Wiki > The Backend System > IOCs > Using LVDCOM > Creating IOC wrapper VI

These are instructions for creating an IOC wrapper for a VI using lvDCOM. It assumes you want to create a "support" type module for lvdcom in ISIS. The Mercury ITC is an example where the below was followed and then an IOC was created using this as a support module.

I plan to make these into a template (so you will just need to run makeBaseApp.pl and not do the edits), but for now this is the manual way.

Please take note of the IOC naming convention before proceeding.

1. Create a public repository to work in called EPICS-<device>.
2. In the EPICS\ISIS directory create a directory called <device>
3. Add the repository as a submodule and clone it into this directory (i.e. with the command git submodule add https://github.com/ISISComputingGroup/EPICS-<device>.git master)
4. Create a basic standard file and directory structure either by copying a similar existing module (and then executing make clean uninstall to remove unnecessary files) or by running makeSupport.pl. Check the results either way.
5. Copy a standard makefile into this directory

Create the IOC in EPICS\IOC\master with (from an EPICS terminal)

1. In the EPICS\IOC\master directory create a directory called
2. In the new directory EPICS\IOC\master\<iocname>, run the following two commands.

 makeBaseApp.pl –t ioc <iocname>
 makeBaseApp.pl –i –t ioc <iocname>

Edit mynameApp/src/build.mak add dbd file

$(APPNAME)_DBD += lvDCOM.dbd

and libraries

$(APPNAME)_LIBS += lvDCOM 
$(APPNAME)_LIBS += asyn

and system library

$(APPNAME)_SYS_LIBS_WIN32 += msxml2

Add the IOC to the makefile in EPICS\ioc\master\Makefile e.g.

## modules not to build if no Windows ATL present (depends on Visual Studio compiler)  
ifneq ($(HAVE_ATL),YES)  
DIRS_NOTBUILD += ISISDAE MERCURY_ITC STPS350 AG53220A STSR400 DELFTSHEAR DELFTDCMAG DELFTARDUSTEP LVTEST SCIMAG3D HIFIMAG + <iocname>
endif

This is a summary of more general LvDCOM instructions.

1. Open the VI in lab view.

2. Export strings from the labview panel (In different version of labview this is different)

   1. 2010: Go to Tools menu, Advanced, Export Strings... and uncheck the wizard option for "block diagram strings" and save the export results to a text file e.g. controls.txt (Note: you may need write access to the VI itself to do this, so might have to make a local copy of the VI first)
   2. 2014:
      1. Menu -> Tools -> Advanced -> Export Strings...
      2. Then save file to (<device>/protocol/controls.txt)
      3. Yes to "Export captions for controls without captions?"
      4. No to "Export block diagram strings?"

3. Generate a corrected xml file. In an epics terminal run in the protocol directory:

    C:\Instrument\Apps\EPICS\ISIS\lvDCOM\master\lvDCOMApp\src\fix_xml.cmd "controls.txt" "controls.xml"
   

4. Generate lvcom file:

   xsltproc C:\Instrument\Apps\EPICS\ISIS\lvDCOM\master\lvDCOMApp\src\lvstrings2input.xsl "controls.xml" > lv_controls.xml
   

5. Edit lv_controls.xml (see below for example)

   1. Check the path is correct for the external interface, it should be:<extint path="$(LVDCOM=$(TOP))/lvDCOMApp/src/extint/Main/Library/External Interface - Set Value.vi"/>
   2. Path in vi element needs path to be vi in the llb containing the vi e.g. C:/LabVIEW Modules/Drivers/Oxford Instruments/Mercury/Mercury - Temperature.llb/<name of vi>
   3. Look at TODO's in this file
   4. Remove unneeded controls or states of those controls (e.g. write for read only values)
   5. If the value is controlled by an event the extint value of set controls should be set to "true". This will make it process the value. If one of the value is true you might as well set them all to be true the only advantage is if the are all false it does not need to load the external interface.

6. Add protocol file to ISIS/<iocname>App/protocol/Makefile as

   DATA += lv_controls.xml
   

1. generate db file from an epics terminal in protocol

   xsltproc C:\Instrument\Apps\EPICS\ISIS\lvDCOM\master\lvDCOMApp\src\lvinput2db.xsl lv_controls.xml > ..\Db\controls.db
   

2. Add db file to <iocname>App\Db\Makefile

   DB += controls.db
   

3. Edit the DB file. I found I wanted many _RBV to be :RBV and to get rid of some of the records (see below for example)

1. Add lvDCOMConfigure("lvfp", "frontpanel", "${TOP}/data/lv_controls.xml", "$(LVDCOM_HOST=)", $(LVDCOM_OPTIONS=1), "$(LVDCOM_PROGID=)", "$(LVDCOM_USER=)", "$(LVDCOM_PASS=)") before loading common records and after IOC initialization (to enable common macros to be used in lv_controls.xml). (see lvDCOMConfigure documentation).

