pico-sdk
The Raspberry Pi Pico SDK is the official toolkit for writing programs that run on Raspberry Pi Pico boards and other devices built around the same RP-series chip. If you want to make a Pico do something, whether blinking an LED or connecting to Wi-Fi, this is the starting point. It gives you the code libraries, header files, and build configuration you need so you can focus on writing your own program rather than figuring out how the hardware works at a low level.
Programs written with this SDK use standard C, C++, or assembly, starting from a familiar main() entry point. This means developers coming from everyday software backgrounds can get going without learning an entirely new programming model. The SDK covers all the hardware features of the RP-series chip, including timers, USB, Wi-Fi, Bluetooth, and a feature called Programmable IO that lets you define custom communication protocols in software. If you do want to touch the hardware at the register level, the SDK includes fully commented register definitions so you do not have to dig through datasheets.
Setting up a project involves a build tool called CMake. You point it at the SDK, write a short configuration file listing your source files and which libraries to include, and CMake handles compiling everything into a file you can load onto the board. The README walks through four different ways to connect your project to the SDK, from cloning it locally to pulling it automatically from GitHub at build time.
For people who prefer a graphical environment, there is an official Visual Studio Code extension that wraps the whole setup process. More complete documentation, including a full PDF reference and an online API browser, is available through the official Raspberry Pi documentation site.
The project also points to a companion repository called pico-examples, which contains ready-to-build sample programs covering common tasks. If the SDK itself does not yet include a library you need, a separate pico-extras repository holds additional work that is still maturing before inclusion.