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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

ESTEC 5-7 May 2003

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