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SOIS and Software Reference Architecture

F. TorelliDASIA 2011 - Malta17/05/2011


SOIS and SW Ref. Architecture | F. Torelli | DASIA 2011 - Malta | 17/05/2011 | TEC-SWS | Slide 2

Outline

1. SOIS architecture and services

2. SOIS architecture and Avionics System Reference Architecture

3. Impacts to the design of flight software

4. Status of SOIS publications and related developments

5. Conclusions



SOIS architecture and services



CCSDS SOIS Architecture

Com

munic

atio

n 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

Standard Services

Standard Services

ECSS Standard Protocols

SOIS provides an abstraction of the functionality of the spacecraft units in a layered fashion.



Sub-Network Services

Sub-network services:

– abstract from the physical location (within the spacecraft) of the unit to be accessed

– abstract from the datalink protocol required by a specific communication media to access a unit

– abstract from time constrains strictly related to the specific communication media used to access a unit

– abstract from the addressing scheme required by a specific communication media to identify a unit.

Com

munica

tion M

anagem

ent


Time AccessService

File &Packet Store

Services


DeviceEnumeration

Service

Packet Service

MemoryAccessService



Test Service


ApplicationLayer


TransferLayer

Subnetwork Layer

Network Protocol

Transport Protocol


MissionSpecific

Applications



Command & Data Acquisition Services

Command & Data Acquisition services:– abstract from the protocol required to control

the device (Device Access Service)

– abstract from the type of communication service (i.e. memory access, packet-base) required to access the device (Device Access Service)

– abstract from time constrains strictly related to the device specific access protocol (Device Access Service)

– decouple device physical access from device data consumption by the applications (Device Data Pooling Service)

– add ontology to the raw command and data information related to devices (Device Virtualisation Service)

– provide a uniform interface for each class of devices, independent from their actual implementation (Device Virtualisation Service).

Com

munica

tion M

anagem

ent


Time AccessService

File &Packet Store

Services


DeviceEnumeration

Service

Packet Service

MemoryAccessService



Test Service


ApplicationLayer


TransferLayer

Subnetwork Layer

Network Protocol

Transport Protocol


MissionSpecific

Applications



Other Application Support Services

Time Access Service:

– abstracts from the mechanisms required to access the on-board reference time and to handle time alarms.

Message Transfer Service:

– provides a high level and uniform mechanism to communicate between software applications within the spacecraft.

File and Packet Store Service:

– provides a standardised interface to mass memory file and packet stores

– abstracts from the implementation details related to the mass memory file systems.

Com

munica

tion M

anagem

ent


Time AccessService

File &Packet Store

Services


DeviceEnumeration

Service

Packet Service

MemoryAccessService



Test Service


ApplicationLayer


TransferLayer

Subnetwork Layer

Network Protocol

Transport Protocol


MissionSpecific

Applications



Plug and Play Services

Plug and Play Services:

– provide mechanisms to discovery and configure devices connected to a sub-network

– provide mechanisms to handle units redundancy

– provide the means to interpret the content of Electronic Data Sheets and to configure the other services accordingly (C&DA).

Com

munica

tion M

anagem

ent


Time AccessService

File &Packet Store

Services


DeviceEnumeration

Service

Packet Service

MemoryAccessService



Test Service


ApplicationLayer


TransferLayer

Subnetwork Layer

Network Protocol

Transport Protocol


MissionSpecific

Applications



Protocols supporting the Services

The services are complemented by protocols

implement the functionality specified by SOIS.

