OPC Gateway (Device Support)

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OPC Gateway (Device Support)
Ralph Lange EPICS Collaboration Meeting March
2008 _at_ SSRF
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OPC Gateway (Device Support)

• Accessing PLCs through EPICS 3.14 Device Support
  running on a Windows box connecting to a
  combination of commercially available OPC client
  and server packages
• Inspired by work from Kay-Uwe KasemirDeveloped
  by Carsten Winkler and Bernhard KunerWith
  additional help from Roland Fleischhauer and
  Ralph Lange

Credits Main Authors and Contributors
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OPC Introduction

• OPC OLE (based on COM) for Process ControlBased
  on DCOM Distributed Component Object Model
• Client/Server ArchitectureScalable and
  distributed over the network
• Data Access SpecificationRead/write
  operations, time stamp, data qualityPolled or
  event driven (callback mechanism)
• Alarm and Event Specification
• Many existing OPC servers only implement a subset
  of the defined OPC features

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OPC Data Flow

• OPC Client LibrariesAvailable for Windows,
  Unixes (see http//www.opcconnect.com)Binary
  distribution of the client library by Softing is
  royalty-free
• OPC Client OPC Server Communicationvia DCOM
  (available by Microsoft and others also for
  Linux)

OPC Server ApplicationAlways available from the
PLC vendorFor wide-spread PLC series there are
alternatives offered by third party vendors (see
link list at http//www.opcconnect.com or e.g.
http//www.matrikonOPC.com) OPC Server PLC
CommunicationProprietary, vendor dependant
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OPC Client Side Data Access

• Connect to Server
• Client will start/stop the server
• Browse Server
• For debugging purposes or dynamic client
  configuration
• Add Group
• Client defines groups with common parameters for
  all items within the group
• Add Items
• Client subscribes for several data objects

OPC Server
1 N
1
OPC Browser
OPC Group
Common Parameters, e.g. Update Rate, Deadband
1 N
OPC Item
Process Variable
1 N

• Properties are
• Value of a common data type
• Quality
• Timestamp

Item Properties
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OPC Device Support Overview

• Supported Record Types
• - ai, ao
• - bi, bo
• - mbbi, mbbo
• - mbbiDirect, mbboDirect
• - longin, longout
• - stringin, stringout
• - waveform
• OPC Client Library
• - Softing OPC Toolbox 3.01
• - Distribution as Windows binary is royalty-free
• - Other client libraries possible

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OPC Device Support Features

• Flexibility
• IOC will connect to multiple and/or remote OPC
  servers
• Data Conversion
• For all integer and float data types
• Timestamp is Set by OPC Server or EPICS Record
  Processing
• Determined by the records TSE field
• OPC Quality Information is Mapped to Records
  STAT/SEVR
• In-Records Read-Only
• Value is written by the PLC
• SCAN I/O Intr (event driven mode)
• or
• .1 second to 10 second (polled mode)
• Out-Records Bidirectional
• Value may be written by the PLC (e.g. local
  control) or by EPICS
• SCAN Passive, but record will still be
  updated when PLC value changes

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BESSY Installation PLC Controlled Beamlines

• 33 Phoenix DIN-Rail PLCs with 700 Channels Each
  Approx. 22,000 Channels
• Phoenix OPC Server Introduces Serious Limitations
• Supports only polling mode no events in the OPC
  server PLC connection
• Max. 2 PLCs per OPC server
• No third-party OPC server available for this
  particular PLC type
• Windows PC Hardware
• 4 Dual-processor 3 GHz 19 rack servers
  (standard high availability servers)
• Each server runs 4 virtual Windows PCs (using
  VMware GSX server software)
• Each of the 16 virtual PCs runs one softIOC and
  one OPC server that connects to 2 PLCs
• PLC data is polled every 100ms or 250ms
  (different OPC Groups)
• Servers are running at 40-50 CPU load

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OPC Device Support Experiences and Status

• The BESSY beamline guys are very satisfied with
  this solution
• OPC is the spreading integration standard in
  scada and industrial automation.
• Vendors simply have to provide OPC servers for
  a PLC if they want to be commercially successful.
  For common PLC series, third-party vendors will
  add competition, leading to better OPC servers.
• This gateway opens up a window from EPICS to
  the whole wide world of industrial automation.
• They are very interested to have more facilities
  use the OPC device support and feedback changes
  as well as improvement requests
• Existing users BESSY, DESY, PSI, SLS, PPPL,
  SNSLatest changes by Sheng Peng are evaluated
  for integration
• Contact
• Roland.Fleischhauer_at_bessy.de Carsten.Winkler_at_bess
  y.de