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LabVIEW Real-Time Module User Manual

1. test site com The host whose domain name is test site com site com All hosts whose domain names end with Site com 130 164 123 123 The host with the IP address 130 164 123 123 130 164 123 All hosts whose IP addresses start with 130 164 123 National Instruments Corporation 3 7 Real Time Module User Manual Chapter 3 Real Time Module Environment To specify an Internet host address enter its domain name or IP address Use the wildcard when specifying Internet host addresses For example you can specify all hosts within the domain site com with the following entry site com You can specify all hosts in the subnet whose first two numbers are 130 164 with the following entry 130 164 The entry is the default RT Target Access List entry and matches all addresses Setting Options for RT Target Start up Applications Use the RT Target Miscellaneous page available by selecting RT Target Miscellaneous from the RT target Options dialog box pull down menu to set RT target start up application options Options RT Target Miscellaneous c ni rt startup a ema e Figure 3 5 RT Target Miscellaneous Page Place a checkmark in the Launch Application at Boot up checkbox shown in Figure 3 5 to launch the application specified in the Application Path text box when you boot up a networked RT target with a media storage device The path specified in the App
2. Refer to the NJ IMAQ User Manual for information about configuring NI IMAQ for use with the Real Time Module Refer to the Serial Hardware and Software for Windows User Manual for information about configuring NI Serial for use with the Real Time Module Real Time Module User Manual Appendix A Configuring and Testing Device Drivers NI VISA NI CAN FieldPoint Refer to the National Instruments Web site at ni com info and enter the info code RTDRVS for information about configuring and testing the NI VISA driver Refer to the NI CAN Hardware and Software Manual for information about configuring NI CAN for use with the Real Time Module Refer to the FP 2000 2010 User Manual for information about configuring FieldPoint for use with the Real Time Module Creating Device Drivers for Third Party PXI Devices Real Time Module User Manual Each I O device requires driver software that is specific to the operating system Refer to the National Instruments Web site at ni com info and enter the info code RTDRVS for information about creating or modifying a device driver for the use with the Real Time Module A 2 ni com Technical Support and Professional Services Visit the following sections of the National Instruments Web site at ni com for technical support and professional services e Support Online technical support resources include the following Self Help Resources For immediate answers and
3. Real Time Module User Manual Use a static IP address if the device must use the same IP address after a reboot Using a static IP address ensures the proper behavior of applications that communicate with the device using a specific IP address Select Edit the IP settings in the IP Settings section and specify the following network parameters e IP address The unique computer readable address of a networked device Each IP address contains a set of four numbers in the range from 0 through 255 Each number is separated by a period For example 130 164 44 143 e Subnet mask A network code that helps a network device determine whether other devices are on the same network For example 255 255 255 0 e Gateway The IP address of the gateway server The gateway server functions as a connection between two separate networks DNS server The IP address of a Domain Name Server DNS that stores host names and translates them into IP addresses You must provide a value for the IP address and Subnet mask If the network does not have a gateway or DNS server set Gateway and DNS server to the default setting of 0 0 0 0 Click the Apply button in the Network Settings tab Click the Yes button when prompted to reboot Downloading Software Complete the following steps to install or upgrade the software on a networked RT Series device 1 2 5 In MAX select the device from the Remote Systems category Click the Software tab
4. ni com connecting to applications running on RT targets 7 5 creating application installer 7 1 installing on RT target with media storage device 7 2 without media storage device 7 1 launching 7 3 automatically on start up 7 4 automatically using command line arguments 7 4 quitting LabVIEW after launch 7 3 saving 7 2 selecting target after launch 7 3 start up applications setting options for 3 8 subVI overhead avoiding 6 5 system time setting for RT targets 2 7 T targets See RT target s TCP communication method 4 10 technical support and professional services B 1 Thread See also multithreaded applications definition 4 1 Tick Count ms function 8 2 time system obtaining for RT targets 2 7 time critical VIs cooperative yielding 4 5 functional global variables 4 6 memory allocation and preallocating arrays 6 1 multithreaded applications 4 4 timing behavior verification 8 2 oscilloscope 8 3 Pentium time stamp counter 8 2 software drivers 8 3 Tick Count ms function 8 2 National Instruments Corporation l 7 Index timing control loops 5 3 hardware method 5 5 AI SingleScan VI 5 5 Counter Control VI 5 6 overview 5 3 software method 5 3 Flat Sequence structure implementation figure 5 5 ideal timing figure 5 4 incorrect timing figure 5 5 parallel implementation figure 5 4 Wait Until Next ms Multiple function 5 3 U UDP communication method 4 11 user interfac
