Input/Output Controller (IOC) Overview

1
Input/Output Controller (IOC) Overview

• Andrew Johnson
• Computer Scientist, AES Controls Group

2
IOC Overview

• What is an EPICS Input/Output Controller
• How to create a new IOC application
• How to build an IOC application
• How to run an IOC application on various
  platforms
• Console interaction with an IOC application
  (iocsh)

3
Reference

• EPICS IOC Application Developers Guide

Go to EPICS home page http//www.aps.anl.gov/epic
s/ then follow links, as shown
4
What is an Input/Output Controller?

• The answer used to be easy A single-board
  computer running the vxWorks real-time operating
  system and installed in a VME chassis.

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What is an Input/Output Controller?

• An IOC can also be an embedded micro-controller,
  a rack-mount server, a laptop PC or Mac, a
  desktop PC or Mac, or a standalone single-board
  computer.
• It may be running on Linux, Windows, Solaris,
  Darwin, RTEMS or vxWorks

RTEMS
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Host-based and Target IOCs

• Host-based IOC
• Runs in the same environment as which it was
  compiled
• Native software development tools (compilers,
  linkers)
• Sometimes called a Soft IOC
• IOC is an program like any other on the machine
• Possible to have many IOCs on a single machine
• Target IOC
• Runs in a different environment than where
  compiled
• Cross software development tools
• vxWorks, RTEMS
• IOC boots from some medium (usually network)
• IOC is the only program running on the machine

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IOC Software Development Area

• IOC software is usually divided into different
  lttopgt areas
• Each lttopgt provides a place to collect and
  compile files and configuration data used by a
  group of similar IOCs, or used to create products
  that are used by different groups of IOCs
• Each lttopgt is managed separately
• A lttopgt is designed to use products from other
  lttopgt areas
• EPICS base can be thought of as a lttopgt providing
  products that all IOCs need to use

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IOC Software Development Tools

• EPICS uses the GNU version of make
• Almost every directory from the lttopgt on down
  contains a Makefile
• Make recursively descends through the directory
  tree
• Determines what needs to be rebuilt
• Invokes compilers and other tools as instructed
  in Makefile
• GNU C/C compilers or vendor compilers can be
  used
• No fancy integrated development environment

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The makeBaseApp.pl program

• Part of the EPICS Base distribution
• Populates a new, or adds files to an existing,
  lttopgt area
• Requires the environment variable EPICS_HOST_ARCH
  be set (EPICS base contains scripts which can
  set this as part of your login sequence)
• linux-x86, darwin-ppc, solaris-sparc, win32-x86
• Creates a directory structure based on a selected
  template
• Templates provided with Base include
• ioc - A generic IOC application skeleton
• example An example IOC application

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Creating a lttopgt directory structure

• Running makeBaseApp.pl using the example template
  creates the following directories in the current
  directory, making it a lttopgt
• configure/ - Configuration files
• testApp/ - Files associated with the testApp
  application
• Db/ - Databases, templates and substitution files
• src/ - Source code
• Every directory contains a Makefile

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lttopgt/configure files

• Some may be modified as needed
• CONFIG_SITE
• Specify make variables (e.g. to build for a
  particular target)
• CROSS_COMPILER_TARGET_ARCHS vxWorks-68040
• RELEASE
• Point to other lttopgt areas used by this lttopgt
  area
• Other files under configure/ are part of the
  (complex!) build system and should be left alone.

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lttopgt directory structure

• Running makeBaseApp.pl from the lttopgt directory
  with a -i flag creates additional directories for
  an IOC to boot from
• iocBoot/ - Directory containing per-IOC boot
  directories
• ioctest/ - Boot directory for the ioctest IOC

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lttopgt directory structure after running make

• Additional directories appear in lttopgt after
  running make
• bin/ - Directory for per-architecture binary
  directories
• linux-x86/ - Executables for this architecture
• lib/ - Directory for per-architecture library
  directories
• linux-x86/ - Object libraries for this
  architecture
• dbd/ - Database definition files
• db/ - Database files (record instances,
  templates)
• There may be other directories under bin/ and
  lib/, too.

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IOC startup

• IOCs read startup commands from a script
• Typically st.cmd in the lttopgt/iocBoot/ltiocnamegt/
  directory
• On vxWorks IOCs the target shell usually executes
  these scripts
• On other OSs the EPICS iocsh shell does the
  execution
• The command syntax is similar, but iocsh is less
  strict
• Script was created by makeBaseApp.pl -i command
• It must usually be edited by hand to add commands
  that configure hardware modules, start sequence
  programs, update log files, etc.

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Example application startup script

• 1 !../../bin/linux-x86/first
• 2
• 3 You may have to change first to something
  else
• 4 everywhere it appears in this file
• 5
• 6 lt envPaths
• 7
• 8 cd TOP
• 9
• 10 Register all support components
• 11 dbLoadDatabase("dbd/first.dbd")
• 12 first_registerRecordDeviceDriver(pdbbase)
• 13
• 14 Load record instances
• 15 dbLoadRecords("db/dbExample1.db","usernorumeH
  ost")
• 16 dbLoadRecords("db/dbExample2.db","usernorumeH
  ost,no1,scan1 second")
• 17 dbLoadRecords("db/dbExample2.db","usernorumeH
  ost,no2,scan2 second")
• 18 dbLoadRecords("db/dbExample2.db","usernorumeH
  ost,no3,scan5 second")
• 19 dbLoadRecords("db/dbSubExample.db","usernorum
  eHost")

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Review

• IOC applications can be host-based or
  target-based
• The makeBaseApp.pl script is used to create IOC
  application modules and IOC startup directories
• The lttopgt/configure/RELEASE file specifies the
  location of other lttopgt areas used by this lttopgt
  area
• lttopgt/iocBoot/ltiocnamegt/st.cmd is an IOC startup
  script
• The EPICS build system requires the use of GNU
  make
• vxWorks IOCs use the vxWorks shell, non-vxWorks
  IOCs use iocsh
• The EPICS Application Developers Guide contains
  a wealth of information