Channel Access in Tcl/Tk

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Channel Access in Tcl/Tk
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Contents

• Tcl/Tk overview
• Graphical user interfaces
• pep
• pvAssign
• SLS widgets
• Direct EPICS access
• pvget, pvput, pvmon
• Problems
• References

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What is Tcl/Tk?

• Tcl is a scripting programming language.
• Tk is a widget toolkit, available for Tcl and
  other languages.
• It provides a command line shell tclsh
• And a GUI shell wish
• And a help program tclhelp
• Tcl can be extended with so called "packages".
• We provide an EPICS package for Tcl/Tk.
• We also provide special widgets for Tcl/Tk.
• Tcl is really well supported by the controls
  section.

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Tcl/Tk quick start

• Tcl is easy
• Tk makes GUI creation simple
• Type wishbutton .b -text "Press me!" -command
  puts "Hello world!"pack .b
• Press button
• Look in tclhelp for button, puts, pack
• Write the program in a file and add first
  line!/usr/bin/wish
• Make file executable chmod x filename

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Graphical user interfaces in Tcl/Tk pep

• pep -mc X11MA-ID1-CHU1I-SET
• connects magnet control widget to
  X11MA-ID1-CHU1I-SET
• pep X11MA-ID1-CHU1I-SET
• asks what widget type to connect to
  X11MA-ID1-CHU1I-SET
• pep f configfile
• loads configfile.prc from . or SLSBASE/sls/config
  /panel
• Try files from /work/sls/config/panel
• Also see "How to use pep" item in Help menu.

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Beyond pep Write your own Tcl-GUI with pvAssign

• Start wish and load pvAssign package
• package require pvAssign
• Create Widget
• label .temperature
• pack .temperature
• Connect EPICS channel
• pvAssign .temperature MTRT1-TEMPREAD
• Enjoy the features
• See value and alarm updates
• Try right click and middle click

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Supported widget types

• Standard Tcl/Tk widgets
• label
• display string/number
• entry
• set string/number
• checkbutton
• set bit
• menubutton
• set enum with menu
• scale
• set number with slider

• Special SLS widgets
• formattedlabel
• display formatted number with units
• comparelabel
• display or ? (compare to 0)
• wheelswitch
• set number
• led
• show bit as LED
• choicebutton
• set enum with row/column of buttons
• Load widget packages
• package require Wheelswitch

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SLS Widgets types Formattedlabel

• Use standalone Formattedlabel
• package require Formattedlabel
• formattedlabel .fl -bg paleGreen -format "9.4f
  mA"
• pack .fl
• .fl set 3.14159265359
• Use Formattedlabel with EPICS
• package require pvAssign
• package require Formattedlabel
• formattedlabel .temp1 -bg paleGreen
• pack .temp1
• pvassign .temp1 MTRT1-LI-COOLTEMP1

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SLS Widgets types Wheelswitch

• Use standalone Wheelswitch
• package require Wheelswitch
• wheelswitch .ws -bg paleGreen -format 9.4 -label
  mA \-min -100 -max -100 -command puts
• pack .ws
• .ws set 3.14159265359
• Use Wheelswitch with EPICS
• package require pvAssign
• package require Wheelswitch
• wheelswitch .limit -bg paleGreen
• pack .limit
• pvassign .limit MTRT1-LI-COOLLIMIT

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SLS Widgets types Led

• Use standalone Led
• package require Led
• led .led -color red
• pack .led
• Use Led with EPICS
• package require pvAssign
• package require Led
• led .status
• pack .status
• pvassign .status MTRT1-LI-COOLSW

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Beyond pvAssign direct EPICS access

• Load EPICS package (which is also used by
  pvAssign)
• package require Epics
• Read value
• pvget MTRT1-LI-COOLTEMP1
• pvget MTRT1-LI-COOLTEMP1 -format
• Write value
• pvput MTRT1-LI-COOLLIMIT 10
• Crate monitor
• pvmon MTRT1-LI-COOLTEMP1 updateTemp1
• Monitors need a callback procedure (here
  updateTemp1)
• proc updateTemp1 iostate value sevr stat time

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Monitor example

• !/usr/bin/tclshpackage require Epics
• proc updateValue channel iostate value sevr
  stat time if iostate ! "OK" puts
  "channel disconnected" return if
  sevr ! "NO_ALARM" puts "channel has
  sevr alarm because of stat status" puts
  "time channel value"
• set device MTEST-VME-T1foreach property UPTIME
  LOAD WD set channel deviceproperty
  pvmon channel "updateValue channel"
• vwait forever

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Frequently asked questions about monitors

• Why can't I simply call pvget in a loop?
• This creates much network overhead.
• It keeps the program and the IOC busy.
• But what about a delay in the loop?
• Then you increase latency when something happens.
• You still have much overhead.
• I don't understand how the monitor function gets
  called.
• Monitors work much the same as for example mouse
  clicks.
• On value change, monitors are called as soon as
  the program is idle.

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Problems with Tcl and EPICS

• What if package require Epics (or pvAssign)
  fails?
• Check environment variable TCLLIBPATH
• echo TCLLIBPATH
• /usr/lib/tcl /work/lib/tcl
• Check that EPICS is installed in /usr/local/epics
  and /work or /prod is mounted.
• Why does pvmon not work in tclsh?
• Monitors need an idle loop to work, wish has one,
  tclsh not.
• Add vwait forever to the end of the script and it
  works.

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Where can I learn more about Tcl/Tk?

• First try tclhelp
• Look at www.tcl.tk
• Ask one of the Tcl experts
• Werner Portmann
• Elke Zimoch
• Dirk Zimoch