Zephyr RTOS Embedded C Programming: Using Embedded RTOS POSIX API

Table of Contents
About the Author
About the Technical Reviewer
Chapter 1: An Introduction
	What This Book Is “All About”
	What Is an RTOS and When and Why “Do You Need One”?
	What Is an RTOS?
	Using Open Source RTOS in Systems Requiring Functional Safety
	Reconciling Certification with Open Source
	Zephyr As a Modular RTOS
	Zephyr As a Fully Featured RTOS
	Arguments for Choosing Zephyr OS
	What Makes Zephyr RTOS Special
	Zephyr and Security
	References
Chapter 2: A Review of RTOS Fundamentals
	Embedded System Software Development Strategies/Options
	Multitasking and Interprocess Communication and Synchronization Concepts and Patterns
		Tasks
	Intertask Communication
	Semaphore
	Binary Semaphore
	Counting Semaphore
	Mutual Exclusions Semaphore (Mutex)
	Priority Inversion Avoidance
	Using Semaphores and Mutexes in Interrupt Service Routines
	Semaphore Usage Patterns and Scenarios
	Wait and Signal Synchronization
	Credit Tracking Synchronization
	Synchronizing Access to a Shared Resource Using a Binary Semaphore
	Message Queueing and Message Queues
	Interlocked, One-Way Data Communication
	Interlocked, Two-Way Data Communication
	Pipes
	Event Objects (Event Registers)
	Condition Variables
	Interrupts and Exceptions
	Timing and Timers
	Memory Management
	Synchronization Patterns and Strategies
	Communication Patterns
	Patterns Involving the Use of Critical Sections
	Common Activity Synchronization Design Patterns
	Common Resource Synchronization Design Patterns
	Some More Advanced Thread Interaction Patterns
	Handling Multiple Data Items and  Multiple Inputs
	Sending Urgent/High Priority Data Between Tasks
	Device Drivers
	References
Chapter 3: Zephyr RTOS Application Development Environments and  Zephyr Application Building Principles
	Setting Up a Zephyr SDK CLI (Command-Line Interface) Development Environment on Microsoft Windows
	Choices of Boards and Development Kits for Getting Started
	Setting Up an nRF Connect SDK Development Environment Using a Microsoft VS Code–Based IDE
	Working in VS Code
	Global Actions
	Application-Specific Actions
	Build-Specific Actions
	Details View
	Devicetree View
	Actions View
	Exercise: Building and Running a Zephyr Sample Application Using VS Code
	Introduction to the Zephyr RTOS Device Driver Model and the Zephyr RTOS Device Driver APIs and Data Structures
	GPIO Inputs
	UART Communications Between a Target Board and a PC
	Zephyr Logging Module
	Plan of Action for Exploring Multithreading and Thread Synchronization
	Using Simulation and Simulators for Testing and Developing Zephyr RTOS Applications
	Zephyr Applications Using Renode
	Renode and Firmware Testing
	Building Machines in Renode
	Emulators vs. Simulators
	Simulator Use Cases
	Emulator Use Cases
	Advantages of Simulators and Emulators
	Disadvantages of Simulators and Emulators
	Summarizing Renode
	References
Chapter 4: Zephyr RTOS Multithreading
	Kconfig
	Devicetrees and Devicetree Configuration
	Kconfig and Devicetree Usage Heuristics
	Multithreading in Zephyr
	Zephyr Kernel Mode and User Mode Threads
	An Overview of Generic Zephyr Features Pertaining to Privilege Modes, Stack Protection and Separation, User Mode Threads, and Memory Domains Privilege Modes
	An Overview of Generic Zephyr Features Pertaining to Privilege Modes, Stack Protection and Separation, User Mode Threads, and Memory Domains Privilege Modes
	Safety Model and Threats That Zephyr RTOS Applications Need to Protect Against
