Also known as: Universal Serial Bus, USB-C

USB (Universal Serial Bus) is the most common standard for connecting peripherals to a computer and for delivering power, using a hot-pluggable, host-controlled serial bus.¹

USB is a strict tree: one host controller at the root, hubs branching below it, and devices at the leaves. Every transfer is directed by the host, and the tiers can nest until the bus reaches its limit of 127 devices — any of which can be plugged or unplugged while the system runs.

Overview

A USB system has one host (the computer) that controls a tree of devices through hubs — keyboards, mice, drives, cameras, dongles. Ports are hot-pluggable, so devices can be attached and removed while running. Successive versions (USB 2.0, 3.x, 4) raised speeds by orders of magnitude, and the reversible USB-C connector added high power delivery (USB-PD), letting one cable both run and charge a device. It is part of a machine’s I/O, distinct from internal expansion buses like PCIe.

What it’s for

USB is how most external hardware reaches the CPU: a single cable carries data and often power to a peripheral. It is central to SDR — an RTL-SDR dongle plugs into a USB port and streams IQ samples to the host, and many capture nodes are powered over the same USB connection. The trade-off versus internal buses is bandwidth and latency: convenient and universal, but a USB link will not match a dedicated PCIe slot for raw throughput.

Sources

1. USB — Wikipedia, on the Universal Serial Bus standard, versions, and connectors. ↩

See also

• Input/output (I/O)
• System bus
• PCI Express (PCIe)
• Peripheral
• Central processing unit (CPU)
• RTL-SDR