Beginner’s Guide to Embedded Systems: Unlock the Basics

Embedded systems are at the heart of the digital devices we use every day. From washing machines to cars, from thermostats to medical devices, embedded systems make modern electronics work intelligently and efficiently.

If you’re new to the world of embedded development, this guide will help you understand what embedded systems are, what they’re used for, and how you can get started. Explanations in this article emphasize 8-bit AVR microcontrollers throughout as an easy start for beginners.

What Is an Embedded System?

An embedded system is a combination of hardware and software designed to perform a specific task. Unlike general-purpose computers, embedded systems are built for dedicated functions within larger systems. These systems are typically constrained by performance, memory, power, and cost, and often run real-time operating systems (RTOS) or bare-metal firmware (embedded software).

Below is an image of a circuit board with a microcontroller chip that is can be used to prototype and develop an embedded system. Embedded systems in real-world applications typically have their own purpose designed microcontroller boards. For example, a modern electric washing machine has its own dedicated microcontroller board running custom embedded software or firmware. This embedded system connects to the control panel buttons and display of the machine, and controls the washing machine drum speed, water valves and heating element.

Key Characteristics of Embedded Systems

Some of the main characteristics of any embedded system are listed below.

• Dedicated Functionality: Built for one main purpose, for example a USB computer keyboard, the electronic controller in a microwave oven.
• Real-time Operation: Often must respond quickly to external events.
• Resource Constraints: Limited CPU, memory, and power consumption.
• Reliability and Stability: Often expected to run for years without failure.
• Low Power Consumption: Especially in battery-operated or portable devices.

Common Examples of Embedded Systems

There are many embedded systems that are used in day-to-day life. Here are examples of just some of them.

• The electronic controller in a microwave oven is an embedded system
• The electronic control circuit in a modern washing machine
• Digital cameras
• Smart TVs
• Automotive ECUs (Electronic Control Units)
• Medical devices like pacemakers
• Routers and network switches
• Industrial automation controllers
• Smart thermostats
• Medical monitoring devices

At the core of most embedded systems is an embedded computer or microcontroller, which executes the code that controls the system.

Embedded Systems vs General Computers

While both embedded systems and general-purpose computers contain processors and memory, they serve very different roles. An embedded system is designed to perform a specific task or set of tasks within a larger device, often with limited resources and minimal user interaction.

In contrast, general computers like desktops and laptops are built to run a wide range of applications and provide full user interfaces. Understanding the differences between these two types of computing platforms is key to grasping the role of embedded systems in the modern world.

The following table compares some of the features of embedded systems with that of general-purpose computers.

Components of an Embedded System

An embedded system usually includes:

• A Microcontroller or Single Board Computer (SBC) – The processing unit
• Memory (RAM and ROM) – For data and code storage
• Input/Output Interfaces – For sensors, buttons, displays, etc.
• Embedded Software – The firmware that runs on the microcontroller

Some advanced embedded systems use single board computers like the Raspberry Pi, while many use microcontrollers like AVR chips due to their simplicity and low power usage.

Who Works with Embedded Systems?

A wide range of professionals work in the field of embedded systems, each with a specific role in designing, building, and maintaining these specialized devices. You’ll often hear terms like embedded engineer, embedded systems engineer, or embedded software engineer. Each of these focus on different aspects of the system.

For example, an embedded software engineer typically writes the embedded software that runs on microcontrollers or embedded computers, often using embedded C programming to interact closely with the hardware. Meanwhile, an embedded developer may handle both the hardware and software side of things, taking a project from concept to completion. On the other hand, an embedded hardware engineer may specialize in embedded hardware development only, designing of microcontroller and electronics circuits and circuit boards.

Across all these roles, responsibilities often include embedded software development, embedded programming, system-level integration, and ensuring smooth communication between hardware and software components.

Embedded Software and Embedded Programming

Embedded systems are powered by software known as firmware. This is often written in low-level languages like C or C++ to give developers fine-grained control over the hardware.

What is Embedded Software?

Embedded software is the specialized program code that runs on an embedded computer or microcontroller. It interfaces with hardware directly and often must meet strict timing and reliability constraints.