	ARM Cortex M Memory Protection Unit (MPU): An Overview
	User syscalls
	Zephyr RTOS Thread Priorities
	Thread Custom Data
	Dropping Privileges
	Thread Termination
	System Threads
	Basic Multithreading Scenarios
	Simple Multithreading Example
	FIFOs in Zephyr
	Synchronizing Threads Using Semaphores and Sleeping
	Signalling Using a Condition Variable
	The Dining Philosophers Problem
	Producers and Consumers and Multithreading
	The Zephyr RTOS Producer-Consumer Example
	Using Zephyr RTOS System Calls: Essential Concepts and Overview
	Producer-Consumer Example Sample Driver Part
	Shared Memory Partition, System Heap, Memory Pool, and Kernel Queues Part
	Application A Part
	APP B Part
	Shared Memory, Protected Memory Partitions, and Memory Domains
	Memory Partitions
	Zephyr Shared Memory Example
	References
Chapter 5: Message Queues, Pipes, Mailboxes, and Workqueues
	Zephyr Message Queue
	Message Queue – Technical Details and the Message Queue API
	Overview of the Message Queue API Functions
	Message Queue Example
	Exercise Scenario Description
	Zephyr Mailbox
	Mailbox Message Format
	Mailbox Message Life Cycle
	Mailbox Sending and Receiving Thread Compatibility
	Mailbox Message Sending – Synchronous and Asynchronous
	The Mailbox API – Data Types and  Functions
	Message Descriptors
	Sending and Receiving Zephyr Mailbox Messages
	Sending a Message
	Receiving a Mailbox Message
	Introductory Zephyr Mailbox Example
	Zephyr RTOS Workqueues
	Delayable Work
	Simple Workqueue Example 1
	Simple Workqueue Example 2
	Simple Workqueue Example 3
	Summary
Chapter 6: Using Filesystems in  Zephyr Applications
	Quad-SPI (QSPI)
	SDC and MMC Cards
	SD Card Support via SPI
	Zephyr RTOS Disk Access API
	Zephyr File System API
	Working with Directories
	File Systems – A High-Level Overview
	Overview of the FAT File System and FatFs
	Overview of the LittleFS File System
	Walkthrough of a LittleFS Example Program
	Summary
	References
Chapter 7: Developing Zephyr BLE Applications
	BLE: A Short History
	Uses of BLE
	BLE Architecture
	BLE Physical Layer
	BLE Link Layer
	BLE Unicast Connection Scenario
	BLE Broadcast Connect Scenario
	BLE Link Layer Addressing
	BLE Packet Types
	Connections and Connection Events
	HCI (Host Controller Interface) Layer
	Logical Link Control and Adaptation Protocol (L2CAP) Layer
	BLE Actors – Peripherals, Broadcasters, Centrals, and Observers
	BLE Peripheral
	BLE Central
	HCI – Generic Access Profile (GAP)
	Attribute Protocol (ATT)
	Data Attributes
	GATT Attribute and Data Hierarchy
	Characteristics
	Profiles
	Attribute Operations
	Requests – Flow Control, Reading Attributes, and Writing to Attributes
	Bluetooth 5
	BLE Security
	Building and Testing Peripheral and Central BLE Applications
	The nRF52840 Dongle and Its Uses
	nRF Connect Bluetooth Low Energy Applications
	Setting Up an nRF52840 Dongle for Use with the nRF Connect for Desktop nRF BLE Application
	Using the Dongle in BLE Central Mode
	BLE Network Connection Map
	Using the Dongle in BLE Peripheral Mode
	Using the Power Mode Emulation to Set Up an Emulated Battery Service
	BLE Application Development APIs Provided by Zephyr and the nRF Connect SDK
	The Source BLE Structure in the Zephyr Source Code
	Building, Programming, and Configuring Host Roles
	Basic Peripheral Example
	Bluetooth: Central/Heart Rate Monitor
	Overview of the Connected Function
	Is It Possible to Run Both a Peripheral and a Central on the Same Board?
	What Next?
