Patent Application
20080126956
The present invention relates to the field of graphical programming, and more particularly to a system and method for asynchronous communication in a graphical program.
Traditionally, high-level text-based programming languages have been used by programmers in writing application programs. Many different high level text-based programming languages exist, including BASIC, C, C++, Java, FORTRAN, Pascal, COBOL, ADA, APL, etc. Programs written in these high level text-based languages are translated to the machine language level by translators known as compilers or interpreters. The high level text-based programming languages in this level, as well as the assembly language level, are referred to herein as text-based programming environments.
Increasingly, computers are required to be used and programmed by those who are not highly trained in computer programming techniques. When traditional text-based programming environments are used, the user's programming skills and ability to interact with the computer system often become a limiting factor in the achievement of optimal utilization of the computer system.
There are numerous subtle complexities which a user must master before he can efficiently program a computer system in a text-based environment. The task of programming a computer system to model or implement a process often is further complicated by the fact that a sequence of mathematical formulas, steps or other procedures customarily used to conceptually model a process often does not closely correspond to the traditional text-based programming techniques used to program a computer system to model such a process. In other words, the requirement that a user program in a text-based programming environment places a level of abstraction between the user's conceptualization of the solution and the implementation of a method that accomplishes this solution in a computer program. Thus, a user often must substantially master different skills in order to both conceptualize a problem or process and then to program a computer to implement a solution to the problem or process. Since a user often is not fully proficient in techniques for programming a computer system in a text-based environment to implement his solution, the efficiency with which the computer system can be utilized often is reduced.
To overcome the above shortcomings, various graphical programming environments now exist which allow a user to construct a graphical program or graphical diagram, also referred to as a block diagram. U.S. Pat. Nos. 4,901,221; 4,914,568; 5,291,587; 5,301,301; and 5,301,336; among others, to Kodosky et al disclose a graphical programming environment which enables a user to easily and intuitively create a graphical program. Graphical programming environments such as that disclosed in Kodosky et al can be considered a higher and more intuitive way in which to interact with a computer. A graphically based programming environment can be represented at a level above text-based high level programming languages such as C, Basic, Java, etc.
A user may assemble a graphical program by selecting various icons or nodes which represent desired functionality, and then connecting the nodes together to create the program. The nodes or icons may be connected by lines, referred to as “wires”, representing data flow between the nodes, control flow, or execution flow. Thus the block diagram may include a plurality of interconnected icons such that the diagram created graphically displays a procedure or method for accomplishing a certain result, such as manipulating one or more input variables and/or producing one or more output variables. In response to the user constructing a diagram or graphical program using the block diagram editor, data structures and/or program instructions may be automatically constructed which characterize an execution procedure that corresponds to the displayed procedure. The graphical program may be compiled or interpreted by a computer.
A graphical program may have a graphical user interface. For example, in creating a graphical program, a user may create a front panel or user interface panel. The front panel may include various graphical user interface elements or front panel objects, such as user interface controls and/or indicators, that represent or display the respective input and output that will be used by the graphical program, and may include other icons which represent devices being controlled.
Thus, graphical programming has become a powerful tool available to programmers. Graphical programming environments such as the National Instruments LabVIEW product have become very popular. Tools such as LabVIEW have greatly increased the productivity of programmers, and increasing numbers of programmers are using graphical programming environments to develop their software applications. In particular, graphical programming tools are being used for test and measurement, data acquisition, process control, man machine interface (MMI), supervisory control and data acquisition (SCADA) applications, modeling, simulation, image processing/machine vision applications, and motion control, among others. Graphical programs may be referred to herein as “virtual instruments” (VIs), and nodes that represent graphical programs or graphical subroutines may be referred to as sub-VIs.
However, in data flow based graphical programs, the wires used to communicate between graphical program nodes (which may themselves be or represent graphical programs) are subject to data flow rules or protocols. For example, in graphical programs that are data flow diagrams, a node will not execute or “fire” until all data inputs to the node are present, and thus communication between nodes via current data flow wires is constrained to be synchronous, which may limit the functionality and execution of graphical programs, especially those that include multiple (substantially) concurrently executing portions, e.g., nodes, VIs, sub-VIs, or other graphical program elements or constructs, which may be referred to herein generally as nodes. In some prior art approaches to asynchronous communication between nodes, variables, such as local or global variables, or queues, may be used to pass data back and forth between the nodes. For example, applications that include communicating concurrent loops typically require queues or global variables to transfer data between the loops. However, there is currently no graphical way of depicting this connection, and moreover, it is not very convenient to construct. For example, using global variables only provides the name association, and using built-in queues involves a non-intuitive construction where the queue is allocated at the top level diagram and the reference is passed down both to the writer and to the reader.
As may be seen, there is no explicit indication of the variable-based means for communicating between the while loops, and so, for program nodes, elements, etc., that are not placed near one another, it may not be clear that such communication is occurring or accommodated, possibly leading to confusion, and/or programming or operational errors.
Thus, improved means for asynchronous communications between graphical program nodes are desired.
