Transcript Mapping of CCSDS SOIS Services on Mil 1553 bus

Prototyping of CCSDS SOIS services on 1553 Bus
CCSDS SOIS Working Group Meeting – Berlin, Germany
14th of October 2008
Sev Gunes-Lasnet, Olivier Notebaert
Astrium Satellites – Data Processing & Advanced studies – ASG74
Astrium Satellites
Prototyping of CCSDS SOIS services on 1553 bus
CCSDS SOIS WG Berlin 2008
1553 SOIS subnetwork services prototyping and porting logic
Inputs
subnetwork
services
Specifications
SOIS green
and
Red books
SOIS
subnetwork
1553 services
This document is the property of Astrium. It shall not be communicated to third parties without prior written agreement. Its content shall not be disclosed.
15/01/2007
Drivers 1553
For SCoC
Synchro
nisation
Test service
Packet
service
Memory
access
service
Device
discovery
Drivers 1553
ECSS-E-50-13
(1553)
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SciSys input
Reference
use case
ECSS -E -40
SOIS
subnetwork
SpW services
SOIS
subnetwork
services
Rasta
drivers
Drivers SpW
Portingto
RAST A
by SciSys
SCoC3 Simulator
Externalinput
Tailored
Astrium input
RAST A platform
IP 1553Gaisler
(Actelcore)
Development
Astrium Satellites
Prototyping of CCSDS SOIS services on 1553 bus
CCSDS SOIS WG Berlin 2008
Prototyping & porting feedback
This document is the property of Astrium. It shall not be communicated to third parties without prior written agreement. Its content shall not be disclosed.
 The SOIS sub-network services layer has been
developed and validated on the SCoC3 platform
15/01/2007
 SCoC3 is a Spacecraft Controller on a Chip which includes a
LEON3 processor and I/O systems for 1553, SpW and Can.
 It has then been ported on the on the RASTA platform
 The RASTA platform is part of the ESA reference avionics
facility test bench allowing to prototype on-board data handling
space applications
 The same set of services is supported for the Bus
Controller on both platforms
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Astrium Satellites
Prototyping of CCSDS SOIS services on 1553 bus
CCSDS SOIS WG Berlin 2008
Prototyping & porting feedback
 Some implementation differences have been introduced
during the porting
This document is the property of Astrium. It shall not be communicated to third parties without prior written agreement. Its content shall not be disclosed.
 The origin for of such differences are:
15/01/2007
 Differences between the MIL-Std-1553B controllers used in SCoC3 and
RASTA, in particular the functions accessible through their drivers
 The absence of an accurate on-board long-range timer on RASTA while
SCoC3 provides a built in HW timer in support of the bus protocol engine
and synchronisation service
 do not affect the nature of services but impacts:
 functions of the underlying communication protocol
 performance of the services
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Astrium Satellites
Prototyping of CCSDS SOIS services on 1553 bus
CCSDS SOIS WG Berlin 2008
Prototyping & porting feedback
 Implementation differences on Synchronisation service:
 For SCoC3 platform
This document is the property of Astrium. It shall not be communicated to third parties without prior written agreement. Its content shall not be disclosed.
 The distributed time data is retrieved from CCSDS Time Manager (CTM)
implemented inside SCoC3.
 It provides a time conform to CCSDS CUC Time format, i.e. a range of 232
second with a precision of 0.5x 2-24 seconds
 This complies to the ECSS-E-50-13 Standard
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 For Rasta platform
 The distributed time data is retrieved from the on-board Leon Timer.
 Software managed clock ticks are used to support the time service.
 The range and precision of the time depend on the clock ticks
configuration.
 In our RTEMS configuration, the effective range of the time is about 4000
seconds and the effective precision is 10 ms.
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Astrium Satellites
Prototyping of CCSDS SOIS services on 1553 bus
CCSDS SOIS WG Berlin 2008
Prototyping & porting feedback:
 Implementation differences on bus profiling:
 For SCoC3 platform
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 The HW clock signal generated by the CTM is used to automatically drive
the cyclical 1553 Communication frame
 The clocks are also used to control message sending time inside such
frames, allowing the definition and utilisation of time intervals.
15/01/2007
 For RASTA platform
 there is no HW support which can be used to drive the communication
frame and message sending. Instead, the software managed timer
generates cyclic events, used to launch each communication frame.
 This method does not provide the same stability of the cycle duration.
 The messages inside a communication frame are transmitted without time
control, i.e. they are sent one after another without delay between them.
 The definition and exploitation of time intervals as defined in ECSS
standard is not really possible.
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Astrium Satellites
Prototyping of CCSDS SOIS services on 1553 bus
CCSDS SOIS WG Berlin 2008
This document is the property of Astrium. It shall not be communicated to third parties without prior written agreement. Its content shall not be disclosed.
Prototyping & porting feedback: performance
15/01/2007
 As a result, key elements driving the SOIS subnetwork
services performance over MIL-STD-1553 have been
identified :
 Theoretically, both platforms have similar HW elements to
support the sub-network services in a similar way, as each of
them integrates a Mil-Std-1553B compliant controller
 But several points shall be considered for the performance of a
specific implementation of the services on a dedicated platform
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Astrium Satellites
Prototyping of CCSDS SOIS services on 1553 bus
CCSDS SOIS WG Berlin 2008
Prototyping and porting feedback:performance
 key elements driving the SOIS subnetwork services
implementation performance over MIL-STD-1553:
This document is the property of Astrium. It shall not be communicated to third parties without prior written agreement. Its content shall not be disclosed.