5. Select a VI by entering the path or by clicking the Browse button and navigating to the location of the VI Select the front panel communication method from the available choices TCP User Datagram Protocol UDP DataSocket or Logos Enter the IP address of the RT target in the IP address of RT target listbox You also can select an RT target IP address from the pull down menu Enter the TCP port to use for communication in the TCP Port text box If you use the UDP protocol you must specify the UDP send and receive ports in the UDP Send Port and UDP Receive Port text boxes Click the Next button The RT Communication Wizard returns a list of controls and indicators present in the time critical VI The RT Communication Wizard replaces front panel controls and indicators in the time critical VI with RT FIFOs Also the RT Communication Wizard places RT FIFOs ina new normal priority VI The RT FIFOs in the normal priority VI and time critical VI send and receive front panel data RT FIFOs are deterministic and do not affect the timing of the time critical code The RT Communication Wizard displays the old control or indicator name and the new RT FIFO name for all controls and indicators 4 8 ni com Chapter 4 Building Deterministic Applications 7 Enter the number of elements in each RT FIFO in the Length text box and click the Next button You must ensure that you set Length large enough to contain the data written to an RT FIFO t
6. running on another computer The SMTP VIs can send electronic mail including attached data and files using the Simple Mail Transfer Protocol SMTP You cannot use the SMTP VIs to receive information SMTP is non deterministic and using SMTP communication inside a time critical VI adds jitter to the application Refer to the LabVIEW User Manual for information about emailing data from a VI Serial Serial communication is the transmission of data between two locations through the serial ports The VISA functions provide serial communication support in LabVIEW for communication between RT targets with serial devices and serial instruments or computers that have a serial connection Serial communication is ideal when transfer data rates are low or for transmitting data over long distances You must install NI Serial RT on the RT target from MAX Mac 0S Install using the Remote System Explorer Serial is non deterministic and using serial communication inside a time critical VI adds jitter to the application Refer to the LabVIEW Help available by selecting Help VI Function amp How To Help for information about using the VISA functions for serial communication National Instruments Corporation 4 13 Real Time Module User Manual Chapter 4 Building Deterministic Applications CAN Controller Area Network CAN is a deterministic multi drop communication bus standardized as ISO 11898 Using CAN you can transfer up to 8 data bytes
7. Figure 6 2 uses the Initialize Array function outside the loop and the Replace Array Subset function inside the loop to create the array No memory allocations use the LabVIEW Memory Manager because the array has been preallocated element default Replace Array Subset lace Array Subset Initialize Arra dimension size E Use the Replace Array Subset function to add the elements to a preinitialized array Figure 6 2 Preallocated Array You must ensure that no memory management occurs inside of time critical VI control loops Real Time Module User Manual 6 2 ni com Chapter 6 Optimizing Applications Casting Data to Proper Data Types Cast data to the proper data type in time critical and non time critical VIs Every time LabVIEW performs a type conversion either implicitly or explicitly LabVIEW makes a copy of the data buffer in memory to retain the new data type after the conversion The LabVIEW Memory Manager must allocate memory for the copy which might affect the determinism of time critical VIs Also creating copies of the data buffer takes up memory resources on an RT target Refer to the LabVIEW User Manual for more information about casting data types Use the smallest data type possible when casting the data type If you must convert the data type of an array do the conversion before you build the array Also keep in mind that a function output reuses an input buffer only if the out
8. Instruments be liable for any damages arising out of or related to this document or the information contained in it EXCEPT AS SPECIFIED HEREIN NATIONAL INSTRUMENTS MAKES NO WARRANTIES EXPRESS OR IMPLIED AND SPECIFICALLY DISCLAIMS ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE CUSTOMER S RIGHT TO RECOVER DAMAGES CAUSED BY FAULT OR NEGLIGENCE ON THE PART OF NATIONAL INSTRUMENTS SHALL BE LIMITED TO THE AMOUNT THERETOFORE PAID BY THE CUSTOMER NATIONAL INSTRUMENTS WILL NOT BE LIABLE FOR DAMAGES RESULTING FROM LOSS OF DATA PROFITS USE OF PRODUCTS OR INCIDENTAL OR CONSEQUENTIAL DAMAGES EVEN IF ADVISED OF THE POSSIBILITY THEREOF This limitation of the liability of National Instruments will apply regardless of the form of action whether in contract or tort including negligence Any action against National Instruments must be brought within one year after the cause of action accrues National Instruments shall not be liable for any delay in performance due to causes beyond its reasonable control The warranty provided herein does not cover damages defects malfunctions or service failures caused by owner s failure to follow the National Instruments installation operation or maintenance instructions owner s modification of the product owner s abuse misuse or negligent acts and power failure or surges fire flood accident actions of third parties or other events outside reasonable control Copyright Under the copyr
9. OPERATING SYSTEM SOFTWARE FITNESS FITNESS OF COMPILERS AND DEVELOPMENT SOFTWARE USED TO DEVELOP AN APPLICATION INSTALLATION ERRORS SOFTWARE AND HARDWARE COMPATIBILITY PROBLEMS MALFUNCTIONS OR FAILURES OF ELECTRONIC MONITORING OR CONTROL DEVICES TRANSIENT FAILURES OF ELECTRONIC SYSTEMS HARDWARE AND OR SOFTWARE UNANTICIPATED USES OR MISUSES OR ERRORS ON THE PART OF THE USER OR APPLICATIONS DESIGNER ADVERSE FACTORS SUCH AS THESE ARE HEREAFTER COLLECTIVELY TERMED SYSTEM FAILURES ANY APPLICATION WHERE A SYSTEM FAILURE WOULD CREATE A RISK OF HARM TO PROPERTY OR PERSONS INCLUDING THE RISK OF BODILY INJURY AND DEATH SHOULD NOT BE RELIANT SOLELY UPON ONE FORM OF ELECTRONIC SYSTEM DUE TO THE RISK OF SYSTEM FAILURE TO AVOID DAMAGE INJURY OR DEATH THE USER OR APPLICATION DESIGNER MUST TAKE REASONABLY PRUDENT STEPS TO PROTECT AGAINST SYSTEM FAILURES INCLUDING BUT NOT LIMITED TO BACK UP OR SHUT DOWN MECHANISMS BECAUSE EACH END USER SYSTEM IS CUSTOMIZED AND DIFFERS FROM NATIONAL INSTRUMENTS TESTING PLATFORMS AND BECAUSE A USER OR APPLICATION DESIGNER MAY USE NATIONAL INSTRUMENTS PRODUCTS IN COMBINATION WITH OTHER PRODUCTS IN A MANNER NOT EVALUATED OR CONTEMPLATED BY NATIONAL INSTRUMENTS THE USER OR APPLICATION DESIGNER IS ULTIMATELY RESPONSIBLE FOR VERIFYING AND VALIDATING THE SUITABILITY OF NATIONAL INSTRUMENTS PRODUCTS WHENEVER NATIONAL INSTRUMENTS PRODUCTS ARE INCORPORATED IN A SYSTEM OR APPLICATION INCLUDING WITHOUT LIMITATION THE APPROPRIA
