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Adafruit TinyUSB Library for Arduino

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This library is a Arduino-friendly version of TinyUSB stack. It is designed with structure and APIs that are easily integrated to an Arduino Core.

Features

Device Stack

Supported device class drivers are:

Host Stack

Host stack is available with either addition of MAX3421E hardware (e.g Host FeatherWing) or rp2040 core (thanks to Pico-PIO-USB). Supported class driver are:

Note: Host stack is still work-in-progress

Supported Cores

There are 2 type of supported cores: with and without built-in support for TinyUSB. Built-in support provide seamless integration but requires extra code added to core's source code. Unfortunately it is not always easy or possible to make those modification.

Cores with built-in support

Following core has TinyUSB as either the primary usb stack or selectable via menu Tools->USB Stack. You only need to include <Adafruit_TinyUSB.h> in your sketch to use.

Note: For ESP32 port, version before v3.0 requires all descriptors must be specified in usb objects declaration i.e constructors. Therefore all descriptor-related fields must be part of object declaration and descriptor-related API have no effect afterwards. This limitation is not the case for version from v3.0.

Cores without built-in support

Following is cores without built-in support

It is still possible to use TinyUSB but with some limits such as:

Class Driver API

More document to write ...

Porting Guide

To integrate TinyUSB library to a Arduino core, you will need to make changes to the core for built-in support and library for porting the mcu/platform.

Arduino Core Changes

If possible, making changes to core will allow it to have built-in which make it almost transparent to user sketch

  1. Add this repo as submodule (or have local copy) at your ArduioCore/libraries/Adafruit_TinyUSB_Arduino (much like SPI).
  2. Since Serial as CDC is considered as part of the core, we need to have #include "Adafruit_USBD_CDC.h" within your Arduino.h. For this to work, your platform.txt include path need to have "-I{runtime.platform.path}/libraries/Adafruit_TinyUSB_Arduino/src/arduino".
  3. In your main.cpp before setup() invoke the TinyUSB_Device_Init(rhport). This will initialize usb device hardware and tinyusb stack and also include Serial as an instance of CDC class.
  4. TinyUSB_Device_Task() must be called whenever there is new USB event. Depending on your core and MCU with or without RTOS. There are many ways to run the task. For example:
  1. TinyUSB_Device_FlushCDC() should also be called often to send out Serial data as well.
  2. Note: For low power platform that make use of WFI()/WFE(), extra care is required before mcu go into low power mode. Check out my PR to circuipython for reference https://github.com/adafruit/circuitpython/pull/2956

Library Changes

In addition to core changes, library need to be ported to your platform. Don't worry, tinyusb stack has already done most of heavy-lifting. You only need to write a few APIs

  1. TinyUSB_Port_InitDevice() hardware specific (clock, phy) to enable usb hardware then call tud_init(). This API is called as part of TinyUSB_Device_Init() invocation.
  2. TinyUSB_Port_EnterDFU() which is called when device need to enter DFU mode, usually by touch1200 feature
  3. TinyUSB_Port_GetSerialNumber() which is called to get unique MCU Serial ID to used as Serial string descriptor.