 Bus Controller integration inside the platform, are any features
disabled ?
 External clock to be used for the bus controller for its
synchronisation or message handling
 Availaibility of software driver allowing to enhance functional
features for the use of the Bus Controller
 How about the cost in term of CPU and memory consuming
when using such driver ?
15/01/2007
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Astrium Satellites
Prototyping of CCSDS SOIS services on 1553 bus
CCSDS SOIS WG Berlin 2008
Drivers related topics (1/2)
 SCoC3 runs with a driver for IP1553 provided by Astrium.
 All functional features necessary to support the sub-network services and
the ECSS protocol are available through this driver.
This document is the property of Astrium. It shall not be communicated to third parties without prior written agreement. Its content shall not be disclosed.
 For RASTA platfom, we use a driver for Actel Core1553BRM
15/01/2007
 Driver distributed by Gaisler Research with its RTEMS distribution.
 The functions provided by this driver do not cover all features of the Actel
Core1553BRM. For instance, no support to perform timing control of
messages handling is provided
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Astrium Satellites
Prototyping of CCSDS SOIS services on 1553 bus
CCSDS SOIS WG Berlin 2008
Drivers related topics (2/2)
 The driver for IP1553 is developed for space on-board software
and adapted for such application
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 For instance, the API and related data structures are defined so that its
use is as easy as possible and its CPU consuming is minimized. In
addition, error handling is considered.
15/01/2007
 The driver for the Actel Core1553BRM, can be considered as in
a prototype form.
 It provides minimum access to 1553 functions without optimisation
 It is used as IO device driver, so that it uses standard IO system call, like
open, close, ioctl.
 Such design introduces an overhead in term of service processing.
 The data structures used by the API for its BC message is in a format neither as
true 1553 message nor as a data format directly suitable for Actel
Core1553BRM controller
 Such data structure definition obviously introduces an overhead of the
processing on the service using it.
 The error handling is in a simple form. Some bugs still exist in the drivers.
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Astrium Satellites
Prototyping of CCSDS SOIS services on 1553 bus
CCSDS SOIS WG Berlin 2008
Prototyping & porting feedback
 Preliminary feedback on SOIS :
 Status failure and status success
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 SOIS requires a Success Status without an error code
 This is not enough for most 1553 based applications which require that a
detailed error 1553 status must go back up to user level (so as to be
treated by the FDIR application).
15/01/2007
The feedback from 1553 users would claim for an error report
delivery to the user of the SOIS subnetwork service
 This is implemented on ECSS-1553 Standard through an OR of all status
words involved in the 1553 messages supporting the service
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Astrium Satellites
Prototyping of CCSDS SOIS services on 1553 bus
CCSDS SOIS WG Berlin 2008
Preliminary feedback on SOIS services
 About the retry function included in the 1553 standard
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 The ECSS standard does not use the built-in retry function;
 Therefore, our reference implementation does not map on the standard
1553 message retry in support of the SOIS guaranteed and assured
quality of service
 SOIS Packet Transfer service implementation can map on the ECSS
verified length QoS of the ECSS Data Block Transfer
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 This allows upper level (on network management) to manage the retry function
for mapping on the SOIS QoS
 The messages status could also be used at upper layers to transmit the
information on bus errors in support of a retry function
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Astrium Satellites
Prototyping of CCSDS SOIS services on 1553 bus
CCSDS SOIS WG Berlin 2008
Preliminary feedback on SOIS services
 Synchronisation issue
 The SOIS communication view is mostly asynchronous
This document is the property of Astrium. It shall not be communicated to third parties without prior written agreement. Its content shall not be disclosed.
 Data is fetched upon need – network should be hidden to the user who
should not have to care how it is fetched on the data link to end terminal
15/01/2007
 1553 systems use mostly synchronous protocols
(Such as the one described in ECSS-E-50-13)
 The delay between Synchronisation and actual data acquisition/command
on the end terminal sensor/actuator defines the real-time performance
(e.g. latency, jitter…) of the data transfer
 The SOIS end-to-end service performance will depend on the coupling of
the user calls with the 1553 synchronisation service.
 Users having high determinism and time accuracy requirements (mostly
command/control and dependable systems in general) will require such
coupling
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Astrium Satellites
Prototyping of CCSDS SOIS services on 1553 bus
CCSDS SOIS WG Berlin 2008
Preliminary feedback on SOIS services
 Prototyping & porting feedback preliminary conclusions
This document is the property of Astrium. It shall not be communicated to third parties without prior written agreement. Its content shall not be disclosed.
 All SOIS Subnetwork services have been implemented and
verified on the MIL-Std-1553B bus using two different MilBus
coupling systems
 Performance of the system is being assessed
 End-to-end real-time performance of SOIS services on 1553
bus is tightly linked to the implementation of synchronisation
between user and the bus system
 Overhead due to HW/SW drivers are much more significant
than those introduced by the SOIS layered architecture
 SOIS subnetwork services should include a interface to report
1553 Status to the user (or to the network management)
15/01/2007
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