2. Load the DB file for the IOC using the dbLoadRecords command.

1. Add these macros to config.xml to allow them to be configured in the GUI:

   <macro name="LVDCOM_OPTIONS" pattern="^\d?\d?$" description="Options that define how the VI is started. Add selected options together to make the final value. 1 - warn if idle, 2 - start if idle, 4 - stop VIs if started on exit, 8 - stop VI on exit. (Default 1)" />
   <macro name="LVDCOM_HOST" pattern="^.*$" description="Host on which the vi is running, blank for localhost (Default '')" />
   <macro name="LVDCOM_PROGID" pattern="^.*$" description="DCOM ProgID, required if connecting to a compiled LabVIEW application (Default '')" />
   

   • Don't add username and password, users can set these in globals.txt

Run the IOC as normal. The IOC should start with no errors and typing "dbl" will list the PVs. Note: unless the VI was already open it will not be visible. If it is not visible, stop the IOC, load the VI and restart the IOC

Now return to the IOC workflow to apply finishing touches like units, PVs of interest and macros. Once the ISIS IOC works you should probably now create an IOC linked to this one in ioc follow a similar pattern to a support modules. Remember that if you do this add your new ioc to the Makefile IOCDIRS and it does not build if there is no ATL so add it to this list too, i.e. edit EPICS\ioc\master\Makefile add to the line:

ifneq ($(HAVE_ATL),YES)  
DIRS_NOTBUILD += ISISDAE MERCURY_ITC STPS350 AG53220A STSR400 DELFTSHEAR DELFTDCMAG DELFTARDUSTEP LVTEST
endif

A numeric indicator:

<param name="ind1" type="float64"> 
    <read method="GCV" target="Some Indicator" />  
</param>

A numeric control:

<param name="cont1" type="float64">
    <read target="Some Control" method="GCV"/>
    <set target="Some Control" method="SCV" extint="false"/>
</param>

A boolean indicator:

<param name="bool_ind" type="int32"> 
    <read method="GCV" target="Some boolean indicator" />
</param>

A string control:

<param name="strcont1" type="string">
    <read target="Some String" method="GCV"/>
    <set target="Some String" method="SCV" extint="false"/>
</param>

An array indicator:

<param name="arrayind1" type="float64array">
    <read target="Some Array" method="GCV"/>
</param>

Push a button when a value is set:

<param name="South_X" type="float64">
  <read method="GCV" target="South X"/>
  <set method="SCV" extint="false" target="South X" post_button="Set South X" post_button_wait="true" />
</param>

A numeric indicator:

record(ai, "$(P)NUM_IND")
{
    field(DTYP, "asynFloat64")
    field(INP,  "@asyn(ex1,0,0)param_name_from_xml")
    field(PREC, "3")
    field(SCAN, ".1 second")
}

A numeric control:

record(ao, "$(P)NUM_CON")
{
    field(DTYP, "asynFloat64")
    field(OUT,  "@asyn(ex1,0,0)param_name_from_xml")
    field(PREC, "3")
}

A boolean indicator:

record(bi, "$(P)BOOL_IND")
{
    field(DTYP, "asynInt32")
    field(INP,  "@asyn(ex1,0,0)param_name_from_xml")
    field(ZNAM, "FALSE")
    field(ONAM, "TRUE")
    field(SCAN, ".1 second")
}

A string control (two records - one for readback and one for writing):

record(stringin, "$(P)STR")
{
    field(DTYP, "asynOctetRead")
    field(INP,  "@asyn(ex1,0,0)param_name_from_xml")
    field(SCAN, ".1 second")
}

record(stringout, "$(P)STRW")
{
    field(DTYP, "asynOctetWrite")
    field(OUT,  "@asyn(ex1,0,0)param_name_from_xml")
}

A numeric array indicator:

record(waveform, "$(P)ARRAY_IND")
{
   field(DTYP, "asynFloat64ArrayIn")
   field(INP,  "@asyn(ex1,0,0)param_name_from_xml")
   field(PREC, "3")
   field(SCAN, ".1 second")
   field(NELM, "10")
   field(FTVL, "DOUBLE")
}

If you are getting file not found errors in your IOC when writing to PVs this will be because the path to the external interface in the generated xml is incorrect.

You can also use the dbior command from the IOC prompt to print out the lvDCOM settings currently in use