What is USB ? USB stands for Universal Computer and is a standard for connectors, cables, and protocols used to transfer data and power between a computer and other electronic device. It was designed in 1995 to provide a single connection method for things like computer keyboards, mice, and printers, as well as connected devices like mp3 players and cameras. The standard USB interface has four wires (USB 3.0 has eight for dual data transfer), two of which act as power wires and two for data transfer. Commercial applications have up to eight wires and connection points, and can also provide 12 or 24 volts in addition to the usual 5 volts. You will see similar systems in cash registers and commercial barcode scanners.
We are most interested in the implementation in mobile devices. Most mobile devices in the world use USB 2.0 for data and/or power. China passed laws forcing manufacturers to adhere to the USB standard for data and power, and in December 2011, a law was written that all mobile phones would be able to use the same micro USB charger as standard. European Committee for Electrotechnical Standardization. This only applies to phones — tablets and laptops are exempt from liability as they have different power requirements.
Most of the new Android phones you buy have a microUSB connector (like the one in the picture above). The data cable will have a small connector for connecting to a phone at one end, and a standard USB connector for connecting to a computer. This cable will allow you to transfer data — copy pictures or music or hack a little, as well as 5 volts to charge the device. Some older models have a miniUSB connector that does the same but with a slightly larger port. MicroUSB is a more reliable connector, rated for 10,000 «insert cycles», so both the port on the phone and the cable should last longer. Some devices require a non-standard USB connector, such as the Galaxy Tab 10.1 (or just about any other Android tablet). The internal design does not allow the use of a standard microUSB connector on the board, so a wider and thinner connector and port was used. Also, some tablets may not be able to get enough power to charge via USB and use a separate DC outlet and charging adapter. For devices such as the iPhone that have a non-standard connection port, an adapter can be made that will allow them to meet the European requirements for a single charger.
Finally, some phones use the microUSB interface for purposes other than data transfer and power. Monitoring the HDMI output transmitted via MHL (Conventional High Definition Ink L ), is becoming quite common and allows the use of a special adapter to transfer high-definition video to TVs or computer monitors. These adapters can be purchased for about $15 (US) and allow you to connect a standard HDMI cable to your phone.
We’ve seen other connection methods come and go, and new ones always work, but USB offers relatively high-speed data transfer, adapts to varying power needs, and is likely to stay around for a long time.
Previously on Android A to Z: What is snapping? ; Find More in Android Dictionary