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Personal Daq User’s Manual Appendix A,

878495

API Custom Program

Models

A-3

All Visual Basic programs should include the

PDAQX.BAS

file into their project. The

PDAQX.BAS

file

provides the necessary definitions and function prototyping for the

DaqX

driver

DLL

handle& = VBdaqOpen&(“PDAQ123456”)
ret& = VBdaqClose&(handle&)

The PersonalDaq device is opened and initialized with the

daqOpen

function.

daqOpen

takes one

parameter—the name of the device to be opened. The device name is the

device serial#

pre-prended with

“

PDAQ

”.

For instance if the serial# for the Personal Daq is 123456 then the device name to use to open that device
would be “

PDAQ123456

”. The

daqOpen

call, if successful, will return a

handle

to the opened device.

This handle may then be used by other functions to configure or perform other operations on the device.
When operations with the device are complete, the device may then be closed using the

daqClose

function. If the device could not be found or opened,

daqOpen

will return

-1

The DaqX library has a default error handler defined upon loading. However; if it is desirable to change
the error handler or to disable error handling, then the

daqSetErrorHandler

function may be used to

setup an error handler for the driver. In the following example the error handler is set to

(no handler

defined) which disables error handling.

ret& = VBdaqSetErrorHandler&(0&)

If there is a Personal Daq error, the program will continue. The function’s return value (an error number or

if no error) can help you debug a program.

If (VBdaqOpen&(“PDAQ123456”) < 0) Then
“Cannot open PDaq”

Personal Daq functions return

daqErrno&

Print “daqErrno& : ”; HEX$(daqErrno&)
End If

The next statement defines an error handling routine that frees us from checking the return value of every
Personal Daq function call. Although not necessary, this sample program transfers program control to a
user-defined routine when an error is detected. Without a Personal Daq error handler, Visual Basic will
receive and handle the error, post it on the screen and terminate the program. Visual Basic provides an
integer variable (ERR) that contains the most recent error code. This variable can be used to detect the
error source and take the appropriate action. The function

daqSetErrorHandler

tells Visual Basic to

assign ERR to a specific value when a Personal Daq error is encountered. The following line tells Visual
Basic to set ERR to 100 when a Personal Daq error is encountered. Other languages work similarly; refer
to specific language documentation as needed.

handle& = VBdaqOpen&(“PDAQ123456”)
ret& = VBdaqSetErrorHandler&(handle&, 100)

On Error GoTo ErrorHandler

The

On Error GoTo

command in Visual Basic allows a user-defined error handler to be provided,

rather than the standard error handler that Visual Basic uses automatically. The program uses

On Error

GoTo

to transfer program control to the routine

ErrorHandler

if an error is encountered.

Personal Daq errors will send the program into the error handling routine. This is the error handler.
Program control is sent here on error.

ErrorHandler:

errorString$ = "ERROR in ADC1"
errorString$ = errorString$ & Chr(10) & "BASIC Error :" + Str$(Err)
If Err = 100 Then errorString$ = errorString$ & Chr(10) & "DaqBook Error

: " + Hex$(daqErrno&)

MsgBox errorString$, , "Error!"

End Sub

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