ECSS-E-ST-50-15C Adoption Notice Maurizio Caramia ESA CAN WorkSohp 2017

CAN + CANOPEN The EXOMARS Mission EXM 2016 Mission EXM RSP Mission The ExoMars mission is split into two steps: The 2016 mission launched on 14th March 2016 consisting of a Trace Gas Orbiter (TGO) and an EDL Demonstrator Module (EDM) The RSP mission (planned in 2020) consists of a Rover accommodated inside a Descent Module (DM) carried to Mars by a Carrier Module (CM) EXM 2016 Mission EXM RSP Mission CAN + CANOPEN ESA CAN WorkSohp 2017

EXOMARS Physical Layer The Selected physical layer is the RS485 (DS16F95 transceiver) with daisy chain topology according one of the two options proposed by the CAN ECSS The fail safe network is implemented within the master node The daisy chain connection is realized at harness connector level ESA CAN WorkSohp 2017

EXOMARS CAN Transfer Layer Taking into account that OBC SW cycle has a period of 100 ms during which TMs have to be acquired/elaborated and CMDs have to be generated, TM/CMD exchange will be regulated according to periodic timing windows delimited by two SYNC messages and divided into two phases: one dedicated to TMs reception (70ms) and one dedicated to CMDs generation (30). The period of each window will be 100 ms. After a node power-on, reset node, reset application or bus switch slaves nodes shall consider the first SYNC message received after an NMT command “Go to OPERATIONAL” as the start of the first TM/CMD window. SYNC t=100ms TPDO TM 1 TPDO TM 2 TPDO TM n TPDO TM k CMD 1 CMD 2 CMD n OBC SW cycle, i CMD sub-window TM sub-window NMT “Go to Operational” TM SDO t=70ms (TBC) t=30ms (TBC) TPDO TM m OBC SW cycle, i+1 t ESA CAN WorkSohp 2017

CABCOM From Scientific to Telecom applications Starting from the EXOMARS experience, TAS executed the ESA CABCOM study with the following main goals: To implement a fully ECSS-E-ST-50-15C compliant CAN bus solution for SATCOM To validate the implemented CAN solution in a dedicated test bench with HW in the loop To upgrade the CCIPC to include: A-cyclic Synchronous PDO capability Reception of Broadcast PDO for time distribution Upgrade the CCIPC reconfiguration algorithm to support the infinite bus toggling. ESA CAN WorkSohp 2017

CABCOM Physical Layer Master Node Subnetwork 1 M R Node 3 Node n Node 32 Subnetwork 2 Node 34 Node 61 Node 62 Subnetwork 3 Node 65 Node 91 Node 92 Subnetwork 4 Node 96 Node 121 Node 31 Two different physical layers have been considered according the CABCOM study requirements: RS-485 network Four subnetworks composed of 31 node each operated in time multiplexing by a single master ISO-11898 network A single network with 120 nodes operated in time multiplexing by a single master Master Node M Node 2 Node 3 Node n Node 121 R ESA CAN WorkSohp 2017

CABCOM CAN Transfer Layer Each TS is organized in different windows in which different message transaction will be applied: Synchronous Window (SW): in this window only Synchronous PDO transactions are allowed The window starts with the SYNC message generated by the Master and last 1 second After the SYNC message, all the S-TPDO generated by the NODEs belonging to the specific TS will be received by the Master The synchronous windows Length parameter of each Slave node will be set to avoid S-TPO transmission outside the SW Asynchronous Window (AW): In this window only the Asynchronous On-request transactions are allowed. The Master will send the TM_RQST command to all slaves belonging to this window The Slave will reply with the requested parameter A complete transaction (Master Request and Slave Reply) will be completed before the start of a new transaction. Only requests to the nodes belonging to the specific TS will issued by the Master The AW will last 6 seconds Configuration Window (AW): In this window only the Configuration (non-acknowledged) commands will be issued by the Master After the Configuration Commands the Master Shall issue its HearthBeat Message The AW will last 1 seconds ESA CAN WorkSohp 2017

ECSS-E-ST-50-15C requirement analysis 226 requirements ESA CAN WorkSohp 2017

ECSS-E-ST-50-15C requirement analysis 21 deleted 12 modified 19 to be tailored 173 accepted 1 new 226 requirements ESA CAN WorkSohp 2017

ECSS-E-ST-50-15C requirement analysis 21 deleted 12 modified 19 to be tailored 173 accepted 1 new 226 requirements Deleted requirements are all related to the RS485 physical layer Modified requirements: typo corrected, all references to RS485 have been removed, references to external standards have been removed as much as possible To be tailored are mission dependent: need for isolated transceiver; bus topology requirements; need for SDO service; need for SCET; bus redundancy architecture New: one requirement dedicated to the Sampling point settings have been added ESA CAN WorkSohp 2017

ECSS-E-ST-50-15C requirement analysis 21 deleted 12 modified 19 to be tailored 173 accepted 1 new 226 requirements 51 SS and EQT 44 SS 110 EQT 205 requirements Deleted requirements are all related to the RS485 physical layer Modified requirements: typo corrected, all references to RS485 have been removed, references to external standards have been removed as much as possible To be tailored are mission dependent: need for isolated transceiver; bus topology requirements; need for SDO service; need for SCET; bus redundancy architecture New: one requirement dedicated to the Sampling point settings have been added ESA CAN WorkSohp 2017

ECSS-E-ST-50-15C requirement analysis 21 deleted 12 modified 19 to be tailored 173 accepted 1 new 226 requirements 51 SS and EQT 44 SS 110 EQT 205 requirements Mandatory: Requirements applicable to both Full and Minimal Protocol implementation covering: Physical layer requirements CAN data link layer requirements CANOpen mandatory services (OD, NMT, PDO) Full Protocol: contain the full set of CANOpen services (EXOMARS heritage) Minimal Protocol: contains a subset of CANOpen services (no SDO) to support SATCOM payload busses (NEOSAT heritage) 49 Full Protocol 112 Mandatory 34 Minimal Protocol 205 requirements ESA CAN WorkSohp 2017

ECSS-E-ST-50-15C requirement analysis 21 deleted 12 modified 19 to be tailored 173 accepted 1 new 226 requirements 51 SS and EQT 44 SS 110 EQT 205 requirements 44 SS only 78 Mandatory 15 Master 34 Slave 171 Full Protocol 49 Full Protocol 112 Mandatory 34 Minimal 205 requirements 41 SS only 66 Mandatory 11 Master 38 Slave 156 Minimal ESA CAN WorkSohp 2017

Conclusions Only 5volts transceiver are available RS485 physical layer has several drawbacks: Limited number of nodes It requires a failsafe network The fail safe network is usually implemented within the On-Board computer electronics : It shall be powered in hot redundancy Special care shall be taken to its distribution to main and redundant OBC boards. Usually the main board accommodate only the main CAN bus fail safe network while the redundant board accommodate the redundant one. Only 5volts transceiver are available Sampling point configuration shall be reprogrammable The sampling point is function of the bus length. The worst case bus length could be reached during the On-ground testing activities if a bus repeater is not introduced between the test equipment and the Spacecraft. Special care shall be taken to the Endianness management. Dedicated guidelines should be added in the ECSS As matter of fact, the protocol above the CANOpen layer is mission dependent. It shall be covered by a dedicated specification explaining how the CANOpen services are used (NOTE: the ECSS only specified which CANOpen services can be used and How they shall be implemented) ESA CAN WorkSohp 2017

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