DMOSI - DMOD Operating System Interface

DMOSI (DMOD Operating System Interface) is an abstraction layer for Real-Time Operating Systems (RTOS) and embedded operating systems. It provides a unified API that allows libraries and modules to interact with operating system primitives independently of the underlying RTOS implementation.

Overview

This repository serves as:

• An abstraction layer for other libraries implementing specific RTOS functionality
• A common interface for modules that need OS services without being tied to a specific RTOS
• A standardized API for embedded systems targeting various RTOS platforms (FreeRTOS, ThreadX, Zephyr, etc.)

Features

DMOSI provides weak implementations (stubs) for the following operating system primitives:

1. Mutex API

Thread synchronization through mutual exclusion locks:

• dmosi_mutex_create() - Create a mutex (recursive or non-recursive)
• dmosi_mutex_destroy() - Destroy a mutex
• dmosi_mutex_lock() - Lock a mutex
• dmosi_mutex_unlock() - Unlock a mutex

2. Semaphore API

Counting semaphores for resource management:

• dmosi_semaphore_create() - Create a semaphore with initial and max counts
• dmosi_semaphore_destroy() - Destroy a semaphore
• dmosi_semaphore_wait() - Wait on a semaphore (with timeout)
• dmosi_semaphore_post() - Post to a semaphore

3. Thread API

Thread creation and management:

• dmosi_thread_create() - Create a new thread
• dmosi_thread_destroy() - Destroy a thread
• dmosi_thread_join() - Wait for thread completion
• dmosi_thread_current() - Get current thread handle
• dmosi_thread_sleep() - Sleep for specified milliseconds

4. Process API

Process-level operations (for RTOS that support processes):

• dmosi_process_create() - Create a new process
• dmosi_process_destroy() - Destroy a process
• dmosi_process_current() - Get current process handle

5. Queue API

Inter-task message queues:

• dmosi_queue_create() - Create a queue with specified item size and length
• dmosi_queue_destroy() - Destroy a queue
• dmosi_queue_send() - Send data to queue (with timeout)
• dmosi_queue_receive() - Receive data from queue (with timeout)

6. Timer API

Software timers for periodic or one-shot callbacks:

• dmosi_timer_create() - Create a timer with callback
• dmosi_timer_destroy() - Destroy a timer
• dmosi_timer_start() - Start a timer
• dmosi_timer_stop() - Stop a timer
• dmosi_timer_reset() - Reset a timer

Usage

Basic Integration

Add DMOSI to your CMake project using FetchContent:

include(FetchContent)

FetchContent_Declare(
    dmosi
    GIT_REPOSITORY https://github.com/choco-technologies/dmosi.git
    GIT_TAG        main
)

FetchContent_MakeAvailable(dmosi)

target_link_libraries(your_target PRIVATE dmosi)

Implementing RTOS-Specific Functions

To implement DMOSI for your specific RTOS, override the weak implementations by providing strong implementations in your library. Create a separate library or repository that links against DMOSI and provides the actual implementations for your target RTOS.

Using DMOSI in Your Application

#include "dmosi.h"

void my_task(void)
{
    // Create a mutex
    dmosi_mutex_t mutex = dmosi_mutex_create(false);
    
    // Lock the mutex
    dmosi_mutex_lock(mutex);
    
    // Critical section
    // ...
    
    // Unlock the mutex
    dmosi_mutex_unlock(mutex);
    
    // Create a thread
    dmosi_thread_t thread = dmosi_thread_create(
        my_thread_function,
        NULL,           // argument
        5,              // priority
        2048            // stack size
    );
    
    // Clean up
    dmosi_mutex_destroy(mutex);
}

Configuration Options

DMOSI_DONT_IMPLEMENT_DMOD_API

By default, DMOSI provides implementations of DMOD mutex API functions (Dmod_Mutex_*) that call the corresponding dmosi_mutex_* functions. If you want to provide your own implementation or don't need this bridge, set this option:

set(DMOSI_DONT_IMPLEMENT_DMOD_API ON CACHE BOOL "Don't implement DMOD API" FORCE)

Building

Build the library:

mkdir build
cd build
cmake ..
make

Build with DMOD API bridge disabled:

mkdir build
cd build
cmake -DDMOSI_DONT_IMPLEMENT_DMOD_API=ON ..
make

Build with tests (if available):

mkdir build
cd build
cmake -DDMOSI_BUILD_TESTS=ON ..
make
ctest

Architecture

┌─────────────────────────────────────────┐
│     Application / DMOD Modules          │
└─────────────────┬───────────────────────┘
                  │
                  │ Uses DMOSI API
                  │
┌─────────────────▼───────────────────────┐
│            DMOSI Library                │
│  (Weak implementations/stubs by default)│
└─────────────────┬───────────────────────┘
                  │
                  │ Overridden by
                  │
┌─────────────────▼───────────────────────┐
│    RTOS-Specific Implementation         │
│   (FreeRTOS, ThreadX, Zephyr, etc.)     │
└─────────────────┬───────────────────────┘
                  │
                  │
┌─────────────────▼───────────────────────┐
│         Hardware / RTOS Kernel          │
└─────────────────────────────────────────┘

Weak Implementations

All functions have weak implementations that return error codes or NULL. This allows:

1. Compilation without errors even when no RTOS is linked
2. Gradual implementation - implement only what you need
3. Testing - stub behavior for unit tests
4. Flexibility - choose which functions to implement

Error Handling

Functions that can fail return:

• 0 on success
• Negative error codes on failure (typically -ENOSYS for unimplemented functions)
• NULL for handle creation failures

Contributing

When implementing DMOSI for a new RTOS:

1. Create a new repository or library (e.g., dmosi-freertos)
2. Link against DMOSI
3. Provide strong implementations for the functions your RTOS supports
4. Document any RTOS-specific limitations or behaviors

License

See LICENSE file for details.

Related Projects

• DMOD - Dynamic Module System
• DMOSI implementations for specific RTOS (to be added)

Support

For issues, questions, or contributions, please visit: https://github.com/choco-technologies/dmosi/issues