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TANGO main concepts

TANGO main concepts. Agenda. How Tango faces the main challenges for a modern Control System Distribution, heterogeneity, O-O paradigm How Tango faces these challenges Tango : main concepts Tango : a software bus Device Commands Attributes Properties and configuration A short summary.

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TANGO main concepts

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  1. TANGO main concepts

  2. Agenda • How Tango faces the main challenges for a modern Control System • Distribution, heterogeneity, O-O paradigm • How Tango faces these challenges • Tango : main concepts • Tango : a software bus • Device • Commands • Attributes • Properties and configuration • A short summary

  3. - I - Challenges for a modern Control System

  4. Distributed systems • The control system components are geographically distributed on different machines interconnected by a computing network: • CPCI ,VME, industrial PC, PC • PLC • Ethernet devices • servers • Problem 1 : How to make all these systems communicate ?

  5. Object Oriented Paradigm • Object oriented approach is now commonly recognized as the best methodology for software construction • « A control system is a sea of networked objects ; every part of the control system should be a network object whether it is a low-level, high-level or application-oriented function » • Problem 2 : How to get such objects on a network level ?

  6. Heterogeneous systems on hardware and software levels • Slow industrial systems: PLC • Fast acquisition systems : CPCI, VME, … • Ready to use systems: • LINAC control/command • Control software sold with equipments (Residual gas analyzers, electron analyzers, detectors, CCD …) • Heterogeneous operating systems • Scientific applications under WIN32/Linux/Solaris/HPUX • Drivers/libraries under WIN32 (or under Linux !) • Problem 3 : How to obtain a coherent whole from such heterogeneous hardware and software?

  7. Host B Host A Application 3 Application 1 L ? L Application 2 Application 4 ? L L OS1 OS2 Problem 1 :communication ? Ethernet - TCP/IP network

  8. Problem 2 : Working with objects at network layer Host B Host A Application3 Application1 L L Application2 Application 4 L L OS1 OS2

  9. Distributed Application Problem 3: a whole homogeneous and coherent

  10. CORBA (Common Object Request Broker Architecture) A software bus of objects

  11. Control System CORBA CORBA limitations • CORBA = 1 generic tool • support to the development of distributed applications • A powerful but cumbersome tool • No functionalities «Control oriented»

  12. Control System Framework CORBA TANGO : introduction • a framework CORBA ctrl/cmd oriented • A toolbox to implement the system • A specialization of CORBA adapted to the Control needs and challenges TANGO CORBA CORBA

  13. TANGO software Bus Device interface Hardware (motor…) Board Tango : A software bus • Analogy with an electronical bus because: • Each card plugged on the bus has a well-identified function • Each card is not or hardly coupled to the others • Development of each card can be decoupled • But each card must respect a strict and well-defined interface in order to connect to the bus

  14. MOTOR: Commands: - GoForward()… Attributes: - Speed (R/W)… Hardware control code Hardware An example of a Device Interface : A motor • The Interface : • describes what the Device is supposed to do • It’s only a promise of the services you may expect from the Device • But there isn’t any magic !!! • Code has to be written to fullfill the promised services Interface

  15. The overall picture Client side Servers side

  16. - II - Mainconcepts

  17. What is a Device ?

  18. TANGO: device: definition • Historically a device is an entity to control • Hardware or software • device = 1 polymorphous object • 1 equipement (ex: 1 power supply) • 1 collection of equipment (ex: 1 motor + 1 coder) • 1 cluster of devices : • a monochromator • a complete subsystem (a LINAC !) • A pure software component e.g : • A scan device • A data fitter device But have in mind that a device is a real and good « Software Component » which respects O-O paradigm (encaspulation, reusability, ..)

  19. Commands • Generics commands • Specifics commands

  20. Commands Attributes Generic Specific Generic Specific Init State Status PowerOn PowerOff - current Hardware control code TANGO: device: interface: command • Has a communication interface • interface = commands + attributes • commands  actions • attributes  physical units TANGO Software Bus Interface

  21. TANGO: device: interface: command • Generic commands exist for EVERY Device • Ping, Init, State, etc … • Specific commands • Are defined by the Device developer • Have : 0 or 1 in argument (argin) • Give : 0 or 1 out argument (argout) • argin & argout = 1 of the 20 TANGO types • Command are started from any client always in the same way : • call the command_inout method on the Device with the following arguments : • command name • In parameter of the command • Output: • result of command execution • Exemple from Python : >> my_motor_device.command_inout(“AxisBackward") >> my_motor_device.command_inout(“GoToPosition“,100)