Sub-Network Protocols:– Mil-Std-1553, ECSS-E-ST-50-13C

– CAN, ECSS-E-ST-50-15C draft

– Spacewire, ECSS-E-ST-50-52 (RMAP), ECSS-E-ST-50-XX (SpW-D)

Message Transfer Service Protocol:– Asynchronous Message Service, CCSDS 735.1-B-0

File and Packet Store Service Protocols:– Network File Access, Network Packet Access and Remote Block

Storage Protocols need to be standardised

Com

munica

tion M

anagem

ent


Time AccessService

File &Packet Store

Services


DeviceEnumeration

Service

Packet Service

MemoryAccessService



Test Service


ApplicationLayer


TransferLayer

Subnetwork Layer

Network Protocol

Transport Protocol


MissionSpecific

Applications

AMSTBD



SOIS and Avionics System Reference Architecture



Avionics System Reference Architecture

Onboard Communications H/W(e.g. MIL-STD-1553B, SpaceWire, CAN RS422)

OBC Hardware

CAN MIL-1553

TM/TC

RS422 SpW

CPU/NGmP

EEPROMBoot

PROM

OBTimer

SGM

HWwatchdo

g

Software bus

SecurityUnit

Solid StateMass

Memory

File/ Compress

/Encrypt

Payloads &Instruments

SSMM

RTU/Intelligent IO

PayloadCompute

rSOIS

Layers

Legacy devices

Standardized devices

Intelligent devices

SOIS Layers

ADCs / DACs

SOIS Layers

Sensorand

actuators

RAM DSP

Digital Sensorbus

SpaceLinux

Application BB (mission dependent)

Plan/ AutonomyFramework

System mode mgmt

Central FDIR

AOCS

P/L Manager

Thermal

Power

OBT Mgmt

Satellite Confand Eqpt

Mgmt

SSMM Mgmt

Execution platform

BSPSOIS Subnetwork layer (1553, CAN, SpW)(including HDSW)

Container services

Connector services

PUS specificComponent

servicesAbstract component

services

PUS and MTL

services

OBCPinterpreter

Avionics Equipment

virtual devices

=SOIS DVS

PUS monitoring

RTOS

Context Mgmt

On-board time

=SOIS TAS

Communication services

addressing physical

distribution across nodes

= SOIS MTS

Libraries:mathematical

, etc.



SOIS in the Avionics System Reference Architecture 1/2

On-Board Computer (OBC):

The full set of SOIS services is intended for implementation in the OBC flight software as part of the Execution Platform building block.

Other Equipments:

A reduced subset of SOIS service is foreseen for the external units such as RTUs, Solid State Mass Memory, Intelligent Sensors and Actuators, Payloads in accordance with their functionality and supported features.



SOIS in the Avionics System Reference Architecture 2/2

Onboard Communications H/W(e.g. MIL-STD-1553B, SpaceWire, CAN RS422)

OBC Hardware

CAN MIL-1553

TM/TC

RS422 SpW

CPU/NGmP

EEPROMBoot

PROM

OBTimer

SGM

HWwdog

Software bus

SecurityUnit

Solid StateMass

Memory

File/ Compress/

Encrypt

Payloads &Instruments

SSMM

RTU/Intelligent IO

PayloadCompute

r

SOIS Layers

Legacy devices

Standardized devices

Intelligent devices

SOIS Layers

ADCs / DACs

SOIS Layers

Sensorand

actuators

RAM DSP

Digital Sensorbus

SpaceLinux

Application BB (mission dependent)

Plan/ AutonomyFramework

System mode mgmt

Central FDIR

AOCS

P/L Manager

Thermal

Power

OBT Mgmt

Satellite Confand Eqpt

Mgmt

SSMM Mgmt

Execution platform

BSPSOIS Subnetwork layer (1553, CAN, SpW)(including HDSW)

Container services

Connector services


servicesAbstract component

services

PUS and MTL

services

OBCPinterpreter

Avionics Equipment

virtual devices

=SOIS DVS

PUS monitoring

RTOS

Context Mgmt

On-board time

=SOIS TAS

Communication services

addressing physical

distribution across nodes

= SOIS MTS

Libraries:mathematical,

etc.

Com

munica

tion M

anagem

ent


Time AccessService

File &Packet Store

Services


DeviceEnumeration

Service

Packet Service

MemoryAccessService



Test Service


ApplicationLayer


TransferLayer

Subnetwork Layer

Network Protocol

Transport Protocol


MissionSpecific

Applications

SOIS Layers



Impacts to the design of flight software



Traditional Flight Software

In a traditional flight SW system, AOCS and equipment time requirements defining the bus schedule also drive the flight SW architecture and the SW tasks schedule.