10. RT Series Plug In Devices section for information about configuring the PXI device Configuring RT Series Plug In Devices Complete the following steps to configure an RT Series plug in device using Measurement amp Automation Explorer MAX 1 Launch MAX and expand the My System Devices and Interfaces and Traditional NI DAQ Devices categories MAX detects the plug in devices you have installed The NI PCI PXI 7030 Series plug in device appears in the Traditional NI DAQ Devices category listed by device number The NI PCI 7041 Series plug in device appears in the Devices and Interfaces category listed by device name In Figure 2 1 an NI PCI PXI 7030 Series plug in device appears with a device number of 1 The data acquisition daughterboard of the NI PCI PXI 7030 Series plug in device appears under the processor board with a device number of 2 An NI PCI 7041 Series plug in device appears with a device name of RT 0 My System Measurement amp Automation Explorer Iof x File Edit view Tools Help Configuration F c Properties Delete Bres Panes Show Help G9 My System Attribute Value Description Data Neighborhood Device Number 1 The NI DAQ device number GM Devices and Interfaces P3exr Slot 0 The position of the device in the PXI cH a Traditional NI DAQ Device Pserial Number OxBOA415 The serial number of the device SB JPXI 7030 Device 1 E 6040E Device 2 HE RT 0 Ports Serial amp Paralle
11. RT target LabVIEW attempts to open the local copy of the VIs to show the front panel ays Note When connecting to an RT Series plug in device if you place a checkmark in the Reset checkbox on the Select Execution Target dialog box LabVIEW clears all VIs in memory on the target If the local copy of the VIs have been moved or modified since you downloaded them to the RT target LabVIEW displays the Changed or Missing VIs dialog box shown in Figure 3 3 Real Time Module User Manual 3 4 ni com Chapter 3 Real Time Module Environment lf Changed or Missing Is RT Execution Engine VIs looper70 vi Legend VI is missing VI doesn t match of J Show path from where VIs were downloaded IV Show only top level VIs Browse for Selected VI Hit the OK button to close any missing VIs and update any changed VIs on the RT Engine Hit the Cancel button to disconnect without closing or updating the RT Engine Is Figure 3 3 Changed or Missing VIs Dialog Box The Changed or Missing VIs dialog box shows the name of the local VIs that are missing or that have been modified and no longer match the VIs running on the RT target From the Changed or Missing VIs dialog box you can browse for a VI that was moved in the host computer file system close all VIs running on the RT target and update them with the latest version of each VI and close the network connection between LabVIEW and the RT target while leaving the VIs run
12. Target dialog box appears You can select any RT target for the application If you do not want to select the RT target each time you run the application remove the checkmark from the Show LabVIEW Real Time target selection dialog when launched checkbox in the Application Settings tab of the Application Builder to make the application run automatically on the host computer You also can use command line arguments with the applications you build to specify the RT target Refer to the Launching Applications Automatically Using Command Line Arguments section for information about command line arguments Quitting LabVIEW after Launch If you design a stand alone application to run on an RT target you might want the host computer to disconnect from the RT target after you download and run the application Place a checkmark in the Quit LabVIEW Real Time host application after downloading checkbox in the Application Settings tab of the Application Builder to have LabVIEW disconnect after launching the application on the RT target Selecting the Quit LabVIEW Real Time host application after downloading option is equivalent to selecting File Exit without closing RT Engine VIs in LabVIEW after downloading and running a VI on an RT target Some RT targets have media storage devices where you can save stand alone applications For example the RT Series PXI controller has a hard disk drive and the FieldPoint 20xx network module has flash You then can au
13. VI Data Acquisition Device Device Figure 5 2 Typical LabVIEW Control Application When you develop a deterministic control application you must consider memory management time critical versus normal priority code and communication Refer to Chapter 4 Building Deterministic Applications for information about deterministic programming techniques Building a deterministic control application includes the following steps 1 Time the control loop 2 Acquire the measurement data 3 Process the measurement data 4 Output the compensation data 5 2 ni com Chapter 5 Creating Deterministic Control Applications Timing Control Loops Because of the preemptive nature of the Real Time Operating System RTOS RT Series devices use a time critical application thread can monopolize the processor on the device A thread might use all processor resources and not allow lower priority threads in the application to execute The time critical task must periodically yield processor resources to the lower priority tasks so they can execute By properly separating the time critical task from lower priority tasks you can reduce application jitter Refer to Chapter 4 Building Deterministic Applications for information about building deterministic VIs that reduce application jitter You can use a software method or hardware methods to time control loops The software method is available for RT Series FieldPoint modules RT Series PXI
