4. LabVIEW Generation from IDL

While creating a DDS application in LabVIEW, the user must create Topic VIs which map to DDS topic types. In addition to registering a topic, the user neeeds to create DDS Read and DDS Write VIs. LabVIEW data is represented in clusters. The DDS Read and Write VIs have terminals that require a LabVIEW cluster. On data writes, the LabVIEW clusters are converted to DDS topic types and on data reads, the DDS topic types are converted to LabVIEW clusters.

The user can generate the LabVIEW clusters and DDS VIs from an IDL file.

The DDS LabVIEW Integration supports generation of LabVIEW typedefs and VIs from IDL. This chapter describes the details of the IDL-LabVIEW binding.

4.1. Generating LabVIEW VIs from an IDL File IDLPP

DDS Topic Types can be described in an IDL file. The LabVIEW IDL generation is done using the Import_IDL Tools menu in LabVIEW.

Tools/VortexDDS/Import_IDL

In the IDL file, ensure that any topic structures have the OSPL specific annotation pragma keylist defined. This value is added as a keylist constant to the key terminal of the generated RegisterTopic.vi.

Select the IDL file and a folder for the generated VIs.

Upon successful generation the VIs are located in the folder that was chosen. A dialog box appears indicating the path of the generated VIs and the IDL file.

4.2. Generated Artifacts

The following table defines the LabVIEW artifacts generated from IDL concepts:

IDL Concept	LabVIEW Concept	Comment
module		Appended to the name of each VI contained in the module
enum	enum	a LabVIEW .ctl file.
enum value	enum value
struct	cluster	a LabVIEW .ctl file.
field	cluster field
sequence	array
array	array

Datatype mappings

The following table shows the LabVIEW equivalents to IDL primitive types:

DDS IDL	LabVIEW Type
boolean	Boolean
char	int8
octet	uint8
short	int16
unsigned short	uint16
long	int32
unsigned long	uint32
long long	int64
unsigned long long	uint64
float	single-precision floating point
double	double-precision floating point
string	String
Unsupported DDS data types
wchar	not supported
wstring	not supported
any	not supported
long double	not supported
union	not supported
inheritance	not supported

Generated VIs and controls

For each struct in the IDL file, the following VIs and controls are generated:

• RegisterTopic.vi

• Write.vi

• Read.vi

• CicoTable.vi (Copy-in copy-out)

• Topic cluster.ctl (corresponds to each struct in IDL File)

• Enum.ctl (corresponds to each enum in IDL File)

The “moduleName_structName” is appended to the name of each VI and control that is generated.

4.3. RegisterTopic.vi

The RegisterTopic.vi represents a DDS topic type. The DDS topic corresponds to a single data type. In DDS, data is distributed by publishing and subscribing topic data samples.

Terminal Type	Optional	Name	Description	Output consumed by
Input	no	DomainParticipantHandle	DDS Domain Participant entity instance
Input	no	TopicName	DDS Topic Name
Input	yes	QosProfilePath	QoS file uri
Input	yes	QoSProfileName	Name of QoS profile
Input	yes	error in (no error)	Input Error cluster
Output	no	topicHandle	DDS Topic entity instance	create_reader.vi create_writer.vi
Output	yes	error out	Error out cluster

4.4. Read.vi

The DDS Read.vi is used to read DDS samples from a specific topic.

Terminal Type	Optional	Name	Description	Output consumed by
Input	no	readerHandle	DDS Reader entity instance
Input	yes	mask	read_condition masks LabVIEW cluster
Input	yes	max_samples	maximum number of samples to read
Input	yes	read_operation	READ or TAKE default operation is TAKE
Input	yes	query_expression	expression to filter samples based on a query
Input	yes	query_parameters	parameters for the query expression
Input	yes	wait_available_data _timeout	wait for data available timeout (seconds)
Input	yes	error in (no error)	Input Error cluster
Output	yes	no_of_samples	Number of samples read	user
Output	no	samples	LabVIEW cluster	user
Output	yes	dds_sample_info_array	sample information	user
Output	yes	error out	Error out cluster

4.4.1. Filters

The filtering of incoming samples can happen based on a query and/or on a sample read condition(s).

Query

query_expression: The expression is a SQL condition.

query_parameters: Each parameter element must be an array element.

Note: Query expressions are only validated at runtime. If they are incorrect, errors will occur while running the VI.

Read Condition

The read condition mask specified will filter the samples that are read or take(n).

Example: For a reader, the Sample State has Not Read selected and Read deselected.

Only samples with a Sample State Not Read will be processed with read or take. Any samples with the Read sample state will not be read or take(n).

4.5. Write.vi

The DDS Write.vi is used to write DDS samples to a specific topic.

Terminal Type	Optional	Name	Description	Output consumed by
Input	no	writerHandle	DDS Writer entity instance
Input	yes	write_op	write operation: WRITE, DISPOSE, WRITE_DISPOSE Default operation: WRITE
Input	no	data	samples LabVIEW cluster	DDS
Input	yes	wait_pub_matched _timeout	wait for publication matched timeout (seconds)
Input	yes	write_after_timeout	write samples after timeout
Input	yes	error in (no error)	Input Error cluster
Output	yes	error out	Error out cluster