Description
Place: Online
Language: English
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Magnus Kindberg (SE, NO)
Phone: +46 (0)40 59 22 22
magnus.kindberg@nohau.se
Heidi Lehtomäki – Finland
phone: +358 40 196 0142
heidi.lehtomaki@nohau.fi
Klaus Ahrensbach – Denmark
Phone: +45 3116 1019
ka@nohau.dk
Zephyr Real Time Programming
Real-time programming applied to the Zephyr operating system
In 2022, Zephyr OS became the largest open-source RTOS project by the number of commits and developers.
Build secure, connected, future-proof devices with Zephyr®
Zephyr RTOS is easy to deploy, secure, connect and manage. It has a growing set of software libraries that can be used across various applications and industry sectors such as Industrial IoT, wearables, machine learning and more. Zephyr is built with an emphasis on broad chipset support, security, dependability, long term support releases and a growing opensource ecosystem.
Objectives:
- Learn how to develop, configure, debug and trace Zephyr applications
- Discover the real time multitasking concept
- Understand Real Time constraints, like determinism, preemption or interrupts
- Understand the Zephyr kernel Services
- Learn communication and synchronization mechanisms
- Interactions with processor architecture features
- Understand Zephyr memory management and data structures
- Understand User mode and kernel mode
- Writing a device tree
- Writing a complete driver
Course environment:
- Theoretical course
- PDF course material (in English)
- The trainer to answer trainees’ questions during the training and provide technical and pedagogical assistance
- Practical activities
- Practical activities represent from 40% to 50% of course duration
- Example code, labs and solutions
- Preconfigured Virtual Machine (VM) for doing labs during of after the training
- STM3240G-Eval physical board or Qemu emulated STM32F4-Discovery board
Course Format:
- Online course, 5 sessions, 6 hours each (excluding break time).
- Lots of hands-on exercises during the course
- Some Labs may be completed between sessions and are checked by the trainer on the next session.
Prerequisites
- good C Language skills
Introduction to Zephyr
- Zephyr Project
- Zephyr Ecosystem
- Why use Zephyr
- Install and Use Zephyr
- Build and Configuration Systems
- West
- CMake
- Kconfig and configuration overlay
- Configuration tools: menuconfig and guiconfig
Zephyr Without Threads
- Operation without Threads
- GPIO
- Random Number Generation
- Utilities
- Data Structures
- Single-linked List
- Double-linked List
- Ring Buffers
Exercise: Hello World from Zephyr, configure and blink LEDs using Zephyr
Exercise: Manage Zephyr linked list and understand container_of macro
Real-Time Concepts
- Base real time concepts
- The Real Time constraints
- Multi-task and real time
- Tasks and Task Descriptors
- Content of the task descriptor
- List of task descriptors
- Context Switch
Demo: Analyse Context Switch internals
Scheduling
- Task Scheduling and Preemption
- Tick based or tickless scheduling
- Scheduling systems and schedulability proof
- Fixed priorities scheduling
- RMA and EDF scheduling
- Scheduling through Zephyr
- Scheduling Algorithm
- Cooperative Time Slicing
- Preemptive Time Slicing
Thread Management
- Thread Control Block
- Creating Threads
- Threads Priorities
- Thread States
- Main and Idle Threads
- Delays
- Changing Thread Priority
- Suspending Threads
- Kernel Structures
- Simple linked-list ready queue
- Red/black tree ready queue
- Traditional multi-queue ready queue
- Thread Custom Data
- Scheduling Traces
- Runtime Statistics
- User-Defined Tracing
- Percepio Tracealyzer
Exercise: Create and manage threads
Exercise: Create periodic threads
Exercise: Create config overlay for visual trace diagnostics using Tracealyzer
Memory Management in Zephyr
- Memory Managers
- Dynamic memory managers
- K_heap
- System heap
- Memory Slabs
- Memory Blocks
- Heap Listeners
- Memory Domains and Partitions
- Stack Overflow detection
- User Mode
- Memory Domains
Exercise: Understand dynamic memory allocation in Zephyr
Exercise: Display threads information and detect stack overflow
Resource Management
- Mutual Exclusion
- Critical Sections
- Mutexes
- Gatekeeper threads
- Atomic
- Lock-Free Data Structures
- SpinLocks
Exercise: Implement mutual exclusion between threads
Synchronization Primitives
- Synchronization
- Semaphores
- The Readers/Writer Problem
- Condition variables
- Events and Event Groups
- Polling
Exercise: The producer-consumer problem, synchronize and avoid concurrent access problems
Exercise: Understanding event bit group by synchronizing several threads
Data Passing
- Message Queues
- Pipes
- Queues
- FIFOs
- LIFOs
- Mailboxes
- Stacks
Exercise: Create a print gatekeeper thread using message queue
Interrupt Management
- Threads and Interrupts
- Interrupts in zephyr
- Interrupts on ARM
- Handler thread
- Queue within an ISR
- Workqueue Threads
- Power Management
Exercise: Understand how to wait on multiple events and interrupt safe APIs
Exercise: Understand how to pass data using Queues from an interrupt to a thread
Exercise: Create and submit work items from interrupts to custom WorkQueue
Software Timers
- Timers
- Defining a Timer
- Using a Timer Expiry Function
- Timer types
- One-shot timers
- Auto-reload timers
- Timer Commands
Exercise: Understand the use of one-shot and auto-reload timers
Modules
- Why to use modules?
- Module structure
- Out-of-tree module
- YAML files
- Module CMakeLists.txt
- How to add and use custom Kconfigs
Exercise: Create a simple hello world module
Exercise: Create a module that uses custom Kconfig options
Zephyr device driver model
- Introduction to Device Drivers
- Overview of the Zephyr device driver model
- Standard Drivers
- The struct device
- Subsystems
- API Extensions
- Initialization Levels
- Dependencies between device drivers
- Define devices programmatically
- Adding In-Tree Code to Zephyr Source Code
Exercise: Create a driver that respects the Zephyr Device Driver Model and define devices
Exercise: Writing in-tree drivers
Device Trees in Zephyr
- Overview of Device Tree (DT) and its role in Zephyr
- Device Tree VS Kconfig
- Device Tree node structure
- Device Tree bindings
- Overlay and yaml files
- APIs to access device tree properties
- Write device drivers using device tree APIs
- Device Tree in Zephyr VS Linux
Exercise: Create a driver that uses custom device tree and Kconfig