14. VIs from the pull down menu 6 Add to the Visible VIs list the VIs that you want to be accessible on the Web Click the OK button to close the Options dialog box 7 Download the VIs to the RT target Refer to the Downloading VIs to an RT Target section of Chapter 3 Real Time Module Environment for information about downloading VIs to an RT target Real Time Module User Manual 4 14 ni com Chapter 4 Building Deterministic Applications With the RT target Web Server enabled you can create HTML files to allow Web browser access to RT target VIs in the Visible VIs list Complete the following steps to create HTML files of VIs and make them available to Web browsers from the RT target Web Server 1 Open in host LabVIEW the VIs you want to publish 2 Select Tools Web Publishing Tool to open the Web Publishing Tool dialog box and create an HTML file that embeds the VI Click the Save to Disk button to create the HTML file 4 Using the FTP client in MAX transfer the HTML file to the RT target directory that you specified as the Web Server root directory Mac OS Use the FTP client of the Remote System Explorer Refer to Chapter 18 Networking in LabVIEW of the LabVIEW User Manual for information about publishing VIs on the Web using the Web Publishing Tool and viewing and controlling front panels remotely Regaining Control of RT Target Vis from Remote Panel Connections If a remote panel connection assumes control of an RT
15. controllers and RT Series plug in devices The hardware method is available only for RT Series plug in devices and RT Series PXI controllers Timing Control Loops Using Software The Wait Until Next ms Multiple function causes a thread to sleep until the operating system millisecond timer value equals a multiple of the millisecond multiple input For example if the Wait Until Next ms Multiple function executes with a millisecond multiple input of 10 ms and the operating system millisecond timer value is 112 ms the VI pauses until the millisecond timer value equals 120 ms because 120 ms is the first multiple of 10 ms after the Wait Until Next ms Multiple function executes Use the Wait Until Next ms Multiple function to synchronize a loop with the operating system millisecond timer value multiple A loop has a period of millisecond multiple if the Wait Until Next ms Multiple function executes in parallel with other code in the same loop However the loop does not have the period of millisecond multiple if the code takes longer to execute than the millisecond multiple Avoid placing the Wait Until Next ms Multiple function in parallel with other code because doing so can result in incorrect timing in a control system Instead use sequence structures to control when the Wait Until Next ms Multiple function executes using data flow Figure 5 3 shows the National Instruments Corporation 5 3 Real Time Module User Manual Chapter 5 Creating D
16. ere ea abe ae E ane eet ee desixel tag eet 4 11 DataSOcket arrsa Oi Be aie Biba ER eee OE 4 11 VISOrverviscdse nist ned Seeks eA Se RA ite a 4 12 SMTP a a e t suaguseseantorse dha cutee E AE RE E 4 13 Seral ind E A ee wee A a 4 13 CAN o erei E OEA E E NE E E EEA boots 4 14 Using Remote Panels with RT Target VIs sssessesesseesseerssrsrssrsresrsresresreresresrsresrrerseeee 4 14 Enabling Remote Panel Connections to RT Target VIs eee eee 4 14 Regaining Control of RT Target VIs from Remote Panel Connections eee es eseeseeseeeseeeesseseeneeesesseeeaeeeees 4 15 Minimizing Memory Usage by the RT Target Web Server ee 4 16 Real Time Module User Manual vi ni com Contents Chapter 5 Creating Deterministic Control Applications Overview of Control Applications cece cece csceeseceeecseeseeeseeeesaeceeeaeeneeeaseneenaes 5 1 Implementing a Deterministic Control Application cies eeeeseeeeeeseteeetseeneeeaees 5 2 Timing Control Loops ieee eee Nie cece ata abe el Paes ed eee 5 3 Timing Control Loops Using Software cece ceeeseeseceseeeeeeseeseeeseensenseeaes 5 3 Timing Control Loops Using Hardwate eee eeeeseesceseeeeeeseereeeseeneenseeaes 5 5 AL SingleScaneV U ei s cccskietessoeictten ecutdereisens neni a 5 5 Counter Control VI e a alee Gee Aa eee aes 5 6 Acquiring Measurement Data ooo ee eee eiee EERE AEA EE E EATE ATER 5 7 Using DAQ Devices to Acquire Measurement Data sseeesseeeeeeeeseesreerreeee 5 8
17. figure 5 1 Controller Area Network CAN 4 14 conventions used in manual ix Counter Control VI 5 6 counters See also timing behavior verification timing control loops configuring for pulse train generation 5 6 Pentium time stamp counter 8 2 Tick Count ms function 8 2 Real Time Module User Manual Index custom error codes defining 8 3 custom error file INI tokens setting 8 4 D data types casting data to 6 3 DataSocket communication method 4 11 debugging deterministic applications 8 1 application behavior verification 8 1 LabVIEW debugging tools 1 4 8 1 Profile window 8 1 error codes defining custom error codes 8 3 setting custom error file INI tokens 8 4 timing behavior verification 8 2 oscilloscope 8 3 Pentium time stamp counter 8 2 software drivers 8 3 Tick Count ms function 8 2 deploying applications See stand alone applications deterministic applications 4 1 See also deterministic control applications communication methods with 4 9 CAN 4 14 DataSocket 4 11 serial 4 13 shared memory 4 10 SMTP 4 13 TCP 4 10 UDP 4 11 VI Server 4 12 debugging 8 1 application behavior verification 8 1 LabVIEW debugging tools 8 1 Profile window 8 1 error codes defining custom error codes 8 3 Real Time Module User Manual l 2 setting custom error file INI tokens 8 4 timing behavior verification 8 2 oscilloscope 8 3 Pentium time stamp counter 8 2 software drivers 8 3 Tick Coun
