This repo has additional libraries that are not yet ready for inclusion the Pico SDK proper, or are just useful but don't necessarily belong in the Pico SDK.

Note that any API here is a work in progress and subject to change.

See pico-playground for buildable example code using these extra libraries.

Library	Description
hardware_rosc	API for the ring oscillator
lwip	Deprecated as of SDK 1.5.0; use pico_lwip and pico_lwip_arch from the SDK instead.
pico_audio	Audio output support; this is highly functional, but the API is subject to change
pico_audio_i2s	Audio output via I2S on 3 GPIOs using PIO. Arbitrary frequency
pico_audio_pwm	Audio output via (PIO) PWM. Currently a bit limited in frequency support (it was developed on FPGA to do 22050Hz at 48Mhz system clock). It does however support error diffusion dithering and noise shaping with 16x oversampling to give surprisingly good audio quality. This code will be split to provide both a fixed frequencie(s) version and a slightly slower but rather better arbitrary frequency version supporting ever higher carrier frequencies
pico_audio_spdif	Audio output in S/PDIF on a GPIO using PIO. Supports up to 192khz stereo. Consumed OK in test, haven't tried it with real hardware
pico_sd_card	1 and 4 bit SDIO support using PIO. This is functional (currently writing is only 1 bit), but the code is very much a prototype and the API is just a placeholder - the command set needs to be separated from the SDIO and shared with SPI. A reference design for an SD card interface can be found in the Hardware design with RP2040 datasheet.
pico_sleep	Low power related APIs, WIP because they are not sufficiently generic and also only handle core 0
pico_scanvideo	Support for video output where every pixel is scanned out every frame. VGA/DPI support is highly functional and stable, but the API is subject to change. A reference design for a VGA board can be found in the Hardware design with RP2040 datasheet.
pico_scanvideo_dbi	currently non-compiling... placeholder for adding scanvideo over MIPI DBI support.
pico_scanvideo_dpi	Highly functional and stable support for parallel RGB output and VSYNC/HSYNC/DEN/CLOCK for VGA/DPI.
pico_util_buffer	Rather incomplete buffer abstraction, used by pico_audio and pico_scanvideo
platypus	Decoder for a custom image compression format suitable for dithered images (good for RGB555) and suitable for decoding on RP2040 at scanline speeds ... i.e you can easily decode a 320x240 image 60x per second to avoid storing the uncompressed image for scanout video. It gets about 50% compression (but is designed only for 4x4 fixed dithered RGB555 images, so is somewhat specific!). TODO add the encoder here :-)
usb_device, usb_common	The custom and somewhat minimal USB device stack used in the bootrom. We now use TinyUSB in the Pico SDK but kept here for posterity
usb_device_msc	USB Mass Storage Class implementation using usb_device

You can add Pico Extras to your project similarly to the SDK (copying external/pico_extras_import.cmake into your project) having set the PICO_EXTRAS_PATH variable in your environment or via cmake variable.

cmake_minimum_required(VERSION 3.12)

# Pull in PICO SDK (must be before project)
include(pico_sdk_import.cmake)

# We also need PICO EXTRAS
include(pico_extras_import.cmake)

project(pico_playground C CXX)
set(CMAKE_C_STANDARD 11)
set(CMAKE_CXX_STANDARD 17)

Alternative you can inject it into an existing project without modifying it via PICO_CMAKE_POST_LIST_DIRS by passing -DPICO_SDK_POST_LIST_DIRS=/path/to/pico_extras to cmake