting to a downstream-facing port of a host or hub) and one Type-B plug (connecting to the upstream-facing port of a hub or peripheral device). Each format has a plug and receptacle defined for each of the A and B ends. A USB cable, by definition, has a plug on each end. With one exception (Type-A to Type-A plugs) every cable had one Type-A plug and one Type-B plug. With the release of Type‑C came transitional cables: a Type‑C plug at one end and a Type-A or a Type-B plug at the other. These transitional cables are still directional, and in such a cable the Type‑C plug is electrically marked as either A or B as appropriate to complement the opposite connector. The modern standard is a cable with a Type-C plug on each end; these cables are non-directional, leaving it to the connected devices to negotiate their respective roles. All legacy receptacles are either Type-A or Type-B except the Micro‑AB and (deprecated) Mini‑AB receptacles. Such an Type-AB receptacle accepts both Type-A and Type-B plugs, and a device with such a receptacle takes the DFP (host, hub DFP) or UFP (peripheral device, hub UFP) role according to the type of plug attached.
There are three sizes of legacy USB connectors: The original Standard, the Mini connectors, which were the first attempt to accommodate handheld mobile equipment (now mostly deprecated), and Micro, all of which were superseded in 2014 by Type‑C, which is required for operation modes with two lanes (USB 3.2 1×2 (10 Gbit/s), USB 3.2 2×2 (20 Gbit/s), or any USB4 modes) and allows power up to 240 watts in either direction.