Supported SoCs

• RTL8721Dx

• RTL8730E

• RTL8721F

USB Overview

USB (Universal Serial Bus) is a standard serial communication interface designed to interconnect host controllers and peripheral devices.

The complete USB specification suite, including electrical, mechanical, and protocol layer documentation, is accessible at http://www.usb.org/developers.

Features

• Supports USB2.0 high-speed (480 Mbps) and full-speed (12 Mbps) modes

• Supports following USB IF standard host class drivers:

  • CDC ACM: Used for transparent communication

  • CDC ECM: Connected to CDC ECM devices for basic communication, or serve as a bridge to support network communication between CDC ECM devices and routers

  • MSC: Support mounting large capacity storage devices such as USB drives to the FatFS file system to implement file reading and writing

  • UVC: Connected to cameras, support MJPEG, H264, YUV format image capture and video stream forwarding

• Supports following USB IF standard device class drivers:

  • CDC ACM: Used for data transparent transmission or as a virtual serial port

  • HID: Used as USB keyboard, mouse and other devices to achieve human-computer interaction functions

  • MSC: Supports SD card or SRAM as storage medium for data storage

  • UAC: Used as USB audio device, it supports audio recording and playback

• Supports following USB composite device class drivers:

  • CDC ACM + HID

  • CDC ACM + UAC

  • HID + UAC

• Supports run-time host/device role switch

• Provides reference design for vendor-specific USB host/device drivers

• Full descriptor customization:

  • VID and PID

  • String descriptors

  • Endpoint mapping

• Configurable host/device core driver parameters

  • Speed mode

  • Data FIFO depth (only for dedicated FIFO mode)

  • Core ISR/thread priority

Note

RTL8721Dx only supports full-speed device mode

Hardware Features

RTL8721DxRTL8730ERTL8721F

• Supports device mode

• Supports USB 2.0 full-speed (12 Mbps) mode

• Supports DMA/slave mode

• Endpoint configurations:

  • EP0: INOUT (for Control transfer only)

  • EP1: IN

  • EP2: OUT

  • EP3: IN

  • EP4: OUT

  • EP5: INOUT

Note

One and only one periodic IN endpoint is supported.

• Shared FIFO with following configurations:

  • Total FIFO depth: 768 DWORD

  • Shared receive FIFO: 472 DWORD (max)

  • Shared non-periodic transmit FIFO: 32 DWORD (max)

  • Dedicated periodic transmit FIFO: 256 DWORD (max)

Note

8 DWORD FIFO shall be reserved for DMA registers in DMA mode.

Software Stack Overview

Software Architecture

The architecture of USB software stack:

RTL8721DxRTL8730ERTL8721F

Where:

• USB HAL driver: Implements SoC-specific hardware driver for power management and phy calibration, exposing unified HAL API to upper-layer core drivers.

• USB host/device core drivers: Integrates USB IP-specific hardware driver, host/device controller driver, enumeration state machine and transfer scheduling algorithms, exposing unified core API for designers to develop classes and applications.

• USB host/device class drivers: Delivers USB-IF class-compliant drivers via class-specific API, enabling rapid deployment of standard USB solutions

• USB host/device applications: Provides reference designs for USB solutions

File Organization

USB HAL Driver

Path	Description
{SDK}/component/soc/amebaxxx/fwlib/include/ameba_usb.h	USB HAL API definition header file, refer to USB硬件抽象层

USB Core Driver

RTL8721DxRTL8730ERTL8721F

Path	Description
{SDK}/component/component/usb/common/	USB common core driver API definition header file
{SDK}/component/component/usb/device/core/usbd.h	USB device core driver API definition header file
{SDK}/amebadplus_gcc_project/project_km4/asdk/lib/application/lib_usbd.a	USB device core driver static library file