Various embodiments of a system and method for enabling asynchronous communications in a graphical program are described. A first node and a second node may be displayed in a graphical program, where the graphical program includes a plurality of interconnected nodes that visually indicate functionality of the graphical program. Each of the first and second nodes preferably has a respective functionality, and includes a respective terminal. In other words, each node may include a terminal for connecting or wiring the node to another graphical program element, such as another node, for sending and/or receiving data to and/or from the other node. The graphical program may implement a measurement function that is desired to be performed, e.g., by one or more instruments. In other embodiments, the graphical program may implement other types of functions, e.g., control, automation, simulation, and so forth, as desired.
An asynchronous wire may be included in the graphical program, where the asynchronous wire connects the first node and the second node via their respective terminals. In other words, a first end of the asynchronous wire may be connected to the terminal of the first node, and a second end of the asynchronous wire may be connected to the terminal of the second node. For example, in one embodiment, the nodes may be specified or intended respectively as source and sink nodes with respect to communication between the nodes. However, it should be noted that in other embodiments, the asynchronous wire may facilitate or implement two-way communication between the nodes, i.e., from the first node to the second and from the second node to the first.
The asynchronous wire may be configured for asynchronous communication between the first and second nodes. For example, various attributes of the asynchronous wire may be configured or set to facilitate asynchronous communication between the first node and the second node. In one embodiment, these attributes may include one or more of: a data structure type included in or used by the wire, e.g., a first in first out (FIFO) queue; a buffer size for the asynchronous wire; read policy, e.g., block reads if the buffer is empty or uninitialized, remove the element upon a read from the buffer (e.g., destructive/non-destructive reads), read chunk size, etc.; write policy, e.g., block all writes to the buffer if the buffer is full, overwrite if the buffer is full or always, write chunk size, etc.; initial value on the wire; directionality of the asynchronous wire; and semantics of wire splits, i.e., how branching of the wire may affect communications using the wire, among others. Note that the various policies specified for use of the asynchronous wire may accommodate various models of computation (MoC) for the graphical program, including, for example, Kahn Process Networks (PN) and Communicating Sequential Processes (CSP), among others.
In some embodiments, the asynchronous wire may have a default configuration, i.e., one or more of the attributes may be preset with default values. Thus, the configuration of the asynchronous wire (at least with respect to the default valued attributes) may effectively occur when the wire is included in the block diagram of the graphical program. Of course, even were some or all of the attributes to have default values, subsequent configuration of the asynchronous wire, e.g., by the user or by another process, may overwrite these default values with new values. In other words, configuring the asynchronous wire may include overwriting at least one of the default values for the one or more attributes of the asynchronous wire with a respective at least one new value.
In one embodiment, a user may be able to configure a terminal on a node to be “asynchronous”, after which wires connected to this terminal may have asynchronous behavior. In other words, connecting a wire to an asynchronous terminal may automatically invoke creation or instantiation of an asynchronous wire, e.g., via conversion of a normal “synchronous” wire to the asynchronous wire, or replacement of the normal wire with the asynchronous wire. Users may then click on the asynchronous wire and configure its run-time behavior, such as the size of the queue and the read/write policies (blocking/non-blocking, destructive/non-destructive reads), as described above. In other words, once a terminal of a node is configured to be asynchronous, any wire connected to that terminal may automatically be configured as an asynchronous wire.
In one embodiment, the asynchronous wire and/or the terminal(s) may be configured via invocation of a graphical user interface (GUI), e.g., one or more dialogs, menus, property pages, attribute nodes, etc., e.g., by the user right-clicking on the asynchronous wire or terminal. The user may then select or input values for various attributes of the asynchronous wire or terminal. Alternatively, or additionally, the asynchronous wire and/or the terminal(s) may be configured via input from another process, such as a graphical program generation program or wizard. For example, in the case of a wizard, the user may provide input to various panels or dialogs specifying the attributes. Thus, in various embodiments, configuration information for the asynchronous wire and/or the node terminals may be provided by a use via a GUI, and/or programmatically by another process, e.g., another program.
The graphical program may then be executed. In preferred embodiments, executing the graphical program includes executing the first and second nodes, where the first and second nodes communicate asynchronously during the execution of the first and second nodes.
Thus, the asynchronous wire may allow users to create a static connection between nodes in a graphical program (e.g., a block diagram of the graphical program) to facilitate asynchronous communication between the nodes. In some embodiments, this connection may be depicted as a special, asynchronous, wire with a specific graphical appearance. For example, in one embodiment, the asynchronous wire may have a 3D tube-like appearance, although any other appearance may be used as desired. In some embodiments, the directionality of the asynchronous wire may also be indicated, e.g., via an arrow or multiple arrows, displayed on or near the asynchronous wire.
Note that in preferred embodiments, an asynchronous wire does not explicitly carry data at run-time, and so it may not be considered as part of the data flow graph (of the graphical program). This means that its fire count (i.e., iterative execution count) may be ignored at run-time and that it may not use explicit tunneling to cross structures. Instead the asynchronous wire may visually “float” over structure boundaries, e.g., over the boundaries of loop nodes.
