USB Stack Skill

Overview

This skill provides USB device and host stack implementation expertise for embedded systems, covering descriptor generation, device class implementation, and protocol debugging.

Capabilities

USB Descriptor Generation

Device descriptor configuration
Configuration descriptors
Interface descriptors
Endpoint descriptors
String descriptors
BOS descriptors (USB 3.x)

Device Class Implementation

CDC (Communications Device Class)
HID (Human Interface Device)
MSC (Mass Storage Class)
DFU (Device Firmware Upgrade)
Audio class
Video class
Custom class implementation

USB Stack Configuration

TinyUSB configuration
STM32 USB stack setup
NXP USB stack integration
Zephyr USB subsystem
Endpoint buffer management

Enumeration and Debugging

Enumeration sequence debugging
Protocol analysis
USB analyzer integration
Descriptor validation
Compliance testing

Advanced Features

Composite device configuration
USB power delivery
High-speed/full-speed selection
Isochronous transfers
Interrupt transfers
Bulk transfers

DFU Implementation

DFU bootloader design
Runtime DFU mode
Detach and download
Upload capability
Manifest phase handling

Target Processes

device-driver-development.js - USB driver implementation
bootloader-implementation.js - USB DFU bootloader
hw-sw-interface-specification.js - USB interface specification

Dependencies

TinyUSB or vendor USB stack
USB protocol analyzers
usb-tools (lsusb, usbmon)

Usage Context

This skill is invoked when tasks require:

USB device implementation
Device class development
USB bootloader creation
Protocol debugging
Descriptor optimization

Device Class Examples

CDC Virtual COM Port

tusb_desc_interface_t cdc_interface = {
    .bLength            = sizeof(tusb_desc_interface_t),
    .bDescriptorType    = TUSB_DESC_INTERFACE,
    .bInterfaceNumber   = 0,
    .bAlternateSetting  = 0,
    .bNumEndpoints      = 2,
    .bInterfaceClass    = TUSB_CLASS_CDC,
    .bInterfaceSubClass = CDC_COMM_SUBCLASS_ACM,
    .bInterfaceProtocol = CDC_COMM_PROTOCOL_NONE,
    .iInterface         = 0
};

HID Report Descriptor

uint8_t const hid_report_desc[] = {
    HID_USAGE_PAGE(HID_USAGE_PAGE_DESKTOP),
    HID_USAGE(HID_USAGE_DESKTOP_MOUSE),
    HID_COLLECTION(HID_COLLECTION_APPLICATION),
        HID_USAGE(HID_USAGE_DESKTOP_POINTER),
        HID_COLLECTION(HID_COLLECTION_PHYSICAL),
            // ... buttons and axes
        HID_COLLECTION_END,
    HID_COLLECTION_END
};

Configuration

usb:
  vid: 0x1234
  pid: 0x5678
  device_class: cdc | hid | msc | dfu | composite
  speed: full | high
  endpoints:
    - ep1_in: bulk, 64
    - ep1_out: bulk, 64

usb-stack