18. hardware or peripheral devices Peripheral Component Interconnect a high performance expansion bus architecture originally developed by Intel to replace ISA and EISA It is achieving widespread acceptance as a standard for PCs and workstations it offers a theoretical maximum transfer rate of 132 Mbytes s Plug in NI PCI PXI RT Series devices with embedded processors Each plug in device contains a processor board and data acquisition daughterboard Execution system scheduling of threads in which higher priority threads execute before all other threads Assigned to VIs to classify execution sequence in the execution system Higher priority threads execute first while threads with a lower priority wait Sets or finds the properties of a VI or application Combination of proportional integral and derivative control actions Refers to a control method in which the controller output is proportional to the error its time history and the rate at which it is changing The error is the difference between the observed and desired values of a variable that is under control action The exact sequence of bits characters and control codes used to transfer data between computers and peripherals through a communications channel such as the GPIB bus PCI eXtensions for Instrumentation A modular computer based instrumentation platform G 4 ni com R real time Real Time Operating System RTOS remote panel round robin schedulin
19. have the Real Time Module installed When you install a stand alone application on an RT target without a media storage device such as an NI PCI 7030 plug in device you also must install the following components from the National Instruments Device Driver CD e Measurement amp Automation Explorer MAX 3 0 e PCI 7041 and PCI PXI 7030 support e Traditional NI DAQ 7 0 National Instruments Corporation 7 1 Real Time Module User Manual Chapter 7 Deploying Applications For targets with a media storage device such as an RT Series PXI controller RT Series FieldPoint module or NI PCI 7041 plug in device you must install the following components from the National Instruments Device Driver CD e MAX 3 0 e PCI 7041 and PCI PXI 7030 support for PCI 7041 e FieldPoint 4 0 support for FieldPoint e Necessary I O hardware drivers B Note RT targets with media storage devices must already have a version of the RT Engine installed that matches the version of LabVIEW used to build the stand alone application Configuring Target Settings On the Target tab the Application Builder determines the target file name destination directory and support file directory from the Application Path setting in the Network Options dialog box available by selecting Tools RT Target x x x x Options where x x x x is the IP address of the RT target and then selecting RT Target Miscellaneous from the pull down menu You cannot change the applicatio
20. live data between VIs and other computers A DataSocket Server running on a host computer acts as a data repository Data placed on the DataSocket Server becomes available for clients to access National Instruments Corporation 4 11 Real Time Module User Manual Chapter 4 Building Deterministic Applications B Note You can bind a DataSocket connection to a front panel object and control the object from a client connection However this feature is not supported by VIs on an RT target because there is no front panel VI Server Real Time Module User Manual One advantage of using DataSocket is that multiple clients can access data on the DataSocket Server A LabVIEW VI can use the DataSocket Write VI to post data to the DataSocket Server Any number of VIs on different RT targets can use the DataSocket Read VI to retrieve the data RT target VIs can post data such as status information to the DataSocket Server for the host computer VI to read DataSocket is non deterministic and using DataSocket functions inside a time critical VI adds jitter to the application Refer to the LabVIEW User Manual for information about DataSocket technology Refer to the LabVIEW Help available by selecting Help VI Function amp How To Help for information about the DataSocket VIs and functions Use the VI Server to monitor and control VIs on a remote RT target Using VI Server technology a LabVIEW VI can invoke RT target VIs The LabVIEW VI can
21. target VI while you have a front panel connection to the RT target Lab VIEW alerts you that control was transferred to a remote client Also if a remote panel connection has control of a VI running on an RT target and you open a front panel connection to the target from the host computer Lab VIEW alerts you that a remote connection exists and has control of the VI You can regain control of an RT target VI from host LabVIEW by opening a front panel connection to the target and clicking the RT Target information banner located on the lower left corner of the VI front panel and selecting Regain Control The remote user receives a message that the server has regained control of the VI The host computer regains and locks control of the VI not allowing remote connections to regain control You can unlock control of the VI by clicking the RT Target information banner and selecting Unlock Control You can switch control of a VI to a user that requested control while the VI was locked by clicking the RT Target information banner and selecting Switch Controller If more than one remote connection requested control of the VI the first connection in the queue assumes control National Instruments Corporation 4 15 Real Time Module User Manual Chapter 4 Building Deterministic Applications Minimizing Memory Usage by the RT Target Web Server To minimize memory usage when you enable the Web Server on the RT target include only the VIs you want to ac
