What is Embedded System Hardware: Types, Design and Development Process

Introduction

Embedded systems are microcontroller or microprocessor based systems designed to perform dedicated functions within larger mechanical or electrical systems. Embedded system hardware refers to the electronic components and devices which make up the embedded system and enable its functioning.

This article provides an in-depth look at embedded system hardware including:

• Major components and devices used
• Hardware architectures and configurations
• Design considerations and selection criteria
• Hardware/software partitioning
• Development and testing process
• Industry applications

Understanding the embedded hardware landscape is crucial for successfully designing and developing embedded products and solutions across consumer, industrial, medical, automotive, aerospace and other segments.

Embedded System Hardware Components

An embedded system consists of both hardware and software elements configured and integrated together on typically a printed circuit board to deliver the desired functionality. The key hardware components include:

Microprocessor/Microcontroller

This is the central processing unit and “brain” of the embedded system. Popular options:

• Microcontrollers – Integrated CPU with memory, I/O, peripherals
• Microprocessors – Standalone general purpose CPU requiring external chips
• Common architectures: x86, ARM, AVR, PIC, 68k, MIPS, PowerPC

Memory Devices

Used to store the executable program code, data and instructions required for the system to function:

• Volatile Memory – SRAM, DRAM lose data when power is removed
• Non-Volatile Memory – Flash, EEPROM retain data without power
• Amount of memory depends on software needs

I/O Interfaces

Allow the processor to receive inputs and drive outputs:

• Parallel interfaces – PCI, SCSI
• Serial interfaces – UART, SPI, I2C, USB
• Wireless – Bluetooth, Wi-Fi, Zigbee
• Analog to Digital Converters (ADCs)
• Digital to Analog Converters (DACs)

Power Supply

Provides regulated voltages to run the electronics:

• Linear regulators – Low noise but less efficient
• Switching regulators – More efficient but with switching noise
• Supervisory circuits – Reset generation, brown-out protection
• Backup supply – Batteries or capacitors

Clock Generation

Produces clock signals to synchronize operations:

• Crystal oscillators
• Phase locked loops (PLLs)
• Real time clocks (RTCs) with backup

Custom Circuits

Application specific standard products (ASSPs), field programmable gate arrays (FPGAs) and other components tailored for embedded use.

Hardware Architectures and Platforms

Embedded system hardware can be architected in different ways based on technical requirements and tradeoffs:

Single Chip Architecture

• All functionality integrated within a microcontroller IC
• Simplest approach
• Constrained by on-chip capabilities
• Examples: SmallInstrumentation, IoT sensors

Microprocessor with Discrete Chips

• Microprocessor coupled with peripherals and interfaces
• More hardware flexibility
• Complex board design
• Obsolescence management challenges
• Widely used in industrial, medical, automotive products

System on Chip (SoC)

• Multiple functions integrated together on a single IC die
• Highest performance and integration
• Longer development timeframes
• Typical in smartphones, gaming consoles, robots

System on Module (SoM)

• Functional blocks implemented together on a small board/module
• Allows customization
• Simplifies development
• Growing approach for industrial automation, gateways

System in Package (SiP)

• Multiple ICs enclosed in a single package
• Reduces size, cost, power
• Limited reconfigurability
• Used where miniaturization is critical

Choosing the right architecture involves tradeoffs between technical needs, timeline, costs, reusability, and other product requirements.

Design Considerations

Key hardware design criteria and considerations for embedded systems:

Processing Power

• Analysis of software tasks to gauge MIPS/DMIPS required
• Headroom for future features/performance
• Selection of optimal micro architecture

I/O Needs

• Interfaces for all sensors, actuators, peripherals
• On-chip vs external options
• Analog vs digital interfaces

Memory Requirements

• Flash, RAM needs based on software
• Expansion capability
• Reliability, endurance factors

Power Requirements

• Source voltage/current specifications
• Backup/battery needs
• Power saving modes

Physical Constraints

• Size, weight limitations
• Environmental factors
• Mechanical integration needs

Reliability Requirements

• Component ratings and lifespans
• Redundancy needs
• Ruggedization
• Heat dissipation

EMI/EMC Considerations

• Shielding
• Filtering
• Isolation
• Minimal radiated/conducted emissions

Compliance Requirements

• Safety, regulatory standards
• Certifications

Budgetary Constraints

• BOM cost targets
• Non-recurring engineering (NRE) costs

Making appropriate hardware choices requires carefully weighing these factors.

