Read Waveform (WDT)
- Updated2023-02-17
- 4 minute(s) read
Read Waveform (WDT)
Returns the acquired waveform data from the subset of channels listed in the channel list parameter as a waveform data type.
The waveform only contains data from the subset of channels specified in the channel list parameter, not from all of the channels listed in the Assign Dynamic Channelsnode, unless you leave the channel list parameter blank.
Inputs/Outputs
session in
Instrument session obtained from the Initialize Acquisition Sessionnode, the Initialize Generation Sessionnode, or the Initialize External Calibrationnode.
timestamp type
Parameter that specifies whether the timestamp for the waveform data is relative or absolute.
channel list
The specified channels from which to read waveform data.
You must assign all channels that you want to read using the niHSDIO Assign Dynamic Channelsnode before selecting those channels with this parameter.
NI-HSDIO reads waveform data in the order that you list channels in this parameter, not in the order that those channels are listed in the niHSDIO Assign Dynamic Channelsnode. If you leave this parameter blank, NI-HSDIO reads all channels that were set using the niHSDIO Assign Dynamic Channelsnode.
Specify multiple channels 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 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 channels 0, 1, and 2).
samples to read
The specified number of samples to fetch.
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 Sizenode.
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 value: 10000
record to fetch
Parameter that specifies which record you want to fetch from onboard memory.
error in
Error conditions that occur before this node runs.
The node responds to this input according to standard error behavior.
Default value: No error
session out
Handle that identifies the session in all subsequent node calls.
The session out parameter is obtained from the Initialize Acquisition Sessionnode or the Initialize Generation Sessionnode.
data
The returned acquired waveform.
number of samples read
The number of samples that were successfully acquired and transferred into data.
error out
Error information.
The node produces this output according to standard error behavior.