In the recent two decades of development in the field of science and technology, USB has played a pivotal role. For example, in terms of data transmission and power consumption, it affects our lives to a large extent. Coupled with the popularization of USB Type-C technology, USB is once again promoted. On the cusp of the storm. For this reason, this article focuses on introducing the basic working principle, development history, and some characteristics of USB3.1 and Type C, and I hope it will be helpful to readers.
USB is an external bus standard, used to regulate the connection and communication between computers and external devices. The USB interface has plug-and-play and hot-swappable functions. The interface can be connected to 127 kinds of peripherals, such as a mouse and a keyboard. USB was launched in 1996 by Intel and other companies jointly at the end of 1994. It has successfully replaced serial and parallel ports, and has become a necessary interface for today's computers and a large number of smart devices.
USB development historyUSB 1.0
USB 1.0 appeared in 1996, and the speed was only 1.5Mb/s. In 1998, it was upgraded to USB 1.1, and the speed was greatly increased to 12Mb/s. This standard interface can still be seen on some old devices. USB1.1 is a relatively common USB specification. The transmission rate of the high-speed mode is 12Mbps, and the transmission rate of the low-speed mode is 1.5Mbps. b/s generally represents the bit transmission rate, and bps represents the bit transmission rate, which are equal in value. B/s and b/s, BPS and bps should not be confused.
USB 2.0
The USB2.0 specification is evolved from the USB1.1 specification, and the transmission rate has reached 480Mbps, which is converted into MB to 60MB/s, which is sufficient to meet the rate requirements of most peripherals. The "enhanced host controller interface" in USB 2.0 defines an architecture compatible with USB 1.1, which can drive USB 1.1 devices with USB 2.0 drivers. In other words, all devices that support USB 1.1 can be used directly on the USB 2.0 interface without worrying about compatibility issues, and accessories such as USB cables, plugs, etc. can also be used directly.
For engineers, the main obstacles to the development of USB2.0 interface products are: to face the complex USB2.0 protocol, to write USB device drivers, and to be familiar with the programming of the microcontroller. This not only requires considerable VC programming experience, but also the ability to write hardware programs for the USB interface, so most people give up on their own development of USB products.
USB 3.0
The USB 3.0 Promoter Group, composed of industry giants such as Intel, Microsoft, Hewlett-Packard, Texas Instruments, NEC, ST-NXP, etc., is responsible for the development of a new generation of USB 3.0 standards. The theoretical speed of USB 3.0 is 5.0Gb/s. In fact, it can only reach 50% of the theoretical value, which is also close to 10 times that of USB 2.0. The physical layer of USB3.0 uses 8b/10b encoding, so the theoretical speed calculated is only 4Gb/s, and the actual speed has to be deducted from the protocol overhead, which should be less on the basis of 4Gb/s. It can be widely used in PC peripherals and consumer electronic products.
USB 3.0 will be called "USB SuperSpeed" in actual device applications, conforming to the previous USB 1.1 FullSpeed ​​and USB 2.0 HighSpeed.
The next-generation type-c USB interface can support both front and back plugs, and has a strong data transmission signal, but there are currently limited manufacturers.
USB 3.1
The USB 3.1 specification was released in 2013 and is divided into two versions, Gen 1 and Gen 2. In fact, the Gen 1 version is just a vest of USB 3.0 (the theoretical maximum is still 5Gbps, and there is no change), but there are still type-c USB 3.1 Gen 1 sold, which is equivalent to USB 3.0 type-c. USB 3.1 still retains the Type-A version. USB 3.1 has changed a lot. Not only the Gen 2 version can provide twice the transmission speed of USB 3.0, but also the type-c interface released at the same time uses a fool-proof design, which supports positive and negative insertion, but USB 3.1 does not support downwards. Need to use adapter.
In December 2013, the USB 3.0 promotion team has announced the rendering of the next-generation USB Type-C connector, and then it is ready for mass production in August 2014. The highlight of the new version of the interface is a slimmer design, faster transmission speed and stronger power transmission. The biggest feature of the Type-C double-sided pluggable interface is that it supports double-sided insertion of the USB interface, which formally solves the worldwide problem of "USB is never inserted correctly". The front and back are plugged in casually, and the USB data cable used with it must also be used. Thinner and lighter.
USB 3.1 and USB Type-C are not a conceptSome people must have noticed that sometimes the terms USB 3.1 and USB Type-C are interchangeable in certain situations, which has caused many people to blur the line between these two concepts. Simply put, USB 3.1 is an industry standard and the revision number of the current standard. This is a technical standard, not a physical product. But USB Type-C is a new type of connector, consisting of Type-C plug and Type-C socket.
More importantly, although USB Type-C is designed based on USB 3.1, it does not mean that devices using this connection method support the USB 3.1 standard. For example, the Nokia N1 tablet, although it also uses a USB Type-C plug, is still a USB 2.0 device. The same concept also applies to OnePlus 2 smartphones.
At the same time, for devices that use the USB 3.0 Type-A interface, this blue-marked interface often appears on laptops and desktops, but is compatible with the USB 3.1 standard. So what's the point of doing this? Why do some devices use a USB Type-C interface that is not compatible with the USB 3.1 standard? That's right, just for convenience.
Generally speaking, USB Type-C has the following characteristics:
1. The maximum data transmission speed reaches 10Gbit/sec, which is also the standard of USB 3.1;
2. The size of the Type-C interface socket end is about 8.3mm×2.5mm slim design;
3. Support the "positive and negative insertion" function that can be inserted from both sides, which can withstand 10,000 times of repeated insertion and removal;
4. The standard specification cable equipped with Type-C connector can pass 3A current, and it also supports "USB PD" that exceeds the existing USB power supply capacity, and can provide a maximum of 100W of power.
USB Type-C will become the dominant USB connectionThe USB Type-C plug and interface can support USB 3.1 high-speed connection, can transmit 4K standard signals in the display port, and bear 100w of power, and all this is done at the same time, as long as all technical standards are met. Since USB Type-C will not be outdated at present, it is likely to become the dominant form of USB connection in the future.
At present, some manufacturers and products have begun to take action. For example, Apple's MacBook uses a Type-C single interface design, which can be used for multiple functions such as charging, data transmission and video output; Google's Chromebook Pixel is also equipped with two USB Type-C interfaces, and achieve the same effect.
However, the gradual popularization of USB Type-C will cause a large number of existing USB data cables to become useless because they are not compatible with USB Type-C. We cannot insert microUSB into the USB Type-C interface, but compared to the more advantages brought by USB Type-C, it is also a general trend to eliminate the old batch of connection standards.
Summary: In the future, there will still be some problems with device compatibility. Before the popularization of USB Type-C interface, users still need to use various conversion devices for interface conversion to be able to use it smoothly. For example, USB-C to USB Adapter converter, USB-C Digital AV Multiport Adapter (HDMI converter), power supply, also need USB-C power adapter.
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