Design of embedded systems

Hardware/Software Co-Hardware/Software Co-Design Design

T S PRADEEPKUMART S PRADEEPKUMAR

SCS, VITSCS, VIT

T S PT S P 22

OutlineOutline

Embedded Hardware Embedded Hardware Embedded SoftwareEmbedded Software Issues in Embedded System DesignIssues in Embedded System Design Hardware/ Software PartioningHardware/ Software Partioning Designing Embedded SystemsDesigning Embedded Systems Co-DesignCo-Design

T S PT S P 33

Embedded SystemsEmbedded Systems

An embedded system An embedded system uses a computer to perform some function, butuses a computer to perform some function, but is not used (nor perceived) as a computeris not used (nor perceived) as a computer

Software is used for features and flexibilitySoftware is used for features and flexibility Hardware is used for performanceHardware is used for performance Typical characteristics:Typical characteristics:

it performs a single functionit performs a single function it is part of a larger (controlled) systemit is part of a larger (controlled) system cost and reliability are often the most cost and reliability are often the most

significant aspectssignificant aspects

T S PT S P 44

Embedded SystemsEmbedded Systems

Satellite

Macro-Cell Micro-Cell

Zone 2: UrbanZone 1: In-Building

Pico-Cell

Zone 4: Global

Zone 3: Suburban

Firmware

CORE

SOC IPBased Design

Software

SOC

µP/CAnalog

Embedded Software

Memory

Embedded System Design

SystemEnvironment

PCB Design

T S PT S P 55

Embedded HardwareEmbedded Hardware

InputInput SensorsSensors Sample and Hold CircuitSample and Hold Circuit A/D ConvertersA/D Converters

CommunicationCommunication UARTUART

Processing UnitsProcessing Units ASICASIC ProcessorsProcessors Reconfigurable processorsReconfigurable processors

T S PT S P 66

Embedded HardwareEmbedded Hardware

MemoriesMemories RAM, ROM, Flash, CacheRAM, ROM, Flash, Cache

OutputOutput D/A Converters,D/A Converters, ActuatorsActuators

T S PT S P 77

Embedded SoftwareEmbedded Software

Real Time Operating SystemsReal Time Operating Systems General RequirementsGeneral Requirements

Scheduling in RTOSScheduling in RTOS AperiodicAperiodic PeriodicPeriodic

Real Time DatabasesReal Time Databases Other Software ArchitecturesOther Software Architectures

Function Queue SchedulingFunction Queue Scheduling Round Robin (with Interrupts)Round Robin (with Interrupts)

T S PT S P 88

Issues while Designing ESIssues while Designing ES

Choosing Right platformChoosing Right platform Memory and I/O RequirementsMemory and I/O Requirements

WDT, Cache, Flash memory, etcWDT, Cache, Flash memory, etc Processors ChoiceProcessors Choice

PLCPLC Micro Controller or DSPMicro Controller or DSP ASIC or FPGAASIC or FPGA

T S PT S P 99

Issues…Issues…

Hardware Software TradeoffHardware Software Tradeoff Porting Issues of OS in the Target Porting Issues of OS in the Target

BoardBoard

T S PT S P 1010

Hardware /Software Hardware /Software PartitioningPartitioning

DefinitionDefinition A HW/SW partitioning algorithm A HW/SW partitioning algorithm

implements a implements a specificationspecification on some on some sort of sort of multiprocessor architecturemultiprocessor architecture

UsuallyUsually Multiprocessor architecture = one CPU Multiprocessor architecture = one CPU

+ some ASICs on CPU bus+ some ASICs on CPU bus

T S PT S P 1111


TerminologyTerminology AllocationAllocation

Synthesis methods which design the Synthesis methods which design the multiprocessor topology along with the multiprocessor topology along with the Process Elements and SW architectureProcess Elements and SW architecture

SchedulingScheduling The process of assigning Process Element The process of assigning Process Element

(CPU and/or ASICs) time to processes to get (CPU and/or ASICs) time to processes to get executedexecuted

T S PT S P 1212


Hw/Sw partitioning can speedup Hw/Sw partitioning can speedup softwaresoftware

Can reduce energy tooCan reduce energy too

In most partitioning algorithmsIn most partitioning algorithms Type of CPU is fixed and givenType of CPU is fixed and given ASICs must be synthesizedASICs must be synthesized

T S PT S P 1313

Designing of Embedded Designing of Embedded SystemsSystems

There are five stages of development of There are five stages of development of Embedded SystemsEmbedded Systems

