OSAL Backend Configuration Guide

This guide provides detailed configuration information for OSAL (Operating System Abstraction Layer) backends in the Nexus Embedded Platform.

Overview

The OSAL provides a unified API for different operating systems and execution environments. Configuration includes:

  • Backend selection (Bare-metal, FreeRTOS, RT-Thread, Zephyr, Linux, Native)

  • System parameters (tick rate, heap size, stack size)

  • Linker script configuration

  • Backend-specific options

Backend Selection

Select one OSAL backend using the choice menu:

choice
    prompt "OSAL Backend"
    default OSAL_BAREMETAL

config OSAL_BAREMETAL
    bool "Bare-metal (No OS)"

config OSAL_FREERTOS
    bool "FreeRTOS"

config OSAL_RTTHREAD
    bool "RT-Thread"

config OSAL_ZEPHYR
    bool "Zephyr RTOS"

config OSAL_LINUX
    bool "Linux"

config OSAL_NATIVE
    bool "Native (PC Simulation)"

endchoice

Only one backend can be selected at a time.

Bare-Metal Backend

Overview

The bare-metal backend provides minimal RTOS functionality without a full operating system.

Features:

  • No RTOS overhead

  • Simple cooperative scheduler

  • Basic synchronization primitives

  • Minimal memory footprint

  • Deterministic behavior

Use Cases:

  • Simple applications

  • Resource-constrained systems

  • Real-time critical systems

  • Bootloaders

Configuration

Basic configuration:

CONFIG_OSAL_BAREMETAL=y
CONFIG_OSAL_BACKEND_NAME="baremetal"

System parameters:

CONFIG_OSAL_TICK_RATE_HZ=1000
CONFIG_OSAL_HEAP_SIZE=16384
CONFIG_OSAL_MAIN_STACK_SIZE=4096

Generated configuration:

#define NX_CONFIG_OSAL_BAREMETAL 1
#define NX_CONFIG_OSAL_BACKEND_NAME "baremetal"
#define NX_CONFIG_OSAL_TICK_RATE_HZ 1000
#define NX_CONFIG_OSAL_HEAP_SIZE 16384
#define NX_CONFIG_OSAL_MAIN_STACK_SIZE 4096

Available APIs

Task Management:

  • osal_task_create() - Create cooperative task

  • osal_task_delete() - Delete task

  • osal_task_delay() - Delay task

  • osal_task_yield() - Yield to other tasks

Synchronization:

  • osal_mutex_create() - Create mutex (simple lock)

  • osal_semaphore_create() - Create counting semaphore

  • osal_queue_create() - Create message queue

Time:

  • osal_get_tick_count() - Get system tick count

  • osal_delay_ms() - Delay in milliseconds

Limitations

  • No preemptive scheduling

  • No priority-based scheduling

  • Limited synchronization primitives

  • No advanced RTOS features

Best Practices

  • Keep tasks short and cooperative

  • Use delays to yield CPU

  • Minimize heap usage

  • Avoid blocking operations

Example Configuration

Minimal bare-metal system:

CONFIG_OSAL_BAREMETAL=y
CONFIG_OSAL_TICK_RATE_HZ=1000
CONFIG_OSAL_HEAP_SIZE=8192
CONFIG_OSAL_MAIN_STACK_SIZE=2048

FreeRTOS Backend

Overview

FreeRTOS is the most popular real-time operating system for embedded systems.

Features:

  • Preemptive multitasking

  • Priority-based scheduling

  • Rich synchronization primitives

  • Mature and well-tested

  • Large ecosystem

  • Commercial support available

Use Cases:

  • General embedded applications

  • Multi-threaded applications

  • Real-time systems

  • Production systems

Configuration

Basic configuration:

CONFIG_OSAL_FREERTOS=y
CONFIG_OSAL_BACKEND_NAME="FreeRTOS"

System parameters:

CONFIG_OSAL_TICK_RATE_HZ=1000
CONFIG_OSAL_HEAP_SIZE=32768
CONFIG_OSAL_MAIN_STACK_SIZE=2048
CONFIG_OSAL_MAX_PRIORITIES=32

Generated configuration:

#define NX_CONFIG_OSAL_FREERTOS 1
#define NX_CONFIG_OSAL_BACKEND_NAME "FreeRTOS"
#define NX_CONFIG_OSAL_TICK_RATE_HZ 1000
#define NX_CONFIG_OSAL_HEAP_SIZE 32768
#define NX_CONFIG_OSAL_MAIN_STACK_SIZE 2048
#define NX_CONFIG_OSAL_MAX_PRIORITIES 32

Available APIs

Task Management:

