Reference notes for the living system
The tutorials tell the story in order. This section keeps the reference material close at hand: how the drivers are shaped, what the boot path assumes, and how hardware tests are run without losing the thread.
Boot, runtime, traps, tasks
The assumptions that hold the examples together: AArch64 entry, exception levels, vectors, stacks, timers, and cooperative runtime rules.
GPIO, UART, mailbox, timer, disk, Ethernet
The low-level hardware layer: MMIO rules, interrupt wiring, ring buffers, firmware calls, block I/O, and DMA-facing driver boundaries.
Build, stage, boot, recover
The practical loop for Raspberry Pi 4 testing: UART, SSH staging, SD boot switching, recovery media, and preflight checks.