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3
The Data Acquisition Session
Creating a Device Object
Device objects are the toolbox components you use to access your hardware
device. They provide a gateway to the functionality of your hardware, and allow
you to control the behavior of your data acquisition application. Each device
object is associated with a specific hardware subsystem.
To create a device object, you call M-file functions called object creation
functions (or object constructors). These M-files are implemented using the
object-oriented programming capabilities provided by MATLAB, which are
described in “MATLAB Classes and Objects” in the Help browser. The device
object creation functions are listed below.
Table 3-1: Device Object Creation Functions
Function
Description
analoginput
Create an analog input object.
analogoutput
Create an analog output object.
digitalio
Create a digital I/O object.
Before you can create a device object, the associated hardware driver adaptor
must be registered. Adaptor registration occurs automatically. However, if for
some reason an adaptor is not automatically registered, then you must do so
manually with the daqregister function. Refer to “Registering the Hardware
Driver Adaptor” on page A-18 for more information.
You can find out how to create device objects for a particular vendor and
subsystem with the ObjectConstructorName field of the daqhwinfo function.
For example, to find out how to create an analog input object for an installed
National Instruments board, you supply the appropriate adaptor name to
daqhwinfo.
out = daqhwinfo('nidaq');
out.ObjectConstructorName(:)
ans =
'analoginput('nidaq',1)'
'analogoutput('nidaq',1)'
'digitalio('nidaq',1)'
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