22. to the update clock or the update clock routed to the scan clock and so on However the drawback is that outputs are always one loop cycle behind the inputs as shown in Figure 5 11 Input Input first point second point 7 y p gt Time lt a _ gt Processing lt q Delay Output irrelevant Output response to first point Shared Clock Figure 5 11 Shared Clock Implementation National Instruments Corporation 5 11 Real Time Module User Manual Chapter 5 Creating Deterministic Control Applications The time delay between analog input and output is exact predictable and subject only to the hardware jitter of the scan clock which is on the order of nanoseconds In Figure 5 11 the output occurs as soon as the processing completes meaning that the software dictates the timing of the output However you can improve the consistency of the delays between the input and output events using hardware timing Use hardware timing and a clock to guarantee that inputs and outputs occur at regular intervals with minimal jitter To minimize the time between an input and its corresponding output consider staggering the scan clock A D and update clock D A as shown in Figure 5 12 Using one clock you can stagger A D and D A conversions by initiating an input on the rising edge of the clock and initiating an output on the falling edge of the same clock Adjusting the clock duty cycle enabl
23. 1 ni com P passing data between VIs 4 5 functional global variables 4 6 global variables 4 5 Real Time FIFO VIs 4 7 PCI plug in devices installing 2 2 Pentium time stamp counter 8 2 PID Control Toolset See LabVIEW PID Control Toolset plug in devices RT series See also PXI controllers RT Series 7041 RT Series plug in devices 1 3 configuring 2 3 creating PXI device drivers A 2 installing 2 2 overview 1 2 preallocating arrays 6 1 preemptive scheduling 4 2 priority inversion induced jitter 6 1 professional services and technical support B 1 Profile window 8 1 programming See deterministic applications deterministic control applications stand alone applications Proportional Integral Derivative PID algorithm 5 10 pulse train generation configuring counter for 5 6 PXI controllers RT Series booting into Real Time Operating System 2 4 overview 1 3 PXI plug in devices RT Series creating PXI device drivers A 2 installing 2 2 R Read Time Stamp Counter RDTSC assembly instructions 8 2 National Instruments Corporation l 5 Index real time system components 1 1 host computer 1 1 LabVIEW software 1 1 RT engine 1 2 RT targets 1 2 Real Time FIFO VIs 4 7 Real Time Module See also RT Engine closing front panel connection without closing VIs 3 4 configuring networked RT target options 3 5 RT target start up applications 3 8 setting access permissions 3 5 connecting
24. 6 6 National Instruments Corporation vii Real Time Module User Manual Contents Chapter 7 Deploying Applications Building Stand Alone Applications 20 0 0 eee ce eeeeseeseceseeseeesececeseeseensecaeeeseteeeeaeesees 7 1 Creating an Application Installer oo ee eecessceeceseeeeeeseeeseeseeeaeseeeseeaeees 7 1 Configuring Target Settings reeeo a ea oka E aerae 7 2 Saving Stand Alone Applications sssssessssesesseeseesrsrestrersresresrsresrsreseesreresee 7 2 Selecting a Target after Launch essesesesrssesreresresrsrrsrrersreresresrses 7 3 Quitting LabVIEW after Launch ssesseeeseeresesrsresreersrrsrsresrerrsrrsrsees 7 3 Launching Stand Alone Applications esessesesesseesssreresrsresrsresrestsrestesrsresterenresrssesesees 7 3 Launching Applications Automatically on Start up eee eee eee eeeeeeee 7 4 Launching Applications Automatically Using Command Line Argument 000 cece es eeceeseeeeeeseeeseeseeneeeseeeeeeaeenees 7 4 Connecting to Applications Running on RT Targets 0 eee eee eeeeseseeeteeeeeeeeeeees 7 5 Chapter 8 Debugging Deterministic Applications Verifying Correct Application Behavior cece ee eeeecceseceeeeseeeeeeeeeseeeeeaeeseeeaeeneens 8 1 Using the LabVIEW Debugging Tools cece eseeseeeseeneceseeeeeseeneenees 8 1 Using the Profile Window sseccssciececces sresivesssu weenie e EEE 8 1 Verifying Correct Timing Behavior 0 eee eeeeeeseeseceseeseeesecseeeseeseeeseceeeaesseeeaees
25. DP is non deterministic and using UDP communication inside a time critical VI adds jitter to the application When using UDP to send data the receiving computer must have a read port open before the transmitting computer sends the data Use the UDP Open function to open a write port and specify the IP address and port of the receiving computer The data transfer occurs in byte streams of varying lengths called datagrams Datagrams arrive at the listening port and the receiving computer buffers and then reads the data It is possible to do bi directional data transfers with UDP With bi directional data transfers both computers specify a read and write port and transmit data back and forth using the specified ports You can use bi directional UDP data transfers to send and receive data from the network communication VI on the RT target UDP has the ability to perform fast data transmissions with minimal jitter However UDP cannot guarantee that all datagrams arrive at the receiving computer Because UDP is not connection based the arrival of datagrams cannot be verified To prevent this you must read data stored in the receiving computer s data buffer fast enough to prevent overflow and loss of data Refer to the LabVIEW Help available by selecting Help VI Function amp How To Help for information about using the UDP functions to exchange data with devices on a remote UDP port DataSocket is an Internet programming technology to share
26. Each protocol has its advantages and disadvantages You can choose any method based on the communication need The following list classifies the different communication methods e Shared Memory Communication Used for communication between LabVIEW and RT Series plug in devices only e Network Communication Used for communication over Ethernet networks TCP UDP National Instruments Corporation 4 9 Real Time Module User Manual Chapter 4 Building Deterministic Applications Shared Memory TCP Real Time Module User Manual DataSocket VI Server SMTP send only Bus Communication Used for communication over different bus communication ports Serial CAN Shared memory is the physical medium through which the host computer and RT Series plug in device communicate In operating systems like Windows two processes or applications can communicate with each other using the shared memory mechanism the operating system provides Similarly RT target VIs and LabVIEW VIs can communicate using shared memory VIs to read and write to the shared memory locations on the RT Series plug in device The Real Time Shared Memory VIs have very low timing overhead and are not a shared resource so they are the only communication method you can place in a time critical VI However the size of the shared memory is limited to 1 KB for 7030 Series plug in device and 512 KB for the 7041 Series plug in devices I
