Learn more about Data Acquisition Toolbox

Getting Help

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The daqhelp Function The propinfo Function

The daqhelp Function

You can use the daqhelp function to:

• Display command-line help for functions and properties.

• List all the functions and properties associated with a specific device object

A device object need not exist for you to obtain this information. For example, to display all the functions and properties associated with an analog input object, as well as the constructor M-file help, enter:

daqhelp analoginput

To display help for the SampleRate property

daqhelp SampleRate

You can also display help for an existing device object. For example, to display help for the BitsPerSample property for an analog input object associated with a sound card

ai = analoginput('winsound');
out = daqhelp(ai,'BitsPerSample');

Alternatively, you can display help via the Workspace browser by right-clicking a device object, and selecting Explore > DAQ Help from the context menu.

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The propinfo Function

You can use the propinfo function to return the characteristics of toolbox properties. For example, you can find the default value for any property using this function. propinfo returns a structure containing the following fields:

propinfo Fields

Field Name	Description
Type	The property data type. Possible values are callback, any, double, and string.
Constraint	The type of constraint on the property value. Possible values are callback, bounded, enum, and none.
ConstraintValue	The property value constraint. The constraint can be a range of valid values or a list of valid string values.
DefaultValue	The property default value.
ReadOnly	Indicates when the property is read-only. Possible values are always, never, and whileRunning.
DeviceSpecific	If the property is device-specific, a 1 is returned. If a 0 is returned, the property is supported for all device objects of a given type.

For example, to return the characteristics for all the properties associated with the analog input object ai created in the The daqhelp Function section, enter:

AIinfo = propinfo(ai);

The characteristics for the TriggerType property are displayed below.

AIinfo.TriggerType
ans = 
               Type: 'string'
         Constraint: 'enum'
    ConstraintValue:  {'Manual'  'Immediate'  'Software'}
       DefaultValue: 'Immediate'
           ReadOnly: 'whileRunning'
     DeviceSpecific: 0

This information tells you that:

• The property value data type is a string.

• The property value is constrained as an enumerated list of values.

• The three possible property values are Manual, Immediate, and Software.

• The default value is Immediate.

• The property is read-only while the device object is running.

• The property is supported for all analog input objects.

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Examining Your Hardware Resources

Examples

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