Transcript Application framework

The Application of
CORBA in a Generic
Data Acquisition
Program
SRCG Team
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Geoff Mant
Paul Stephenson
Mike Miller
Steve Kinder
Karen Ackroyd
N Vasanthi
Motivation
 Construction of Data Acquisition program for a
combined technique station.
 Integration of Unix, PC and VME environments.
 Provide software with a common ‘Look and Feel’
across stations to make set up and data collection
easy. Integrating all detectors and ancillary equipment
into one interface.
 Create “plug and play” components with well defined
interfaces using object-oriented programming
principles to provide flexibility to cope with future
changes.
 Provide an interpreter for complicated and rapidly
changing experiment protocols
Schematic
GUI
Interpreter
Beam-line Components
EPICS Devices
Devices
Design Decisions
• UML (Unified Modelling Language) for analysis and
design.
• C++ for OS-9 programming.
• Java for beam-line components and graphical user
interface (easier to program, large number of built in
class libraries, garbage collection, threads,
portability).
• CORBA for middleware (Orbacus)
• Jython as an interpreter
• Allow multiple client access.
Component Overview
ABA/App
GUI
OE Object
Existing Code
ADC
McLennan:Motor
McLennan:Motor
SRS122:Motor
Why CORBA
• Industry standard supported by the OMG
• Provide connectivity between VME, PC and Unix
systems
• Orbacus CORBA was chosen for its C++ and Java
flavours and its was FREE or so we thought!
• Robust communication, hiding socket programming
and retaining a strongly typed interface. i.e. multiple
idl files specifying wide interfaces.
Features
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Factories for object creation
Name Server for location of objects
Event Server for asynchronous communication
XML for configuration
Overall Design
Client
Client
Client
Naming Service
Event Service
OE Server
Object Server
Application framework
Client
Naming Service
Table
Slit
ObjectServer
Adapter Pattern - Server side
Adapter pattern to provide some independence from the
middle-ware and also to allow the components to
interact as a monolithic system should the need arise.
Create Any
Insert the Temperature Event into Any
Publish on the EventService
«datatype»
TemperatureEvent
«interface»
IObserver
+Update()
«interface»
IObservable
TemperatureImpl
«interface»
Temperature
ObservableComponent
TemperatureBase
LaudaWaterBath
_OrbacusTemperatureImplBase
Adapter Pattern - Client side
The client side adapter contains code to allow the reconnection to the server if this has died and been
restarted.
«interface»
IObserver
+Update()
Client
ObservableComponent
Create a filter for events with TemperatureEvent datatype
Subscribe to the Event Service with filter
Method inform notifies all IObservers
«interface»
Temperature
TemperatureAdapter
«interface»
Subscriber
«interface»
IObservable
«interface»
OrbacusTemperature
StubForOrbacusTemperature
Creation of Objects
Finder
FactoryImpl
+find() : Findable
+addFactory()
1
+configure()
+create()
«interface»
Findable
TemperatureImpl
0..*
«interface»
Temperature
«interface»
Factory
+configure()
+create()
Serial
LocalFactory
+configure()
+create() : Findable
AdapterFactory
Server Startup
Parse the xml resource file
Creates a local factory
create NetService
create EventService
create an adapter factory
add local and adapter factories to finder
create the factoryImpl
configure from resource data
Drawbacks
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Cost of Orbacus(Iona) CORBA licence
Now frozen at release 3.1.3
Old OMG CORBA specification
Can’t pass Java objects, although if you know its only
Java to Java serialization is one option.
• We have used inheritance based CORBA which is
now problematic on the server side. Tie mechansim
would be better but not ideal.
• numerous idl interfaces (pro or con?)
• Java multiple inheritance in our design
Align Beam-line
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Aligns beamline for
data collection.
OEMove provides
a standard tool to
allow the control
and set up of
Optical Elements.
Easily configurable
for different
stations.
One tool meets
needs of many
projects.
Xafs
• Standard absorption
edge scan interface.
• Will support multiple
modes, Angle, KSpace
and Fast.
• GUI completely
detached from control.
• Scans done via
JCLAM (scripting
language - python
extension).
PX Data Collection
•
Data collection
making good
progress, tested
with Q4 and
MAR180 & MAR345
detectors.
•
Same GUI
independent of
detector in use.
•
Detector specific
bits provided by
Detector
implementation.
NCD Configuration
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Configuration of the
timer frame
generator for
multiple frames and
profiles
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Detector set-up with
memory usage
feedback.
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Data output details
Interpreter
• Load, save
and execute
scripts
Future
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Another brand of CORBA
Utilise Java offering
RMI over IIOP
Get rid of OS-9 in favour of Linux
SOAP