USB Basics

Host-controlled, self-describing, and far more complex than UART: enumeration, descriptors, endpoints, and the four transfer types, plus device classes like CDC that need no custom driver.

22 min read

In this lesson:

USB's host-centric model (one master, passive devices)
enumeration: how a device introduces itself on plug-in
descriptors and endpoints, the device's self-description and data channels
the four transfer types (control, bulk, interrupt, isochronous)
device classes (CDC/HID/MSC) and why you use a USB stack, not raw registers

USB is far more complex than UART/SPI/I2C. This is the conceptual map, on an MCU you drive it through a vendor stack, not bare registers.

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