zephyr

Primary Git Repository for the Zephyr Project. Zephyr is a new generation, scalable, optimized, secure RTOS for multiple hardware architectures.

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Quick Overview

Zephyr is an open-source, real-time operating system (RTOS) designed for resource-constrained devices, particularly in the Internet of Things (IoT) space. It supports multiple architectures and provides a robust, scalable platform for embedded systems development.

Pros

Wide hardware support, including various architectures and boards
Modular and highly configurable, allowing for optimized resource usage
Strong focus on security, with features like memory protection and secure boot
Active community and commercial backing from the Linux Foundation

Cons

Steeper learning curve compared to some simpler embedded development platforms
Documentation can be overwhelming for beginners due to the project's extensive features
Some users report occasional issues with stability in certain configurations
Limited support for some advanced networking protocols compared to more specialized IoT platforms

Code Examples

Basic "Hello World" application:

#include <zephyr/kernel.h>

void main(void)
{
    printk("Hello World! %s\n", CONFIG_BOARD);
}

Creating and using a thread:

#include <zephyr/kernel.h>

#define STACK_SIZE 1024
#define THREAD_PRIORITY 7

void thread_entry(void *p1, void *p2, void *p3)
{
    while (1) {
        printk("Thread running\n");
        k_msleep(1000);
    }
}

K_THREAD_DEFINE(my_thread, STACK_SIZE, thread_entry, NULL, NULL, NULL,
                THREAD_PRIORITY, 0, 0);

Using a semaphore for synchronization:

#include <zephyr/kernel.h>

K_SEM_DEFINE(my_sem, 0, 1);

void producer_thread(void *p1, void *p2, void *p3)
{
    while (1) {
        // Do some work
        k_sem_give(&my_sem);
        k_msleep(1000);
    }
}

void consumer_thread(void *p1, void *p2, void *p3)
{
    while (1) {
        k_sem_take(&my_sem, K_FOREVER);
        printk("Semaphore acquired\n");
    }
}

Getting Started

Install Zephyr SDK and dependencies:

wget https://github.com/zephyrproject-rtos/sdk-ng/releases/download/v0.15.2/zephyr-sdk-0.15.2_linux-x86_64.tar.gz
tar xvf zephyr-sdk-0.15.2_linux-x86_64.tar.gz
cd zephyr-sdk-0.15.2
./setup.sh

Set up Zephyr workspace:

west init zephyrproject
cd zephyrproject
west update

Build and flash a sample application:

cd zephyr/samples/basic/blinky
west build -b <your_board>
west flash

Replace <your_board> with your target board name (e.g., qemu_x86 for QEMU emulation).

Competitor Comparisons

mbed-os

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Arm Mbed OS is a platform operating system designed for the internet of things

Pros of mbed-os

Extensive hardware support for ARM-based microcontrollers
Comprehensive libraries and APIs for rapid development
Strong focus on security features and connectivity options

Cons of mbed-os

Limited support for non-ARM architectures
Steeper learning curve for beginners compared to Zephyr
Less flexible configuration options for advanced users

Code Comparison

mbed-os example:

#include "mbed.h"

DigitalOut led(LED1);

int main() {
    while (1) {
        led = !led;
        ThisThread::sleep_for(500ms);
    }
}

Zephyr example:

#include <zephyr/kernel.h>
#include <zephyr/drivers/gpio.h>

#define LED0_NODE DT_ALIAS(led0)

static const struct gpio_dt_spec led = GPIO_DT_SPEC_GET(LED0_NODE, gpios);

int main(void) {
    gpio_pin_configure_dt(&led, GPIO_OUTPUT_ACTIVE);
    while (1) {
        gpio_pin_toggle_dt(&led);
        k_msleep(500);
    }
}

Both examples demonstrate LED blinking, but Zephyr uses a more hardware-abstracted approach with Device Tree support, while mbed-os provides a simpler, more intuitive API for common tasks.

FreeRTOS

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'Classic' FreeRTOS distribution. Started as Git clone of FreeRTOS SourceForge SVN repo. Submodules the kernel.

Pros of FreeRTOS

Simpler and more lightweight, making it suitable for resource-constrained devices
Extensive documentation and community support
Widely adopted in the industry, with a large ecosystem of compatible tools and libraries

Cons of FreeRTOS

Limited built-in features compared to Zephyr's comprehensive set of functionalities
Less focus on standardization and portability across different hardware platforms
Fewer networking and security features out-of-the-box

Code Comparison

FreeRTOS task creation:

void vTaskFunction(void *pvParameters) {
    for (;;) {
        // Task code here
    }
}

xTaskCreate(vTaskFunction, "Task1", configMINIMAL_STACK_SIZE, NULL, 1, NULL);

Zephyr thread creation:

void thread_entry(void *p1, void *p2, void *p3) {
    while (1) {
        // Thread code here
    }
}

K_THREAD_DEFINE(thread_id, STACK_SIZE, thread_entry, NULL, NULL, NULL, PRIORITY, 0, 0);

Both FreeRTOS and Zephyr provide similar basic RTOS functionalities, but Zephyr offers a more comprehensive set of features and better standardization across different hardware platforms. FreeRTOS, being lighter and simpler, may be preferred for projects with limited resources or when extensive customization is required.

