Embedded USB Programming on STM32: Build Real USB Devices

==> Note: This course is still under development. The instructor is actively adding new videos every week <==

Do you want to build practical USB skills that are useful in real embedded product development? Then this is the right course for you

USB is one of the most widely used interfaces for connecting embedded devices to computers. Keyboards, mice, webcams, storage devices, measurement instruments, audio devices, and many other products rely on USB for communication with a host system.

However, implementing USB in an embedded system is considerably more involved than working with interfaces such as UART, SPI, or I2C.

One of the main difficulties is that USB is not simply a peripheral interface. It is a host-controlled communication protocol with multiple layers of operation, standardized device classes, descriptors, endpoints, transfer types, configuration rules, timing requirements, and host-side expectations.

Engineers learning USB commonly encounter several challenges.

The USB specification is extensive and uses terminology that can be difficult to understand without first developing a clear protocol model. Concepts such as enumeration, descriptors, configurations, interfaces, endpoints, control transfers, interrupt transfers, bulk transfers, device classes, requests, packets, transactions, and transfer scheduling are closely related. Understanding one concept often depends on understanding several others.

USB development also requires understanding the interaction between multiple layers:

• The USB electrical interface

• The USB protocol

• The USB device controller inside the microcontroller

• Device descriptors and class-specific descriptors

• Endpoint configuration

• USB device classes

• MCU vendor HAL or low-level drivers

• USB middleware

• Host operating-system behavior

• Host-side drivers and class support

Another difficulty is debugging. A USB device may compile and run correctly on the microcontroller while still failing to enumerate on the host. A small error in a descriptor field, endpoint definition, USB clock configuration, request response, or middleware configuration can cause the operating system to reject the device.

Learning resources can also be fragmented. Some material concentrates only on the USB specification, while other material demonstrates vendor-generated code without adequately explaining the protocol behind it. Example projects can therefore be difficult to modify because the relationship between the generated firmware, USB descriptors, middleware, and host behavior is not always clear.

This course is designed to address these problems systematically.

Course Approach

The course begins with the USB architecture and protocol before moving to STM32 implementation.

You will first understand questions such as:

• What is USB?

• What is the role of the USB host?

• What is the role of the USB device?

• Why is USB host controlled?

• How does a device detect and establish a connection with the host?

• What happens during USB enumeration?

• What information does the device provide during enumeration?

• What are USB descriptors?

• How are configurations, interfaces, and endpoints represented?

• What are control, interrupt, bulk, and isochronous transfers?

• How does the host determine which driver or USB class should handle a device?

These concepts are explained before examining the STM32 USB implementation so that the generated firmware can be understood in the context of the USB protocol.

Hands-On Projects

The course includes two complete USB device implementations.

USB HID Mouse

You will configure an STM32 microcontroller as a USB Human Interface Device and implement a USB mouse.

This project introduces the HID class and demonstrates concepts including:

• HID descriptors

• Report descriptors

• Interrupt endpoints

• HID reports

• Host polling

• Device enumeration

• Mouse movement data

• Interaction with the operating system's standard HID driver

The host PC will recognize the STM32 as a USB mouse without requiring a custom host driver.

USB Mass Storage Device

You will then configure the STM32 as a USB Mass Storage Class device that can be mounted by the host operating system as a storage drive.

This project introduces a substantially different USB class and allows you to examine:

• Mass Storage Class descriptors

• Bulk endpoints

• Bulk transfers

• Host storage requests

• USB Mass Storage middleware

• Storage abstraction

• Host file-system interaction

The objective of using two different USB classes is to demonstrate how the same USB architecture supports devices with very different communication requirements.

Capstone Exercise

After completing the HID mouse implementation, you will extend the HID concepts by developing a custom HID keyboard with macro keys.

The purpose of this exercise is to apply the protocol concepts independently rather than reproducing an existing implementation.

You will need to modify the HID configuration, report descriptor, report format, and application behavior according to the requirements of the new device.

Why USB Is an Important Embedded-System Skill

USB is a valuable skill for engineering students, early-career engineers, and experienced embedded professionals. It helps you move beyond basic GPIO, UART, SPI, and I2C projects and work on real products that communicate directly with a PC. Understanding USB descriptors, enumeration, endpoints, device classes, and debugging can strengthen your practical skills, improve your career opportunities, and help you handle real USB development and debugging tasks with confidence.

Use of AI During Course Development

AI-assisted tools were used during preparation of some slide decks, supporting notes, and portions of development work for this course.

The technical material is reviewed by engineers before publication. Technical claims are subjected to an additional scrutiny process against the relevant USB specification and expected hardware behavior.

The practical projects are also implemented and tested on the target hardware before being included in the course.

AI is therefore used as an engineering productivity tool during preparation rather than as the authority for technical correctness.

If an error or ambiguity is identified in the slides, notes, or implementation, students are encouraged to report it through the course Q&A or direct-message facility so that it can be reviewed and corrected.

Use of AI Tools by Students

The course does not require the use of a particular AI development tool.

Students may use development assistants such as Claude Code, ChatGPT, GitHub Copilot, or other tools if they choose.

The important USB firmware sections are explained in the course so that the implementation can be understood independently of whether an AI-assisted development workflow is used.

The course is intended to provide both the protocol knowledge and practical implementation experience required to approach USB device development systematically.

Hardware and Software Used in This Course

1. Hardware

To test all the exercise code and projects throughout this course, we use the FastBit Nano board, which is based on the STM32F303CC microcontroller.

However, you are not required to use the same board. You can use any STM32 development board or even a board from a different MCU vendor, as long as the microcontroller supports a USB Full-Speed (USB FS) peripheral. Some minor code or configuration changes may be required depending on the board you use.

2. Software

We use STM32CubeIDE and STM32CubeMX throughout the course for development and configuration.

Both tools are free to download and use.

==> Note: This course is still under development. The instructor is actively adding new videos every week <==