AnalogMultiChannelReader.BeginMemoryOptimizedReadWaveform Method (TimeSpan, AsyncCallback, Object, AnalogWaveform(Double)[], ReallocationPolicy)
- Updated2023-02-21
- 3 minute(s) read
Namespace: NationalInstruments.DAQmx
Assembly: NationalInstruments.DAQmx (in NationalInstruments.DAQmx.dll) Version: 20.7.40.49302
Syntax
public IAsyncResult BeginMemoryOptimizedReadWaveform( TimeSpan duration, AsyncCallback callback, Object state, AnalogWaveform<double>[] data, ReallocationPolicy policy )
Public Function BeginMemoryOptimizedReadWaveform ( duration As TimeSpan, callback As AsyncCallback, state As Object, data As AnalogWaveform(Of Double)(), policy As ReallocationPolicy ) As IAsyncResult
Parameters
- duration
- Type: SystemTimeSpan
The duration of time to read the waveform. The duration specified must be long enough to read at least one sample at the configured SampleClockRate. - callback
- Type: SystemAsyncCallback
An optional asynchronous callback that is called when the read is complete. Specify if you do not want a callback when the read is complete. - state
- Type: SystemObject
A user-provided object that distinguishes this asynchronous read request from other requests. Use this parameter to provide information to the callback. Specify if you do not need to pass any additional information to the callback. - data
- Type: NationalInstrumentsAnalogWaveformDouble
An initialized 1D array of AnalogWaveformTData that contains the read data. Each element in the array corresponds to a channel in the task. The order of the channels in the array corresponds to the order in which you add the channels to the task or to the order of the channels you specify in ChannelsToRead. - policy
- Type: NationalInstruments.DAQmxReallocationPolicy
Dictates the reallocation behavior of the read operation. Refer to ReallocationPolicy for more information.
Return Value
Type: IAsyncResultAn IAsyncResult that represents the asynchronous call.
Remarks
To get the read data or any exceptions that occurred during an asynchronous read initiated with BeginMemoryOptimizedReadWaveform(TimeSpan, AsyncCallback, Object, AnalogWaveformDouble, ReallocationPolicy), call EndMemoryOptimizedReadWaveform(IAsyncResult), passing the returned IAsyncResult.
NI-DAQmx scales the read data to the units of the measurement, including any custom scaling you apply to the channel. You specify these units when creating channels using the create channel methods or the DAQ Assistant.
The data returned from analog waveform reads is affected by the WaveformAttributeMode property of the DaqStream being read.
NI-DAQmx read and write methods time out after the amount of time specified by the Timeout property on the Stream object used for the reads or writes.
Refer to NI-DAQmx Readers and Writers for more information about memory limitations in NI-DAQmx read methods.
 Note |
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| Refer to Asynchronous Reads and Writes for additional information. |