USB (Universal Serial Bus) is a serial bus standard that connects computer systems with external devices, and is also a technical specification for input/output interfaces. It is widely used in information communication products such as personal computers and mobile devices, and has been extended to other related fields such as photography equipment, digital TVs (set-top boxes), game consoles, etc.
1. USB History
The USB interface was jointly developed by computer and communication companies such as Intel, Compaq, Digital, IBM, Microsoft, NEC, and Northern Telecom in 1995. After nearly 30 years of development, it gradually formed the current industry standard.
USB has iterated several versions including USB1.0/1.1, USB2.0, and USB3x, ultimately evolving into the current USB4; The transmission rate has also significantly increased from the initial 1.5Mbps to the latest 40Gbps!
1.2 USB Features
USB has the advantages of fast transfer speed, easy use, support for hot swapping, flexible connection, independent power supply, and protocol backward compatibility. It can connect various peripherals such as keyboards, mice, and large capacity storage devices. This interface is also widely used in smartphones.
2 USB transmission standards for various versions
The USB transmission standard has evolved from USB1.0/USB1.1->USB2.0->USB3x ->USB4.0. The flags, transmission rates, and theoretical speeds for each version are shown in the following figure.
Today, the latest version has been updated to USB4!
USB 4 -> USB 4 Gen3x2
USB 1.0 -> USB 2.0 Low-Speed
USB 1.1 -> USB 2.0 Full-Speed
USB 2.0 -> USB 2.0 High-Speed
USB 3.0 -> USB 3.1 Gen1 -> USB 3.2 Gen1
USB 3.1 -> USB 3.1 Gen2 -> USB 3.2 Gen2x1
USB 3.2 -> USB 3.2 Gen2x2
USB Type C interface
Also known as USB-C, as a new generation universal interface, it integrates functions such as USB data, PD charging, audio and video display output, and is expected to become the unified interface in the market. It was proposed along with the USB 3.1 (specifically referring to USB 3.1 Gen2, now known as USB 3.2 Gen 2, the same below) standard.
USB4 only has one physical interface, USB Type-C. USB4 divides different "tunnels" on the transmission link to transmit data, and can "dynamically allocate bandwidth" by dynamically adjusting the bandwidth of each part based on the real-time situation of each "tunnel". Currently supports three types: data transmission (USB 3.2 tunnel), video transmission (DisplayPort 1.4a tunnel), and optional tunnel (PCI-E tunnel).