USB Class Driver

Path	Description
{SDK}/component/component/usb/device/cdc_acm/	CDC ACM device class driver
{SDK}/component/component/usb/device/composite/	Composite device class driver
{SDK}/component/component/usb/device/hid/	HID device class driver
{SDK}/component/component/usb/device/inic/	INIC device class driver (non-standard)
{SDK}/component/component/usb/device/msc/	MSC device class driver
{SDK}/component/component/usb/device/uac/	UAC device class driver
{SDK}/component/component/usb/device/vendor/	Vendor-specific device class driver
{SDK}/component/component/usb/host/cdc_acm/	CDC ACM host class driver
{SDK}/component/component/usb/host/cdc_ecm/	CDC ECM host class driver
{SDK}/component/component/usb/host/msc/	MSC host class driver
{SDK}/component/component/usb/host/uvc/	UVC host class driver
{SDK}/component/component/usb/host/vendor/	Vendor-specific host class driver

Host Class driver, refer to Host Class driver

Device Class driver, refer to Device Class driver

USB Application

Path	Description
{SDK}/component/component/example/usb/usbd_cdc_acm/	Transparent communication device example based on CDC ACM device class
{SDK}/component/component/example/usb/usbd_cdc_acm_hid/	Composite device example based on CDC ACM and HID device classes
{SDK}/component/component/example/usb/usbd_cdc_acm_uac/	Composite device example based on CDC ACM and UAC device classes
{SDK}/component/component/example/usb/usbd_uac_hid/	Composite device example based on HID and UAC device classes
{SDK}/component/component/example/usb/usbd_hid/	HID device example
{SDK}/component/component/example/usb/usbd_inic/	INIC device example
{SDK}/component/component/example/usb/usbd_msc/	Mass storage device example based on MSC device classes
{SDK}/component/component/example/usb/usbd_uac/	Audio device example based on UAC device classes
{SDK}/component/component/example/usb/usbd_vendor/	Vendor-specific device example
{SDK}/component/component/example/usb/usbh_cdc_acm/	Transparent communication host example based on CDC ACM host class
{SDK}/component/component/example/usb/usbh_cdc_ecm/	Ethernet communication host example based on CDC ECM host class
{SDK}/component/component/example/usb/usbh_msc/	Mass storage host example based on MSC host classe
{SDK}/component/component/example/usb/usbh_uvc/	Video host example based on UVC host classe
{SDK}/component/component/example/usb/usbh_vendor/	Vendor-specific host example
{SDK}/component/component/example/usb/usbh_wifi_bridge/	Ethernet communication bridge example based on CDC ECM host class
{SDK}/component/component/example/usb/usb_drd/	DRD example based on MSC host class and MSC device classe

Host Solutions, refer to Host Solutions

Device Solutions, refer to Device Solutions

Menuconfig and Build

Configure

Type command ./menuconfig.py under {SDK}/amebaxxx_gcc_project, choose CONFIG USB —> Enable USB, then choose the class(es) as needed:

[*] Enable USB
        USB Mode (Device)  --->
[ ] CDC ACM
[ ] Composite
[ ] HID
[ ] MSC
[ ] UAC

Save and exit.

Build

Type command ./build.py -a <example> under {SDK}/amebaxxx_gcc_project, build the USB example as needed.

Note

The <example> specified in above command shall be the USB example forder name under component/example/usb, and to successfully build the example, corresponding class driver shall be enabled during configuration.

USB Certification

USB certification generally refers to USB-IF certification, i.e. USB-IF compliance testing, which validates devices against USB-IF electrical, protocol and functional requirements to ensure interoperability, security and reliability. Certified devices are authorized to use USB logos.

While USB-IF certification is not mandatory, it is required when:

• Products intend to use USB logos

• Marketing materials claim USB specification compliance or certification

For certification procedures and requirements, refer to https://www.usb.org documentation or contact USB-IF authorized test labs.

Additional Compliance Requirements for USB Devices:

• FCC/CE: Mandatory for USB devices sold in EU/US markets

• ISO 26262: Required for automotive USB devices (functional safety)

• Windows Logo Program: Necessary for “Certified for Windows” branding

• MFi: Mandatory for Apple-specific USB accessories