Space Plug-and-Play Architecture (SPA) and SSM

Introduction

SPA implements a self-configuration Publish/Subscribe methodologyComputer-negotiated interfaces permit the elements of a complex system to interoperate without the need of traditional interface control documentsSPA processing sequence:

1. Network discovery and configuration2. Component registration (Publish)3. Component queries4. Component subscriptions (Subscribe)

Introduction

Accelerates the development and integration process by reducing or eliminating error-prone human interpretationStandards based

SPA standards submitted to AIAAProvides a contract between component providers that if their component is SPA compliant they can expect full interoperability on a SPA system

Software Architecture

Non-SPA Applications

Board Support Package

Operating System and System Services

Libraries

Platform Abstraction Library

SPA MiddlewareCore

LibrariesCore

ServicesSubnet

Management

SPA API

SPA Applications


SPA MiddlewareSoftware required in order to support SPA infrastructure and functionalityOpen source SPA middleware reference implementation provided by AFRL - SPA Services Manager (SSM)SSM Target Architectures

VxWorks 6.x using Real Time Processes (RTPs), Linux 2.6.x, and Windows XP and 7Design uses a Platform Abstraction Layer (PAL) to ease port to other platforms


SPA Middleware Core ServicesDiscovery and addressing service

Network topology discovery, component discovery, and component addressing methodology

Publication serviceComponent registration, re-registration, deregistration

Query serviceQuery methodology in order to identify components that provide required data consumption and/or functionality

Subscription serviceMethodology to subscribe and unsubscribe to required data and/or functionality


SPA Middleware Core Services cont.System status monitoring service

Methodology to monitor overall SPA system status and provide appropriate response to SPA system anomalies

SPA Middleware Core LibrariesA Collection of commonly used SPA functions, constants, classes, utilities, etc that provide basic functionality to perform several SPA tasksDynamically or statically linkable


SPA Middleware Subnet ManagementSubnet management for multiple heterogeneous subnets. For example, SpaceWire (SM-S), USB (SM-U), I2C (SM-1), etc. Provides interoperability between different types of SPA subnets

Example SPA System

SPA Network

SPA Processor Resource

SPA Core Component

SPA Application

R1

SM-SSM-L

SM-S

SM-L

CAS

SPA PR1 SPA PR2LS

R2 R3

SM-S

SPA Router

SPA-S Device

SPA-U Device

SPA-1 Device

SM-U SM-1

SPA PR3

SM-SA1 A2A3 A4

A3SM-L


PhysicalMedia, signal and binary

transmission

Data LinkPhysical addressing

NetworkPath determination and logical

addressing

TransportEnd-to-end connection and

reliability

ApplicationData, application-to-application

communication

SPA-X ProtocolsSPA-S, SPA-U, etc

SPA Subnet Managers

SPA Messaging Interface

Applications & Devices

I2C, USB, SpaceWire, Sockets

OSI Model SPA Model


Platform Abstraction LibraryAbstracts OS and architecture differences

Threading, semaphores, file I/O, timing, XML parsing, etcCode modifications needed to port to a specific OS should only happen inside this platform specific library

SPA Application Programming Interface (API) Defines a standard programming interface which allows a software application to interoperate with other software applications or devicesCould be used to abstract different PnP middleware implantations

SPA Services Manager

Mark Greenman

central address service

Computer-negotiated Interfaces

Extended Transducer Electronic Data Sheet (xTEDS)Contains a complete interface description of a SPA component

Component-specific service requestComponent-specific service request repliesCommandsData messages

eXtensible Markup Language (XML) basedSchema controlled

Common Data Dictionary

A universal dictionary of terms, names, definitions, qualifiers, units, scales, formats, interfaces, etc.Available as a standard referenceA living document

Appliqué Sensor Interface Module (ASIM)

Provides SPA interface to a legacy or simple device Pre-programmed to support SPA messaging, xTEDS registration, and Subscription/Publishing.SM-S (SpaceWire) ASIMs are currently available

SM_U (USB), SM-1 (I^2C), and SM-C (CAN) ASIMs are currently being developed

Validation - Component

Use SPA Test Suite (SPATS) to validate SPA core components against Standards documents.SPATS will test each component in isolation (the Unit-Under-Test or UUT), simulating the non-UUT components in a protocol exchangeVerifies protocols and message formats are followedHardware support required for SM-X and SPA Device SPATS testing

SPATS• Java GUI and core code• Suite of SpatsTests• Match SpatsTests to UUT Component Type• Each SpatsTest exercises set of protocols• SPATS verifies protocol content, sequence,

and messages are correct

CAS

SM-L

LS

SM-S

SM-1

SM-U

Components to test as UUT

SPA Application

SM-S ASIM / Component

SM-U ASIM / Component

SM-1 ASIM / Component

With Hardware SupportOn System w IP

CubeFlow Tools

Creating SPA software can be more complicated than creating traditional software.

xTEDS – Not many people are used to handcrafting XMLASIM – ASIM protocol is a different way of thinking about embedded softwarePnP Flight Software using standard interface and data centric publish/subscribe paradigm

CubeFlow tools automate many common SPA software development requirements

Open source web based tool suite

CubeFlow Tools

xTEDS DeveloperAssists a user in creating and maintaining xTEDS through a UI without requiring full XML knowledge

CubeFlow Tools

ASIM WizardAids creation of ASIM code for supported platforms by generating the code templates that match the selected xTEDS

CubeFlow Tools

App WizardAids creation of SPA application templates that will utilize a given device kind, as specified through the selected xTEDS

Common Data Dictionary Tool

Common Data Dictionary (CDD) ToolUsed to manage and define the Common Data Dictionary

CubeFlow Training Courses & Development Kits

SDL and COSMIAC have developed a training course including hardware / software to introduce SPA conceptsDevelopment kit contains all the items needed to develop xTEDs, ASIMs, and applications, and test their functionality

CubeFlow Training Courses & Development Kits

As of Dec 2010 there are 343 registered users on the CubeFlow siteOver 500 individuals trained from 100+ organizations including:

NASALockheedBoeingNROORSUniversities

Space Plug-and-Play Architecture (SPA) and SSM

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