Using labCA

labCA consists of a set of shared libraries which in turn reference other shared libraries (most notably the channel access client libraries from EPICS BASE). It is of crucial importance that the operating system locates the correct versions at run-time (i.e. the same versions labCA was linked against). Otherwise, the run-time linker/loader could fail to load the required objects — leaving the user (expecially in matlab) at the prompt with obscure error messages.

Under linux or solaris, the LD_LIBRARY_PATH environment variable or the ld.so.conf / ldconfig facility are used to point to the executable shared libraries (located in lib/<arch>). The PATH variable also should point to bin/<arch> so that the CA repeater executable is found. If you build from source using your own EPICS base installation then we assume that locating the CA repeater has already been taken care of.

Under win32/64, the PATH environment variable must point to the correct EPICS BASE and labCA DLLs (located in bin/<arch>).

Note that the paths to the correct EPICS BASE and labCA shared libraries must be set up prior to starting the scilab or matlab application. It is usually not possible to change the system search path from within an application.

Possible problems could occur because

third party setup scripts modify LD_LIBRARY_PATH / PATH.
your EPICS BASE was not built with shared libraries but shared libraries of a different release are found somewhere.
a “innocent-looking” directory present in LD_LIBRARY_PATH before EPICS BASE actually contains shared libraries of an older release.
Note that the system search path is not identical with the matlab path — changing the matlab path (from withing matlab) has no influence on the system search path.

Using labCA with scilab

Set up the shared library search path (as described above) and start scilab. Run the labCA.sce script which was generated by the build process (<labCA-top>/bin/<arch>/labCA.sce) to load the labCA interface. The script also adds to the %helps variable making on-line help available¹³.

The script can be installed at any convenient location — the lines setting up the %helps path (or add_help_chapter(), respectively) need to be adapted in this case.

It is also possible to permanently link labCA to scilab. Consult the scilab documentation for more information.

Using labCA with matlab

Every entry point / lcaXXX routine is contained in a separate shared object (AKA “mex-”) file in the <labCA-top>/bin/<arch>/labca¹⁴ directory which must be added to the matlab search path. Note that this is in addition to setting the system library search path which must be performed prior to starting matlab (see previous section). All necessary objects and libraries are transparently loaded simply by invoking any of the entry point routines. Note that on-line help files are also installed to be located automatically.

Footnotes

... available ¹³: Under scilab-5 %helps is no longer relevant but add_help_chapter() is used insted.
... CLASS="textbf">labCA-top>/bin/<arch>/labca ¹⁴: the extra subdirectory was added in order for the matlab help command to easily locate the Contents.m file when the user types help labca.