	Summary
	References
Chapter 8: Zephyr RTOS and  Ethernet, Wi-Fi, and TCP/IP
	Zephyr and Network Management
	The Nucleo-F767ZI Board
	Building and Troubleshooting the Zephyr Network Programming Examples Using the STM32 Nucleo-F767ZI Board
	The BSD Sockets API
	A Zephyr Echo Server Example Overview
	Zephyr OS Services Module
	Strategies for Studying and Reverse Engineering (Where Necessary) Zephyr Application Code
	Zephyr Network Management API
	How to Request a Defined Procedure
	Listening for Network Events
	How to Define a Network Management Procedure
	Signalling a Network Event
	Network Management Interface Functions
	Zephyr Shell Module
	Shell Commands
	Command Creation Macros
	Creating Static Commands
	Dictionary Commands
	The Shell and the Echo Server Example
	Configuring a TCP Server Application to Use a Separate Thread for Each Connection
	Data Structures Associated with TCP/IP Server-Side Connections
	Thread Structures Pool for Handling Threads Involved in TCP/IP Server Connections
	Echo Server on the STM32 Nucleo-F767ZI Board
	Summary
	References
Chapter 9: Understanding and Working with the Devicetree in General and SPI and I2C in Particular
	Firmware Development Aspects of Application Development
	Overview of SPI and I2C
	SPI Explained
	Advantages and Disadvantages of SPI
	I2C Explained
	Devicetree Configuration
	Device Tree Source (DTS) Representation of Devicetrees
	Unit Addresses and the Devicetree
	Devicetree Processing
	Devicetree Bindings
	The Syntax of Binding Files
	Binding and Bus Controller Nodes
	Phandles, Phandle-Array Type Properties, and Specifier Cell Names
	Including .yaml Binding Files
	Accessing the Devicetree in C and C++ Application Code
	Working with Devices in Applications
	Working with reg and interrupts Properties
	Working with Devices
	Overview of How the DEVICE_DT_GET Macro Works
	I2C Case Study Example
	Summary
	References
Chapter 10: Building Zephyr RTOS Applications Using Renode
	Simulator Use Cases
	Emulator Use Cases
	Advantages of Simulators and Emulators
	Disadvantages of Simulators and Emulators
	Renode
	Renode Installation
	Renode Scripts
	What Is Needed to Emulate a Zephyr Application Using Renode?
	Boards and Processors Supported by Zephyr That Are Also Supported by Renode
	Building an nRF52840 DK Application and Running It in Renode
	Summary and Where Next?
	References
Chapter 11: Understanding and Using the Zephyr ZBus in Application Development
	Zephyr ZBus
	ZBus Architecture
	The ZBus and Code Reusability
	Limitations of the ZBus
	ZBus Message Delivery Guarantees and Message Delivery Rates
	ZBus Message Delivery Sequence Guarantees
	ZBus Programming in Practice
	Hard Channels and Message Validation
	Overview of ZBus Features and Their Uses
	Publishing and Reading to and from a  Channel
	Claiming and Finishing a Channel
	Ensuring a Message Will Not Be Changed During a Notification
	Iterating over Channels and Observers
	Overview of the Virtual Distributed Event Dispatcher (VDED)
	Walkthrough of a VDED Execution Scenario
	Walking Through Some Selected Zephyr ZBus Examples
	Zephyr ZBus Hello World
	Zephyr Bus Workqueue Example
Chapter 12: Zephyr RTOS Wi-Fi Applications
	Approaches to Tackling the Various Wi-Fi MAC Problems
	Security Issues
	WPA3 SAE Key Exchange Protocol
	How Wi-Fi Uses the Radio Spectrum Allocated to It
	Wi-Fi Frames and the 802.11 Packet Structure – An Overview
	Access Points
	Discovering an Access Point
	Authentication and Association
	Zephyr RTOS and Wi-Fi Application Development
	nRF7002 DK Board – An Overview
	Wi-Fi Scanning Example Walkthrough Using the nRF7002 DK
	Zephyr Network Management – An Overview
	Requesting a Defined Network Management Procedure
	Listening to Network Events
	Defining Network Management Procedures
	Signalling Network Events
	Building the Wi-Fi Scan Example from the nRF Connect SDK Repository
	Structured Overview of the Code of the Scan Example from the nRF Connect SDK Repository
	Exploring the nRF Connect SDK Wi-Fi Shell Example
	Basic TCP/IP Application Programming Using the nRF7002 DK
	Structured Exploration of the nRF Connect SDK Wi-Fi sta Example
	Wi-Fi BSD Sockets Programming
	nRF7002 DK – Basic TCP and UDP Example
	Project source code directory structure
	The Led Toggling Task
	UDP Server Task on Target Board
	Python UDP Client to Test Out UDP Server on Target Board
	TCP Server Task on Target Board
	UDP Echo Client Task on Target Board
	TCP Echo Client Task on Target Board
	Testing Out the BSD Sockets Example
	References
Index