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SOIS P&P input

2

Introdcution

• As part of the work to standardise onboard communication services, the CCSDS SOIS WG has recently delivered new draft standards on File and packet stores / message exchange; these standards are presently undergoing Agency review.

• In parallel solid progress has been made in refining the communications architecture related to addressing and plug and play.

• In particular, efforts are being made to align the SOIS work with existing developments, in particular IEEE 1451 and the AFRL SPA related standards released by the AAIA, with the intention of developing a CCSDS recommendation for the use of Electronic data sheets

• In addition, ESA led activities such as SAVOIR are pushing ahead with industrial studies to further coordinate the provision of a reference avionics architecture with standard interfaces and building blocks

• Finally, there are many TRP and GSTP research activities under release which are intended to support or implement the new building blocks

• While all of the above can be considered as a successful demonstration of a coordinated approach, there is a real danger (with so many parallel activities), that efforts will diverge.

• This presentation provides the outlook from a CCSDS SOIS viewpoint indicating how the work so far should be applied

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SOIS motivation

• The main motivation behind SOIS is reduce development costs and risks associated with interconnecting elements of the flight avionics

• The SOIS approach is to define a set of communication services at both application and subnetwork layers. These services are supplemented by protocols developed either by ECSS or CCSDS

• The approach provides a common interface to applications independent of the topology of and specific details of the underlying hardware

• Onboard subnets provide a common set of services regardless of the physical media and associated data link protocol

• Data link protocols are fully specified in accordance with the SOIS services, thus removing the need for ad-hoc development and mission specific testing

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CCSDS SOIS Status

• The completion of the CCSDS SOIS effort to standardise onboard communications services and protocols is now in sight with many standards already released

• Efforts are now concentrating on standardising the interfaces to onboard sensors and actuators both at the communication and functional levels

• At the communication level, the existing IEEE1451 standards for smart transducers is presently the most likely candidate including the use of the Transducer electronic data sheet (EDS)

• For the functional interface, consideration is being given align with the AFRL developed Extended TEDS (X-TEDS). This is being used as part of the SPA initiative for rapid spacecraft development and is undergoing standardisation by the AAIA

• The architecture supporting the above is described in an updated version of the SOIS Green book (Http ref xxx)

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Standards Availability

CMD & DataAcquisitionServices

Time AccessService

File & packet Store

Services

Message TransferService

DeviceEnumeration

Service

Packet Service

MemoryAccessService

SynchronisationService

DeviceDiscoveryService

Test Service

ApplicationSupport Layer

Subnetwork Layer

All standards completed

3 standards completed

In accordance with SOIS services

ECSS DatalinkStandards Milbus Spacewire Canbus Serial

Underway, completion 2011 Planned completion

2012

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SOIS P&P architecture

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Device VirtualisationService

Device VirtualisationService

Device AccessService

Device AccessService

SubnetworkPacket or Memory

Access Service

SubnetworkPacket or Memory

Access Service

SubnetworkProtocol

Implementations

SubnetworkProtocol

Implementations

SOIS

HardwareDevice

HardwareDevice

SubnetworkImplementation

Hardware

Applications

ApplicationApplication

Physical Device

Interface to subnetwork service

Provides acquisition of device vales

Permits device commanding

Manages underlying device modes

Handles device protocol

Standardises device values

Standardises device semantics

Provides all necessary operations

Standard interface

Subnetwork service implementation

SOIS P&P architecture

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Device Electronic Datasheet

(SOIS)

Device Electronic Datasheet

(IEEE 1451)

TranslationDVS and DAS

Implementations

Auto-Coding

Virtual DeviceInterface

Definitions(xTEDS)

Extract and Publish

If Device has IEEE 1451 Datasheet

If Device Datasheet is Complete and Device is

Standard Type

Or Auto-Configuration

Use of Electronic data sheets

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IEEE 1451 standards

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IEEE 1451 – “RTU Architecture”

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1451 – use of TEDs

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RTU as element of P/F Avionics:

CDMU

RTURTU2015

P/F Bus

P/L Bus

MIL-STD-1553BCANRS-422SpW

ECSS-E-ST-50-13CECSS-E-ST-50-12C,…ECSS-E-ST-50-15dr

Sensors &Actuators(T, AOCS,Propulsion, …)

ECSS-E-ST-50-14CECSS for digital sensor busses

MIL-STD-1553B, CAN, SpW

MMU P/LP/LSpW, HSSL,SpF

PCU/PCDU

Power Bus

Load

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RTU : possible configurations

OBC/CDMU/SMU

RTU2015 #2

Backplane

DC/DC Controller

SpWRTC

SpWRouter

RTU2015 #1

Backplane

DC/DC Controller

FPGAWith

CCIP/1553/RS422 I/F

uControllerWith CAN/

1553/RS422 I/F

HK

SLAVE

MOD

SADM

CTRL

MOD

HK

SLAVE

MOD

DigSERIAL

Bus

MOD

WIRELESS

DataCollec.

MOD.

CAN/1553B/RS422

SpW

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Questions for SOIS WG

• IEEE1451 use the same architecture as the proposed ESA RTU. 1451 uses XTEDS for devices but presents a standard API for access over the user network – How does this fit with the SOIS P&P architecture, in particular the DAS and DVS

• ESA is also standardising the use of CANBus as a primary onboard bus. CANBus has its own (text based) EDS – how does this fit with the SOIS P&P architecture? (important as use of CAN will force equipment suppliers to provide EDS’s)

• There are several “object dictionaries” (1451, CAN, XTEDS) available – how (should we) do we rationalise these into a single view and document?

• Our diagrams to not yet reflect the use of a device specific protocol to support the device access service – propose this should be identified/specified as this will be needed e.g. for standard access to an RTU

• The SPA guidebook contains a section on SOIS – is everybody happy that the text correctly reflects the comparison with SPA?

• The Green book has been updated, are there still actions and updates and what are the plans for the review and release?

• Although we made a great step forwards at the last meeting and reflected the results in the Green book, I’m concerned that the GB text is a little ‘academic’ and would benefit from a practical example to supplement the layered model – comments anyone?