In one embodiment, asynchronous wires may be evaluated during a type propagation phase, e.g., at compile time. This wire evaluation may be performed as a part of the type propagation phase, e.g., in the LabVIEW development system. In this phase the diagram may be traversed and logically executed by type (not by value), so that it is possible to compute the types of all wires and terminals, and thus to type-check the diagram. For example, constant folding may be used to propagate constant values from the source of an asynchronous wire to its sink. In this approach, as a part of type propagation, the values of constants are evaluated as far as possible on the diagram. This allows the elimination of dead code, such as unreachable cases in a case statement. This may allow the end points to share static entities such as block diagram constants and constant references, such as references to a VI instance. At run-time this may result in a connection between source and sink that does not obey standard (e.g., LabVIEW) data-flow rules.
For example, a source and sink in a graphical program may be connected through an asynchronous wire that may carry a string constant used to access a common, named queue, which is a FIFO data structure. Note that a significant difference between a traditional LabVIEW wire and the asynchronous wire connection between the source and sink is that there is no data flow dependency between them in the latter case, and so the two graphical program nodes can run in parallel, while exchanging data. In other words, the asynchronous wire is a new type of wire with different semantics, where, in particular, there is not the normal data flow dependency between nodes connected with an asynchronous wire, and in fact, nodes connected by such a wire are actually supposed to run in parallel, as opposed to serially when connected with a regular wire. Note that in general, it would be an error to connect two nodes with both a regular wire and an asynchronous wire. Note further that asynchronous wires may be allowed to create cycles in a graphical program, e.g., in a LabVIEW graph, since doing so may not introduce a danger of deadlock or undefined behavior at run-time. Additionally, in some embodiments, multiple sources on asynchronous wires may be facilitated. Similarly, in some embodiments, multiple sinks on asynchronous wires may be allowed.
The asynchronous wire may be denoted by a type attribute (and so behaviorally polymorphic nodes may be possible), namely, a typedef with a special name. In other words, asynchronous wires may have a data type, and so may benefit from the many uses of such typing, as is well known to those of skill in the programming arts, e.g., polymorphism and type checking, among others.
It should be noted that while the example uses of asynchronous wires described herein are within a single program, in other embodiments, asynchronous wires may be used to connect different programs, e.g., to connect nodes that are comprised in different respective graphical programs. Moreover, in some embodiments, the different programs may be even running on different processors or programmable hardware elements, such as field programmable gate arrays (FPGAs).
In preferred embodiments, the asynchronous wires may each be implemented by a respective graphical program. In other words, the functionality of an asynchronous wire may be provided by an associated graphical program. More specifically, each asynchronous wire may use, be associated with, or represent, an instance of a graphical program, which, for brevity, may be referred to simply as a graphical program. Thus, multiple asynchronous wires may each utilize or have a respective instance of the same graphical program. The graphical program for each asynchronous wire may be configured to implement and enforce the various communication policies of the wire, e.g., read and write policies, as discussed above. Thus, each instance of the graphical program may be configured for the particular behavior desired for the respective asynchronous wire. Note that since graphical programs may store and maintain state information, the data transmitted on or by the asynchronous wire may also be included in or implemented by the graphical program. Note also that the graphical program associated with an asynchronous wire may not generally be visible to the user, i.e., may be hidden, although of course, means may be provided for displaying the graphical program of an asynchronous wire for development purposes.
Since the endpoints of an asynchronous wire may share a common, static reference to a VI instance it may be possible to implement a wide variety of run-time connections between the endpoints, thus allowing custom run-time behavior of a node. For example, in various embodiments, some of the possible behaviors of an asynchronous wire may include: implementing queues of various kinds, including FPGA FIFOs and RT (real time) FIFOs; single element communication (e.g., anonymous global variables); synchronization primitives, such as notifiers, semaphores, rendesvous and occurrences; and expressing a connection to and from a part of a diagram that is being executed on a remote target, e.g., “roping in” of a piece of a diagram so that it can execute on the remote target in conjunction with local execution of the remainder of the diagram.
In some embodiments, an asynchronous wire may not be limited to propagating information from terminal sources to terminal sinks. In other words, in some embodiments, the asynchronous wire (and possibly the terminals of the connected nodes) may be configured to transmit data in either direction or in both directions. In other words, in some embodiments and configurations, the asynchronous wire may facilitate two-way communications between the connected nodes. For example, in one embodiment, a dual queue may be used to facilitate such two-way communications, where one queue is used for a first direction, and another queue is used for a second direction, although any other data structures and techniques may be used as desired.
Thus, various embodiments of the asynchronous wire(s) described herein may facilitate asynchronous communications between nodes in a graphical program, or between graphical programs.
A better understanding of the present invention can be obtained when the following detailed description of the preferred embodiment is considered in conjunction with the following drawings, in which:
While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the present invention as defined by the appended claims.
The following references are hereby incorporated by reference in their entirety as though fully and completely set forth herein:
U.S. Pat. No. 4,914,568 titled “Graphical System for Modeling a Process and Associated Method,” issued on Apr. 3, 1990.
U.S. Pat. No. 5,481,741 titled “Method and Apparatus for Providing Attribute Nodes in a Graphical Data Flow Environment”.
