USB Serial Bus Decoding

USB (Universal Serial Bus) is widely adopted in today’s personal computers and tablets for communication and power to printers, keyboard, mice, memory devices and many other peripherals. It is also used for chip-to-chip and module-to-module communication in many other types of electronic devices and embedded systems. The USB specification has evolved several times since its launch in 1996.

• USB 1.1 LS (Low Speed) data rate: 1.5 Mbit/s
• USB 1.1 FS (Full Speed) data rate: 12 Mbit/s
• USB 2.0 LS (Low Speed) data rate: 1.5 Mbit/s
• USB 2.0 FS (Full Speed) data rate: 12 Mbit/s
• USB 2.0 HS (High Speed) data rate: 480 Mbit/s

Most of the USB devices being used today conform to the USB 2.0 specification.

The USB 3.0 “SuperSpeed” specification was released in 2008 with 5 Gbit/s data rate plus backward compatibility with USB 2.0 devices. USB 3.1, released in 2013, introduced a faster transfer mode called "SuperSpeed USB 10 Gbit/s" and backwards compatible with USB 3.0 and USB 2.0.

USB configurations have a single host (Master) controller that controls all bus traffic with up to 127 devices. Optional hubs can be used to expand the bus.

USB 2.0 transfers are negotiated starting at full-speed and then transition to high speed if both devices will support it. Speed of a USB 2.0 bus is limited by the slowest device connected to the host controller. With SuperSpeed USB, two host controllers are used: one for SuperSpeed USB devices and one for USB 2.0 devices.

USB settings panel in PicoScope