USB Basics - Coolgear

Advantages of USB

USB has gained in popularity over many of its predecessors like serial and parallel ports for many reasons. Here are a few that make USB a popular choice for connectivity:

Plug and Play – USB devices can be plugged right into the port and are ready for use once the driver software is loaded.
Speed – USB 1.0 can transfer data up to 1.5 MB/Sec, USB 2.0 can reach speeds of 60 MB/Sec. USB 3.0 can reach speeds of 625 MB/Sec (also known as SuperSpeed), while USB 3.1 (SuperSpeed+) can reach speeds of up to 2.5 GB/Sec.
Cost Effective/Expandable – USB hubs and cables are extremely inexpensive making the ability to build an infrastructure very affordable. By using hubs and cables, as many as 127 USB devices can be connected to one port.
Hot Swappable – USB devices can be connected and disconnected without first turning the power off.
Noise Immunity – For applications like remote or industrial I/O, the use of USB devices moves sensitive data conversion circuitry out of the noise filled PC environment and places it up to 5 meters away at the other end of the USB cables.

USB Protocols

The protocols in current use are USB 2.0, 3.0, and 3.1. Earlier versions are obsolete. Each version is fully compatible with earlier versions; a USB 3.1 hub can communicate with a 2.0 device, though it will be limited to 2.0 data rates. Each protocol supports more than one speed, including all the ones earlier versions support. The maximum speeds are can be seen here.

USB 2.0

USB 3.0

USB-C

Bridging the Generation Gap

The USB-C standard bridges the gap between what was USB 3.0, to the new renamed USB 3.1 Generation 1 and 2. Gen 1 of USB 3.1 supports up to 5 Gbps data transmission speed while Gen 2 supports up to 10 Gbps. Both generations of USB 3.1 are backwards compatible to earlier versions of USB, but speed is fully dependent upon the USB version of the connected device.

Compatibility runs in both directions. You can use a USB 3.1 drive with a computer that supports only 2.0, or the other way around. Of course, you’ll only get USB 2.0 speeds in either case. You should get a hub which supports a protocol version at least as high as the computer you’ll use it with.