Measurement Computing Personal Daq rev.6.0 - Manual (Page 149)

Personal Daq User’s Manual Appendix B, 887095 API Commands B-17
daqAdcTransferSetBuffer
DLL Function daqAdcTransferSetBuffer(DaqHandleT handle, PVOID buf, DWORD scanCount,
DWORD transferMask);
C daqAdcTransferSetBuffer(DaqHandleT handle, PVOID buf, DWORD scanCount,
DWORD transferMask);
Visual BASIC VBdaqAdcTransferSetBufferSingle&(ByVal handle&, buf!(), ByVal ScanCount&, ByVal
transferMask&)
Delphi daqAdcTransferSetBuffer( handle:DaqHandleT; buf:pointer; scanCount:DWORD;
transferMask:DWORD )
handle Handle to the device for which an ADC transfer is to be performed.
buf Pointer to the buffer for which the acquired data is to be placed.
scanCount The total length of the buffer (in scans).
Parameters
transferMask Configures the buffer transfer mode.
Returns DerrNoError No error
See Also daqAdcTransferStart, daqAdcTransferStop, daqAdcTransferGetStat, daqAdcSetAcq,
daqAdcTransferBufData
Program References ADCEX1.C, FREQEX1.C, PULSEEX1.C, MULTEX1.C, DAQEX.FRM (VB), DAQEX.PAS (Delphi)
Used With All devices
Description
daqAdcTransferSetBuffer allows you to configure transfer buffers for ADC data acquisition. This function can be used to configure
the specified user- or driver-allocated buffers for subsequent ADC transfers.
If a user-allocated buffer is to be used, two conditions apply:
The buffer specified by the buf parameter must have been allocated by the user prior to calling this function.
The allocated buffer must be large enough to hold the number of ADC scans as determined by the current ADC scan group configuration.
The scanCount parameter is the total length of the transfer buffer in scans. The scan size is determined by the current scan group
configuration. Refer to the daqAdcSetScan and daqAdcSetMux functions for further information on scan group configuration.
The character of the transfer can be configured via the transferMask parameter. Among other things, the transferMask specifies the
update, layout/usage, and allocation modes of the buffer. The modes can be set as follows:
•
DatmCycleOn - Specifies the buffer to be a circular buffer in buffer-cycle mode; allows the transfer to continue when the end of the
transfer buffer is reached by wrapping the transfer of scan data back to the beginning of the buffer. In this mode, the transfer
buffer will continue to be wrapped until the post-trigger count has been reached (specified by daqAdcSetAcq) or the
transfer/acquisition is halted by the application (daqAdcTransferStop, daqAdcDisarm). The default setting is DatmCycleOff.
•
DatmUpdateSingle - Specifies the update mode as single sample. The update mode can be set to update for every sample or
for every block of data. The update-on-single setting allows the transfer buffer to be updated for each sample collected by the
Personal Daq. The default setting is DatmUpdateSingle.
•
DatmSavePreTrigBuf - Specifies that the driver save the pre-trigger data once the trigger event has been satisfied. This option
allows the driver to save pre-trigger data in a separate linear buffer once the trigger event has occurred. By doing so the pre-
trigger data buffer can be accessed at any time after the trigger event without having the possibility of the pre-trigger data being
overwritten by new data being written to the driver buffer. When the trigger event occurs the driver writes the specified amount
(daqAdcSetMode) of pre-trigger data to an internal pre-trigger buffer which the driver allocates. The pre-trigger data may then be
accessed via the daqAdcTransferBufData function. This option must be used in conjunction with the DatmDriverBuf option.
•
DatmDriverBuf - Specifies that the driver allocate the acquisition buffer as a circular buffer whose length is determined by the
scanCount parameter with current scan group configuration. This option allows the driver to manage the circular acquisition buffer
rather than placing the burden of buffer management on the user. This option should be used with the
daqAdcTransferBufData
to access the acquisition buffer. The daqAdcTransferStop or the daqAdcDisarm function will
stop the current transfer and de-allocate the driver-supplied ADC acquisition buffer. The default setting is DatmUserBuf. The
DatmUserBuf
option specifies a user-allocated acquisition buffer. Here, buffer management must be done in user code. This
option should be used with the daqAdcTransferStart function to perform the data transfer operation.