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CAN in Space Workgroup. Status Report L. Stagnaro & P. Roos. Presentation overview. History Workgroup Objectives & Planning Status Overview of key CANOpen features CANOpen add-ons for space adaptation Resources & Contact Points. History.

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Can in space workgroup

CAN in Space Workgroup

Status Report

L. Stagnaro & P. Roos


Presentation overview

Presentation overview

  • History

  • Workgroup Objectives & Planning

  • Status

    • Overview of key CANOpen features

    • CANOpen add-ons for space adaptation

  • Resources & Contact Points

ESTEC 5-7 May 2003


History

History

  • Since the start of the SMART-1 spacecraft development and the development of the ESA free CAN core (Hurricane), CAN technology had raised increasing interest in the European aeronautic industry

  • Standard CAN needs to be completed with an high level protocol and an electrical interface before it can be used onto a spacecraft

ESTEC 5-7 May 2003


History cont d

History Cont’d

  • There was the need to provide guidelines for the use of CAN in ESA missions, in order to standardize its use and prevent the proliferation of dialects and custom solutions.

  • It was decided to start a workgroup formed by member of ESA, Industry and Academia to provide the needed recommendations.

ESTEC 5-7 May 2003


Workgroup objectives

Workgroup Objectives

  • Selection of high level protocol industrial standard that most suit the spacecraft on-board applications.

  • Definition of the electrical/physical interface that fulfill the requirements of a spacecraft avionics.

  • Definitions of a selected number of features to complete the standard in aspects that are specific of a spacecraft avionics such as redundancy.

ESTEC 5-7 May 2003


Workgroup objectives cont d

Workgroup Objectives Cont’d

  • The working group will complete the task in one year time frame.

  • The product of the working group will be a set of recommendations that will become part of the ECSS standard.

    (1st Draft of recommendation available)

ESTEC 5-7 May 2003


Workgroup planning 1

Selection

Implementation

Validation

Workgroup Planning (1)

CAN Workshop

(Dec 2002)

1st Meeting

(5-6 March 2003)

2nd Meeting

3rd Meeting

4th Meeting

  • Task

    • Preliminary definition of services

    • Demonstrator specification

    • Physical Layer requirements definition

  • Output

    • 1st Draft available

    • Demonstrator Specification

ESTEC 5-7 May 2003


Workgroup planning 2

Selection

Implementation

Validation

Workgroup Planning (2)

CAN Workshop

(Dec 2002)

1st Meeting

(5-6 March 2003)

2nd Meeting

3rd Meeting

4th Meeting

  • Task

    • Consolidate the selected services

    • Implement services in demonstrator

  • Output

    • 2nd Draft of recommendation

ESTEC 5-7 May 2003


Workgroup planning 3

Selection

Implementation

Validation

Workgroup Planning (3)

CAN Workshop

(Dec 2002)

1st Meeting

(5-6 March 2003)

2nd Meeting

3rd Meeting

4th Meeting

  • Task

    • Implement services in demonstrator (cont’d)

    • Validation tests including physical layer

    • Define Device Profiles for typical S/C equipments

  • Output

    • Draft Device Profiles

    • 3rd Draft of recommendation

ESTEC 5-7 May 2003


Workgroup planning 4

Selection

Implementation

Validation

Workgroup Planning (4)

CAN Workshop

(Dec 2002)

1st Meeting

(5-6 March 2003)

2nd Meeting

3rd Meeting

4th Meeting

  • Task

    • Implement and validate Device Profiles

    • Finalisation of the tests and simulations

    • Finalisation of draft recommendation

  • Output

    • Final draft of recommendation

ESTEC 5-7 May 2003


Canopen

CANOpen

  • After an initial investigation among the industry standard protocol the CANOpen has been selected.

