Operating Systems Concepts for IoT (Internet of Things)

Fundamentals

A task is a program, program unit, process, or thread (lightweight process). It could be a sequential function with an infinite loop. Usually can be of two types user or kernel.

Why do we need an operating system (OS)?

• Manage hardware and software resources
• Power Management
• Task schedulers
• Task management
• supports multitasking
• Inter-process communications
• Memory allocation and management
• Managing I/O devices and peripherals 
• Analog 
• motors
• valves
• Digital
• Hardware Interrupts
• ISR (Interrupt Service Routines)

Task Scheduling Algorithms

• Time-sharing task scheduling 
• Pre-emptive
• Non-preemptive

• Priority-based Round Robin Scheduling

Timers

• Internal core timers
• Software timers
• One shot timers
• Auto-reloaded timers

Task Management

• Managing the Task States
• Running 
• Not Running
• Ready
• Suspended
• Blocked
• Context Switching

Race Condition

• Undesirable condition when multiple tasks (or threads) try to access and change the shared data simultaneously.

Thread Safety

• Locking shared resources/data using a critical section
• Intertask communication

Deadlock

Two tasks are waiting for the same resource held by the other

Deadlock Prevention

- planning resource allocation

Interprocess Communications

- Message Queues

- Interrupts

- Mutex - provides mutual exclusion when concurrent tasks access a shared resource

- semaphore 

Dynamic Memory Allocation

- Heap

- First Fit Memory Allocation

Static Memory Allocation

 - Stack

Characteristics

• Small Footprint
• Modularity
• Extensibility
• Flexible
• Easy to use API
• Portability
• Tools Support

Should we use an OS in IoT?

• to build an ecosystem for device drivers.
• support for extensibility
• Security

Why ecosystem

• vendor 
• open source community
• user support 
• community

IoT System

• managing processor

Types of Operating Systems

• General Purpose 
• rich functionality
• complex functionality
• Embedded OS for resource constraint device
• e.g. coffee machines, smart sensors, wireless routers
• small footprint
• high reliability
• for optimized performance
• e.g. FreeRTOS (real-time OS), Android Things
• limited file system support