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Chapter 2 Function Reference — DAQ_Check
NI-DAQ FRM for PC Compatibles 2-116
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National Instruments Corporation
automatically rearranges the array upon completion of the acquisition so that the oldest data
point is at the beginning of the array. Thus, retrieved always equals 0 upon completion of a
pretrigger mode acquisition.
Note C Programmers—daqStopped and retrieved are pass-by-reference parameters.
Using This Function
DAQ_Check checks the current background DAQ operation to determine whether it has
completed and returns the number of samples acquired at the time that you called
DAQ_Check. If the operation is complete, DAQ_Check sets daqStopped = 1. Otherwise,
daqStopped is set to 0. Before
DAQ_Check returns daqStopped = 1, it calls DAQ_Clear,
allowing another Start call to execute immediately.
If
DAQ_Check returns an overFlowError or an overRunError, the DAQ operation is
terminated; some A/D conversions were lost due to a sample rate that is too high (sample
interval was too small). An overFlowError indicates that the A/D FIFO memory overflowed
because the DAQ servicing operation was not able to keep up with sample rate. An
overRunError indicates that the DAQ circuitry was not able to keep up with the sample rate.
Before returning either of these error codes,
DAQ_Check calls DAQ_Clear to terminate the
operation and reinitialize the DAQ circuitry.