Component Selection Process

Choosing the right components is key to building optimized embedded systems. The selection process involves:

Defining Technical Needs

• Processing performance specifications
• Memory and storage needs
• I/O interfaces and peripherals required
• Power budgets
• Physical form factors
• Life expectancy and use conditions
• EMI/EMC requirements
• Other technical requirements derived from product specs

Evaluating Options

• Review potential component choices from reputable suppliers
• Compare technical capabilities to identify devices that fulfill needs
• Get samples for evaluation if required
• Assess development tools and OS/software support
• Review technical datasheets in detail

Analysis and Decision Factors

• Make components choices based on how closely they meet technical requirements
• Evaluate cost impact (unit cost, BOM cost)
• Consider availability, lifecycle, obsolescence risks
• Assess development effort needed (drivers, firmware, tools)
• Analyze power consumption tradeoffs
• Consider previous experience and expertise with components
• Take inputs from procurement team

Final Component Selection

• Select optimal components for each system function based on analysis
• Ensure all design requirements are fully met
• Validate choices via prototype evaluations
• Lock down part numbers, suppliers, procurement specs early
• Formalize technical datasheets for chosen components
• Setup lifecycle monitoring in case of obsolescence risks

Getting components selection right from the start prevents extensive redesigns later and leads to better performing, compliant, and cost-effective embedded products.

Hardware and Software Partitioning

Determining which functions to implement in hardware vs software is a key partitioning decision:

Hardware Implementation

• Provides better performance, speed
• Hard to modify or upgrade post-production
• Suited for time-critical functions
• Examples: real time I/O, complex processing

Software Implementation

• More flexible, easier to change
• Simplifies upgrades/bug fixes
• Better for non-real time tasks
• Examples: application logic, UI, network stacks

Partitioning Guidelines

• Implement timing critical functions in hardware
• Keep hardware as simple as possible
• Use software for higher level tasks
• Consider upgrade needs during product lifecycle
• Leverage hardware accelerators where possible
• Evaluate CPU load and memory bandwidth needs
• Maintain balance – don’t over burden hardware or software

Well planned partitioning allows focusing hardware on key strengths like speed, while software manages evolving functionality over time.

Embedded Hardware Design Process

Developing optimized embedded system hardware requires progressing through a structured design flow:

Requirements Analysis

• Capture detailed hardware requirements and specs
• Cover functionality, performance, reliability needs
• Input from electrical, mechanical, software teams
• Account for use cases, edge conditions
• Define project deliverables

System Architecture

• Translate requirements into high-level system architecture
• Block diagrams showing key hardware elements
• Hardware/software partitioning
• Interface definitions
• Input/Output detail

Component Selection

• Choose most appropriate components matching requirements
• Microprocessor/microcontroller
• Peripherals, external interfaces
• Memory devices
• Oscillators, crystals

Circuit Design

• Design supportive circuits for power, reset, clocking
• I/O signal conditioning
• Protection against faults, transients
• EMI/EMC control measures
• High speed PCB layout considerations

Prototyping

• Create prototype PCB layout for evaluation
• Assemble prototype using chosen components
• Write basic test firmware for functionality validation
• Iterate on design based on lab tests, debug data

compliance Testing

• Test prototype against complete requirements
• Address any gaps or issues observed
• Confirm compliance with applicable standards
• Iterate until all criteria are met

Documentation

• Comprehensive datasheet detailing hardware design
• Block diagrams, schematics, PCB layout data
• Component technical specs, BOM
• Compliance reports

Production Release

• Finalize design for volume production
• Quality checks to ensure reproducible builds
• Release to manufacturing with comprehensive documentation

This structured hardware design flow is key to avoiding costly mistakes and building robust, compliant embedded systems.