• Requirement AnalysisRequirement Analysis• DesignDesign

• Data Structures, Software Architecture, Data Structures, Software Architecture, Interfaces and algorithmsInterfaces and algorithms

• CodingCoding• TestingTesting• MaintenanceMaintenance

T S PT S P 1414

Designing of Embedded Designing of Embedded SystemsSystems

There are three Design FlowsThere are three Design Flows• Waterfall ModelWaterfall Model• Spiral ModelSpiral Model• Successive refinementSuccessive refinement

For Designing, Unified Modeling For Designing, Unified Modeling Language (UML) is usedLanguage (UML) is used

T S PT S P 1515

Embedded System DesignEmbedded System DesignTraditional MethodologyTraditional Methodology

HW Design& Build

Hardware/SoftwarePartitioning and Allocation

SW Design& Code

InterfaceDesign

HW/SWIntegration

T S PT S P 1616

Problems with Past Design Problems with Past Design MethodMethod

Lack of unified system-level representationLack of unified system-level representation Can't verify the entire HW-SW systemCan't verify the entire HW-SW system Hard to find incompatibilities across HW-SW boundaryHard to find incompatibilities across HW-SW boundary

(often found only when prototype is built) (often found only when prototype is built)

Architecture is defined Architecture is defined a prioria priori, based on expert , based on expert evaluation of the functionality and constraintsevaluation of the functionality and constraints

Lack of well-defined design flowLack of well-defined design flow Time-to-market problemsTime-to-market problems Specification revision becomes difficultSpecification revision becomes difficult

T S PT S P 1717

Embedded System DesignEmbedded System DesignHW/SW Co-Design MethodologyHW/SW Co-Design Methodology

HW Design& Build

Hardware/SoftwarePartitioning and Allocation

SW Design& Code

InterfaceDesign

HW/SWIntegration

T S PT S P 1818

Co-Design FrameworkCo-Design Framework

T S PT S P 1919

Co-DesignCo-Design

The software functionality should be The software functionality should be partitioned in such a fashion that partitioned in such a fashion that processors in the system do not get processors in the system do not get overloaded when the system is overloaded when the system is operating at peak capacity. operating at peak capacity.

This involves simulating the system This involves simulating the system with the proposed software and with the proposed software and hardware architecture. hardware architecture.

T S PT S P 2020

Co-DesignCo-Design

The system should be designed for The system should be designed for future growth by considering a scalable future growth by considering a scalable architecture, i.e. system capacity can architecture, i.e. system capacity can be increased by adding new hardware be increased by adding new hardware modules. The system will not scale modules. The system will not scale very well if some hardware or software very well if some hardware or software module becomes a bottleneck in module becomes a bottleneck in increasing system capacity. increasing system capacity.

T S PT S P 2121

Co-DesignCo-Design

Software modules that interact very Software modules that interact very closely with each other should be closely with each other should be placed on the same processor, this placed on the same processor, this will reduce delays in the system.will reduce delays in the system.

Higher system performance can be Higher system performance can be achieved by this approach by inter-achieved by this approach by inter-processor message communication.processor message communication.

T S PT S P 2222

Embedded Controller Example:Embedded Controller Example:Engine Control Unit (ECU)Engine Control Unit (ECU)

Task: control the torque produced by the engine

by timing fuel injection and spark

Major constraints:Major constraints:

Low fuel consumptionLow fuel consumption

Low exhaust emissionLow exhaust emission

T S PT S P 2323

ECU ECU Task: control injection time (3 sub-tasks)

computeair flow compute

injectiontime drive

actuators

airflow

injectiontime

air temperature

engine temperature

engine speed

throttle position

look-up table

PWM signalsair pressure

T S PT S P 2424

32 bit CPU

A/DActuations (PWM)

Analog inputs

Digital inputs

ECU- Option 1ECU- Option 1

computeair flow

computeinjection

timedrive

actuators

airflow

injectiontime

air temperature

engine temperature

engine speed

throttle position

look-up table


T S PT S P 2525

16 bit CPU

A/D

Actuations (PWM)

Analog inputs

Digital inputs

FPGA


computeair flow

computeinjection

timedrive

actuators

airflow

injectiontime

air temperature

engine temperature

engine speed

throttle position

look-up table


T S PT S P 2626

8 bit CPUDSP

Actuations (PWM)

Analog inputs

Digital inputs

FPGAA/D


computeair flow

computeinjection

timedrive

actuators

airflow

injectiontime

air temperature

engine temperature

engine speed

throttle position

look-up table


T S PT S P 2727

Thank YouThank You

Education

Design of embedded systems