USB (Arduino and Adafruit_TinyUSB)
Two USB stacks are present in the core. Users can choose the simpler
Pico-SDK version or the more powerful Adafruit TinyUSB library.
Tools->USB Stack menu to select between the two.
Pico SDK USB Support
This is the default mode and automatically includes a USB-based
Serial as well as supporting automatic reset-to-upload
from the IDE.
The Arduino-Pico core includes ported versions of the basic Arduino
Joystick libraries. These libraries
allow you to emulate a keyboard, a gamepad or mouse (or all together)
with the Pico in your sketches.
See the examples and Arduino Reference at https://www.arduino.cc/reference/en/language/functions/usb/keyboard/ and https://www.arduino.cc/reference/en/language/functions/usb/mouse
Adafruit TinyUSB Arduino Support
Examples are provided in the Adafruit_TinyUSB_Arduino for the more advanced USB stack.
To use Serial with TinyUSB, you must include the TinyUSB header in your sketch to avoid a compile error.
If you need to be compatible with the other USB stack, you can use an ifdef:
Also, this stack requires sketches to manually call
Serial.begin(115200) to enable the USB serial port and automatic
sketch upload from the IDE. If a sketch is run without this command
setup(), the user will need to use the standard “hold BOOTSEL
and plug in USB” method to enter program upload mode.
Adafruit TinyUSB Configuration and Quirks
The Adafruit TinyUSB’s configuration header for RP2040 devices is stored
In some cases it is important to know what TinyUSB is configured with. For example, by having set
#define CFG_TUD_CDC 1
#define CFG_TUD_MSC 1
#define CFG_TUD_HID 1
#define CFG_TUD_MIDI 1
#define CFG_TUD_VENDOR 1
this configuration file defines the maximum number of USB CDC (serial)
devices as 1. Hence, the example sketch cdc_multi.ino
that is delivered with the library will not work, it will only create one
USB CDC device instead of two. It will however work when the above
CFG_TUD_CDC macro is defined to 2 instead of 1.
To do such a modification when using the Arduino IDE, the file can be
locally modified in the Arduino core’s package files. The base path can
be found per this article,
then navigate further to the
folder to find the Adafruit TinyUSB library.
When using PlatformIO, one can also make use of the feature that TinyUSB allows redirecting the configuration file to another one if a certain macro is set.
And as such, in the
platformio.ini of the project, one can add
and further add create the file
include/custom_tusb_config.h as a copy
of the original
tusb_config_rp2040.h but with the needed modifications.
Note: Some configuration file changes have no effect because upper levels
of the library don’t properly support them. In particular, even though the
maximum number of HID devices can be set to 2, and two
can be created, it will not cause two HID devices to actually show up, because
of code limitations.