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Fetch (Fetch Bus Waveform (WDT)) (G Dataflow)

Version:
    Last Modified: September 27, 2017

    Fetches an array of data using the waveform data type and returns an array of waveforms, one for each element in the channel list array.

    This node allows you to fetch data in any order or subset that you desire without the need to manipulate the data after fetching it.

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    timestamp type

    Parameter that specifies whether the timestamp for the waveform data is relative or absolute.

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    channel list

    channel list specifies the channels from which to fetch waveform data. You must assign all channels that you want to fetch using the Assign Dynamic Channels node before selecting those channels with this parameter.

    NI-HSDIO fetches waveform data in the order that you list channels in this parameter, not in the order that those channels are listed in the Assign Dynamic Channels node. If you leave this parameter blank, NI-HSDIO fetches all channels.

    Each element in this array, consisting of its specified channels, is output as a single waveform in the data parameter. Specify multiple channels in each element by using a channel list or a channel range. A channel list is a comma (,) separated sequence of channel names (for example, 0,2 specifies a waveform showing channels 0 and 2). A channel range is a lower bound channel followed by a hyphen (-) or colon (:) followed by an upper bound channel (for example, 0-2 specifies a waveform showing channels 0, 1, and 2).

    You can include the same channel in multiple elements of this array. For example, if you choose 0:2 as the first element, 0, 2 as the second element, and 0 as the third element, the data parameter returns three waveforms: the first depicting channels 0 through 2, the second depicting channels 0 and 2, and the third depicting just channel 0.

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    session in

    Instrument session obtained from the Initialize Acquisition Session node, the Initialize Generation Session node, or the Initialize External Calibration node.

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    error in

    Error conditions that occur before this node runs.

    The node responds to this input according to standard error behavior.

    Standard Error Behavior

    Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.

    error in does not contain an error error in contains an error
    If no error occurred before the node runs, the node begins execution normally.

    If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out.

    If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out.

    Default: No error

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    samples to read

    The specified number of samples to fetch per waveform.

    If you specify a value for samples to read that is greater than the number of samples in the device memory, NI-HSDIO returns the samples that are acquired after max time milliseconds. Setting this parameter to -1 acquires the samples per record specified in the niHSDIO Configure Acquisition Size node.

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    maximum time (ms)

    The time, in milliseconds, allotted for the node to complete before NI-HSDIO returns a timeout error.

    If you set the value to -1, the node never times out. If you set this parameter to 0, the node returns immediately with up to the number of samples specified in samples to read.

    If samples to read is greater than the number of samples in the device memory and all the available samples are acquired before a timeout, NI-HSDIO returns the available samples.

    Default: 10000

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    starting record

    The record at which you want to start fetching data.

    Default: 0

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    session out

    Handle that identifies the session in all subsequent node calls.

    The session out parameter is obtained from the Initialize Acquisition Session node or the Initialize Generation Session node.

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    error out

    Error information.

    The node produces this output according to standard error behavior.

    Standard Error Behavior

    Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.

    error in does not contain an error error in contains an error
    If no error occurred before the node runs, the node begins execution normally.

    If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out.

    If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out.
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    data

    The acquired data as an array of waveforms, one for each element in the channel list parameter.

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    number of samples read

    The number of samples that were successfully acquired and transferred into data.

    Where This Node Can Run:

    Desktop OS: Windows

    FPGA: Not supported

    Web Server: Not supported in VIs that run in a web application


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