U.S. Pat. No. 6,173,438 titled “Embedded Graphical Programming System” filed Aug. 18, 1997.
U.S. Pat. No. 6,219,628 titled “System and Method for Configuring an Instrument to Perform Measurement Functions Utilizing Conversion of Graphical Programs into Hardware Implementations,” filed Aug. 18, 1997.
U.S. Patent Application Publication No. 20010020291 (Ser. No. 09/745,023) titled “System and Method for Programmatically Generating a Graphical Program in Response to Program Information,” filed Dec. 20, 2000.
The following is a glossary of terms used in the present application:
Memory Medium—Any of various types of memory devices or storage devices. The term “memory medium” is intended to include an installation medium, e.g., a CD-ROM, floppy disks 104, or tape device; a computer system memory or random access memory such as DRAM, DDR RAM, SRAM, EDO RAM, Rambus RAM, etc.; or a non-volatile memory such as a magnetic media, e.g., a hard drive, or optical storage. The memory medium may comprise other types of memory as well, or combinations thereof. In addition, the memory medium may be located in a first computer in which the programs are executed, or may be located in a second different computer which connects to the first computer over a network, such as the Internet. In the latter instance, the second computer may provide program instructions to the first computer for execution. The term “memory medium” may include two or more memory mediums which may reside in different locations, e.g., in different computers that are connected over a network.
Carrier Medium—a memory medium as described above, as well as signals such as electrical, electromagnetic, or digital signals, conveyed via a communication medium such as a bus, network and/or a wireless link.
Programmable Hardware Element—includes various types of programmable hardware, reconfigurable hardware, programmable logic, or field-programmable devices (FPDs), such as one or more FPGAs (Field Programmable Gate Arrays), or one or more PLDs (Programmable Logic Devices), such as one or more Simple PLDs (SPLDs) or one or more Complex PLDs (CPLDs), or other types of programmable hardware. A programmable hardware element may also be referred to as “reconfigurable logic”.
Medium—includes one or more of a memory medium, carrier medium, and/or programmable hardware element; encompasses various types of mediums that can either store program instructions/data structures or can be configured with a hardware configuration program. For example, a medium that is “configured to perform a function or implement a software object” may be 1) a memory medium or carrier medium that stores program instructions, such that the program instructions are executable by a processor to perform the function or implement the software object; 2) a medium carrying signals that are involved with performing the function or implementing the software object; and/or 3) a programmable hardware element configured with a hardware configuration program to perform the function or implement the software object.
Program—the term “program” is intended to have the full breadth of its ordinary meaning. The term “program” includes 1) a software program which may be stored in a memory and is executable by a processor or 2) a hardware configuration program useable for configuring a programmable hardware element.
Software Program—the term “software program” is intended to have the full breadth of its ordinary meaning, and includes any type of program instructions, code, script and/or data, or combinations thereof, that may be stored in a memory medium and executed by a processor. Exemplary software programs include programs written in text-based programming languages, such as C, C++, Pascal, Fortran, Cobol, Java, assembly language, etc.; graphical programs (programs written in graphical programming languages); assembly language programs; programs that have been compiled to machine language; scripts; and other types of executable software. A software program may comprise two or more software programs that interoperate in some manner.
Hardware Configuration Program—a program, e.g., a netlist or bit file, that can be used to program or configure a programmable hardware element.
Graphical Program—A program comprising a plurality of interconnected nodes or icons, wherein the plurality of interconnected nodes or icons visually indicate functionality of the program.
The following provides examples of various aspects of graphical programs. The following examples and discussion are not intended to limit the above definition of graphical program, but rather provide examples of what the term “graphical program” encompasses:
The nodes in a graphical program may be connected in one or more of a data flow, control flow, and/or execution flow format. The nodes may also be connected in a “signal flow” format, which is a subset of data flow.
Exemplary graphical program development environments which may be used to create graphical programs include LabVIEW, DasyLab, DiaDem and Matrixx/SystemBuild from National Instruments, Simulink from the MathWorks, VEE from Agilent, WiT from Coreco, Vision Program Manager from PPT Vision, SoftWIRE from Measurement Computing, Sanscript from Northwoods Software, Khoros from Khoral Research, SnapMaster from HEM Data, VisSim from Visual Solutions, ObjectBench by SES (Scientific and Engineering Software), and VisiDAQ from Advantech, among others.
The term “graphical program” includes models or block diagrams created in graphical modeling environments, wherein the model or block diagram comprises interconnected nodes or icons that visually indicate operation of the model or block diagram; exemplary graphical modeling environments include Simulink, SystemBuild, VisSim, Hypersignal Block Diagram, etc.
A graphical program may be represented in the memory of the computer system as data structures and/or program instructions. The graphical program, e.g., these data structures and/or program instructions, may be compiled or interpreted to produce machine language that accomplishes the desired method or process as shown in the graphical program.
Input data to a graphical program may be received from any of various sources, such as from a device, unit under test, a process being measured or controlled, another computer program, a database, or from a file. Also, a user may input data to a graphical program or virtual instrument using a graphical user interface, e.g., a front panel.
