sypstraw/rpi4-osdev

This is a tutorial series written by a tech CEO who used time freed up during a Covid-19 lockdown to pursue a long-held ambition: writing a bare metal operating system for a Raspberry Pi 4. The project is both the written tutorial and the accompanying code, structured as a series of parts that walk you through the process from scratch. Bare metal programming means writing software that talks directly to the hardware of a computer, without relying on an existing operating system to handle the low-level details. Normally when you write an app, it talks to the operating system, which in turn talks to the hardware. Bare metal programming removes the operating system from the picture entirely: you are the operating system, and you are responsible for making the hardware do anything useful at all. The Raspberry Pi 4 was chosen because it is inexpensive, widely used, and runs on an Arm processor, which is the same architecture found in most smartphones. The tutorial targets the 64-bit quad-core version of the board. To follow along, you need a Raspberry Pi 4 with a power supply, an HDMI monitor, and a micro-SD card. You also need a development machine (Windows or Mac) with a cross-compiler installed, which is a tool that compiles code on your laptop but produces a program that runs on the Raspberry Pi's different processor architecture. The README covers how to set this up on Windows using WSL, on macOS using LLVM via Homebrew, and on the Raspberry Pi itself. The tutorial is organized into numbered parts, each covering a step in the process of building the OS. The README functions as an introduction and explains what an operating system is, why bare metal programming matters, and what hardware you need before diving in. The author acknowledges drawing inspiration from other bare metal Raspberry Pi tutorials, particularly one for the older Raspberry Pi 3.