23 rd October 2009 Stuart Fowell SciSys and Astrium SOIS Projects - CCSDS Fall 2009 Meeting.
The CCSDS Spacecraft Onboard Interface Services (SOIS) Standards An Introduction
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Transcript of The CCSDS Spacecraft Onboard Interface Services (SOIS) Standards An Introduction
1st May 2012
Stuart Fowell
The CCSDS Spacecraft Onboard Interface Services (SOIS) StandardsAn Introduction
2 SOIS Introduction
Overview
SOIS Standardisation, OSI and SOASOIS ArchitectureSOIS ServicesSOIS Prototyping and Reference Implementation
3 SOIS Introduction
CCSDS SOIS Standardisation
The Consultative Committee for Space Data Standards (CCSDS) developing recommendations for communication services onboard a spacecraft, handled by the Spacecraft Onboard Interface Services (SOIS) areaSOIS aims to provide a consistent interface to various low-level access methods, enabling a common interface to the application software
This is achieved through the providing a uniform set of services over any subnetwork
Eventual goal is reusable software that can be easily ported to new missions and run on a range of onboard buses without substantial modification
Beyond the uniform set of services over any subnetwork, this goal is to standarise interfaces to devices
Late configuration changes, e.g. relocation of thermistor, can be accommodated through simple spacecraft database changes without affecting onboard softwareConsistent interface should provide an enabler for more complex, higher-level software architectures, e.g. fault-tolerant, distributed, software frameworks and autonomous, onboard mission planners
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SOIS, OSI and SOA
SOIS defined with reference to OSI, similar to aspects of SOASOIS defined as a layered architecture and services provided by each layerEach service defined in terms of:
Service interface offered to higher layersProtocol engine (procedures and PDUs)
May include time-outs on receiving PDUsRequired services from lower layersManagement Information Base (MIB)All defined using structured English
Abstract definition, with no reference to implementation in hardware or software, programming languages, APIs etc.
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SOIS Architecture
Organised into layers:Subnetwork Layer provides access to the Data Link medium and provides a set of SOIS-defined services over the subnetwork defined by that medium Transfer Layer optionally provides Transport- and Network-layer services based on existing protocols Application Support Layer provides a number of capabilities commonly required onboard a spacecraftApplication Layer consists of mission-dependent applications that make use of the SOIS-defined services
All managed by Communication Management
Com
munica
tion M
anagem
ent
CMD & DataAcquisitionServices
Time AccessService
File &Packet Store
Services
Message TransferService
DeviceEnumeration
Service
Packet Service
MemoryAccessService
SynchronisationService
DeviceDiscoveryService
Test Service
Datalink Convergence Protocols
ApplicationLayer
ApplicationSupport Layer
TransferLayer
Subnetwork Layer
Network Protocol
Transport Protocol
Milbus SpaceWire CAN Wireless
MissionSpecific
Applications
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Typical subnetwork
Physical I/F
Data Link Protocol
Physical I/F
Data Link ProtocolSubnetwork =
RS422
Data Link Protocol
RS422
Data Link Protocol
Milbus
ECSS Milbus Ext protocol
Milbus
ECSS Milbus Ext protocol
ECSS SpaceWire Physical
ECSS SpaceWire Datalink
ECSS SpaceWire Physical
ECSS SpaceWire Datalink
Physical = Connector, Pinout, electrical
Datalink = Basic communication protocol
7 SOIS Introduction
SOIS Services
SOIS Subnetwork LayerDevice Commanding, Data Acquisition & VirtualisationFile and Packet Store AccessOnboard Time AccessMessage TransferDevice Plug-and-Play
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SOIS Subnetwork Layer
Standardise basic communication services to be provided by a subnetwork
Services are mapped onto protocols and services provided by different data medium e.g. SpaceWire, MIL-STD-1553B and CANNot all services need to be provided by a subnetwork typeProvision against system requirement should be used to drive subnetwork selection
Packet Service – providing packet delivery over a single subnetworkMemory Access Service – providing direct access (memory location read/write, includes block move and read/modify/write) to device memorySynchronisation Service – providing spacecraft time and event synchronisationTest Service – providing establishment of subnetwork functionality and availability
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SOIS Subnetwork Layer Mappings
MIL-STD-1553BECSS-E-ST-50-13C, “Interface and communication protocol for MIL-STD-1553B data bus onboard spacecraft”, 15 November 2008Influenced by early drafts of SOIS servicesPrototype mapping for BCs done by Astrium, RUAG Recommended mapping for BCs and RTs to be produced in SOIS prototype