A graphical program may optionally have a GUI associated with the graphical program. In this case, the plurality of interconnected nodes are often referred to as the block diagram portion of the graphical program.
Node—In the context of a graphical program, an element that may be included in a graphical program. A node may have an associated icon that represents the node in the graphical program, as well as underlying code or data that implements functionality of the node. Exemplary nodes include function nodes, terminal nodes, structure nodes, etc. Nodes may be connected together in a graphical program by connection icons or wires.
Data Flow Graphical Program (or Data Flow Diagram)—A graphical program or diagram comprising a plurality of interconnected nodes, wherein the connections between the nodes indicate that data produced by one node is used by another node.
Graphical User Interface—this term is intended to have the full breadth of its ordinary meaning. The term “Graphical User Interface” is often abbreviated to “GUI”. A GUI may comprise only one or more input GUI elements, only one or more output GUI elements, or both input and output GUI elements.
The following provides examples of various aspects of GUIs. The following examples and discussion are not intended to limit the ordinary meaning of GUI, but rather provide examples of what the term “graphical user interface” encompasses:
A GUI may comprise a single window having one or more GUI Elements, or may comprise a plurality of individual GUI Elements (or individual windows each having one or more GUI Elements), wherein the individual GUI Elements or windows may optionally be tiled together.
A GUI may be associated with a graphical program. In this instance, various mechanisms may be used to connect GUI Elements in the GUI with nodes in the graphical program. For example, when Input Controls and Output Indicators are created in the GUI, corresponding nodes (e.g., terminals) may be automatically created in the graphical program or block diagram. Alternatively, the user can place terminal nodes in the block diagram which may cause the display of corresponding GUI Elements front panel objects in the GUI, either at edit time or later at run time. As another example, the GUI may comprise GUI Elements embedded in the block diagram portion of the graphical program.
Front Panel—A Graphical User Interface that includes input controls and output indicators, and which enables a user to interactively control or manipulate the input being provided to a program, and view output of the program, while the program is executing.
A front panel is a type of GUI. A front panel may be associated with a graphical program as described above.
In an instrumentation application, the front panel can be analogized to the front panel of an instrument. In an industrial automation application the front panel can be analogized to the MMI (Man Machine Interface) of a device. The user may adjust the controls on the front panel to affect the input and view the output on the respective indicators.
Graphical User Interface Element—an element of a graphical user interface, such as for providing input or displaying output. Exemplary graphical user interface elements comprise input controls and output indicators
Input Control—a graphical user interface element for providing user input to a program. Exemplary input controls comprise dials, knobs, sliders, input text boxes, etc.
Output Indicator—a graphical user interface element for displaying output from a program. Exemplary output indicators include charts, graphs, gauges, output text boxes, numeric displays, etc. An output indicator is sometimes referred to as an “output control”.
Computer System—any of various types of computing or processing systems, including a personal computer system (PC), mainframe computer system, workstation, network appliance, Internet appliance, personal digital assistant (PDA), television system, grid computing system, or other device or combinations of devices. In general, the term “computer system” can be broadly defined to encompass any device (or combination of devices) having at least one processor that executes instructions from a memory medium.
Measurement Device—includes instruments, data acquisition devices, smart sensors, and any of various types of devices that are operable to acquire and/or store data. A measurement device may also optionally be further operable to analyze or process the acquired or stored data. Examples of a measurement device include an instrument, such as a traditional stand-alone “box” instrument, a computer-based instrument (instrument on a card) or external instrument, a data acquisition card, a device external to a computer that operates similarly to a data acquisition card, a smart sensor, one or more DAQ or measurement cards or modules in a chassis, an image acquisition device, such as an image acquisition (or machine vision) card (also called a video capture board) or smart camera, a motion control device, a robot having machine vision, and other similar types of devices. Exemplary “stand-alone” instruments include oscilloscopes, multimeters, signal analyzers, arbitrary waveform generators, spectroscopes, and similar measurement, test, or automation instruments.
A measurement device may be further operable to perform control functions, e.g., in response to analysis of the acquired or stored data. For example, the measurement device may send a control signal to an external system, such as a motion control system or to a sensor, in response to particular data. A measurement device may also be operable to perform automation functions, i.e., may receive and analyze data, and issue automation control signals in response.
The computer system 82 may include a memory medium(s) on which one or more computer programs or software components according to one embodiment of the present invention may be stored. For example, the memory medium may store one or more graphical programs that are executable to perform the methods described herein. Also, the memory medium may store a graphical programming development environment application used to create and/or execute such graphical programs. The memory medium may also store operating system software, as well as other software for operation of the computer system. Various embodiments further include receiving or storing instructions and/or data implemented in accordance with the foregoing description upon a carrier medium.
In one embodiment, the graphical user interface of the graphical program may be displayed on a display device of the computer system 82, and the block diagram may execute on a device 190 connected to the computer system 82. The device 190 may include a programmable hardware element and/or may include a processor and memory medium which may execute a real time operating system. In one embodiment, the graphical program may be downloaded and executed on the device 190. For example, an application development environment with which the graphical program is associated may provide support for downloading a graphical program for execution on the device in a real time system.
