ESP Hardware Abstraction Layer for USB Peripheral(s)

[!NOTE] This component is currently in beta. Its API, behavior, and compatibility may change at any time and without notice; backward compatibility is not guaranteed. Use caution when integrating into production systems.

Overview

The esp_hal_usb component provides a Hardware Abstraction Layer for USB controllers and PHYs across all ESP-IDF supported targets. USB (Universal Serial Bus) enables communication between the ESP device and USB hosts or devices, supporting various USB speeds and transfer types for data exchange.

Architecture

The USB HAL is structured in two main sub-layers:

1. HAL Layer (Upper): Defines the operational steps and data structures required to control USB peripherals (e.g., initialization, endpoint configuration, transfer management, PHY control).

2. Low-Level Layer (Bottom): Serves as a translation layer between the HAL and the register files defined in the soc component, handling target-specific register configurations.

Supported USB Controllers and PHYs

This HAL supports various USB controller and PHY types depending on the ESP chip:

• USB-DWC (DesignWare USB Controller): The main USB OTG controller supporting USB Host and Device modes

• USB Serial JTAG: A special USB peripheral that combines USB CDC-ACM functionality with JTAG debugging capabilities

• USB WRAP: A wrapper/peripheral controller that provides additional USB functionality and GPIO matrix integration

• USB PHY Types:

  • FSLS (Full Speed/Low Speed) Internal PHY: Built-in PHY supporting USB Full Speed and Low Speed operation
  • FSLS External PHY: Support for external FSLS PHY via GPIO matrix
  • UTMI PHY: UTMI+ compliant PHY interface for High Speed USB support

Features

• USB controller initialization and configuration
• Endpoint management (IN/OUT endpoints)
• Transfer type support (Control, Bulk, Interrupt, Isochronous)
• USB speed detection and configuration (High Speed, Full Speed, Low Speed)
• FIFO configuration and management
• PHY initialization and control (FSLS and UTMI)
• GPIO matrix signal routing for USB PHY interfaces
• OTG (On-The-Go) signal handling
• Interrupt management and event handling
• Multi-controller support (on chips with multiple USB controllers)

Usage

The HAL functions primarily serve ESP-IDF USB drivers, primarily the USB Host stack.

Dependencies

• soc: Provides chip-specific register definitions
• hal: Core hardware abstraction utilities and macros

Hardware configuration

The USB-DWC2 peripheral has many internal configuration parameters. The configuration is saved GHWCFGx registers. Configuration parameters which are often checked in run-time, are cached in USB-HAL context variable usb_dwc_hal_context_t::constant_config to limit access to the registers and offload system bus.

Selected configuration parameters across ESP SoCs

	S2, S3, H4 & P4-OTG1.1	P4-OTG2.0, version < 3	P4-OTG2.0, version >= 3
HS PHY interface	None	UTMI+ 16bit	UTMI+ 16bit
Single point	Yes	No (SPLIT supported)	No (SPLIT supported)
Number of channels	8	16	16
FIFO depth	256 lines (1024 bytes)	1024 lines (4096 bytes)	1024 lines (4096 bytes)
Perio queue depth	8	4	16
NPerio queue depth	4	4	8
Transfer cnt width	16bits (max 65,535)	16bits (max 65,535)	19bits (max 524,287)
Packet cnt width	7bits (max 127)	7bits (max 127)	10bits (max 1,023)