National Instruments 320685D-01 RS-232 Library , VISA Library, IVI Library

Chapter 9 Checking for Errors in LabWindows/CVI

National Instruments Corporation 9-5 LabWindows/CVI Programmer Reference Manual

iberr. After each GPIB call, your program should check whether the ERR bit is set to

determine if an error has occurred, as shown in the following code segment.

if (ibwrt(bd[instrID], buf, cnt) & ERR)

PREFIX_err = 230;

Refer to your NI-488.2 Function Reference and user manuals for detailed information on

GPIB global variables and listings of status and error co des. LabWindows/CVI function panel

help also has listings of status and error codes.

RS-232 Library

The RS-232 library returns status information through a global variable called rs232err. If

this variable is negative after the function returns, an error occurred. Notice that many of the

functions return a value in addition to setting the global variable. Usually, this value contains

information on the result of the function that can also be used to detect a problem. Each

function should be checked individually. Refer to the RS-232 section in the LabWindows/CVI

Standard Libraries Reference Manual or the function panel h elp for a listing of the error codes

and information on the individual functions. Yo u can use GetRS232ErrorString to get the

error message associated with each RS-232 Library errorcode.

Note If your program uses multiple threads, use the ReturnRS232Err function in

place of the rs232err global variable.

VISA Library

The VISA Library functions return a negative value when they detect an error. They return a

positive value as a warning when they can complete their task but not in the way you might

expect. This library uses a common set of error and warning codes, but the warning code

values are entirely separate from the error code values. The error codes always contain

0xBFFF in the upper two bytes. The warning codes always contain 0x3FFF in the upper two

bytes. Refer to the NI-VISA Programmer Reference Manual or the function panel help for a

listing of the error and warning codes and information on the individual functions. You can

use viStatusDesc to obtain the error message associated with each VISA Library error

code.

IVI Library

The IVI Library functions return a negative value when they detect an error. This library uses

a common set of error codes. Refer to the LabWindows/CVI Instrument Driver Developers

Guide or the function panel help for a listing of the error codes and information on the

individual functions. IVI Library functions sometimes also provide a secondary error code or

an elaboration string to give you additional information about an error condition. You can use

Ivi_GetErrorInfo to obtain the primary error code, secondary error code, and the

elaboration string. You can use Ivi_GetErrorMessage to obtain the error message

associated with each IVI Library error code.