Embodiments of the present invention may be involved with performing test and/or measurement functions; controlling and/or modeling instrumentation or industrial automation hardware; modeling and simulation functions, e.g., modeling or simulating a device or product being developed or tested, etc. Exemplary test applications where the graphical program may be used include hardware-in-the-loop testing and rapid control prototyping, among others.
However, it is noted that the present invention can be used for a plethora of applications and is not limited to the above applications. In other words, applications discussed in the present description are exemplary only, and the present invention may be used in any of various types of systems. Thus, the system and method of the present invention is operable to be used in any of various types of applications, including the control of other types of devices such as multimedia devices, video devices, audio devices, telephony devices, Internet devices, etc., as well as general purpose software applications such as word processing, spreadsheets, network control, network monitoring, financial applications, games, etc.
The one or more instruments may include a GPIB instrument 112 and associated GPIB interface card 122, a data acquisition board 114 and associated signal conditioning circuitry 124, a VXI instrument 116, a PXI instrument 118, a video device or camera 132 and associated image acquisition (or machine vision) card 134, a motion control device 136 and associated motion control interface card 138, and/or one or more computer based instrument cards 142, among other types of devices. The computer system may couple to and operate with one or more of these instruments. The instruments may be coupled to a unit under test (UUT) or process 150, or may be coupled to receive field signals, typically generated by transducers. The system 100 may be used in a data acquisition and control application, in a test and measurement application, an image processing or machine vision application, a process control application, a man-machine interface application, a simulation application, or a hardware-in-the-loop validation application, among others.
The one or more devices may include a data acquisition board 114 and associated signal conditioning circuitry 124, a PXI instrument 118, a video device 132 and associated image acquisition card 134, a motion control device 136 and associated motion control interface card 138, a fieldbus device 170 and associated fieldbus interface card 172, a PLC (Programmable Logic Controller) 176, a serial instrument 182 and associated serial interface card 184, or a distributed data acquisition system, such as the Fieldpoint system available from National Instruments, among other types of devices.
In one embodiment of the invention, one or more graphical programs may be created which are used in performing rapid control prototyping. Rapid Control Prototyping (RCP) generally refers to the process by which a user develops a control algorithm and quickly executes that algorithm on a target controller connected to a real system. The user may develop the control algorithm using a graphical program, and the graphical program may execute on the controller 92, e.g., on a computer system or other device. The computer system 82 may be a platform that supports real time execution, e.g., a device including a processor that executes a real time operating system (RTOS), or a device including a programmable hardware element.
In one embodiment of the invention, one or more graphical programs may be created which are used in performing Hardware in the Loop (HIL) simulation. Hardware in the Loop (HIL) refers to the execution of the plant model 94 in real time to test operation of a real controller 92. For example, once the controller 92 has been designed, it may be expensive and complicated to actually test the controller 92 thoroughly in a real plant, e.g., a real car. Thus, the plant model (implemented by a graphical program) is executed in real time to make the real controller 92 “believe” or operate as if it is connected to a real plant, e.g., a real engine.
In the embodiments of
Graphical software programs which perform data acquisition, analysis and/or presentation, e.g., for measurement, instrumentation control, industrial automation, modeling, or simulation, such as in the applications shown in
The computer may include at least one central processing unit or CPU (processor) 160 which is coupled to a processor or host bus 162. The CPU 160 may be any of various types, including an x86 processor, e.g., a Pentium class, a PowerPC processor, a CPU from the SPARC family of RISC processors, as well as others. A memory medium, typically comprising RAM and referred to as main memory, 166 is coupled to the host bus 162 by means of memory controller 164. The main memory 166 may store the graphical program operable to implement various embodiments of the asynchronous communications techniques disclosed herein. The main memory may also store operating system software, as well as other software for operation of the computer system.
The host bus 162 may be coupled to an expansion or input/output bus 170 by means of a bus controller 168 or bus bridge logic. The expansion bus 170 may be the PCI (Peripheral Component Interconnect) expansion bus, although other bus types can be used. The expansion bus 170 includes slots for various devices such as described above. The computer 82 further comprises a video display subsystem 180 and hard drive 182 coupled to the expansion bus 170. In some embodiments, the computer 82 may also include or be coupled to other buses and devices, such as, for example, GPIB card 122 with GPIB bus 112, an MXI device 186 and VXI chassis 116, etc., as desired.
As shown, a device 190 may also be connected to the computer. The device 190 preferably includes a programmable hardware element. The device 190 may also or instead comprise a processor and memory that may execute a real time operating system. The computer system may be operable to deploy a graphical program to the device 190 for execution of the graphical program on the device 190. The deployed graphical program may take the form of graphical program instructions or data structures that directly represent the graphical program.
Alternatively, the deployed graphical program may take the form of text code (e.g., C code) generated from the graphical program. As another example, the deployed graphical program may take the form of compiled code generated from either the graphical program or from text code that in turn was generated from the graphical program.
First, in 602 a first node and a second node may be displayed in a graphical program, where the graphical program includes a plurality of interconnected nodes that visually indicate functionality of the graphical program. Each of the first and second nodes preferably has a respective functionality, and includes a respective terminal. In other words, each node may include a terminal for connecting or wiring the node to another graphical program element, such as another node, for sending and/or receiving data to and/or from the other node.
