DAQmxReadDigitalU8

NI-DAQmx C Functions

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DAQmxReadDigitalU8

int32 DAQmxReadDigitalU8 (TaskHandle taskHandle, int32 numSampsPerChan, float64 timeout, bool32 fillMode, uInt8 readArray[], uInt32 arraySizeInSamps, int32 *sampsPerChanRead, bool32 *reserved);

Purpose

Reads multiple 8-bit integer samples from a task that has one or more multiple digital input channels. Use this function for devices with up to 8 lines per port. The samples are returned in unsigned byte format.

Parameters

Input
Name Type Description
taskHandle TaskHandle The task to write samples to.
numSampsPerChan int32 The number of samples, per channel, to read. The default value of -1 (DAQmx_Val_Auto) reads all available samples. If readArray does not contain enough space, this function returns as many samples as fit in readArray.
NI-DAQmx determines how many samples to read based on whether the task acquires samples continuously or acquires a finite number of samples.
If the task acquires samples continuously and you set this parameter to -1, this function reads all the samples currently available in the buffer.
If the task acquires a finite number of samples and you set this parameter to -1, the function waits for the task to acquire all requested samples, then reads those samples. If you set the Read All Available Samples property to TRUE, the function reads the samples currently available in the buffer and does not wait for the task to acquire all requested samples.
timeout float64 The amount of time, in seconds, to wait for the function to read the sample(s). The default value is 10.0 seconds. To specify an infinite wait, pass -1 (DAQmx_Val_WaitInfinitely). This function returns an error if the timeout elapses.
A value of 0 indicates to try once to read the requested samples. If all the requested samples are read, the function is successful. Otherwise, the function returns a timeout error and returns the samples that were actually read.
fillMode bool32 Specifies whether or not the samples are interleaved.
Value Description
DAQmx_Val_GroupByChannel Group by channel (non-interleaved)
DAQmx_Val_GroupByScanNumber Group by scan number (interleaved)
arraySizeInSamps uInt32 The size of the array, in samples, into which samples are read.
reserved bool32 * Reserved for future use. Pass NULL to this parameter.
Output
Name Type Description
readArray uInt8 [] The array to read samples into, organized according to fillMode.
sampsPerChanRead int32 * The actual number of samples read from each channel.

Return Value

Name Type Description
status int32 The error code returned by the function in the event of an error or warning. A value of 0 indicates success. A positive value indicates a warning. A negative value indicates an error.
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