USB Complete or USB Confusing?



Is USB too universal? So far we don’t have fewer cables, just USB cables. And USB Type-C promises much.

One of the first technical books that I read cover-to-cover was not The Art of Electronics (although a good reference). It was USB Complete by Jan Axelson. I had recently begun a new role at TI in the Connectivity group, and her book helped me bootstrap myself into the detailed technical world of USB. Axelson has written several books, and as I await my copy of USB Complete (5th edition), I have to wonder where USB will go from here. SuperSpeed Plus (SS+), a.k.a. USB 3.1 Gen 2, can transfer data at up to 10 Gbps and reduces the power needed to transfer large amounts of data (over USB 2.0/High Speed).

The first USB chip was released by Intel® in 1995. The USB 1.0 specification was introduced in January 1996 and defined low speed at 1.5 Mbps and full speed at 12 Mbps. USB was originally devised to create a “plug and play” experience that also consolidated many cables and protocols. USB has replaced parallel ports for printers, PS/2 for the mouse, RS232 serial cables, and even A/C adapters.

USB has become complicated as the latest specs include up to 100 watts of power delivery (USB-PD), a connector that is impossible to plug in upside down (USB Type-C), and multiple data transfer rates while being backward compatible through all speeds defined in USB 2.0 specs. The USB-PD spec also defines USB alternate mode, enabling USB-C cables to support HDMI, DisplayPort, Thunderbolt™, MHL, and PCIe as a “full-featured” cable.

Should USB Complete be named USB Confusing? Most laptops still come with a mixture of USB ports, presumably slower USB ports for a mouse and/or keyboard (how fast can you type?). This makes sense until you connect a couple of external monitors via USB and plug into one of the slower ports. Not all USB Type-C cables are created equal. Apparently, many USB-C cables are not made to spec and can destroy connected electronics.

USB Type-C, USB 3.1, and USB-PD are not yet in wide use together as all-in-one, full-featured cables. We can look forward to reducing the total number of cables. Global adoption of USB Type-C appears to be primarily in the wireless segment.

 

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