Embedded Programming Languages

• Embedded C: The C programming language is the most widely used language in embedded development. It offers direct access to hardware registers and is ideal for writing compact, efficient code.
• Assembly Language: Used when utmost performance and size optimization are required.
• C++: Increasingly popular for larger embedded systems with more complex needs.

Real-Time Operating Systems (RTOS)

An RTOS manages multiple tasks and handles scheduling, inter-task communication, and timing constraints. While many small systems run on bare-metal firmware without an OS, larger embedded systems often use an RTOS to manage complexity.

Benefits of Using an RTOS

• Task scheduling and prioritization
• Deterministic (real-time) response times
• Easier management of multitasking and timing
• Modular software design

Popular RTOS examples include:

• FreeRTOS
• Zephyr
• VxWorks
• ThreadX

Debugging Embedded Systems

Debugging is performed by embedded software developers on embedded code. It is the act of searching for and finding ‘bugs’ or errors in the embedded program code, and correcting or fixing these errors.

Where do software bugs come from? Errors or bugs are unintentionally added to the software or code during the software development process, by the embedded software developer. This is an unfortunate, although expected occurrence, that is a part of any software development, be it embedded software development, or any other software development, such as for the web, smart phones or computers.

Debugging embedded systems can be challenging due to their limited resources, complex hardware interactions, and the fact that they often operate in real-time environments. However, effective debugging is crucial for ensuring the reliability and performance of embedded applications. Below are some common methods and tools used for debugging embedded systems:

1. In-Circuit Debugger (ICD) or In-Circuit Emulator (ICE)

In-circuit debuggers are hardware tools that interface with the embedded system’s microcontroller or processor to allow real-time debugging. These debuggers can stop the execution of the program, inspect variables, step through code line by line, and modify memory contents. Popular ICDs include the Segger J-Link and Microchip’s MPLAB ICD. These tools are vital for identifying issues in the system’s operation, such as incorrect memory access, faulty interrupts, or timing problems.

2. Serial Debugging

Serial debugging involves using serial communication (such as UART or USB) to send debug messages to a host computer. These messages may include variable values, error codes, or general system status, which help developers understand what’s happening inside the embedded system during runtime. Although it doesn’t allow for stepping through code, serial debugging is useful in embedded systems with limited resources where more complex debugging tools cannot be used.

3. JTAG Debugging

Joint Test Action Group (JTAG) is a standard for debugging and testing embedded systems. It provides access to the processor’s internal registers and memory, enabling developers to inspect system state and control execution. JTAG allows for both low-level hardware debugging and high-level software debugging, making it an essential tool for identifying issues that might not be apparent in software alone.

4. Real-Time Operating System (RTOS) Tracing

For embedded systems running an RTOS, using real-time tracing can help identify performance issues such as missed deadlines or inefficient task scheduling. Tracing tools monitor task execution and events, recording timestamps and allowing developers to visualize how tasks are executed and where potential bottlenecks occur. RTOS-based debuggers like FreeRTOS’s Tracealyzer and embOS’s embOSView offer graphical representations of task execution, helping to pinpoint problems.

5. Simulation and Emulation

Simulators and emulators allow developers to run embedded software on a virtual platform before deploying it to actual hardware. This approach can be particularly useful for debugging complex algorithms or checking system behavior without requiring access to the physical device. Tools like QEMU and Renode are popular choices for simulating embedded systems. While emulation is slower than running code on actual hardware, it can help catch errors early in the development cycle.

6. Logic Analyzers and Oscilloscopes

Logic analyzers and oscilloscopes are used to observe the electrical signals in an embedded system. By analyzing signal waveforms, developers can identify issues related to timing, voltage levels, or signal integrity. These tools are essential when debugging problems that are hard to catch through software debugging alone, such as signal collisions or communication errors between peripherals.

7. Watchdog Timers

Watchdog timers are hardware components that automatically reset the embedded system if it stops responding or gets stuck in an infinite loop. By integrating a watchdog timer into the system, developers can ensure that the system recovers from failures, especially in safety-critical applications. While not a debugging tool per se, it can help prevent failures from causing prolonged system downtime, providing valuable time for further debugging. Many modern microcontrollers have built in watch dog timers, so do not need an external watchdog timer circuit.

