Learning operating system development on raspi
The Yocto Project is an open source collaboration project that provides templates, tools and methods to help you create custom Linux-based systems for embedded products regardless of the hardware architecture. It was founded in 2010 as a collaboration among many hardware manufacturers, open-source operating systems vendors, and electronics companies to bring some order to the chaos of embedded Linux development.
RIOT: The friendly Operating System for the Internet of Things.
RIOT powers the Internet of Things like Linux powers the Internet. RIOT is a free, open source operating system developed by a grassroots community gathering companies, academia, and hobbyists, distributed all around the world.
RIOT supports most low-power IoT devices and microcontroller architectures (32-bit, 16-bit and 8-bit). RIOT implements all relevant open standards supporting an Internet of Things that is connected, secure, durable, and privacy-friendly.