A Procedure for Designing Abstract Interfaces for Device Interface Modules

1
A Procedure for Designing Abstract Interfaces for
Device Interface Modules

• Presented By
• Andy Mroczkowski
• Dan Talaber
• Tracy Xie
• Joshua Wetzel

David Parnas
2
Overview

• Definitions
• Examples of Device Interface
• Car
• JINI
• Embedded Real-Time Controller
• Summary
• Questions?

3
Definitions
User Program
Device 1
Abstract Interface
Device Interface Modules 1
Hardware Interface
Device 1
Abstract Interface
Device Interface Modules 1
Hardware Interface
Legend
hardware
software
interface
4
Car Example
5
Car Example

• Driving

Brakes
OperateCar
Brake Pedal
BrakeController
Brake Line
Engine
Accelerator
ThrottleController
Fuel
WheelAngle
Steering Wheel
Steering system
SteeringColumn
6
Car Example

• Braking

Disc Brakes
OperateCar
BrakePedal
Brake Controller
Brake Line
Disc Brakes
Brake Pedal
ABS Controller
BrakeLine
7
Car Example

• Braking

Disc Brakes
OperateCar
BrakePedal
Brake Controller
Brake Line
Perform- ance Brakes
Brake Pedal
BrakeLine
Brake Controller
8
Car Example

• Design Approach
• Assumption List Characterizing the Virtual Device
• The device provides a mechanism which slows the
  car at variable rates.
• Programming Constructs Embodying the Assumptions
• INCREASE_BRAKING
• DECREASE_BRAKING

9
Jini

• What is Jini?
• A dynamic distributed computing architecture that
  provides spontaneous networking between clients
  and services.
• Effective use of abstract interfaces and device
  interface modules.

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Jini Architecture in a Nutshell
Clients
Lookup Service
Proxies
Services
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Service and Lookup Service
Service
Lookup Service
Proxy, Interface
Legend
Repository
Communication
Java Object
HW/SW/Both
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Client and Lookup Service
Interface
Lookup Service
Client
Proxy
Legend
Communication
Repository
Java Object
Java Interface
SW w/ JVM
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Client and Service
Client
Service
request
Proxy
Legend
HW/SW/Both
Java Software
Communication
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How Jini Relates to Parnas Model
Proxy objects implement an interface and
encapsulate differences (e.g. protocols) among
various service providers.
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Intro of Embedded Software System

• An embedded software system is a single
  component of a significantly larger hardware or
  software system.

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Embedded Software Design with Abstract Interface
User Interface Client Control Builder Station BigB
lue
Data Access Interface
Firmware_Ver1
FIM
DeviceA (I/O)
Firmware_Ver2
IOLIM
DeviceB (IOP)
Different Vendor Image Version
Interface Module
DeviceC
Legend
Group
software
interface
hardware
Note FIM (Fieldbus Interface Module) IOLIM(I/O
Link Interface Module) IOP (I/O Processor)
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Embedded Software Architecture
Ethernet
Data Access Interface
User Interface
Control Net
Pressure
Device Interface Module
Temperature
I/O Control Net
Flow
Data bus
Valves
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Embedded Software

• Features
• Redundant Hardware Interface
• Primary, Secondary (OPM)
• Flexible Hardware Interface
• Sub-Interface Module
• Relation between Virtual Device and Hardware
  Device
• Configuration-time/Load-time/Run-time

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References

• Ilango S. Kumaran, Jini Technology An Overview,
  ISBN 0-13-033385-9
• Jim Waldo and The Jini Techology, The Jini
  Specifications, Second Edition, edited by Ken
  Arnold, ISBN 0-201-72617-3
• Picture of Parnas http//www.martinfowler.com/art
  icles/xp2002.html