  • osal_task_create() - Create task with priority

  • osal_task_delete() - Delete task

  • osal_task_suspend() - Suspend task

  • osal_task_resume() - Resume task

  • osal_task_delay() - Delay task

  • osal_task_delay_until() - Delay until absolute time

  • osal_task_get_priority() - Get task priority

  • osal_task_set_priority() - Set task priority

Synchronization:

  • osal_mutex_create() - Create mutex

  • osal_mutex_lock() - Lock mutex

  • osal_mutex_unlock() - Unlock mutex

  • osal_semaphore_create() - Create semaphore

  • osal_semaphore_give() - Give semaphore

  • osal_semaphore_take() - Take semaphore

  • osal_queue_create() - Create queue

  • osal_queue_send() - Send to queue

  • osal_queue_receive() - Receive from queue

  • osal_event_group_create() - Create event group

Memory:

  • osal_malloc() - Allocate memory

  • osal_free() - Free memory

Time:

  • osal_get_tick_count() - Get system tick count

  • osal_delay_ms() - Delay in milliseconds

Tick Rate Configuration

Standard tick rate (1000 Hz):

CONFIG_OSAL_TICK_RATE_HZ=1000

  • 1 ms resolution

  • Good balance

  • Most common

High resolution (10000 Hz):

CONFIG_OSAL_TICK_RATE_HZ=10000

  • 0.1 ms resolution

  • Higher CPU overhead

  • For precise timing

Low resolution (100 Hz):

CONFIG_OSAL_TICK_RATE_HZ=100

  • 10 ms resolution

  • Lower CPU overhead

  • For power-sensitive applications

Heap Configuration

Small system (16 KB):

CONFIG_OSAL_HEAP_SIZE=16384

Medium system (32 KB):

CONFIG_OSAL_HEAP_SIZE=32768

Large system (64 KB):

CONFIG_OSAL_HEAP_SIZE=65536

Priority Configuration

Standard priorities (32 levels):

CONFIG_OSAL_MAX_PRIORITIES=32

  • 0 = Idle priority

  • 1-30 = Application priorities

  • 31 = Highest priority

Minimal priorities (8 levels):

CONFIG_OSAL_MAX_PRIORITIES=8

  • Lower memory usage

  • Simpler scheduling

Best Practices

  • Use appropriate task priorities

  • Avoid priority inversion

  • Use mutexes for shared resources

  • Keep ISRs short

  • Use queues for inter-task communication

  • Monitor stack usage

  • Configure heap size appropriately

Example Configurations

General purpose application:

CONFIG_OSAL_FREERTOS=y
CONFIG_OSAL_TICK_RATE_HZ=1000
CONFIG_OSAL_HEAP_SIZE=32768
CONFIG_OSAL_MAIN_STACK_SIZE=2048
CONFIG_OSAL_MAX_PRIORITIES=32

Resource-constrained system:

CONFIG_OSAL_FREERTOS=y
CONFIG_OSAL_TICK_RATE_HZ=1000
CONFIG_OSAL_HEAP_SIZE=16384
CONFIG_OSAL_MAIN_STACK_SIZE=1024
CONFIG_OSAL_MAX_PRIORITIES=8

High-performance system:

CONFIG_OSAL_FREERTOS=y
CONFIG_OSAL_TICK_RATE_HZ=1000
CONFIG_OSAL_HEAP_SIZE=65536
CONFIG_OSAL_MAIN_STACK_SIZE=4096
CONFIG_OSAL_MAX_PRIORITIES=32

RT-Thread Backend

Overview

RT-Thread is a Chinese open-source RTOS with rich features and IoT support.

Features:

  • Preemptive multitasking

  • Priority-based scheduling

  • Rich middleware (file system, network stack)

  • IoT protocols (MQTT, CoAP)

  • Device driver framework

  • Package manager

Use Cases:

  • IoT applications

  • Connected devices

  • Applications requiring middleware

  • Chinese market

Configuration

Basic configuration:

CONFIG_OSAL_RTTHREAD=y
CONFIG_OSAL_BACKEND_NAME="rtthread"

System parameters:

CONFIG_OSAL_TICK_RATE_HZ=1000
CONFIG_OSAL_HEAP_SIZE=32768
CONFIG_OSAL_MAIN_STACK_SIZE=2048
CONFIG_OSAL_MAX_PRIORITIES=32

Available APIs

RT-Thread provides similar APIs to FreeRTOS through the OSAL abstraction:

  • Task management

  • Synchronization primitives

  • Memory management

  • Time management

Best Practices

  • Use RT-Thread’s device driver framework

  • Leverage built-in middleware

  • Use package manager for components

  • Follow RT-Thread conventions

Example Configuration

CONFIG_OSAL_RTTHREAD=y
CONFIG_OSAL_TICK_RATE_HZ=1000
CONFIG_OSAL_HEAP_SIZE=32768
CONFIG_OSAL_MAIN_STACK_SIZE=2048
CONFIG_OSAL_MAX_PRIORITIES=32

Zephyr Backend

Overview

Zephyr is a Linux Foundation RTOS with modern architecture and extensive hardware support.

