The universal serial bus has become the standard interface for connecting devices to computers. Whether it's an external hard drive, camera, mouse, printer, or scanner, the physical connection to transfer data between devices is typically via a USB cable. The interface is certainly universal. USB technology has been in development for more than 20 years since 1993. The first official definition, USB1.0, was introduced in 1996. It provides a low transfer rate of 1.5MB/s for the subchannel keyboard and mouse, and a transfer rate of 12MB/s at full speed channel. USB2.0 was introduced in 2001, achieving a leap forward in transmission rates of up to 480MB/s. In 2010, USB3.0 finally hit the market. USB3.0 is the third major version of the universal serial bus standard for computer connectivity. Among other improvements, USB3.0 adds a new transmission mode called "superfast," capable of transmitting data at speeds up to 5GB/s, more than 10 times the speed of the USB2.0480MB/s. In addition to the different connectors used on the USB3.0 cable, the various USB3.0 connectors also have SS uppercase letters on the blue ports or plugs that differ from version 2.0. A successor, called USB3.1, was introduced in July 2013 and offers speeds up to 10GB/s, about the same as the first version of Thunderbolt.

USB2.0 (high speed USB)

Updated specification USB 2. 0, also known as high speed USB2. 0, launched in 2002. It increases the data transfer rate from PC to USB device to 480 Mbps, 40 times faster than USB1. 1 specification. Peripherals that require higher bandwidth and higher throughput, such as digital cameras, CD recorders, and video devices, can now also be connected to USB. In addition, it allows multiple high-speed devices to run simultaneously. 0 is it can support Windows xp through Windows update." .

Physical differences

Physical differences between USB 2. 0 and USB 3. 0 depends on the number of connections. This new topology can significantly increase the utilization of the bus and thus the throughput of the system. USB 2.0 supports half-duplex communication using a four-wire connection. In this architecture, as long as there is a two-way data pipeline, one-way transmission of data can be realized at any given time. By contrast, USB 3. 0 add 5 connections to bring the total number of connections to 9, and use unicast duplex data interface to allow two one-way data pipes to handle one-way communication separately.

Greater bandwidth

Usb 3.0 improves the bulk data transfer mechanism of Usb. The effective available bandwidth of the volume transfer method is about 400Mb/s, about 10 times that of USB2. 0, this important transfer mechanism allows machine vision camera manufacturers to build high throughput USB 3. Camera. This not only creates an opportunity for the integrator to save a lot of cost, but also improves the speed and efficiency of the whole system. Users can now cover the same imaging area with a high resolution USB 3.0 camera while using fewer cameras. In addition, greater bandwidth allows for faster frame rates and higher system performance.

The power output

USB3.0 also provides more efficient power management capabilities and greater power output than USB2.0. The USB3.0 device can support 900 mA of ultra-high speed current, increasing the total power output from 2.5w to 4.5w (voltage 5V).

Better communication quality

USB 2. 0 adopts a communication architecture in which data transactions must be initiated by the host. The host frequently polls the device and requests data, and the device only sends data when the host makes a request. High polling frequencies increase power consumption and transmission latency because data is sent only when the host polls the device. USB3. An improvement on 0 based on this communication mode not only reduces transmission latency by minimizing polling frequency, but also enables the device to transmit data as quickly as possible.

Low power consumption, high power supply capacity

USB3.0 reduces power consumption while increasing support and power output. The introduction of the USB battery charging specification 1.2 allows for up to 7.5w of power to be supplied to USB3.0 devices. In addition, USB3.0 can also provide an improved mechanism for entering and exiting low-power states based on whether the device is active, thereby eliminating more power-consumption polling.

The length of the cable

The standard maximum cable length for USB2.0 devices is 5 meters. The USB3.0 standard does not specify a standard length; The maximum cable length currently supported by USB3.0 is 3 meters.

The time stamp

Unlike the USB2.0 camera, which has an accuracy range of 0 to 125us, the timestamp from the USB3.0 camera is more accurate and can mimic the accuracy of the FireWire camera's 1394 cycle timer.

Phy register and network topology

You can view the network topology of the USB3.0 camera on the bus. However, PHY node information is not available. The USB2.0 camera does not provide an interface to view topology or PHY node information.

Usb 3.0 vision

There are some machine vision standards for common interfaces, such as the iidc interface for fire wire and the gigevision interface for Ethernet. Although there is currently no camera control standard for us b2.0 cameras, a new standard for us b3.0 cameras called us b3vision was approved in 2013.. Data flow mechanisms, mechanical requirements, and testing frameworks.

Better error management, more efficient power supply, longer cables, lower latency and jitter times overcome all of these limitations, making the interface a practical choice for cameras within a year and laying a solid foundation for the official acceptance of the USB3.0 vision standard in January 2013.