Moonix

• A Real-Time Operating System(RTOS) targeted for the ARM Cortex-A8 board.

1. Key Features

• Non-Preemptive Scheduling
• Configuration and management of Timer, UART, and Interrupt Controller.
• Interrupt and Exception Handling
• Inter-Process Communication (IPC)
• Synchronization Mechanism

2. Development Environment

Category	Tool/Technology
Languages	C, ARMv7-A Assembly
Editor	vim
Build Tools	gcc-ARM-none-eabi
Other Tools	git, make, shell scripts, gdb, qemu

3. Design

• Selection of operational modes for ARM to optimize performance.
• Utilized HAL to enhance code portability across different hardware platforms.
• Designed the memory structure.
• Designed kernel data structures for Tasks, Interrupts/Exceptions, and IPC.
• Chose Non-Preemptive Scheduling to manage process execution priorities.
• Developed mechanisms for task synchronization within the kernel.
• Designed kernel API functions to facilitate interaction with the OS functionalities.

4. Implementation

• Conducted initial hardware setup upon power-up of the ARM core.
• Differentiated and processed various types of interrupts using the Interrupt Controller.
• Developed kernel API functions and essential libraries.
• Implemented context switching and designed scheduler/dispatcher
• Developed IPC mechanisms using message queues and event flags.
• Implemented semaphores as a synchronization tool to manage access to resources.

5. Directory Structure

moonix
├── boot
│ ├── Entry.S //  Contains the exception vector table.
│ ├── Handler.c // Defines IRQ and FIQ exception handlers.
│ └── Main.c
├── hal // Hardware Abstraction Layer
│ ├── HalInterrupt.h // Common API functions for interrupts.
│ ├── HalTimer.h // Common API functions for timer management.
│ ├── HalUart.h // Common API functions for UART.
│ ├── rvpb // Machine-specific code for RealView PB.
│ │ ├── Interrupt.c // Interrupt-specific common API functions.
│ │ ├── Interrupt.h // Interrupt controller structure declaration.
│ │ ├── ISP1761.h // USB structure declaration.
│ │ ├── Regs.c // Variables for hardware access.
│ │ ├── Timer.c // Timer-specific common API functions.
│ │ ├── Timer.h // Timer structure declaration.
│ │ ├── Uart.c // UART-specific common API functions.
│ │ └── Uart.h // UART structure declaration.
│ └── versatilepb // Machine-specific code for Versatile PB.
│ └── nuri // Machine-specific code for Nuri.
├── include
│ ├── ARMv7AR.h // Macros for operating modes.
│ ├── CtrlBit.h // Bit manipulation macros.
│ ├── MemoryMap.h // Memory mapping macros.
│ ├── stdarg.h // Variable arguments macros.
│ ├── stdbool.h
│ └── stdint.h // Primitive system data types (C99).
├── kernel
│ ├── message.c // Message queue.
│ ├── message.h
│ ├── event.c // Event flag.
│ ├── event.h
│ ├── kernel.c // Kernel API.
│ ├── kernel.h
│ ├── priorityBased.c // Priority scheduling.
│ ├── roundrobin.c // Round-robin scheduling.
│ ├── task.c // Task creation and initialization, TCB.
│ └── task.h // TCB and task context structures.
├── lib
│ ├── armcpu.c // Code to enable/disable IRQ and FIQ.
│ ├── armcpu.h
│ ├── dispatch.c // Context switching.
│ ├── dispatch.h
│ ├── stdio.c // Defines the printf function.
│ └── stdio.h
│ └── stdlib.c // Defines library functions.
│ └── stdlib.h
├── Makefile
├── moonix.ld // Linker script.
└── README.md

6. References

• ARM info center

6-1. Timer (SP804)

• Summary of registers
• Interface reset

6-2. Philips ISP1761 controller

• Data sheet
• USB interface

6-3. UART (PL011)

• Summary of registers
• UARTDR
• UART base address

6-4. GIC

• GIC registers
• GIC-interput signal

6-5. RealView PB

• SYS_ID