The graphical program may be created or assembled by the user arranging on a display a plurality of nodes or icons and then interconnecting the nodes to create the graphical program. In response to the user assembling the graphical program, data structures may be created and stored which represent the graphical program. The nodes may be interconnected in one or more of a data flow, control flow, or execution flow format. The graphical program may thus comprise a plurality of interconnected nodes or icons that visually indicates the functionality of the program. As noted above, the graphical program may comprise a block diagram and may also include a user interface portion or front panel portion. Where the graphical program includes a user interface portion, the user may optionally assemble the user interface on the display. As one example, the user may use the LabVIEW graphical programming development environment to create the graphical program.
In an alternate embodiment, the graphical program may be created by the user creating or specifying a prototype, followed by automatic or programmatic creation of the graphical program from the prototype. This functionality is described in U.S. patent application Ser. No. 09/587,682 titled “System and Method for Automatically Generating a Graphical Program to Perform an Image Processing Algorithm”, which is hereby incorporated by reference in its entirety as though fully and completely set forth herein. The graphical program may be created in other manners, either by the user or programmatically, as desired. The graphical program may implement a measurement function that is desired to be performed by one or more instruments. In other embodiments, the graphical program may implement other types of functions, e.g., control, automation, simulation, and so forth, as desired.
In 604, an asynchronous wire may be included in the graphical program, where the asynchronous wire connects the first node and the second node via their respective terminals. In other words, a first end of the asynchronous wire may be connected to the terminal of the first node, and a second end of the asynchronous wire may be connected to the terminal of the second node. For example, in one embodiment, the nodes may be specified or intended respectively as source and sink nodes with respect to communication between the nodes.
In 606, the asynchronous wire may be configured for asynchronous communication between the first and second nodes. For example, various attributes of the asynchronous wire may be configured or set to facilitate asynchronous communication between the first node and the second node. In one embodiment, these attributes may include one or more of: a data structure type included in or used by the wire, e.g., a first in first out (FIFO) queue; buffer size for the asynchronous wire; read policy, e.g., block reads if the buffer is empty or uninitialized, remove the element upon a read from the buffer (e.g., destructive/non-destructive reads), read chunk size, etc.; write policy, e.g., block all writes to the buffer if the buffer is full, overwrite if the buffer is full or always, write chunk size, etc.; initial value on the wire; directionality of the asynchronous wire; and semantics of wire splits, i.e., how branching of the wire may affect communications using the wire, among others. Note that the various policies specified for use of the asynchronous wire may accommodate various models of computation (MoC) for the graphical program, including, for example, Kahn Process Networks (PN) and Communicating Sequential Processes (CSP), among others.
In some embodiments, the asynchronous wire may have a default configuration, i.e., one or more of the attributes may be preset with default values. Thus, the configuration of the asynchronous wire (at least with respect to the default valued attributes) may effectively occur when the wire is included in the block diagram of the graphical program. Of course, even were some or all of the attributes to have default values, subsequent configuration of the asynchronous wire, e.g., by the user or by another process, may overwrite these default values with new values. In other words, configuring the asynchronous wire may include overwriting at least one of the default values for the one or more attributes of the asynchronous wire with a respective at least one new value.
In one embodiment, a user may be able to configure a terminal on a node to be “asynchronous”, after which wires connected to this terminal may have asynchronous behavior. In other words, connecting a wire to an asynchronous terminal may automatically invoke creation or instantiation of an asynchronous wire, e.g., via conversion of a normal “synchronous” wire to the asynchronous wire, or replacement of the normal wire with the asynchronous wire. Users may then click on the asynchronous wire and configure its run-time behavior, such as the size of the queue and the read/write policies (blocking/non-blocking, destructive/non-destructive reads), as described above. In other words, once a terminal of a node is configured to be asynchronous, any wire connected to that terminal may automatically be configured as an asynchronous wire.
In one embodiment, the asynchronous wire and/or the terminal(s) may be configured via invocation of a graphical user interface (GUI), e.g., one or more dialogs, menus, property pages, attribute nodes, etc., e.g., by the user right-clicking on the asynchronous wire or terminal. The user may then select or input values for various attributes of the asynchronous wire or terminal. Alternatively, or additionally, the asynchronous wire and/or the terminal(s) may be configured via input from another process, such as a graphical program generation program or wizard. For example, in the case of a wizard, the user may provide input to various panels or dialogs specifying the attributes. Thus, in various embodiments, configuration information for the asynchronous wire and/or the node terminals may be provided by a use via a GUI, and/or programmatically by another process, e.g., another program.
In 608, the graphical program may be executed. In preferred embodiments, executing the graphical program includes executing the first and second nodes, where the first and second nodes communicate asynchronously during the execution of the first and second nodes.