8. Static and Dynamic Analysis

Static analysis tools scan the source code before execution to identify potential issues such as memory leaks, uninitialized variables, or unused functions. These tools provide insight into code quality and potential runtime problems. This makes them an essential part of the debugging process. Dynamic analysis, on the other hand, examines the system during runtime. It focuses on memory usage, thread synchronization, and error handling.

9. Embedded System Debugging Best Practices

• Start Simple: Begin by focusing on simple debugging methods like print statements or serial communication. Once the basic functionality is confirmed, move on to more advanced debugging tools.
• Isolate Components: If debugging a complex system, try isolating individual components (e.g., sensors or communication modules) to narrow down the source of the issue.
• Use Assertions: Incorporate assertions into your code to check assumptions and catch errors during development.
• Automated Testing: Automating tests can help catch errors early in the development cycle and ensure the system behaves as expected after each update.

By employing a combination of the above methods and tools, embedded system developers can efficiently identify and resolve bugs, leading to more reliable and stable systems.

Tracing in Embedded Systems

Tracing is a powerful debugging and performance analysis technique supported by many RTOSes. It allows developers to record system events over time and analyze how tasks interact, how resources are used, and where bottlenecks occur.

Types of Tracing

• Software-Based Tracing: No special hardware needed. Uses hooks or macros to record events in memory. May impact CPU and RAM usage.
• Hardware-Based Tracing: Uses specialized tools and interfaces (like SWO, JTAG) to collect real-time data with minimal overhead.

Tracing helps developers understand timing issues, improve performance, and ensure reliable behavior, especially in safety-critical systems.

Reliability in Embedded Systems

Reliability is a top priority in embedded systems. Devices often operate for years without maintenance and sometimes in remote or hazardous environments.

Challenges

• Inaccessibility for repairs (e.g., satellites, underwater systems)
• Safety-critical roles (e.g., automotive, aviation, medical)
• Financial impact from failure (e.g., telecom, banking infrastructure)

Reliability Techniques

• Watchdog Timers: Reset the system if software hangs.
• Hypervisors: Isolate components to prevent fault propagation.
• Trusted Computing Base (TCB): Core components are kept secure and verified.
• Immunity-Aware Programming: Following coding standards like MISRA C/C++ to prevent common runtime errors.
• Static Analysis Tools: Automatically check code for safety and reliability issues.

High vs. Low Volume Embedded Systems

• High Volume: Products like smartphones are optimized for cost and efficiency. Hardware is selected to meet exact needs without overprovisioning.
• Low Volume: Prototypes and industrial systems may use general-purpose computers with embedded software or RTOS for flexibility.

Embedded Software Architecture Types

Embedded systems can be designed using various software architectures based on complexity and responsiveness.

1. Simple Control Loop

A basic loop monitors inputs and updates outputs in sequence. This is ideal for very simple systems. Anyone familiar with Arduino will recognize the loop() function in the Arduino software as a simple control loop.

2. Interrupt-Controlled Systems

Event-driven design where tasks are triggered by interrupts. Fast and efficient for real-time responses. Microcontrollers typically have built-in interrupt systems that can be enabled and used in software.

3. Cooperative Multitasking

Each task voluntarily yields control to others. Easy to implement but requires careful task design.

4. Preemptive Multitasking

Tasks are scheduled by an RTOS (real-time operating system) using timers and interrupts. Allows for complex, parallel task execution with synchronization mechanisms like semaphores and message queues.

Embedded Kernels: Types and Tradeoffs

Microkernels

Minimalist kernel that handles only essential functions like task switching. More secure but more complex to develop for.

Exokernels

Give applications near-direct access to hardware via minimal abstraction layers. Extremely flexible but rare in commercial use.

Monolithic Kernels

Large, feature-rich kernels that include many services like networking and file systems. Examples: Embedded Linux, VxWorks, Windows CE.

Monolithic kernels are increasingly popular in high-end embedded devices like routers, GPS units, and multimedia players.