  • From the CAN Justification file

    • CANOpen seems definitively the most advanced/flexible among the analysed protocols, supporting many needed functions. In addition the capability of configuring a node is attractive for inter-operability of units

ESTEC 5-7 May 2003


Can industrial presence

CAN Industrial presence

ESTEC 5-7 May 2003


Canopen at a glance

CANOpen at a glance

  • Two main communication objects

    • SDO (Service Data Object) for transfer of complex and large data

    • PDO (Process Data Object) for simple or short real-time communication

  • Node Object dictionary

    • Allow the configuration of a unit for the specific network

    • Contains information about the unit capabilities

    • Device profiles

  • Sync message for cyclic coordination

  • High accuracy time distribution (~1 us)

  • Defined Node and Error Handling

    • Defines Node state machines

    • Predefined error codes

    • Specific Unit Codes

ESTEC 5-7 May 2003


Canopen object dictionary

CANOpen Object Dictionary

  • An object dictionary is a node shared memory area that can be read/written by any other node on the network

    • To understand node type, capabilities and messages structure (READ)

    • To configuring the node for the network in which the node is inserted, as for example the data period. (WRITE)

  • A mandatory set of entry in the dictionary is established by the standard device profile to which the node belongs.

ESTEC 5-7 May 2003


Canopen dictionary example

Entry

Type

Parameter

Data Length

Mode

Set of defined

Parameter

By the unit

manufactures

0

VAR

Scaling rad/sec per byte

BYTE

R/W

R/W

1

VAR

Low Pass Filter Frequency

BYTE

R

2

VAR

Gyro 1 rate

WORD

Message

Entry

Parameter Entry

Data Length

Mapping

To

Write Messages

A

1

0

BYTE

A

2

1

BYTE

User

Configured

Mapping

To

Read Messages

Message

Entry

Parameter Entry

Data Length

B

3

2

WORD

Cyclic

At every Sync

CANOpen Dictionary Example

  • Device Profile: AOC Sensor/Actuators Interface

ESTEC 5-7 May 2003


Canopen sync

SYNC

SYNC

SYNC

Event

time

Cyclic

Acyclic

CANOpen Sync

  • Transmission type

    • Event driven (spontaneous)

    • Polled

    • Synchronous cyclic or acyclic

ESTEC 5-7 May 2003


Canopen network management

reset

Initialization

Pre-operational

Stopped

Operational

CANOpen Network Management

  • CANOpen defines a set of services to startup the network before commencing the nominal work of the system.

  • During the network startup each node is configured (if needed) and take to the operational state.

Reset of Settings

Configuration of the device

Device Operation

Stop of all communication

ESTEC 5-7 May 2003


Add on to canopen

Large Data Unit Transfers

Optional protocol compatible with CANOpen

Co-exists with CANOpen

Reduced overhead compared to CANOpen

Physical Layer

Shall be suitable for vast majority of missions

Insure device-on-bus electrical compatibility and device-across-the-industry electrical compatibility

Redundancy

Management of bus redundancy

Informative examples to be put in recommendation annex

Relationship between CANOpen Node State Diagram and redundancy

Hot/cold bus and node redundancy

Add-on to CANOpen

ESTEC 5-7 May 2003


Physical layer

Physical Layer

  • Mandatory

    • ISO-11898: 1993 (Automotive) and ISO 11898 Amendment 1:1995

    • Up to 1Mbps – CAN Hi-speed

  • Recommendation

    • Number of Nodes: 32 Minimum

    • Bus cabling ISO 11898 compliant

    • Connector types

  • Optional

    • Single-point failure tolerant/Dual Redundant I/F

    • High Speed Optical coupler

    • Power thru CAN bus connector

ESTEC 5-7 May 2003


Resources

Resources

  • Yahoo group page:

    • http://groups.yahoo.com/group/CAN_Space/

    • Discussion forum

  • Web page:

    • http://users.skynet.be/cotectic/CAN-WG/

    • Draft recommendation

    • Minutes of Meetings etc. related to the CAN WG activities.

ESTEC 5-7 May 2003


Contact persons

Contact Persons

  • Luca Stagnaro (Chairman)

    • [email protected]

  • Peter Roos (Secretary)

    • [email protected]

  • Rodger Magness (Physical Layer)

    • [email protected]

  • Patrick Plancke (Head of Computer & Data Systems section)

    • [email protected]

ESTEC 5-7 May 2003


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