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83 lines
4.9 KiB
Markdown
83 lines
4.9 KiB
Markdown
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# Adafruit TinyUSB Library for Arduino
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[](https://github.com/adafruit/Adafruit_TinyUSB_Arduino/actions) [](https://opensource.org/licenses/MIT)
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This library is a Arduino-friendly version of [TinyUSB](https://github.com/hathach/tinyusb) stack.
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It is designed with structure and APIs that are easily integrated to an Arduino Core.
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## Features
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### Device Stack
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Supported device class drivers are:
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- Communication (CDC): which is used to implement `Serial` monitor
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- Human Interface Device (HID): Generic (In & Out), Keyboard, Mouse, Gamepad etc ...
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- Mass Storage Class (MSC): with multiple LUNs
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- Musical Instrument Digital Interface (MIDI)
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- WebUSB with vendor specific class
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### Host Stack
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Host support is still work-in-progress but currently available with rp2040 core thanks to [Pico-PIO-USB](https://github.com/sekigon-gonnoc/Pico-PIO-USB). Supported class driver are:
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- Communication (CDC)
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- MassStorage class
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## Supported Cores
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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.
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### Cores with built-in support
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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.
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- [adafruit/Adafruit_nRF52_Arduino](https://github.com/adafruit/Adafruit_nRF52_Arduino)
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- [adafruit/ArduinoCore-samd](https://github.com/adafruit/ArduinoCore-samd)
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- [earlephilhower/arduino-pico](https://github.com/earlephilhower/arduino-pico)
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- [espressif/arduino-esp32](https://github.com/espressif/arduino-esp32)
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ESP32 port relies on Espressif's [esp32-hal-tinyusb.c](https://github.com/espressif/arduino-esp32/blob/master/cores/esp32/esp32-hal-tinyusb.c) for building usb descriptors which 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 for this port.
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### Cores without built-in support
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Following is cores without built-in support
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- **mbed_rp2040**
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It is still possible to use TinyUSB but with some limits such as:
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- `TinyUSB_Device_Init()` need to be manually called in setup()
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- `TinyUSB_Device_Task()` and/or `TinyUSB_Device_FlushCDC()` may (or not) need to be manually called in loop()
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- Use `SerialTinyUSB` name instead of Serial for serial monitor
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- And there could be more other issues, using on these cores should be considered as experimental
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## Class Driver API
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More document to write ...
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## Porting Guide
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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.
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### Arduino Core Changes
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If possible, making changes to core will allow it to have built-in which make it almost transparent to user sketch
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1. Add this repo as submodule (or have local copy) at your ArduioCore/libraries/Adafruit_TinyUSB_Arduino (much like SPI).
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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"`.
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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.
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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:
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- Use USB IRQn to set flag then invoke function later on after exiting IRQ.
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- Just invoke function after the loop(), within yield(), and delay()
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5. `TinyUSB_Device_FlushCDC()` should also be called often to send out Serial data as well.
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6. 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
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### Library Changes
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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
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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.
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2. `TinyUSB_Port_EnterDFU()` which is called when device need to enter DFU mode, usually by touch1200 feature
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3. `TinyUSB_Port_GetSerialNumber()` which is called to get unique MCU Serial ID to used as Serial string descriptor.
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