Overview
This document describes a set of IDL classes which have been written for use
with EPICS. These classes presently provide support for the motor, scaler and
MCA records.
There are some significant advantages of using classes (i.e. objects) to access
these devices, rather than simply a set of subroutines:
This is an early release of the EPICS class library. There are likely to be modifications as experience is gained with the interface.
EPICS_MOTOR are created with the standard IDL
obj_new() function as follows:
IDL> motor = obj_new('EPICS_MOTOR', pvname)
where pvname is the name of an EPICS motor record.
pvname can include a field name which will be stripped off. For
example '13IDA:Slit_Pos' and '13IDL:Slit_Pos.DESC'
are both valid. This makes
it convenient when dragging process variable names from MEDM
windows to IDL windows.
When creating a new motor object with obj_new() the
resulting object reference can be checked with obj_valid()
to make sure that the object was created successfully.
When a new EPICS_MOTOR object is created the initialization function
EPICS_MOTOR::INIT() is called automatically. For efficiency it
sets channel access monitors on all of the record fields which the object
methods read.
The following example shows how easy it is to create a new motor object and use it:
IDL> motor = obj_new('EPICS_MOTOR', '13IDA:Slit_Pos')
IDL> motor->move, 10. ; Move to absolute position 10.
IDL> motor->wait ; Wait for it to get there
The methods provided by the EPICS_MOTOR class are described
in detail in the EPICS_MOTOR Class Reference.
The files for the EPICS_MOTOR class are available in the file epics_classes.tar
EPICS_SCALER are created with the standard IDL
obj_new() function as follows:
IDL> scaler = obj_new('EPICS_SCALER', pvname)
where pvname is the name of an EPICS scaler record.
pvname can include a field name which will be stripped off. For
example '13IDC:scaler1' and '13IDC:scaler1.S2'
are both valid. This makes
it convenient when dragging process variable names from MEDM
windows to IDL windows.
When creating a new scaler object with obj_new() the
resulting object reference can be checked with obj_valid()
to make sure that the object was created successfully.
When a new EPICS_SCALER object is created the initialization function
EPICS_SCALER::INIT() is called automatically. For efficiency it
sets channel access monitors on all of the record fields which the object
methods read.
The following example shows how easy it is to create a new scaler object and use it:
IDL> scaler = obj_new('EPICS_SCALER', '13IDA:Slit_Pos')
IDL> scaler->start, 10. ; Start counting for 10 seconds
IDL> scaler->wait ; Wait for it to finish
IDL> counts = scaler->read() ; Read out the counts on each channel
The methods provided by the EPICS_SCALER class are described
in detail in the EPICS_SCALER Class Reference.
The files for the EPICS_SCALER class are available in the file epics_classes.tar
This class is a device independent class. The MCA class itself is most commonly used for reading data from disk files. More importantly, this class is the superclass of the EPICS MCA class.
MCA are created with the standard IDL
obj_new() function as follows:
IDL> mca = obj_new('MCA')
obj_new() always succeeds when creating MCA objects.
The following example shows how easy it is to create a new MCA object and use it:
IDL> mca = obj_new('MCA')
IDL> mca->READ_FILE, 'mca.001' ; Read a disk file
IDL> data = mca->GET_DATA()
IDL> energy = mca->CHAN_TO_ENERGY(findgen(mca->GET_NCHANS()))
IDL> plot, energy, counts
The methods provided by the MCA class are described
in detail in the MCA Class Reference.
The files for the MCA class are available in the file idl_mca.tar
This is the device dependent MCA class. It uses the EPICS MCA record. The EPICS_MCA class is a subclass of MCA, and so all methods defined for the MCA class are also valid for EPICS_MCA.
EPICS_MCA are created with the standard IDL
obj_new() function as follows:
IDL> mca = obj_new('EPICS_MCA', pvname)
where pvname is the name of an EPICS MCA record.
pvname can include a field name which will be stripped off. For
example '13IDC:mca1' and '13IDC:mca1.DESC'
are both valid. This makes
it convenient when dragging process variable names from MEDM
windows to IDL windows.