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Pros of RIOT

More lightweight and suitable for resource-constrained devices
Broader support for microcontroller architectures
Stronger focus on IoT and low-power applications

Cons of RIOT

Smaller community and ecosystem compared to Zephyr
Less extensive documentation and tutorials
Fewer advanced features for complex embedded systems

Code Comparison

RIOT example (main.c):

#include <stdio.h>

int main(void)
{
    puts("Hello World!");
    return 0;
}

Zephyr example (main.c):

#include <zephyr/kernel.h>
#include <zephyr/sys/printk.h>

void main(void)
{
    printk("Hello World!\n");
}

Both RIOT and Zephyr are open-source real-time operating systems for embedded devices. RIOT is more focused on IoT and low-power applications, while Zephyr offers a broader range of features for various embedded systems. RIOT's lightweight nature makes it suitable for highly constrained devices, but Zephyr's larger community and more extensive documentation may be advantageous for some developers. The code examples show similar simplicity in basic applications, with minor differences in include statements and printing functions.

contiki-ng

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Contiki-NG: The OS for Next Generation IoT Devices

Pros of Contiki-NG

Lightweight and efficient, ideal for resource-constrained IoT devices
Strong focus on IPv6 and 6LoWPAN networking protocols
Extensive simulation support through Cooja simulator

Cons of Contiki-NG

Limited hardware support compared to Zephyr
Smaller community and ecosystem
Less frequent updates and releases

Code Comparison

Contiki-NG (main.c):

#include "contiki.h"
#include "net/netstack.h"
#include "net/ipv6/simple-udp.h"

PROCESS(example_process, "Example Process");
AUTOSTART_PROCESSES(&example_process);

PROCESS_THREAD(example_process, ev, data) {
  PROCESS_BEGIN();
  // Process logic here
  PROCESS_END();
}

Zephyr (main.c):

#include <zephyr/kernel.h>
#include <zephyr/net/socket.h>

void main(void) {
    // Application logic here
}

Contiki-NG uses a process-based programming model, while Zephyr follows a more traditional RTOS approach. Contiki-NG's code structure is centered around processes, whereas Zephyr uses a main function and supports multiple threads. Zephyr's networking stack is more flexible, supporting various protocols beyond just IPv6.

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README

.. raw:: html

The Zephyr Project is a scalable real-time operating system (RTOS) supporting multiple hardware architectures, optimized for resource constrained devices, and built with security in mind.

The Zephyr OS is based on a small-footprint kernel designed for use on resource-constrained systems: from simple embedded environmental sensors and LED wearables to sophisticated smart watches and IoT wireless gateways.

The Zephyr kernel supports multiple architectures, including ARM (Cortex-A, Cortex-R, Cortex-M), Intel x86, ARC, Nios II, Tensilica Xtensa, and RISC-V, SPARC, MIPS, and a large number of supported boards_.

.. below included in doc/introduction/introduction.rst

Getting Started

Welcome to Zephyr! See the Introduction to Zephyr_ for a high-level overview, and the documentation's Getting Started Guide_ to start developing.

.. start_include_here

Community Support

Community support is provided via mailing lists and Discord; see the Resources below for details.

.. _project-resources:

Resources

Here's a quick summary of resources to help you find your way around:

Getting Started

| ð Zephyr Documentation_ | ð Getting Started Guide_ | ðð½ Tips when asking for help_ | ð» Code samples_

Code and Development

| ð Source Code Repository_ | ð¦ Releases_ | ð¤ Contribution Guide_

Community and Support

| ð¬ Discord Server_ for real-time community discussions | ð§ User mailing list (users@lists.zephyrproject.org)_ | ð§ Developer mailing list (devel@lists.zephyrproject.org)_ | ð¬ Other project mailing lists_ | ð Project Wiki_

Issue Tracking and Security

| ð GitHub Issues_ | ð Security documentation_ | ð¡ï¸ Security Advisories Repository_ | â ï¸ Report security vulnerabilities at vulnerabilities@zephyrproject.org

Additional Resources

| ð Zephyr Project Website_ | ðº Zephyr Tech Talks_

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