User`s guide

7 Storing Adaptor Information in an IMDF File
7-2
Using the IMDF Markup Language
This chapter describes how to use an XML-based markup language to specify source,
property, and hardware trigger information in an Imaging Device File (IMDF).
Note Creating an IMDF is required. Using an IMDF file can simplify the coding of your
adaptor's getDeviceAttributes() function. In addition, it is the only convenient way
to make help text available for the device-specific properties your adaptor creates.
User Scenario
When a user calls the imaqhwinfo function, the toolbox searches for adaptor DLLs.
When it finds a DLL, it also looks for a matching IMDF file in the same directories. If
found, the engine stores path information to the IMDF file. An IMDF file must reside in
the same directory as your DLL and the .imdf file extension, such as demoimaq.imdf.
When a user calls the videoinput function to create a video input object, the engine
reads and processes the IMDF file. When it reads the file, it processes the property,
trigger, and source information specified at the top-level of the file. (To understand
the hierarchical arrangement of an IMDF file, see “Elements of the IMDF Markup
Language” on page 7-2.)
After reading all the top-level elements, the engine looks for a device element that
matches the device the user specified in the videoinput function. If found, the engine
then looks for video format element in the device element.
The engine then calls your adaptor's getDeviceAttributes() function, as described in
“Implementing Get and Set Support for Device-Specific Properties” on page 6-10, to set
up device properties.
Elements of the IMDF Markup Language
The following figure shows the hierarchical relationship of the elements of the XML-
based markup language for IMDF files. The figure shows which elements can be children
of other elements. Elements at the top-level of an IMDF file (elements that are children
of the ImageAcquisitionInfo element apply to an entire adaptor. Elements that are
children of a Device element apply only to that device. To simplify the diagram, all
possible subordinate elements are not always shown for elements below the top-level.
When used in an IMDF file, elements are called nodes.