Embedded Systems - Software Design

Flashcards covering key vocabulary from lecture notes on embedded systems software design.

Embedded Systems Software

Software in embedded systems interacts directly with hardware and operates under strict timing, memory, and power limitations.

Embedded Software

Code specifically written to run on embedded systems that interacts directly with hardware through I/O ports, memory-mapped registers, and interrupts.

Bare metal programming

A type of software development where applications interact directly with a system's hardware, bypassing any operating system or virtualization layers.

Firmware

The low-level software that directly interfaces with the hardware components, stored in read-only memory or flash storage.

Real-time operating system

Designed to provide minimal services necessary for running embedded applications, managing hardware resources and meeting real-time requirements.

Middleware

A layer of software that provides additional services needed by application software, such as communication protocols and device drivers.

Application Software

Software designed to accomplish specific tasks that the embedded system is intended for, interacting with the operating system and hardware.

Sequential or Superloop Model

Organizing tasks into a continuous loop where each task executes sequentially in a predetermined order.

Event-Driven Model

Organizes system behavior around the occurrence of external or internal events, triggering specific functions or routines.

Interrupt-Based Model

Uses hardware or software interrupts to respond immediately to specific conditions or events, suspending the main program temporarily.

RTOS-Based Model

Introduces an operating system layer which schedules tasks and manages time, memory, and resources.

Threads

Schedulers

Semaphores

Timers

Queues

Concepts in RTOS-based model

Separate units of execution.

Determine which task runs when.

Manage resource sharing and prevent conflicts.

Trigger actions at defined intervals.

Used for inter-task communication

Limited RAM and ROM

Embedded systems often operate with limited memory resources.

The RAM is used for the Stack, Heap, and Buffers. The ROM is used for firmware, lookup

tables, and constant data.

Static Memory Allocation

is preferred because it is predictable and avoids memory fragmentation

Dynamic Memory Allocation

can be risky due to memory leaks and heap fragmentation, especially in systems with long uptime or safety requirements.

Optimization Technique

It is advisable that programmers will reuse memory where possible such as minimizing global variables and use smaller data types

Deterministic Behavior

Embedded software often needs predictable execution timing, especially in real-time systems. Tasks must execute within strict time limits to meet deadlines (e.g., respond to sensor input in milliseconds).

Software Delay

loops are inefficient and inaccurate because they depend on clock speed and processor load

Hardware Timer

provide precise time tracking and are better suited for generating delays, scheduling, and timeouts.

Task Scheduling

In RTOS-based systems, task priorities and deadlines must be carefully managed. Consider the worst-case execution time (WCET) of tasks to prevent deadline misses.

Power considerations

Power Budget and Energy Constraint

Usage of Low-Power Operating Modes

Peripheral Power Management

Editor

the development environment where a programmer writes the software in the programming language of choice, which becomes the source code for the device.

Compiler

transforms the code into low-level executable code that is specific to

the target microprocessor hosted by the device.

Assembler

converts human-written assembly code into machine language.

Debugger

a tool that allows a developer to thoroughly go through the code and makes sure there are no errors

Linker

that pulls together and formats low–level executable code in a

manner so that it executes properly on a target device

Libraries

rewritten program that is read to use and provides specific

functionalities. These can be system-provided or user-provided

Simulator

helps users see how the code works in real time. The input values can be changed to see corresponding outputs and parameter changes.