27. Lab VIEW Real Time Module User Manual Wy NATIONAL April 2003 Edition p INSTRUMENTS Part Number 322154D 01 Worldwide Technical Support and Product Information ni com National Instruments Corporate Headquarters 11500 North Mopac Expressway Austin Texas 78759 3504 USA Tel 512 683 0100 Worldwide Offices Australia 02 612 9672 8846 Austria 43 0 662 45 79 90 0 Belgium 32 0 2 757 00 20 Brazil 55 11 3262 3599 Canada Calgary 403 274 9391 Canada Montreal 514 288 5722 Canada Ottawa 613 233 5949 Canada Qu bec 514 694 8521 Canada Toronto 905 785 0085 Canada Vancouver 514 685 7530 China 86 21 6555 7838 Czech Republic 420 2 2423 5774 Denmark 45 45 76 26 00 Finland 385 0 9 725 725 11 France 33 0 1 48 14 24 24 Germany 49 0 89 741 31 30 Greece 30 2 10 42 96 427 India 91 80 51190000 Israel 972 0 3 6393737 Italy 39 02 413091 Japan 81 3 5472 2970 Korea 82 02 3451 3400 Malaysia 603 9131 0918 Mexico 001 800 010 0793 Netherlands 31 0 348 433 466 New Zealand 64 09 914 0488 Norway 47 0 32 27 73 00 Poland 48 0 22 3390 150 Portugal 351 210 311 210 Russia 7 095 238 7139 Singapore 65 6226 5886 Slovenia 386 3 425 4200 South Africa 27 0 11 805 8197 Spain 34 91 640 0085 Sweden 46 0 8 587 895 00 Switzerland 41 56 200 51 51 Taiwan 886 2 2528 7227 Thailand 662 992 7519 United Kingdom 44 0 1635 523545 For further support information refer to the Technical Support and Professional Services appendix To comment on the do
28. TE DESIGN PROCESS AND SAFETY LEVEL OF SUCH SYSTEM OR APPLICATION Contents About This Manual GOMVEMEONS saias en bani casei E E lead decknedunsoendea saad E A E ix Related Documentation irrisica inoin E E E R x Chapter 1 Introduction Real Time System Components 00 cceeeecceseesseeseeseceseesceeaeceseeseceeeeaeseeeeaeeseeeeesseeaees 1 1 Host Computer sieve sts ssa eles sces sates cdeck scestascadescaevessheaied ea savesddtes Abdensfessapdevdeavagedias 1 1 Lab VIEW ni Sth nian Mile ee A A 1 1 RTENE isi sche coves savanoits state E suas saseacedasasceadeeaduseages E R aT 1 2 RT Tarsetesiics cis sosss vacesveceetavisd as ede A sees AAR el es 1 2 RT Series Plug In Devices 00 0 eee ec ceeeeeseesseeseceeeeseenseeaesneeeseenaes 1 2 Networked RT Series Devices 000 0 eee eseeseeseeeeceseeseeeseeeeenseesees 1 3 Communicating with RT Target VIs occ ceeeseeseeeseessceseeseeesecseceseseseaesseseaeesees 1 3 Front Panel Communication ec eeeececeseseeeeeeseeeseeseeeseceecesscneesaeseeeeaeenaes 1 4 Network Communication 0 cece esesseceseeseeeseeeeeseeseeeaecseeesecseseaesneseaeenees 1 5 Real Time Module and Express VI Considerations 0 0 0 cc eeeceseeeeceeseeeseeeeeeeeseenees 1 6 Unsupported LabVIEW Features cece eceeeesscesceseeseeeseseeeeseeseeeaeeseeeaeeeeeaesneseaeeaaes 1 7 Modifying Front Panel Objects of RT Target VIs 0 eee ee eeeeeeseeeeeees 1 7 Using OS Specific Technologies in RT Target VIs 0 eee eeeeseeeeeeee
29. Using FieldPoint Devices to Acquire Measurement Data eee 5 9 Processing Measurement Data norintis itr ernn ae aae as e e e eaaa 5 10 Outputting Compensation Data 0 ieee ec eeceeeseceeeeseessecseceseeseeseeeaecneeeaeeneesaeseeenaessaes 5 11 Using NI DAQ VIs to Output Control Data eee eee eeeeseeereteeeeeeenees 5 11 Using FieldPoint VIs to Output Control Data eee cece eeeeseeeeeenees 5 14 Using Watchdogs in Applications oo eee eeeeceseeeceeseceeecseceeesseeseesaeeseeeaeeneeesesseenaes 5 14 Inactivity Watch do sof cscs shee a ea e Ee AE E ee i EE E ENERE 5 15 Network Watchdogs inorse iiaia asee nRa E E a R 5 15 Chapter 6 Optimizing Applications Avoiding Shared ReSourCe Sorner e a aE E ER E a E S 6 1 Memory Allocations and Preallocating Arrays sssseesesseseesesrseesreersreseseeses 6 1 Casting Data to Proper Data Types sssesessesesesssseerssrsresrsreereresrrsrsresrsresresene 6 3 Reducing the Use of Global Variables nseesssseseeresssrssessesesesreresrereseseneeses 6 3 Avoiding Contiguous Memory Conflicts seessseesseesseeeseestssesresesresrssrsrenteresteeresesresrses 6 3 Avoiding SubVrOverhedd 3 25 3 Maisie o lain des EE Sle aie 6 5 Settna VI Properes espe esse E AE EE EER sis iteassevi Soup eceuvea tees 6 5 Disabling the Disk Cacheiro eea rai a dies eas ected ngeltican O ees 6 5 setting BIOS Options moerore na i as ee a ee A Bs eee 6 6 Mass Compiling VIS sc2 c taii tienen Aha tenia eh Aaah ees
30. VI runs at the subroutine priority level it effectively takes control of the thread in which it is running and it runs in the same thread as its caller No other VI can run in that thread until the subroutine VI finishes running even if the other VI is at the subroutine priority level Assigning Vis to Execution Systems LabVIEW has the following six execution systems to categorize VIs e user interface e standard e instrument I O e data acquisition e other 1 e other 2 The names of the execution systems are suggestions for the type of VIs to place within the execution system By default all VIs run in the standard execution system at normal priority The user interface execution system handles all user interface tasks Instrument I O and data acquisition task VIs can be assigned to other execution systems but you can use the labels to understand the organization In addition to the six execution systems you also can assign VIs to the same as caller execution system The same as caller category is not a true execution system because it runs subVIs in the same execution system as the VI that called the subVI Every execution system except user interface has a thread queue For example if you have three threads assigned to an execution system at any time one thread might run and the other two wait in the queue Assuming all threads have the same priority one of the threads runs for a certain amount of time The thread then moves t