SpaceWireECSS-E-ST-50-12C, “SpaceWire - Links, nodes, routers and networks”, 31 July 2008ECSS-E-ST-50-51C, “SpaceWire protocol identification”, 5 February 2010ECSS-E-ST-50-52C, “SpaceWire - Remote memory access protocol”, 5 February 2010ECSS-E-ST-50-53C, “SpaceWire - CCSDS packet transfer protocol”, 5 February 2010QoS being addressed in variety of R&D projects, e.g. SpaceWire-RT/T/D protocols from SpaceNet project (University of Dundee)Prototype mappings done by SciSys, UoDRecommended mapping to be produced in SOIS prototype
CANECSS working group in progressMapping to SOIS included in WG charterDraft expected end 3Q 2010
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Device Commanding, Data Acquisition & Virtualisation
Typically used to access spacecraft hardware devices such as sensors and actuatorsAllows reconfiguration of subsystems (e.g. change location, port etc) or replacement of devices (Star Tracker type A -> B) without affecting users
Device Access Service – device-dependant driver providing basic reading from and writing to devices regardless of location
Encapsulates device-specific access protocols (protocol and addressing) to devicesMapped onto subnetworks’ Memory Access and/or Packet ServicesMay be driven by Electronic Data Sheets (dynamic or build-time auto-code build-time auto-code generationgeneration)
Device Virtualisation Service – standard device driver providing reference to a device using a virtual, i.e., generic, image of a physical device
Standardise device interfaces into classes and associated functionsMap class interfaces to actual interfaces – “virtualisation” – device abstraction control proceduresMay be driven by Electronic Data Sheets (dynamic or build-time auto-code build-time auto-code generationgeneration)
Device Data Pooling Service – maintaining an image of the states of a number of devices
Periodic data acquisitions from devices
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Device Commanding, Data Acquisition & Virtualisation
Device 1 OBCUser
Applications
Subnetwork Packet Service
Device 1 AccessProtocol
Device 1 Functionality
Subnetwork Packet Service
Device Access Service
Device 1 AccessProtocol
Device Virtualisation Service
Device 1Class & Type
Subnetwork Memory Access Service
Device 2Class & Type
Device 2 Value ID to Address Protocol
Mapping
Device 2
Device 2 Access Protocol
Device 2 Functionality
Device 1 Value ID to Access Protocol
Mapping
Subnetwork-Specific Packet Protocol
Subnetwork-Specific Packet Protocol
Subnetwork-Specific Memory Access
Protocol
Subnetwork-Specific Memory Access Protocol
Device 3Class & Type
Device 3 Value ID to Driver Mapping
Device 3 AccessProtocol
Device 2 AccessProtocol
Subnetwork Memory Access Service
Device 3 Functionality
Local Driver
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File and Packet Store Access
Provides access to the spacecraft storage systemEncapsulates access methods (protocol and addressing) to storage systems (e.g. mass memories)Can be provided at 2 levels:
Network file access protocol, e.g. NFS, mapped onto subnetwork’s Packet ServiceRemote block storage protocol, e.g. ATA, mapped onto subnetwork’s Memory Access Service, e.g. RMAP, or subnetwork’s Packet Service
File Access Service – allows access to files and portions of their contents in local or remote file storesFile Management Service – allows management of files and directories in local or remote file stores
Packet Store Access Services – allows storage, retrieval and deletion of packets in a local or remote packet storePacket Store Management Services – allows management of packet stores in local or remote packet store systems
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File & Packet Store Services
OBC
File and Packet Store Services
UserApplications
Subnetwork Packet Service
Network File and Packet Store Access Protocols
Subnetwork Packet Service
Subnetwork-Specific Packet Protocol
Subnetwork-Specific Packet Protocol
File and PacketStore System
Data Storage
Remote BlockStorage ProtocolBlock Access
SSMM providing flat Memory I/F
Subnetwork Packet Service
Subnetwork-Specific Packet Protocol
Data Storage
Remote BlockStorage Protocol
SSMM providing a File & Packet Store System I/F
Subnetwork Packet Service
Network File and Packet Access Protocols
File and PacketStore System
Subnetwork-Specific Packet Protocol
Data Storage
Block Access
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Onboard Time Access
Providing access to a local time sourceLocal time source may be synchronised with a master time source using a subnetwork’s Synchronisation Service
Time Access Service – providing access to, one-shot alarms and metronomes based on local time source
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Message Transfer
Discrete message transfer between applications/higher-level servicesIsolates users from locationFor inter-processor comms, maps onto subnetwork’s Packet ServiceFor intra-processor comms can use RTOS message queues
Four messaging models:Send/receiveQuery/responsePublish/subscribeAnnounce (similar to multi-cast)
Can be used as basis for middlewares/software bus or for inter-partition communication
Message Transfer Service – providing application-to-application message exchange
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Device Plug-and-Play
Plug-and-play of devicesDevice (and network) discovery
E.g. discovery of powered up 1553 RTs or SpaceWire links, routers etc.