The system is designed as a “monolithic” entity tailored for the specific mission.

tMajor Frame (1 sec)

Minor Frame 0 (125 msec)


AOCS Acquisitions

Payload 1 Acquisitions

MTL Manager



Payload 2 Commanding

AOCS Processing

TC Manager

HK TM Processing


Payload 2 Manager

OBCP Interpreter

HK TM Processing

Payload 1 Manager

EEPROM Manager

MilBus Manager

MilBus Manager

MilBus Manager

MilBus Manager

AOCS Commanding


MilBus Manager


Large Data Transfer

…

MilBus Manager

Mass Memory

HK TM Processing Monitoring

Mode Manager

Science TM Processing

Scrubbing

MTL Manager

Bu

s a

nd

AS

W T

ime D

om

ain

Mix

ed



Motivations for an Improvement

Such a synchronous schedule works to accomplish relatively simple

mission requirements, however:

1. to improve the development process,

2. to accommodate more functions on board,

3. to enable new emerging technologies (e.g. multi-core processors, time and space partitioning, increased autonomy)

It is advisable to move towards an avionics architecture based on

composable building blocks where functional and timing

requirements, if possible, are addressed at component level

(separation of concerns).



Proposed Way Forward

SOIS Services:

The introduction of the previously mentioned SOIS standardised

services supports this approach allowing to decouple the functional and

timing requirements strictly related to the communication protocols

from the ones related to the device access protocols and again from

the ones related to the applications algorithms.

These concepts will be briefly discussed for:

- Sub-Network Services

- Command & Data Acquisition Services

- Message Transfer Service.



Sub-Network Services Characterisation

Sub-Network Service Primitives

Bus Protocol

Bus Profile

AOCS Frequency

Sensor Max

Latency

Command Accuracy

Sensor Access Time

Equipment Physical Address

Bus Bandwidth Allocation

Equipment Physical Address

Equip. Physical Address

Sensor Access Time

Sensor Access Time

Actuators Access Time



Command AccuracyCommand Accuracy

Sensor Max

Latency

Sensor Max

Latency

AOCS Algorithm Duration Service Time and

Functional Characterisation

Traffic Scenario for the Nodes

Low level communication req. can be captured in the sub-network layer to define the bus profile and to expose to the upper layers of the flight software functional and non-functional attributes of the services primitives.



Command & Data Acquisition Services Characterisation

Sub-Net Service Timing

Raw Data

Format

Common Data

Dictionary

Device Access Req.

Calib. Curves

Engineering Data Format

Device Required Interface

Electronic Data Sheet

Device Virtualisation

Service

Device Access Service

Device Enumeration

Service

Service Time and Functional Characterisation

Raw Command/Acquisition Sequence

The requirements related to the mechanisms to access the on-board devices can also be isolated within the C&DA services group, mainly in DAS and DVS.

The services can be automatically configured and instantiated during the design phase based on the description of the EDS and provide a well characterised and standardised interface.



Message Transfer Service Characterisation

Message Transfer Service Primitives

Asynchronous Message Transfer Service Protocol

Registration Table

APID Definition

TM/TC Formats

Tasks Deadlines

External Nodes

Routing

PUS Services

Service Time and Functional Characterisation

Message Traffic with Local and Remote SW Entities

Sub-Net Service Timing

In the Avionics System Reference Architecture, the Software Bus entity is in charge to support the communication between applications and SW components.Although the Software Bus can be implemented with different mechanisms, it is clear that the SOIS MTS provides the needed infrastructure.



Flight Software using SOIS Services

ASW tasks schedule and I/O schedule are now related each others only due to the AOCS dependencies and the I/O operations are represented in terms of services (SOIS request & indication, time events).

