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