The standard USB ports and connectors are designed to make it easier to install and use peripherals on computers. Prior to this type of connection, devices such as printers, modems and zip drives, for example, used parallel ports with low data rates. If there was a need for an internal installation, it was necessary to configure Jumpers or IRQs directly on the motherboard, which implied the opening of the computer and need to have some notion of how to configure them correctly.
In addition, each peripheral had a different type of connector on the motherboard and these connectors were not always standardized. It was not uncommon to have to resort to adapters because of a particular connector shape that is difficult to find or even completely cease to exist.
The installation of these devices was also complex because they were not automatically recognized by the computer and required model and brand specific drivers that were not always available. For these and other reasons, installing peripherals was a delegated task for technicians and, sometimes, people just gave up having a certain device on the computer.
Today, thanks to this standard, you can find virtually all peripherals and devices – from mice and keyboards to printers and cameras – compatible with this type of connector, as well as storage and data transfer media (memory cards and memory cards). Another feature brought with USB (For other USB acronyms, check ABBREVIATIONFINDER) was that the newer motherboards have at least four inputs of this type, very different from the old parallel port, which with luck you could get two.
The speed of data transmission is also significantly greater and the recognition and installation of the devices necessary for the operation of the peripherals is by the Operational System (Plug & Play), rarely requiring external drivers. In addition, you do not need to restart the computer after connecting a USB device for detection.
USB connectors type A and B
The standard Type A USB connector is the one whose image already forms in our mind when we think of this type of input – the rectangular and flattened. This type takes care of data transmission and power (remember that many USB devices can be charged by their respective cables) and are usually cables with fixed connectors.
The type B is a somewhat square in shape and is usually part of a removable cable.Unlike the USB A connector, this type of input is connected to the device instead of being connected to the computer and is usually used for sending power.
There are devices (such as cell phones, for example) that use the mini and micro USB types (A and B). These devices use cables with one of these inputs for connection to itself and another standard for connection to the computer.
USB Cables and Operation
The USB cable connectors have four internal wires, two of which are responsible for power and grounding (each for one of these functions) and two for data transmission. A USB cable can be up to 5 meters long so the data transmission time does not exceed the limit and there is no data loss. If you need larger sizes, you need to use a hub or some other equipment to repeat the communication signals.
You can connect up to 127 devices to a single USB port through a hub. The communication between these devices is done through protocols, where the Host (in this case the computer) maps through a signal everything that is connected to the USB bus and determines an address for each one of them (process called enumeration).
When this connection is properly established, the Host will also have the information pertinent to what type of data transfer each of the devices are using, which can basically be of four types:
Isochronous: used for continuous transmission devices in which the data is transferred in real time and practically without interruptions.In this type of communication there is no error detection / correction to avoid delays.A loudspeaker, for example, uses this type of connection.
Bulk: applied by devices that receive large blocks of data (larger packets). This type of connection has error detection capabilities to ensure that the information is correct and to ensure its integrity. This type of transfer is used by printers and scanners, for example.
Interrupt: This type of connection is for those devices whose data transfer rate is relatively small, such as keyboards, mice and joysticks.
Control: Used by the Host for transmission or verification of control parameters and device configuration.
As the devices are properly enumerated, the Host controls the bandwidth of the data transmission it occupies according to its type of data transmission. The distribution is up to 90% for isochronous and interrupt type transfers and 10% for bulk and control packets.
Perhaps in the future the USB standard will be completely replaced by wireless technologies, but it represented a great advance not only in the speed of data transfer, but also in the issue of standardization of wires and connections to peripherals, not to mention the Convenience of USB storage devices.