Writes the specified number of samples to the digital channels at the indicated sampling rate.

Namespace:  Quanser.Hardware
Assembly:  Quanser.Hardware.Hil (in Quanser.Hardware.Hil.dll)

Syntax

Visual Basic (Declaration)
Public Sub WriteDigitalBuffer ( _
	clock As Hil..::.Clock, _
	frequency As Double, _
	numSamples As Integer, _
	channels As Integer(), _
	buffer As SByte() _
)
C#
public void WriteDigitalBuffer(
	Hil..::.Clock clock,
	double frequency,
	int numSamples,
	int[] channels,
	sbyte[] buffer
)
Visual C++
public:
void WriteDigitalBuffer(
	Hil..::.Clock clock, 
	double frequency, 
	int numSamples, 
	array<int>^ channels, 
	array<signed char>^ buffer
)
JavaScript
function writeDigitalBuffer(clock, frequency, numSamples, channels, buffer);

Parameters

clock
Type: Quanser.Hardware..::.Hil..::.Clock

The clock used to time the operation. Note that some clocks allow faster sampling rates than others. See the Hil..::.Clock enumeration for more information on clocks.

Select a board type to the list for board-specific details: .

frequency
Type: System..::.Double

The frequency in Hertz at which to write to the digital output channels. For example, if frequency is set to 1000, then the WriteDigitalBuffer method will write all the selected channels every millisecond.

numSamples
Type: System..::.Int32

The number of samples to generate. Each "sample" consists of all the digital output channels specified. For example, if frequency is set to 1000 and numSamples is set to 5000, then the WriteDigitalBuffer method will return after 5 seconds, having written 5000 samples. If 3 channels have been selected, then the buffer must therefore contain 15,000 elements.

channels
Type: array< System..::.Int32 >[]()[]

An array containing the numbers of the digital output channels to which to write. Channel numbers are zero-based. Thus, channel 0 is the first channel, channel 1 the second channel, etc.

Select a board type to the list for board-specific details: .

buffer
Type: array< System..::.SByte >[]()[]

An array containing the binary values to write to the digital outputs. The array must contain channels.Length * numSamples elements. The array must be organized as a linear array of samples, with each sample consisting of a group of channels. For example, if digital output channels 0, 1 and 3 are being written, than the data must appear in the array as follows, where the numbers correspond to channel numbers:

0 1 3 0 1 3 ...

Remarks

The WriteDigitalBuffer method writes the specified number of samples to the digital channels at the given sampling frequency. This method does not return until all the data has been written.

Warning

Many cards allow the digital I/O lines to be programmed as inputs or outputs. The digital I/O lines are configured as inputs or outputs using the SetDigitalDirections(array<Int32>[]()[], array<Int32>[]()[]) method. All the channels which will be used as digital inputs or outputs must be configured accordingly using this function. Failure to configure the digital I/O may result in the WriteDigitalBuffer(Hil..::.Clock, Double, Int32, array<Int32>[]()[], array<SByte>[]()[]) method failing to write the digital I/O as expected.

Examples

This example illustrates how to write digital outputs at a specified rate. It writes 5000 samples to digital channels 0-3 at 1 kHz. The call to WriteDigitalBuffer does not return until all the samples have been written, 5 seconds later. Square waves of differing frequencies are written to the outputs. Exceptions are ignored for simplicity.
C# Copy Code
int []    channels  = { 0, 1, 2, 3 };
double    frequency = 1000;
int       samples   = 5000;
double [] buffer    = new double [samples * channels.Length];
int       s, c;

for (s = 0; s < samples; s++) {
   for (c = 0; c < channels.Length; c++) {
       buffer[s * channels.Length + c] = (s % (c + 2)) >= (c + 2)/2;
   }
}
   
card.WriteDigitalBuffer(Hil.Clock.Hardware0, frequency, samples, channels, buffer);
Visual Basic Copy Code
Dim channels() As Integer = {0, 1, 2, 3}
Dim frequency As Double = 1000
Dim samples As Integer = 5000
Dim buffer(samples * channels.Length - 1) As Double
Dim time As Double
Dim s As Integer
Dim c As Integer

For s = 0 To samples
   time = s / frequency
   For c = 0 To channels.Length
       buffer(s * channels.Length + c) = (s Mod (c + 2)) >= (c + 2)/2
   Next
Next

card.WriteDigitalBuffer(Hil.Clock.Hardware0, frequency, samples, channels, buffer)
Visual C++ Copy Code
array<int>^    channels  = { 0, 1, 2, 3 };
double         frequency = 1000;
int            samples   = 5000;
array<double>^ buffer    = gcnew array<double>(samples * channels->Length);
double         time;
int            s, c;

for (s = 0; s < samples; s++) {
   time = s / frequency;
   for (c = 0; c < channels->Length; c++) {
       buffer[s * channels->Length + c] = (s % (c + 2)) >= (c + 2)/2;
   }
}
   
card->WriteDigitalBuffer(Hil::Clock::Hardware0, frequency, samples, channels, buffer);

Exceptions

ExceptionCondition
Quanser.Hardware..::.HilException If the write cannot be performed then an exception is thrown. This situtation typically arises if the board does not support digital outputs or the hardware resources required are in use by a task.

See Also