HIL Read Buffer

Reads the number of samples from a combination of input channels of a hardware-in-the-loop card at the specified rate.

Library

Description

The HIL Read Buffer block reads the specified number of samples from a combination of input channels at the given sampling rate. The values read from these channels are output from the block after all the samples have been read. This block is more suited for data acquisition applications, rather than control, because it processes inputs in bulk rather than one sample at a time. If different types of channels are being read it is more efficient to use a single HIL Read Buffer block than multiple buffered I/O blocks specific to each type of channel.

All the channels which will be used as digital inputs must be entered in the Digital input channels field of the Digital Inputs pane in the HIL Initialize block's parameters dialog. Doing so ensures that those channels will be configured as inputs when using a card for which the digital I/O lines are programmable as inputs or outputs. Failure to configure these channels in the Digital input channels field as inputs may result in the HIL Read Buffer block failing to read those inputs.

Input Ports

This block has no input ports.

Output Ports

The number of output ports depends on the Frame-based output parameter. If this option is checked then there is one output for each type of channel (analog, encoder, digital or other) and each output is a frame containing the values read from the channels specified in the corresponding Channels parameter. Otherwise there is one output port for each channel and each port outputs the values read from the corresponding channel. Refer to the documentation on the Frame-based output parameter below for more details. Note that a license for the Signal Processing Blockset from The MathWorks is required in order to use frame-based outputs.

Data Type Support

The HIL Read Buffer block outputs real signals of type double or the analog and other outputs. For encoder inputs, it outputs signals of type int32, uint32 or double, and for digital inputs it outputs signals of any of the standard Simulink data types. See the Signal Data Types pane below for information on how the output data type is determined.

Parameters and Dialog Box

Individual Panes

• Main
• Signal Data Types

Main Pane

The Main pane of the dialog appears as follows:

Board Name

The name of the board whose other channels will be read. Boards are configured using the HIL Initialize block. Place an HIL Initialize block in your diagram to add a board name to the list.

Clock

The clock to use as a basis for sampling the specified channels. In general, both system clocks and hardware clocks specific to the board are supported. This parameter must be a scalar. A positive value indicates a hardware clock. For example, enter 0 for HARDWARE_CLOCK_0, 1 for HARDWARE_CLOCK_1, etc. The number of hardware clocks available depends on the board selected. A negative value indicates a system clock. For example, enter -1 for SYSTEM_CLOCK_1, -2 for SYSTEM_CLOCK_2, etc. The sampling rate for the buffered operation is determined by the Frequency parameter. Refer to Clocks for more information.

Select a board type from the list for board-specific details:

Frequency

The frequency at which to sample the specified channels, in Hertz. Sampling of the channels is done by the driver for the board itself, not by the diagram. As the driver typically executes in kernel mode, this approach minimizes jitter in the samples.

Number of samples

The number of samples to read. One "sample" consists of all of the input channels. Hence, if there are three input channels and five samples requested, then fifteen measurements will be made, with three measurements made each of the five sampling instants.

Analog channels

The analog channels to read. The number of analog channels available depends on the board selected. Refer to Channels for more information.

Select a board type from the list for board-specific details:

Encoder channels

The encoder channels to read. The number of channels available depends on the board selected. Refer to Channels for more information.

Select a board type from the list for board-specific details:

Digital channels

The digital channels to read. The number of channels available depends on the board selected. Refer to Channels for more information.

Select a board type from the list for board-specific details:

Other channels

The other channels to read. The number of channels available depends on the board selected. Refer to Other Channels for more information about other channels in QUARC.

Most boards do not support other channels. Select a board type from the list for board-specific details:

Sample time

The sample time of the block. A sample time of 0 indicates that the block will be treated as a continuous time block. A positive sample time indicates that the block is a discrete time block with the given sample time.

A sample time of -1 indicates that the block inherits its sample time. Since this is a source block, only inherent the sample time when it is placed in a conditionally executed subsystem, like a Triggered or Enabled Subsystem, or in a referenced model.

The default sample time is set to qc_get_step_size, which is a QUARC function that returns the fundamental sampling time of the model. Hence, the default sample time is a discrete sample time with the same sampling time as the fixed step size of the model.

Frame-based output

If this option is checked then the block will have a single frame output for each type of channel (analog, encoder, digital and other) and for each frame there will be one row in the frame for each sample, and one column for each channel. The values read from each channel will appear in the frame in the same order as the channels in the corresponding Channels parameter. Note that a license for the Signal Processing Blockset from The MathWorks is required in order to use frame-based outputs.

If this option is not checked then the block will have one output for each channel. Each output will be a vector containing the measurements for that channel at each sampling instant. The output ports will appear in the same order as the channels in the Channels parameter. Each port will be labeled with the corresponding channel number and a prefix indicating the type of channel.

Signal Data Types Pane

The Signal Data Types pane of the dialog appears as follows:

Output data type mode

Sets the data types of the outputs to be inherited by back propagation or to be specified explicitly in the dialog.

If back propagation is selected then the data types of the outputs will be determined by the blocks to which the outputs are connected. If an output is not connected or it is connected to a block which supports multiple datatypes, then the output data type will be double.

Otherwise the data types of the outputs can be specified explicitly using the Encoder output data type and Digital output data type parameters.

Encoder output data type

Sets the data type of the encoder outputs explicitly.

Digital output data type

Sets the data type of the digital outputs explicitly.

Targets

See Also

• Accessing Hardware
• MATLAB Hardware Functions
• Hardware-in-the-Loop C API

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