Features:

  • Modern C-based RTOS

  • Extensive hardware support

  • Device tree configuration

  • Networking stack

  • Bluetooth stack

  • Security features

Use Cases:

  • Modern embedded applications

  • IoT devices

  • Bluetooth applications

  • Security-critical systems

Configuration

Basic configuration:

CONFIG_OSAL_ZEPHYR=y
CONFIG_OSAL_BACKEND_NAME="zephyr"

System parameters:

CONFIG_OSAL_TICK_RATE_HZ=100
CONFIG_OSAL_HEAP_SIZE=32768
CONFIG_OSAL_MAIN_STACK_SIZE=2048
CONFIG_OSAL_MAX_PRIORITIES=32

Best Practices

  • Use device tree for hardware configuration

  • Leverage Zephyr’s networking stack

  • Use Zephyr’s security features

  • Follow Zephyr conventions

Example Configuration

CONFIG_OSAL_ZEPHYR=y
CONFIG_OSAL_TICK_RATE_HZ=100
CONFIG_OSAL_HEAP_SIZE=32768
CONFIG_OSAL_MAIN_STACK_SIZE=2048
CONFIG_OSAL_MAX_PRIORITIES=32

Linux Backend

Overview

The Linux backend uses POSIX threads for testing on Linux systems.

Features:

  • POSIX threads

  • Standard Linux tools

  • Easy debugging

  • Fast development

Use Cases:

  • Development and testing

  • Algorithm validation

  • CI/CD pipelines

Configuration

Basic configuration:

CONFIG_OSAL_LINUX=y
CONFIG_OSAL_BACKEND_NAME="linux"

System parameters:

CONFIG_OSAL_TICK_RATE_HZ=1000
CONFIG_OSAL_HEAP_SIZE=65536
CONFIG_OSAL_MAIN_STACK_SIZE=4096

Best Practices

  • Use for development and testing

  • Validate algorithms before hardware deployment

  • Use standard Linux debugging tools

Example Configuration

CONFIG_OSAL_LINUX=y
CONFIG_OSAL_TICK_RATE_HZ=1000
CONFIG_OSAL_HEAP_SIZE=65536
CONFIG_OSAL_MAIN_STACK_SIZE=4096

Native Backend

Overview

The Native backend provides PC simulation for development and testing.

Features:

  • Cross-platform (Windows, Linux, macOS)

  • Fast development iteration

  • No hardware required

  • Standard debugging tools

Use Cases:

  • Development and testing

  • Algorithm validation

  • CI/CD pipelines

Configuration

Basic configuration:

CONFIG_OSAL_NATIVE=y
CONFIG_OSAL_BACKEND_NAME="native"

System parameters:

CONFIG_OSAL_TICK_RATE_HZ=1000
CONFIG_OSAL_HEAP_SIZE=65536
CONFIG_OSAL_MAIN_STACK_SIZE=4096

Best Practices

  • Use for development and testing

  • Validate configuration before hardware deployment

  • Use for CI/CD testing

Example Configuration

CONFIG_OSAL_NATIVE=y
CONFIG_OSAL_TICK_RATE_HZ=1000
CONFIG_OSAL_HEAP_SIZE=65536
CONFIG_OSAL_MAIN_STACK_SIZE=4096

Backend Comparison

Feature Comparison

Feature

Bare-metal

FreeRTOS

RT-Thread

Zephyr

Linux

Native

Preemptive

No

Yes

Yes

Yes

Yes

Yes

Priorities

No

Yes

Yes

Yes

Yes

Yes

Memory

Minimal

Small

Medium

Medium

Large

Large

Middleware

No

Limited

Rich

Rich

Full

Full

Maturity

N/A

Very High

High

High

Very High

N/A

Ecosystem

N/A

Large

Medium

Large

Very Large

N/A

Use Case Recommendations

Bare-metal:

  • Simple applications

  • Bootloaders

  • Resource-constrained systems

  • Deterministic behavior required

FreeRTOS:

  • General embedded applications

  • Production systems

  • Multi-threaded applications

  • Industry standard

RT-Thread:

  • IoT applications

  • Chinese market

  • Applications requiring middleware

  • Connected devices

Zephyr:

  • Modern embedded applications

  • Bluetooth applications

  • Security-critical systems

  • Extensive hardware support needed

Linux:

  • Development and testing

  • Algorithm validation

  • CI/CD pipelines

Native:

  • Development and testing

  • Cross-platform development

  • CI/CD pipelines

See Also