6th October 2009

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

4 SOIS Introduction

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.

5 SOIS Introduction

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

6

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

8 SOIS Introduction

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

9 SOIS Introduction

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

10 SOIS Introduction

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 access methods (protocol and addressing) to devicesMapped onto subnetworks’ Memory Access and/or Packet ServicesMay be driven by Electronic Data Sheets (dynamic or build-time auto-build-time auto-code generationcode generation)

Device Data Pooling Service – maintaining an image of the states of a number of devices

Periodic data acquisitions from devicesDevice 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”May be driven by Electronic Data Sheets (dynamic or build-time auto-build-time auto-code generationcode generation)

11 SOIS Introduction

Device Commanding, Data Acquisition & Virtualisation

Device 1

OBC

UserApplications

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 Translation

Device 2

Device 2 Memory Locations

(e.g. Status and Command Registers)

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 Packet Protocol

Device 3Class & Type

Device 3 Value ID to Driver Mapping

Device 3 Driver

Device 3 Functionality

12 SOIS Introduction

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

13 SOIS Introduction

File Services

OBC

File Access andManagement Services

SSMMproviding a File System I/F

UserApplications

Subnetwork Packet Service

Network FileAccess Protocol

File System

Subnetwork Packet Service

Network FileAccess Protocol

Subnetwork Packet Service

SSMMproviding flat Memory I/F

Subnetwork-Specific Packet Protocol

Subnetwork-Specific Packet Protocol

Subnetwork-Specific Packet Protocol

File System

Data Storage

Data Storage

Remote BlockStorage Protocol

Data Storage

Remote BlockStorage Protocol

Service Primitives

Subnetwork Packet Service

Subnetwork-Specific Packet Protocol

14 SOIS Introduction

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

15 SOIS Introduction

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

16 SOIS Introduction

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

17 SOIS Introduction

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 2010

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 2009

Under PublicationSOIS Device Access Service, CCSDS 871.0-R-2.1, March 2010SOIS Device Data Pooling Service, CCSDS 871.1-R-2.1, March 2010SOIS Time Access Service, CCSDS 872.0-R-2.1, March 2010

About to undergo 2nd and final agency review:SOIS File and Packet Store Services, CCSDS 873.0-R-1.5, March 2010

About to undergo 1st agency review:SOIS Message Transfer Service, CCSDS 875.0-R-0.4, March 2010

Under developmment:SOIS Device Virtualisation Service, CCSDS 871.2-R-0.2, January 2009SOIS Device Enumeration Service, CCSDS 871.3-R-0.1, January 2009

18 SOIS Introduction

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

19 SOIS Introduction

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

20 SOIS Introduction

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

21 SOIS Introduction

SOIS Proof of Concept

SOIS Proof of Concept StudyESA TRPDecember 2009 – January 2011SciSys 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 Units

Prototype use of Electronic Data Sheets for SOIS Plug-and-PlayDevelop SOIS DemonstratorProvide Feedback to CCSDS