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CAN in Space Workgroup
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  1. CAN in Space Workgroup Status Report L. Stagnaro & P. Roos

  2. 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

  3. 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

  4. 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

  5. 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

  6. 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

  7. 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

  8. 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

  9. 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

  10. 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

  11. 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

  12. CAN Industrial presence ESTEC 5-7 May 2003

  13. 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

  14. 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

  15. 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

  16. SYNC SYNC SYNC Event time Cyclic Acyclic CANOpen Sync • Transmission type • Event driven (spontaneous) • Polled • Synchronous cyclic or acyclic ESTEC 5-7 May 2003

  17. 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

  18. 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

  19. 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

  20. 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

  21. Contact Persons • Luca Stagnaro (Chairman) • luca.stagnaro@esa.int • Peter Roos (Secretary) • peter.roos@esa.int • Rodger Magness (Physical Layer) • rodger.magness@esa.int • Patrick Plancke (Head of Computer & Data Systems section) • patrick.plancke@esa.int ESTEC 5-7 May 2003