RK0 - The Real-Time Kernel '0'

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Know it

RK0 is a lean, highly deterministic Real-Time Kernel for deeply embedded solutions.

• See the RK0 Docbook for a thorough design description.
• Check the RK0 Blog for some quick reads.

Supported Architectures: ARMv6M (Cortex-M0/0+) and ARMv7M (Cortex-M3/4/7).

Use it

• Emulated hardware: the provided Makefile targets QEMU

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System Architecture

If no more details are to be provided, the kernel has a top and a bottom layer. On the top, the Executive manages the resources needed by the application. On the bottom, the Low-level Scheduler works as a software extension of the CPU. Together, they implement the Task abstraction — the Concurrency Unit that enables a multitasking environment.

In systems design jargon, the Executive enforces policy (what should happen). The Low-level Scheduler provides the mechanism (how it gets done). The services are the primitives that transform policy decisions into concrete actions executed by the Scheduler.

Features (V0.5.0-dev)

• Priority Preemptive Scheduler (Low-latency, O(1): 4¹ CPU cycles pick-next algorithm).
• FPU support.
• Inter-Task Communication: a composable rich set of synchronisation and message-passing mechanisms, designed with different best-use cases in mind
• High-precision application timers.
• Efficient fixed-size Memory Allocator (Memory Pools)
• Footprint² is less than 3KB ROM (core features).
• Highly modular: features are independent. You don't pay for what you don't use.
• Clean uniform API.

¹ On ARMv7M. ARMv6M yields O(1), ~11 cycles

² Core system, does not account optional services and application size.

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Code Quality

RK0 source code compiles cleanly with the following GCC flags:

-Wall -Wextra -Wsign-compare -Wsign-conversion -pedantic

Static Analysis (Cppcheck) is clean with no warnings, errors, or style issues.

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Dependencies

• ARM-GCC, CMSIS-GCC

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Copyright (C) 2025 Antonio Giacomelli | All Rights Reserved | www.kernel0.org