DAQmx Read Properties
Use the DAQmx Read properties to configure read operations, such as from what position in a buffer you want to read, and to query the current status of read operations.
| Property | Description |
|---|---|
| RelativeTo | Specifies the point in the buffer at which to begin a read operation. If you also specify an offset with Offset, the read operation begins at that offset relative to the point you select with this property. The default value is Current Read Position unless you configure a Reference Trigger for the task. If you configure a Reference Trigger, the default value is First Pretrigger Sample. Details |
| Offset | Specifies an offset in samples per channel at which to begin a read operation. This offset is relative to the location you specify with RelativeTo. Details |
| Channels to Read | Specifies a subset of channels in the task from which to read. Details |
| Waveform Attributes | Specifies the waveform data type attributes to return. Returning fewer attributes increases performance. Details |
| Read All Available Samples | Specifies whether subsequent read operations read all samples currently available in the buffer or wait for the buffer to become full before reading. NI-DAQmx uses this setting for finite acquisitions and only when the number of samples to read is -1. For continuous acquisitions when the number of samples to read is -1, a read operation always reads all samples currently available in the buffer. Details |
| Auto Start | Specifies if DAQmx Read automatically starts the task if you did not start the task explicitly by using DAQmx Start Task. The default value is TRUE. When DAQmx Read starts a finite acquisition task, it also stops the task after reading the last sample. Details |
| OverWrite Mode | Specifies whether to overwrite samples in the buffer that you have not yet read. Details |
| Status:Current Read Position | Indicates in samples per channel the current position in the buffer. Details |
| Status:Available Samples Per Channel | Indicates the number of samples available to read per channel. This value is the same for all channels in the task. Details |
| Status:Total Samples Per Channel Acquired | Indicates the total number of samples acquired by each channel. NI-DAQmx returns a single value because this value is the same for all channels. Details |
| Status:Overcurrent:Overcurrent Channels Exist | Indicates if the device(s) detected an overcurrent condition for any virtual channel in the task. Reading this property clears the overcurrent status for all channels in the task. You must read this property before you read OvercurrentChans. Otherwise, you will receive an error. Details |
| Status:Overcurrent:Overcurrent Channels | Indicates the names of any virtual channels in the task for which an overcurrent condition has been detected. You must read OvercurrentChansExist before you read this property. Otherwise, you will receive an error. On some devices, you must restart the task for all overcurrent channels to recover. Details |
| Status:Open Current Loop:Open Current Loop Channels Exist | Indicates if the device(s) detected an open current loop for any virtual channel in the task. Reading this property clears the open current loop status for all channels in the task. You must read this property before you read OpenCurrentLoopChans. Otherwise, you will receive an error. Details |
| Status:Open Current Loop:Open Current Loop Channels | Indicates the names of any virtual channels in the task for which the device(s) detected an open current loop. You must read OpenCurrentLoopChansExist before you read this property. Otherwise, you will receive an error. Details |
| Status:Overload:Overloaded Channels Exist | Indicates if the device(s) detected an overload in any virtual channel in the task. Reading this property clears the overload status for all channels in the task. You must read this property before you read OverloadedChans. Otherwise, you will receive an error. Details |
| Status:Overload:Overloaded Channels | Indicates the names of any overloaded virtual channels in the task. You must read OverloadedChansExist before you read this property. Otherwise, you will receive an error. Details |
| Status:Advanced:ChangeDetection:Overflowed | Indicates if samples were missed because change detection events occurred faster than the device could handle them. Some devices detect overflows differently than others. Details |
| Advanced:Raw Data Width | Indicates in bytes the size of a raw sample from the task. Details |
| Advanced:Number of Channels | Indicates the number of channels that DAQmx Read reads from the task. This value is the number of channels in the task or the number of channels you specify with ChannelsToRead. Details |
| Advanced:Digital Input:Number of Booleans Per Channel | Indicates the number of Booleans per channel that NI-DAQmx returns in a sample for line-based reads. If a channel has fewer lines than this number, the extra Booleans are FALSE. Details |
| Advanced:Wait Mode | Specifies how DAQmx Read waits for samples to become available. Details |
| Advanced:Sleep Time | Specifies in seconds the amount of time to sleep after checking for available samples if WaitMode is Sleep. Details |