SetAttrCoerceCallbackViBoolean

IVI Library

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Ivi_SetAttrCoerceCallbackViBoolean

Usage

ViStatus Ivi_SetAttrCoerceCallbackViBoolean(ViSession vi, ViAttr attributeID, CoerceAttrViBoolean_CallbackPtr coerceCallback);

Purpose

This function sets the coerce callback function for a ViBoolean attribute. The IVI engine calls the coerce callback function when you attempt to set the attribute to a new value. The job of the coerce callback for a ViBoolean attribute is to convert the value you specify into either VI_TRUE (1) or VI_FALSE (0). The IVI engine invokes the coerce callback after it invokes the check callback.

The IVI engine automatically installs its default coerce callback when you create the attribute. The default callback coerces all non-zero values to VI_TRUE (1). If you do want the IVI engine to invoke a coerce callback for the attribute, pass VI_NULL for the Coerce Callback parameter.

If you want to specify your own callback function but you want to use the default coerce callback within your function, you can call Ivi_DefaultCoerceCallbackViBoolean.

Parameters

Name	Type	Description
vi	ViSession	The ViSession handle that you obtain from Ivi_SpecificDriverNew. The handle identifies a particular IVI session.
attributeID	ViAttr	Pass the ID of an attribute for this parameter. The include file for a specific instrument driver defines constant names for all of the user-accessible attributes that apply to the driver. This includes attributes that the IVI engine defines, attributes that the instrument class defines, and attributes that are specific to the particular instrument. Each defined constant name begins with PREFIX_ATTR_, where PREFIX is the specific instrument prefix. For each IVI engine attribute, the specific driver include file uses the same constant name that appears in ivi.h, except that the specific instrument prefix replaces the IVI prefix. For example, ivi.h defines IVI_ATTR_CACHE, and the Fluke 45 include file, fl45.h, defines the following constant name: #define FL45_ATTR_CACHE IVI_ATTR_CACHE For each instrument class attribute, the specific driver include file uses the same constant name that appears in the instrument class include file, except that the specific instrument prefix replaces the class prefix. For example, the DMM class include file, ividmm.h, defines IVIDMM_ATTR_RANGE, and fl45.h defines the following constant name: #define FL45_ATTR_RANGE IVIDMM_ATTR_RANGE For each specific instrument attribute, the specific driver include file defines a constant name and assigns a value that is an offset from IVI_SPECIFIC_PUBLIC_ATTR_BASE. For example, fl45.h defines the following constant name: #define FL45_ATTR_HOLD_THRESHOLD \ (IVI_SPECIFIC_PUBLIC_ATTR_BASE + 3L) For each attribute that is private to an instrument driver, the instrument driver source file defines a constant name and assigns a value that is an offset from IVI_SPECIFIC_PRIVATE_ATTR_BASE. For example, hp34401a.c defines the following constant name: #define HP34401A_ATTR_TRIGGER_TYPE \ (IVI_SPECIFIC_PRIVATE_ATTR_BASE + 1L)
coerceCallback	CoerceAttrViBoolean_CallbackPtr	Specify the coerce callback function you want the IVI engine to invoke when you attempt to set the attribute to a new value. The function must have the following prototype: ViStatus _VI_FUNC Callback(ViSession vi, ViConstString repCapName, ViAttr attributeId, ViBoolean value, ViBoolean *coercedValue); If you want to use the Edit IVI Specific Driver Attributes dialog box to develop your instrument driver source code, retain the parameter names as shown in the prototype for the callback. If you do not want to use a coerce callback function, pass VI_NULL.

Name

Type

Description

ViSession

The ViSession handle that you obtain from Ivi_SpecificDriverNew. The handle identifies a particular IVI session.

attributeID

ViAttr

Pass the ID of an attribute for this parameter.

The include file for a specific instrument driver defines constant names for all of the user-accessible attributes that apply to the driver. This includes attributes that the IVI engine defines, attributes that the instrument class defines, and attributes that are specific to the particular instrument. Each defined constant name begins with PREFIX_ATTR_, where PREFIX is the specific instrument prefix.

For each IVI engine attribute, the specific driver include file uses the same constant name that appears in ivi.h, except that the specific instrument prefix replaces the IVI prefix. For example, ivi.h defines IVI_ATTR_CACHE, and the Fluke 45 include file, fl45.h, defines the following constant name:

#define FL45_ATTR_CACHE IVI_ATTR_CACHE

For each instrument class attribute, the specific driver include file uses the same constant name that appears in the instrument class include file, except that the specific instrument prefix replaces the class prefix. For example, the DMM class include file, ividmm.h, defines IVIDMM_ATTR_RANGE, and fl45.h defines the following constant name:

#define FL45_ATTR_RANGE IVIDMM_ATTR_RANGE

For each specific instrument attribute, the specific driver include file defines a constant name and assigns a value that is an offset from IVI_SPECIFIC_PUBLIC_ATTR_BASE. For example, fl45.h defines the following constant name:

#define FL45_ATTR_HOLD_THRESHOLD \ (IVI_SPECIFIC_PUBLIC_ATTR_BASE + 3L)

For each attribute that is private to an instrument driver, the instrument driver source file defines a constant name and assigns a value that is an offset from IVI_SPECIFIC_PRIVATE_ATTR_BASE. For example, hp34401a.c defines the following constant name:

#define HP34401A_ATTR_TRIGGER_TYPE \ (IVI_SPECIFIC_PRIVATE_ATTR_BASE + 1L)

coerceCallback

CoerceAttrViBoolean_CallbackPtr

Specify the coerce callback function you want the IVI engine to invoke when you attempt to set the attribute to a new value.

The function must have the following prototype:

ViStatus _VI_FUNC Callback(ViSession vi, ViConstString repCapName, ViAttr attributeId, ViBoolean value, ViBoolean *coercedValue);

If you want to use the Edit IVI Specific Driver Attributes dialog box to develop your instrument driver source code, retain the parameter names as shown in the prototype for the callback.

If you do not want to use a coerce callback function, pass VI_NULL.

Return Value

Contains the status code that the function call returns. IVI engine functions can return error and warning values from several sets of status codes. Some status codes are unique to the IVI engine. Other status codes are the same codes that VISA Library functions return. Still others are error or warning values that functions in specific instrument drivers return. Each set of status codes has its own numeric range.

Regardless of the source of the status code, 0 always indicates success, a positive value indicates a warning, and a negative value indicates an error.