Awareness | USB Connection Process Explained

Gain a better understanding of the USB connection process.

Updated at November 17th, 2023

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Table of Contents


USB Enumeration

When a USB device is connected to a computer, it undergoes a process called enumeration. Enumeration is the process of the host computer identifying the device and assigning it a unique address, after which the device becomes available for communication with the host. 

USB Enumeration Process

  1. Device Connection: The USB device is physically connected to the USB port of the host device.
  2. Bus Power and Speed: The host sends a signal to the device to supply power and negotiate the data transfer speed.
  3. Device Descriptor Request: The host request the device descriptor, which contains information such as the manufacturer ID, product ID, and USB version.
  4. Configuration Descriptors: The device sends configuration descriptors to the host, which describe the device's configuration settings, such as the number of interfaces and endpoints.
  5. Interface and Endpoint Descriptors: The device sends interface and endpoint descriptors to the host, which describe the communication protocols used by the device.
  6. Device Configuration: The host selects a configuration based on the information provided by the device and configures the device.
  7. Device Enumeration: The device is assigned a unique address, after which it becomes available for communication with the host.
  8. Device Operation: The device can now be used by the host computer to send and receive data.


The USB enumeration process is an important part of the USB standard, as it allows devices to be recognized and configured by the host device, and enables communication between the two devices.


Example 1


Example 2