PCB Design and Layout

The printed circuit board (PCB) physically houses the embedded components and interconnects them together via copper traces. Good PCB design is critical for reliability. Key aspects include:

Schematics

• Detailed schematics with component symbols, values, and labels
• Schematic-PCB cross probing for easy navigation
• Adherence to industry standards

Component Placement

• Group related circuits together
• Ensure serviceability around key components
• Optimize for manufacturability

Routing

• Use appropriate trace widths for signals
• Provide adequate clearances
• Include ground and power planes
• Control impedance for high speed traces
• Minimize length of high current paths

EMI/EMC Control

• Enclose circuits in ground planes
• Include filtering components
• Careful use of spacing, stitching vias
• Controlled impedances

Thermal Management

• Ensure component temperature limits are not exceeded
• Use thermal relief cutouts, thermal vias
• Specify appropriate surface finishes

Mechanical Integration

• Mounting holes, brackets, specialty connectors
• Clearance for fixtures/housings
• Shock/vibration resistance measures

Investing in optimal PCB design upfront avoids expensive re-spins later and leads to rugged, reliable embedded hardware.

Embedded Hardware Testing

Thorough testing across unit, subsystem, and system levels is crucial for validating embedded hardware designs:

Component Level Testing

• Confirm electrical performance of individual ICs
• Stress tests for endurance, lifecycle estimation
• Benchmark to datasheet parameters

Subsystem Validation

• Focused testing of specific circuits (I/O, power, clocking, communications)
• Verify conformance to multi-year lifetime under use conditions
• Characterize EMI, power consumption

System Level Integration Testing

• Validation of fully populated PCB assembly
• Stress testing system level reliability – thermals, vibration…
• Functional testing with production ready software
• Compliance verification to standards

Product Level QA

• Testing in actual end product enclosures
• User environmentals – temperature, humidity, shock…
• Lifecycle testing – thermal cycling, HALT, reliability simulations
• Final validation of all requirements

Continuous testing at increasing levels of assembly ensures the hardware design and production processes achieve the reliability metrics mandated for the product.

Applications of Embedded Hardware

Embedded hardware spans a diverse range of applications across industries:

Industrial Automation

• Programmable Logic Controllers (PLCs)
• Human Machine Interface (HMI) terminals
• Process transmitters, field instruments
• Motor drives, robotics

Medical Equipment

• Diagnostic imaging systems
• Patient monitoring systems
• Infusion pumps, ventilators
• Surgical robots, prosthetics

Building Automation

• Smart energy meters
• Lighting, HVAC, access control systems
• Fire alarm systems
• Video intercoms, security systems

Transportation

• In-vehicle infotainment
• Advanced driver assistance systems (ADAS)
• Railway signal control
• Aircraft flight systems, black boxes

Consumer Electronics

• Home automation systems
• Smartphones, tablets, smart watches
• Gaming consoles
• Digital cameras

Energy

• Smart grid sensors and automation
• Solar micro-inverters
• UPS systems
• Oil and gas instrumentation

Whether enabling smarter factories, autonomous vehicles, or IoT connectivity – embedded hardware delivers the core electronics in millions of products we use daily across industries.

Conclusion

Embedded system hardware provides the underlying electronics comprising the processing, communications, user interfaces, and control capabilities in dedicated devices. Well designed embedded hardware is vital for reliably and securely running the software driving intelligent behavior in connected systems.

A methodical approach to hardware selection, partitioning, prototyping and testing enables the development of optimal PCB assemblies despite severe constraints. As embedded technology expands into AI, industrial IoT, robotics, and other fields – robust, high performance hardware remains essential for unlocking next generation innovations.

Frequently Asked Questions

Here are some common questions about embedded system hardware answered:

Q: What are the main hardware components in an embedded system?

A: The core hardware components include the CPU (microprocessor or microcontroller), memory devices, I/O interfaces, power supply, clocks, and custom ICs/accelerators tailored for the application.

Q: How is hardware/software partitioning done?

A: Time critical functions are implemented in hardware for performance while higher level application logic and networking layers are partitioned to software for flexibility.

Q: What are the main steps in the embedded hardware design process?

A: The main steps include – requirements analysis, system architecture, component selection, circuit design, prototyping, testing, documentation, and production release.

Q: What are some key considerations in embedded hardware design?

A: Key considerations include – processing power, I/O needs, memory requirements, power budgets, physical constraints, reliability, standards compliance, EMI/EMC, thermal management, and cost.

Q: How is PCB layout optimized in embedded systems?

A: Good PCB layout focuses on schematic-board correlation, optimal component placement, controlled routing, thermal management, and EMI/EMC control measures for reliability.