AKOS - Real-Time Operating System

AKOS is an open-source preemptive real-time operating system designed for learning and reference purposes in embedded systems education. It combines a priority-based scheduler with an event-driven programming model built around tasks, signals, timers, and state machines.

AKOS helps students understand how an RTOS works internally and serves as a practical reference for those who want to build their own real-time operating system from the ground up.

Architecture

┌─────────────────────────────────────────────────────────────────────┐
│ APPLICATION LAYERS                                                  │
│                                                                     │
│ Tasks · Signals · Software Timers · Logic                           │
└─────────────────────────────────────────────────────────────────────┘
┌─────────────────────────────────┐ ┌─────────────────────────────────┐
│ AKOS RTOS                       │ │ PLATFORM SUPPORT LAYER          │
│                                 │ │                                 │
│ ┌─────────────────────────────┐ │ │ ┌─────────────────────────────┐ │
│ │ KERNEL SERVICES             │ │ │ │ BSP                         │ │
│ │                             │ │ │ │                             │ │
│ │ Core · Thread               │ │ │ │ Startup · Vector Table      │ │      
│ │ Memory · Message            │ │ │ │ Clock · Pinmux · Console    │ │
│ └─────────────────────────────┘ │ │ └─────────────────────────────┘ │
│                                 │ │                                 │
│ ┌─────────────────────────────┐ │ │ ┌─────────────────────────────┐ │
│ │ PORT                        │ │ │ │ DRIVERS                     │ │
│ │                             │ │ │ │                             │ │
│ │ Context Switch · SysTick    │ │ │ │ GPIO · UART · Timer         │ │
│ │ SVC · PendSV · IRQ Ctrl     │ │ │ │ I2C · SPI · Flash           │ │
│ │ Stack Frame                 │ │ │ │                             │ │
│ └─────────────────────────────┘ │ │ └─────────────────────────────┘ │
└─────────────────────────────────┘ └─────────────────────────────────┘
┌─────────────────────────────────────────────────────────────────────┐
│ HARDWARE LAYER                                                      │
│                                                                     │
│ CPU Core · NVIC · SysTick · Flash · SRAM                            │
│ GPIO · UART · Timer · I2C · SPI · External Devices                  │
└─────────────────────────────────────────────────────────────────────┘

Hardware support

Board	MCU	Status
AK Embedded Base Kit V2&3	STM32L151CBT6 (ARM Cortex-M3)	Primary target (AK_BASE_KIT_V2_3, application at 0x08003000)
STM32F030F4P6 board	STM32F030F4P6 (ARM Cortex-M0)	Example target
Blue Pill	STM32F103C8T6 (ARM Cortex-M3)	Example target

AK Base Kit V2&3 flash layout

Address	Region	Image or purpose
0x08000000	Boot	ak-base-kit-stm32l151-boot.bin
0x08002000	BSF	Memory for data sharing between Boot and Application
0x08003000	Application	ak-base-kit-stm32l151-application.bin

The default board builds only the Application region. Flash its generated .bin with ak-flash at address 0x08003000; do not flash it at the beginning of internal Flash.

Quick start

Prerequisites:

sudo apt-get install gcc-arm-none-eabi cmake ninja-build

The blink LED example on AK Embedded Base Kit V2&3:

git clone https://github.com/the-ak-foundation/akos
cd akos
make help
make clean all

The command above defaults to BOARD=AK_BASE_KIT_V2_3 and EXAMPLE=thread. An explicit equivalent is:

make BOARD=AK_BASE_KIT_V2_3 EXAMPLE=thread clean all

Examples

The best starting point is examples/README.md.

Each application in examples owns its Makefile. The root Makefile is only a shortcut that forwards the selected board and example to that application. Board make fragments select the MCU and include kernel/kernel.mk.

Run make help to list the available board and example values.

Contributing

The kernel source code uses the akos_ prefix for all public APIs. New code should follow the existing naming conventions and keep board-specific logic isolated within example applications or platform-specific implementations.

License

Apache License 2.0. See LICENSE.