Reads the specified number of samples from the encoder input channels and writes the specified number of samples to the PWM output channels at the indicated sampling rate.

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

Syntax

Visual Basic (Declaration)
Public Sub ReadEncoderWritePwmBuffer ( _
	clock As Hil..::.Clock, _
	frequency As Double, _
	numSamples As Integer, _
	inputChannels As Integer(), _
	outputChannels As Integer(), _
	inputBuffer As Integer(), _
	outputBuffer As Double() _
)
C#
public void ReadEncoderWritePwmBuffer(
	Hil..::.Clock clock,
	double frequency,
	int numSamples,
	int[] inputChannels,
	int[] outputChannels,
	int[] inputBuffer,
	double[] outputBuffer
)
Visual C++
public:
void ReadEncoderWritePwmBuffer(
	Hil..::.Clock clock, 
	double frequency, 
	int numSamples, 
	array<int>^ inputChannels, 
	array<int>^ outputChannels, 
	array<int>^ inputBuffer, 
	array<double>^ outputBuffer
)
JavaScript
function readEncoderWritePwmBuffer(clock, frequency, numSamples, inputChannels, outputChannels, inputBuffer, outputBuffer);

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 read from the encoder input channels and write to the PWM output channels. For example, if frequency is set to 1000, then the ReadEncoderWritePwmBuffer method will read all the input channels and write all the output channels every millisecond.

numSamples
Type: System..::.Int32

The number of samples to generate. Each "sample" consists of all the encoder input channels and all the PWM output channels specified. For example, if frequency is set to 1000 and numSamples is set to 5000, then the ReadEncoderWritePwmBuffer method will return after 5 seconds, having read 5000 samples and written 5000 samples. If three input channels have been selected, then the inputBuffer will contain 15,000 elements. If two output channels have been selected, then the outputBuffer must contain 10,000 elements.

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

An array containing the numbers of the encoder input channels from which to read. 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: .

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

An array containing the numbers of the PWM 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: .

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

An array for receiving the count values read from the encoder inputs. The array must contain inputChannels.Length * numSamples elements. The array is organized as a linear array of samples, with each sample consisting of a group of channels. For example, if encoder input channels 0, 1 and 3 are being read, than the data appears in the array as follows, where the numbers correspond to channel numbers:

0 1 3 0 1 3 ...
outputBuffer
Type: array< System..::.Double >[]()[]

An array containing the values to write to the PWM outputs. How these values are interpreted depends on the PWM mode. The PWM mode is configured using the SetPwmMode(array<Int32>[]()[], array<Hil..::.PwmMode>[]()[]) method. The array must contain outputChannels.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 PWM 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 ReadEncoderWritePwmBuffer method reads the specified number of samples from the encoder input channels and writes to the specified PWM output channels at the given sampling rate in a single method call. Each sampling instant, the write operation occurs immediately following the read operation. Since the read-write operation occurs at the lowest level the read and write occur virtually concurrently. The method does not return until all the data has been read and written. This method is particularly useful for system identification since the read and write operations are synchronized. In particular, the value read in one sampling instant is the result of the write operation in the previous sampling instant.

The interpretation of the PWM samples to be written depends upon the PWM mode. Typically the data is interpreted as a duty cycle, in which a magnitude of 0.0 denotes a 0% duty cycle and magnitude of 1.0 indicates a 100% duty cycle. The sign determines the polarity of the output for those boards supporting bidirectional PWM outputs. However, other PWM modes are possible with some boards. Refer to the SetPwmMode(array<Int32>[]()[], array<Hil..::.PwmMode>[]()[]) method for details.

Examples

This example illustrates how to read encoder inputs and write PWM outputs at a specified rate, in one operation. It reads 5000 samples from encoder input channels 0-3 and writes at the same time to PWM output channels 0-1 at 1 kHz. The call to ReadEncoderWritePwmBuffer does not return until all the samples have been read and written, 5 seconds later. One Hertz sine waves are written to the outputs, by varying the duty cycle from 0% to 100% in a sine wave pattern. Unipolar PWM outputs are assumed. Exceptions are ignored for simplicity.
C# Copy Code
int []    inputChannels  = { 0, 1, 2, 3 };
int []    outputChannels = { 0, 1 };
double    frequency      = 1000;
int       samples        = 5000;
int []    inputBuffer    = new int [samples * inputChannels.Length];
double [] outputBuffer   = new double [samples * outputChannels.Length];
double    time;
int       s, c;

for (s = 0; s < samples; s++) {
   time = s / frequency;
   for (c = 0; c < outputChannels.Length; c++) {
       outputBuffer[s * outputChannels.Length + c] = 0.5 + 0.5 * Math.sin(2 * Math.PI * time);
   }
}
   
card.ReadEncoderWritePwmBuffer(Hil.Clock.Hardware0, frequency, samples,
    inputChannels, outputChannels, 
    inputBuffer, outputBuffer);
Visual Basic Copy Code
Dim inputChannels() As Integer = {0, 1, 2, 3}
Dim outputChannels() As Integer = {0, 1}
Dim frequency As Double = 1000
Dim samples As Integer = 5000
Dim inputBuffer(samples * inputChannels.Length - 1) As Integer
Dim outputBuffer(samples * outputChannels.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 outputChannels.Length
       outputBuffer(s * outputChannels.Length + c) = 0.5 + 0.5 * Math.sin(2 * Math.PI * time)
   Next
Next

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

for (s = 0; s < samples; s++) {
   time = s / frequency;
   for (c = 0; c < outputChannels->Length; c++) {
       outputBuffer[s * outputChannels->Length + c] = 0.5 + 0.5 * Math::sin(2 * Math::PI * time);
   }
}
   
card->ReadEncoderWritePwmBuffer(Hil::Clock::Hardware0, frequency, samples,
    inputChannels, outputChannels, 
    inputBuffer, outputBuffer);

Exceptions

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

See Also