Management of subnetworkE.g. allocation of addressing, configuration of routing
Service discoveryE.g. by reading Electronic Data Sheets (xTEDS) from device
User notification of discovered devices
Subnetwork Device Discovery Service – providing dynamic device recognitionDevice Enumeration Service – providing support for dynamic spacecraft configuration or enumeration
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SOIS Recommendations
Latest draft documents can be found in the SOIS working group’s collaborative working environment (CWE)
http://cwe.ccsds.org/sois/default.aspx
CCSDS SOIS Informational Report, CCSDS 850.0-G-1, June 20072nd issue being published in 2012
Published as standard:SOIS Subnetwork Packet Service, CCSDS 851.0-M-1, December 2009SOIS Subnetwork Memory Access Service, CCSDS 852.0-M-1, December 2009SOIS Subnetwork Synchronisation Service, CCSDS 853.0-M-1, December 2009SOIS Subnetwork Device Discovery Service, CCSDS 854.0-M-1, December 2009SOIS Subnetwork Test Service, CCSDS 855.0-M-1, December 2009SOIS Time Access Service, CCSDS 872.0-M-1, January 2011
Under PublicationSOIS File and Packet Store Services, CCSDS 873.0-M-0.1, February 2012SOIS Device Access Service, CCSDS 871.0-R-2.2, April 2012SOIS Device Data Pooling Service, CCSDS 871.1-M-0.1, April 2012SOIS Message Transfer Service, CCSDS 875.0-M-0.1, April 2012
About to undergo 1st Agency review:SOIS Device Virtualisation Service, CCSDS 871.2-R-0.2, April 2012SOIS Device Enumeration Service, CCSDS 871.3-R-0.2, April 2012
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SOIS Reference Implementation
SOIS Reference Implementation StudyESA TRPJan 2008 – Feb 2009SciSys prime, EADS Astrium sub-contractor
ObjectivesPrototype the SOIS Software Suite within ESA’s RASTA facilityProvide feedback on the outcome of the prototyping in order to refine and complete the CCSDS SOIS recommendations
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RASTA Test Facility
Reference Avionics System Test-bench Activity (RASTA)RASTA OBC supplied by Aeroflex Gaisler
LEON2 ASIC (100 MHz) @ ESA or LEON3 FPGA (40 MHz) @ SciSys3 x SpaceWire links2 x MIL-STD-1553B BC, RT or BM+ others (CAN, Ethernet, UART and Direct I/O)
RTEMS 4.6.5 + driversSTARDundee USB-SpaceWire Router & Linux PCsPCI MIL-STD-1553B cards & Linux PCs
Ground PC
Power strip
RASTA Server
RASTA MonitorGround PC
SpW router
RASTA 01
RASTA 02
RASTA 03
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SOIS Software Suite Acceptance Testing – Reference Mission
Data Storage InstrumentStar Tracker
Platform OBC Payload OBC
SpWRouter
MIL-STD-1553B
SpaceWire Link
SpaceWire Link
SpaceWire Link
SpaceWire Link
ReactionWheel
TM/TC Module
SpaceWire Link
Low Cost, Single Instrument, Earth Observation Mission
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SOIS Proof of Concept
SOIS Proof of Concept StudyESA TRPDecember 2009 – May 2012SciSys prime, EADS Astrium sub-contractor, Gaisler equipment supplier
Objectives:Standardise SOIS APIsImplement all SOIS services, running over SpaceWire and MIL-STD-1553B
Inc. mapping onto ECSS-E-ST-50-13C for MIL-STD-1553B (BC and RT)
Optimise and characterise implementation of SOIS services on RASTAIntegrate SOIS services with other Avionics Components
TM/TC Module and Ground Unit, PUS, CFDPSpaceWire-based Advanced Mass Memory & File StoreLegacy MIL-STD-1553B Remote Terminal Unit (ACRA Control)
Develop SOIS DemonstratorProvide Feedback to CCSDS