Additional Software Components in Embedded Systems

Many embedded systems integrate higher-level components depending on their functionality:

• Network Protocols: TCP/IP, CAN, MQTT, HTTP, FTP
• Storage: FAT filesystem, flash memory managers
• Audio/Video Codecs: For multimedia applications
• Security: TLS/SSL libraries, secure boot, encryption engines

Domain-Specific Architectures

Some industries standardize embedded system architectures:

• AUTOSAR (Automotive Open System Architecture): Widely used in automotive software to standardize communication, diagnostics, and safety.
• IoT Frameworks: Such as ARM mbed OS or Amazon FreeRTOS for connected devices.

Single Board Computers (SBCs) in Embedded Systems

A Single Board Computer (SBC) is a complete computer built on a single circuit board. Popular examples include the Raspberry Pi, BeagleBone, and Arduino (which is more of a microcontroller board).

SBCs are often used for:

• Prototyping
• Low-cost production units
• Educational and hobbyist projects

Microcontroller manufacturers typically have their own evaluation boards that developers buy and used to get familiar with a particular microcontroller, or microcontroller family. There are many AVR Evaluation Board examples, from microchip and other vendors.

Careers in Embedded Systems

If you’re interested in this field, here are some related roles:

• Embedded Software Engineer: Specializes in the development of embedded software, but must have an understanding of the hardware that the software is being developed for.
• Embedded Systems Engineer: Usually more concerned with the architecture of embedded systems. Must have an understanding of the hardware and software of the system, and a good knowledge of embedded system development in general.
• Embedded Developer: Typically develops both hardware and software.
• Firmware Engineer: Another name for an embedded software engineer.
• Embedded Hardware Developer: Specializes in hardware development and electronics.

Skills in Embedded C, RTOS, device drivers, and debugging tools are especially valuable. Understanding microcontrollers, hardware interfaces (UART, SPI, I2C), and low-level system behavior is also key.

Embedded Systems Using 8-Bit AVR Microcontrollers

Now that you understand the basics, let’s explore how 8-bit AVR microcontrollers from Microchip fit into the world of embedded systems. These microcontrollers are ideal for beginners and hobbyists due to their simplicity, affordability, and robust community support.

Why AVR Microcontrollers Are Still Relevant in Embedded Systems

When talking about embedded systems, especially from a hobbyist or educational perspective, it’s hard not to mention AVR microcontrollers. These chips have powered countless projects for decades, thanks to their simplicity, affordability, and accessibility.

Originally developed by Atmel in the 1990s and now part of Microchip Technology, the AVR family of microcontrollers helped shape the embedded development landscape. If you’re new to AVR, be sure to check out our beginner’s guide to 8-bit AVR microcontrollers for a full introduction to these devices and some of the available programming environments for them.

What Can You Build with AVR Microcontrollers?

8-bit AVR chips are used in a wide range of embedded development projects. Hobbyists often use them in home automation systems, like motion-sensing lights or smart thermostats. They’re also ideal for building DIY gadgets such as digital clocks, LED light controllers, and USB game controllers.

In the world of education, AVR-based development boards are widely used to teach students the fundamentals of embedded programming and embedded C, often through platforms like Arduino. Beyond the classroom, you’ll find AVR chips in real-world products like electronic door locks, small-scale robotics, temperature sensors, and handheld test instruments.

The Role of Embedded C in AVR Projects

Most AVR projects are programmed in the C programming language. Embedded C programming gives developers precise control over hardware without the overhead of high-level frameworks. It’s one of the key skills for any aspiring embedded systems engineer or embedded software engineer.

Why Choose AVR for Your Next Embedded Project?

While more powerful 32-bit microcontrollers and single board computers (like the Raspberry Pi) are available, 8-bit AVR chips are still a smart choice for many projects. Their low power consumption, robust documentation, and active community make them ideal for learning and prototyping. Whether you’re an electronics hobbyist, a student, or a budding embedded developer, AVR microcontrollers offer a solid foundation for your embedded systems journey.

Final Thoughts on AVR Microcontrollers and the World of Embedded Systems

Embedded systems are everywhere, and learning how to work with them opens up a world of possibilities in both hobby electronics and professional engineering. Starting with 8-bit AVR microcontrollers is an excellent path into this field. Whether you’re aspiring to become an embedded software engineer or just exploring your first project, AVR8 is here to guide you step by step.