  22. TANGO: device: interface: command TANGO Description • About argin & argout types… DEV_VOID no argin and/or no argout DEV_STATE device status DEV_STRING characters array DEV_BOOLEAN boolean DEV_SHORT Signed 16 bits integer DEV_USHORT Unsigned 16 bits integer DEV_LONG Signed 32 bits integer DEV_ULONG Unsigned 32 bits integer DEV_FLOAT 32 bits floating point DEV_DOUBLE 64 bits floating point DEVVAR_CHARARRAY table of bytes (i.e. characters ) DEVVAR_ SHORTARRAY table of signed 16 bits integers DEVVAR_ USHORTARRAY table of unsigned 16 bits integers DEVVAR_ LONGARRAY table of signed 32 bits integers DEVVAR_ ULONGARRAY table of unsigned 32 bits integers DEVVAR_ FLOATARRAY table of 32 bits floating points

  23. Attributes

  24. Commands Attributes Generics Specifics Generics Specifics Init State Status PowerOn PowerOff - current Hardware control code TANGO: device: interface • Has a communication interface • interface = commands + attributes • commands  actions • attributes  physical units TANGO Software Bus Interface

  25. TANGO: device interface: attribute • Definition • Physical unit produced or administrated by the device • ex: motor position, power emitted by a power supply, … • Format : from 0 to 2 dimensions • SCALAR • SPECTRUM (i.e. vector) • IMAGE (i.e. matrix) • Type • DEV_SHORT, DEV_LONG, DEV_DOUBLE • scalar, spectrum or image • DEV_STRING • scalar only • Accessibility • READ • read-only access • WRITE • write-only access • READ_WRITE • Read-and-write access • set valuesvs actual value

  26. TANGO: device: interface: attribute • Obtain/modify the current value of an attribute from any client ? • Prog. Env. OO (C++, Java, Python) • dev.read_attribute(s) (attr_name_list) • dev.write_attribute(s) (attr_name_list) • Python Example: >> x = my_motor_device.read_attribute (”position") >> print x.value >> x.value=100 >> my_motor_device.write_attribute (x)

  27. State/status

  28. TANGO: device: state • Tango internally manages a state Machine • Each Device has an associated state • Device behavior = fonction (internal state) • query -> internal state-> execute or error • internal status generated by the device developer • 14 predefined status • ON, OFF, CLOSE, OPEN, • INSERT, EXTRACT, MOVING, • STANDBY, FAULT, INIT, RUNNING, • ALARM, DISABLE, UNKNOWN • a color code defined by Tango is associated to each status

  29. TANGO: device: status • How to be more precise than one of these 14 predefined states ? • To inform operator of an abnormal condition • To give the expert a detailed diagnostic • Or to say that everything is OK • Use the status information • which is a free text field • which must be managed by the device developper • “ Motor has reached backward limit switch” • “Power unit is in default ( internal driver error 435-ER)” • “Ready to move”

  30. Configuration of the control system through “Properties”

  31. Configuration: needs • How to Define devices present in the Control system • How to set devices parameters • Parameters linked to the Hardware (GPIB address, etc.. ) • Min and max attributes values • Alarm thresholds, etc .. • “Tango Properties” are the configuration parameters

  32. Configuration: static database • Configuration database • Critical element of the system • unique source of information for devices and clients • Implementation • 1 dedicated device = TANGO interface of a SGBD • The TANGO_HOST environment variable = host_name:host_port (ex: localhost:20000) defines the static database that is used TANGO Software Bus • 1 dedicated TANGO device = TANGO interface of a SGBD Configuration • 1 information storage medium: 1 computing database

  33. An invisible but mandatory Device : The “DeviceServer”

  34. Device Device Device TANGO: device server • Practically, 1 executable called DeviceServer • Is in charge of « connecting » several Devices to the bus • The system can be parameterized so as to change the list of Devices, which 1 DeviceServer has to administrate TANGO Software Bus Bus Logiciel TANGO Dev Dev Dev Dev Dev Dev DServer Device Server

  35. - III - Short summary

  36. A tango Device is a networked object • All Devices share the same Interface for clients applications Device State Status read_attribute(s) write_attribute(s) command_inout()

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