When creating a new EPICS_MCA object with obj_new() the
resulting object reference can be checked with obj_valid()
to make sure that the object was created successfully.
When a new EPICS_MCA object is created the initialization function
EPICS_MCA::INIT() is called automatically. For efficiency it
sets channel access monitors on all of the record fields which the object
methods read.
The following example shows how easy it is to create a new EPICS_MCA object and use it:
IDL> mca = obj_new('EPICS_MCA', '13IDC:mca1')
IDL> mca->erase ; Erase the spectrum
IDL> mca->acquire_on ; Turn on acquisition
IDL> data = mca->get_data() ; Read the counts
The methods provided by the EPICS_MCA class are described
in detail in the EPICS_MCA Class Reference.
The files for the EPICS_MCA class are available in the file idl_mca.tar
Multi-element detector (MED) class
This class is a device independent class. The MED class is basically a collection of MCA objects. Its methods generally simply apply the MCA class methods to each MCA object in the collection. The MED class itself is most commonly used for reading data from disk files. More importantly, this class is the superclass of the EPICS MED class.
MED are created with the standard IDL
obj_new() function as follows:
IDL> mca = obj_new('MED', n_detectors) ; n_detectors defaults to 13
obj_new() always succeeds when creating MED objects.
The following example shows how easy it is to create a new MED object and use it:
IDL> med = obj_new('MED')
IDL> med->READ_FILE, 'med.001' ; Read a disk file
IDL> data = med->GET_DATA()
IDL> plot, data[*,0]
IDL> oplot, data[*,1]
The methods provided by the MED class are described
in detail in the MED Class Reference.
The files for the MED class are available in the file idl_mca.tar
This is the device dependent MED class. It uses an EPICS MED database. The EPICS_MED class is a subclass of MED, and so all methods defined for the MED class are also valid for EPICS_MED.
EPICS_MED are created with the standard IDL
obj_new() function as follows:
IDL> med = obj_new('EPICS_MED', prefix)
where prefix is the prefix of the EPICS MED database.
When creating a new EPICS_MED object with obj_new() the
resulting object reference can be checked with obj_valid()
to make sure that the object was created successfully.
When a new EPICS_MED object is created the initialization function
EPICS_MED::INIT() is called automatically. For efficiency it
sets channel access monitors on all of the record fields which the object
methods read.
The following example shows how easy it is to create a new EPICS_MED object and use it:
IDL> med = obj_new('EPICS_MED', '13IDC:med:')
IDL> med->erase ; Erase the spectrum
IDL> med->acquire_on ; Turn on acquisition
IDL> data = med->get_data() ; Read the counts
The methods provided by the MED class are described
in detail in the EPICS_MED Class Reference.
The files for the EPICS_MED class are available in the file idl_mca.tar
This class is used to contain powder diffraction information. It is used by the IDL MCA display program for displaying diffraction lines. It can be used to compute diffraction line positions at high pressure and temperature.
JCPDS are created with the standard IDL
obj_new() function as follows:
IDL> jcpds = obj_new('JCPDS')
When creating a new JCPDS object with obj_new() the
resulting object reference can be checked with obj_valid()
to make sure that the object was created successfully.
The following example shows how easy it is to create a new JCPDS object and use it:
IDL> jcpds = obj_new('JCPDS')
IDL> jcpds->read_file('alumina.jcpds') ; Read a file into the object
The methods provided by the JCPDS class are described
in detail in the JCPDS Class Reference.
The IDL files for the JCPDS class are available in the file idl_mca.tar
The data files for the GSECARS JCPDS database are available in the file jcpds.tar
The class reference for each of the classes contains up-to date documentation and release note information.
Future Additions
There are many features of the motor and scaler records which the IDL class
libraries do not yet support. These features will be added as we find the
need or in response to requests from others.
Suggestions and comments to: Mark Rivers : (rivers@cars.uchicago.edu)