Components can be designed independently according to the functional and non-functional attributes of the interfaces.

tMajor Frame (1 sec)



AOCS Acquisitions


MTL Manager



Payload 2 Commanding

AOCSTC

Manager


Payload 2 Manager

OBCP Interpreter

Payload 1 Manager

EEPROM Manager

SOIS Sub-Network

SOIS Sub-Network

SOIS Sub-Network

SOIS Sub-Network

AOCS Commanding


SOIS Sub-Network


Large Data Transfer

…

SOIS Sub-Network

SOIS FPSSHK TM Processing Monitoring

Mode Manager

Science TM Processing

ScrubbingSOIS C&DA

SOIS C&DA

Bu

s T

ime

Dom

ain

AS

W T

ime D

om

ain



Improvements to Flight Software

Some of the beneficial effects of the introduction of

standard services:

– the possibility to develop and analyse the software applications/components based on clear interfaces

– the possibility to deploy some of the applications on a different processing core or partition without impacting the design of the avionics system

– the possibility to exchange software/hardware components (e.g. sub-network services) with minimal impacts to the overall design.



Status of SOIS publications and related developments



Status of SOIS documentation

SOIS Sub-Network Services:– published in 2009 and are currently used to drive new and upgraded

ECSS protocols for CAN and Spacewire.

SOIS Application Support Services:– Time Access Service published in 2011

– File and Packet Store Service and Message Transfer Service are currently under Agency review and will be published in 2011

– C&DA services are planned for 2011/2012

CCSDS SOIS work is now concentrated on: – the refinement of the communication architecture, particularly in

terms of addressing and the provision of software APIs

– The use of electronic data sheets to automate the process of interface definition and integration (C&DA and DES)



Present and Future Developments

Ongoing activities supporting standardisation:– A SOIS prototype is presently being prepared by SciSys (UK) in collaboration with ASTRIUM (F).

This will result in an upgraded RASTA system at ESTEC and a published set of IPR free API’s.– A prototype of the CCSDS file transfer protocol (CFDP) mapped to an implementation of the SOIS

file and packet store services is being prepared by Spacebel (B). This will also result in an upgraded RASTA system.

– Packet Store Services have also implemented by Scisys (UK) in the frame of the MARC project.– An ECSS standard for CAN Bus is under preparation. This is being driven by the Exomars program

and will result in an IP core compatible with SOIS sub-network services.– A SOIS/ECSS software component for Mil1553 Bus Controller has been developed by RUAG

(S) and its counter part for Remote Terminal Units is being implemented. These software building blocks are produced in compliance with the flight software ECSS standards and validated on the RUAG’s flight hardware platforms (Tiger and Panther boards).

– An alternative SOIS/ECSS sub-network services implementation for Mil1553 Bus Controller have been developed by Terma (DK) and integrated in the Avionics System Test Bench at ESA.

On 2011 the following additional activities are planned:– A TRP activity exploring the use of Electronic Data Sheets.– A TRP activity demonstrating Plug and Play techniques.– A TRP activity proving an end-to-end test-bed for the evaluation of file based communication

and operations.



Conclusions



Conclusions 1/2

– The key characteristics of the SOIS services architecture have been presented.

– It has been shown that some of the essential features of the Execution Platform in the Avionics System Reference Architecture can be specified and implemented using the SOIS services.

Execution platform

BSPSOIS Sub-Network

Container services

Connector services


services

Abstract component

services

PUS and MTL

services

OBCPinterpreter

SOIS C&DA

PUS monitoring

RTOS

Context Mgmt

On-board time

=SOIS TAS

SOIS MTS

Libraries:mathematical,

etc.

EDS

Bus Profile

Reg Table



Conclusions 2/2

– Some services have been discussed in the context of the avionics and flight software design phase, here the flexibility given by these services demonstrates to be very beneficial as it allows to characterise the service interfaces without modifying the primitives.

– A number of prototypes and flight software developments are ongoing under ESA contracts and in the near future will allow consolidate further the CCSDS standard specifications.


SOIS and Software Reference Architecture

F. TorelliDASIA 2011 - Malta17/05/2011

esa unclassified – for official use sois and software reference architecture f. torelli dasia 2011...

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