Thus, the asynchronous wire may allow users to create a static connection between nodes in a (block diagram of) a graphical program to facilitate asynchronous communication between the nodes. In some embodiments, this connection may be depicted as a special, asynchronous, wire with a specific graphical appearance. For example, in one embodiment, the asynchronous wire may have a 3D tube-like appearance, although any other appearance may be used as desired. Examples of such a graphically rendered asynchronous wire are illustrated in
Note that in preferred embodiments, an asynchronous wire does not explicitly carry data at run-time, and so it may not be considered as part of the data flow graph (of the graphical program). This means that its fire count (i.e., iterative execution count) may be ignored at run-time and that it may not use explicit tunneling to cross structures. Instead the asynchronous wire may visually “float” over structure boundaries, e.g., over the boundaries of loop nodes, as may be seen in
For example, in the simple example program of
The asynchronous wire may be denoted by a type attribute (and so behaviorally polymorphic nodes may be possible), namely, a typedef with a special name. In other words, asynchronous wires may have a data type, and so may benefit from the many uses of such typing, as is well known to those of skill in the programming arts, e.g., polymorphism and type checking, among others.
It should be noted that while the example uses of asynchronous wires described herein are within a single program, in other embodiments, asynchronous wires may be used to connect different programs, e.g., to connect nodes that are comprised in different respective graphical programs. Moreover, in some embodiments, the different programs may be even running on different processors or programmable hardware elements, such as field programmable gate arrays (FPGAs).
In preferred embodiments, the asynchronous wires may each be implemented by a respective graphical program. In other words, the functionality of an asynchronous wire may be provided by an associated graphical program. More specifically, each asynchronous wire may use, be associated with, or represent, an instance of a graphical program, which, for brevity, may be referred to simply as a graphical program. Thus, multiple asynchronous wires may each utilize or have a respective instance of the same graphical program. The graphical program for each asynchronous wire may be configured to implement and enforce the various communication policies of the wire, e.g., read and write policies, as discussed above. Thus, each instance of the graphical program may be configured for the particular behavior desired for the respective asynchronous wire. Note that since graphical programs may store and maintain state information, the data transmitted on or by the asynchronous wire may also be included in or implemented by the graphical program. Note also that the graphical program associated with an asynchronous wire may not generally be visible to the user, i.e., may be hidden, although of course, means may be provided for displaying the graphical program of an asynchronous wire for development purposes.
Since the endpoints of an asynchronous wire may share a common, static reference to a VI instance it may be possible to implement a wide variety of run-time connections between the endpoints, thus allowing custom run-time behavior of a node. For example, in various embodiments, some of the possible behaviors of an asynchronous wire may include: implementing queues of various kinds, including FPGA FIFOs and RT (real time) FIFOs; single element communication (e.g., anonymous global variables); synchronization primitives, such as notifiers, semaphores, rendesvous and occurrences; and expressing a connection to and from a part of a diagram that is being executed on a remote target, e.g., “roping in” of a piece of a diagram so that it can execute on the remote target in conjunction with local execution of the remainder of the diagram.
In some embodiments, an asynchronous wire may not be limited to propagating information from terminal sources to terminal sinks. In other words, in some embodiments, the asynchronous wire (and possibly the terminals of the connected nodes) may be configured to transmit data in either direction or in both directions. In other words, in some embodiments and configurations, the asynchronous wire may facilitate two-way communications between the connected nodes. For example, in one embodiment, a dual queue may be used to facilitate such two-way communications, where one queue is used for a first direction, and another queue is used for a second direction, although any other data structures and techniques may be used as desired.
As
The split node 914 may also provide the received signal to downsample node 916 via asynchronous wire 915, where the downsample node 916 may operate to downsample the received signal by a factor of 2, and transmit the resultant downsampled signal over asynchronous wire 917 to delay node 916. Note that the delay node 918 is initialized with 150 values (samples), and may operate to provide 1 sample at a time to the merge node 912, introduced above. Thus, the merge node 912 may receive data from asynchronous wires 919 and 911, and interleave samples to generate the signal transmitted on asynchronous wire 913, as described above. Note that merge node 912 illustrates a sink (merge node 912) with two sources (split node 910 via asynchronous wire 911, and delay node 918 via asynchronous wire 919). Note also that nodes 912, 914, 916, and 918 form a cycle via respective asynchronous wires 913, 915, 917, and 919, which is not supported in standard data flow diagrams, thus, as noted above, the asynchronous wires may facilitate or accommodate non-data flow behaviors.
As shown, a downsample node, whose functionality is illustrated in the top block diagram 1108 of
Similarly, to transmit data as output onto the asynchronous wire exiting the downsample node, the node may access and write data to a queue referenced by an output queue reference, denoted in the top block diagram as QRef Out (see far right of the block diagram). The node preferably accesses and writes data to the queue of the output asynchronous wire using an enqueue process implemented in an enqueue block 1106, illustrated in the bottom right block diagram 1120 of
While the example asynchronous wires/terminals presented above use queues, it should be noted that any other types of data structure may be used as desired, e.g., other FIFO structures, stacks, graphs, arrays, lists, and so forth.
Although the embodiments above have been described in considerable detail, numerous variations and modifications will become apparent to those skilled in the art once the above disclosure is fully appreciated. It is intended that the following claims be interpreted to embrace all such variations and modifications.
