Universal Serial Bus (USB) connectors and ports are tools that allow you to connect computer peripherals to computers, keyboards, external hard drives, or storage keys.
The numbers following the USB symbol simply correspond to the version of the USB standard in question, since the series 3.0 and 3.1 are the most recent at the time when these lines are written.
In addition to the color of its connectors (version 3.0 is generally blue), it is the data transfer rate that is the main difference between these two standards.
Therefore, the 2.0 USB standard, introduced in 2000, has ensured a much higher transfer rate than the previous standard: from 1.5 MB per second to the theoretical 60 MB! USB 3.0, released in 2008, multiplied this transfer rate of 10, reaching the theoretical rate of 625 MB per second!
Be careful, if backward compatibility is supported in the case of the 3.0 USB connectors (for example, the device with a 3.0 USB port will run on your computer with USB sockets 2.0), the transfer rate will remain blocked at 2.0 standard…
Standard USB. As soon as 1995, the USB standard was developed to connect a wide range of devices.
The 1.0 USB standard provides two modes of communication: 12 MB/s in high-speed mode.
1.5 MB/s at low speed.
The 1.1 USB standard provides some clarification to USB device manufacturers, but does not change the bit rate.
The 2.0 USB standard delivers speeds of up to 480 MBit/s.
The 3.0 USB standard delivers speeds of up to 4.8 Gbps.
In the absence of a logo, the best way to determine if it is a low or high speed USB device is to consult the product documentation until the connectors are the same.
Compatibility between 1.0, 1.1 and 2.0 USB devices is guaranteed. However, using a 2.0 USB device on a low-speed USB port (for example, 1.0 or 1.1) will limit the 12-Mbps bit rate. In addition, the operating system can display a message explaining that the stream will be limited.
There are two types of USB connectors: The so-called type A connectors, whose shape is rectangular and generally used for low-bandwidth devices (keyboard, mouse, Webcam, etc.);
The so-called type B connectors, whose shape is square and used primarily for high-speed devices (external hard drives, etc.).
Description: Type A and type B USB connectors
- Maximum power + 5v (vbus) 100 ma 2. Data (D-) 3. Data (D +) 4. Earth (GND)
USB Bus operation
The USB architecture has the characteristic of powering the connecting devices, up to a maximum of 15 W per device. It uses a cable consisting of four wires (GND Ground, Vbus power supply and two wires of data named D-and D +).
Description: USB Cable
The USB standard allows device chaining, using a bus or star topology. The devices can then be connected one after the other or branched.
Branching is done using the boxes named “Hub “, with only one input and several outputs. Some are active (providing electricity), other liabilities (computer-powered).
Description: USB Bus Port topology Description: Star USB port topology
The communication between the host (the computer) and the peripherals is performed according to a protocol (communication language) based on the token ring principle. This means that bandwidth is temporarily shared across all connected devices. The host (the computer) sends a sequence start signal every millisecond (MS), a time interval during which it will simultaneously give each of the “speech “. When the host wants to communicate with a device, it sends a token (a data packet, which contains the device address, encoded in 7 bits) by designating a device, so it is the host that decides the “Dialog ” with the devices. If the appliance recognizes its address in the token, it sends a data packet (8 to 255 bytes) in the response, otherwise it forwards the packet to other connected devices. The data thus exchanged are encoded according to the NRZI coding.
Since the address is 7-bit encoded, 128 devices (2 ^ 7) can be connected simultaneously to a port of this type.
I think I covered all the information related to the USB 2.0 and USB 3.0. If you have any questions then make comments so you can clarify your thinking.