Measurement-computing Personal Daq rev.6.0 Uživatelský manuál stáhnout pdf (Strana 133)

Personal Daq User’s Manual Appendix B, 887095 API Commands B-1

API Commands B

Overview

This appendix includes information regarding type-sensitive API function wrappers for Visual Basic,

Personal Daq driver commands for Windows

in 32-bit mode, parameter definitions such as A/D

channels, event-handling, hardware, A/D gain, general I/O, digital I/O port connection (page B-29), and

API error codes (page B-33).

Type-Sensitive API Function Wrappers for Visual Basic

Each API function has a wrapper serving as an interface between the Visual Basic program and the actual

API function calls. API function prototypes (made available by

PDAQX.DLL) are declared in the header

file (

PDAQX.BAS) as follows:

Declare Function BdaqAdcTransferSetBuffer& Lib "pdaqx.dll" Alias _

"daqAdcTransferSetBuffer" (ByVal handle&, buf As Any, ByVal ScanCount&, _

ByVal transferMask&)

Ideally, any application written in Visual Basic should call the function above by using the function

wrapper,

VbdaqAdcTransferSetBuffer, rather than calling the API function directly via

BdaqAdcTransferSetBuffer. The standard wrapper for this function is:

Function VBdaqAdcTransferSetBuffer&(ByVal handle&, buf%(), ByVal ScanCount&,

ByVal transferMask&)

Dim lb1&

lb1& = LBound(buf%)

daqErrno& = BdaqAdcTransferSetBuffer&(handle&, buf%(lb1&), ScanCount&,

transferMask&)

If ((daqErrno& <> 0) And (daqErrnum& <> 0)) Then Error daqErrnum&

VBdaqAdcTransferSetBuffer& = daqErrno&

End Function

For Visual Basic versions preceding 5.0, proper error handling is made possible with the use of wrappers.

In cases where API functions return structured information, the function wrappers assist in presenting that

information to the programmer. For

VBdaqGetDeviceList the information in the byte array (returned by

the DLL) is transferred to a standard VB string array that is easier to work with on the programming end.

It is important to note that while every API function supported in Visual Basic has at least one associated

wrapper, the API functions that include buffer references have two different associated wrappers

(dependent on the buffer’s data type). For example, consider the

daqAdcTransferSetBuffer function.

The prototype has a buffer parameter declared as type

Any (see previous wrapper code). Data acquisition

buffers can contain either integers (16-bit numbers), or single-precision floating-point numbers (Single

data type).

VBdaqAdcTransferSetBuffer - would be used to call the daqAdcTransferSetBuffer function with a

buffer containing integers.

VBdaqAdcTransferSetBufferSingle - would be used for a buffer containing single-precision

floating-point numbers.

The only difference between the

VBdaqAdcTransferSetBuffer and VBdaqAdcTransferSetBufferSingle

functions is that the

buf parameters consist of different data types for each wrapper.

The following table lists buffer-related API functions and associated wrappers.

API Function Integer Wrapper Floating-Point Wrapper

BdaqAdcTransferSetBuffer VBdaqAdcTransferSetBuffer VBdaqAdcTransferSetBufferSingle

BdaqAdcTransferBufData VBdaqAdcTransferBufData VBdaqAdcTransferBufDataSingle

BdaqAdcRdScan VBdaqAdcRdScan VBdaqAdcRdScanSingle

BdaqAdcRdN VBdaqAdcRdN VBdaqAdcRdNSingle

BdaqAdcRdScanN VBdaqAdcRdScanN VBdaqAdcRdScanNSingle

BdaqAdcGetBufData VBdaqAdcGetBufData VBdaqAdcGetBufDataSingle

BdaqAdcRd VBdaqAdcRd VBdaqAdcRdSingle

BdaqCvtRawDataFormat VBdaqCvtRawDataFormat VBdaqCvtRawDataFormatSingle

1 2 ... 128 129 130 131 132 133 134 135 136 137 138 ... 169 170

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