31. W that runs on the RT target The RT Engine runs the VIs you download to the targets from LabVIEW on the host computer The RT Engine provides deterministic real time performance for the following reasons e The RT Engine is designed for real time performance e The RT Engine runs on a real time operating system RTOS which ensures that the LabVIEW execution system and other operating system services adhere to real time operation Refer to Chapter 4 Building Deterministic Applications for information about the LabVIEW execution system e The RT Engine runs on RT Series hardware Other applications or device drivers commonly found on the host computer do not run on RT targets The absence of additional applications or devices means that a third party application or driver does not impede the execution of VIs e RT Series hardware uses no virtual memory which eliminates a major source of unpredictability in deterministic systems RT Target An RT target refers to RT Series hardware that runs the RT Engine and VIs you create using LabVIEW There are two types of RT targets RT Series plug in devices and networked RT Series devices RT Series Plug In Devices The RT Series plug in devices are plug in PCI PXI devices with embedded processors Each plug in device contains a processor board and data acquisition daughterboard The processor board contains a microprocessor that runs LabVIEW VIs This manual does not contain information a
32. ait or sleep until the next wake up edge but returns immediately In other words a wake up edge sets a wake up flag and the Counter Control VI waits for and clears the flag If the Counter Control VI is in a time critical VI lower priority VIs do not have a chance to run Acquiring Measurement Data Use the AI Sample Channel VI to acquire a single point of data from a single channel of a data acquisition device The block diagram in Figure 5 8 illustrates an acquisition loop timed using the Wait Until Next ms Multiple function and implements a single point data acquisition using the AI Sample Channel VI National Instruments Corporation 5 7 Real Time Module User Manual Chapter 5 Creating Deterministic Control Applications Read amp chart data until the stop button pressed Control execution flow with sequence structure to ensure consistent wait behavior Figure 5 8 Acquiring Single Points of Data from a Single Channel The software timed implementation of the data acquisition has obvious limitations First the acquisition cannot be faster than 1 kHz because the Wait Until Next ms Multiple function is bounded by the resolution of the OS system clock Second the acquisition is subject to software jitter We can increase the loop rate and decrease jitter by using hardware timing methods Using DAQ Devices to Acquire Measurement Data The block diagram in Figure 5 9 uses the AI SingleScan VI to acquire one a
33. al Time Operating Operating Operating System System System RTOS RTOS RTOS RT Engine RT Engine RT Engine a KEE Se ArrayMaker vi anay nee a gt Real Time Module User Manual Figure 6 3 Memory Diagrams of an RT Target The RT Engine uses available memory for running RT target VIs and storing data In diagram 2 of Figure 6 3 ArrayMaker vi creates Array 1 All elements in Array must be contiguous in memory The RTOS reuses the same memory addresses if you stop a VI and then run it again with arrays of the same size or smaller In diagram 3 of Figure 6 3 ArrayMaker vi creates Array 2 The RTOS creates Array 2 in the reserved memory space previously occupied by Array 1 Array 2 is small enough to fit in the reserved memory space that was allocated to Array 1 The extra contiguous memory used for Array 1 remains in the reserved memory space as shown in diagram 3 of Figure 6 3 When ArrayMaker vi runs for a third time with a larger array or if another VI generates a larger array the RT Engine must find a large enough contiguous space In diagram 4 of Figure 6 3 ArrayMaker vi must create Array 3 larger than the previous arrays in the available memory Even when ArrayMaker vi stops running the RT Engine continues to run Previously reserved memory is not available If ArrayMaker vi runs a fourth time and attempts to create an array larger than Array 3 the operation fails There is no contiguous memory
34. area large enough to create 6 4 ni com Chapter 6 Optimizing Applications the array because of the memory fragmentation You can preserve memory space by preallocating array space equal to the largest use case Avoiding SubVI Overhead When you call a subVI there is a certain amount of overhead associated with the call Although the overhead is small compared to I O operations it adds up if you call a subVI multiple times in a loop Instead embed the loop in the subVI You also can convert subVIs into subroutines by changing the VI priority The LabVIEW execution system minimizes the overhead to call subroutines Subroutines are short frequently executed tasks and are generally most appropriate when used with VIs that do not require user interaction Subroutines cannot display front panel data and do not multitask with other VIs Also avoid using timing or dialog box functions in subroutines Refer to the Chapter 4 Building Deterministic Applications for information about setting VI priorities Setting VI Properties To reduce memory requirements and increase performance of VIs disable nonessential options in the VI Properties dialog box available by selecting File VI Properties Select Execution from the Category pull down menu and remove checkmarks from the Allow debugging and Auto handle menus at launch checkboxes By disabling these options VIs use less memory compile quicker and perform better overall Disabling
35. ays Note Application Path and Downloaded VI Path refer to the file system on the RT target National Instruments Corporation 3 9 Real Time Module User Manual Building Deterministic Applications This chapter explains how to build deterministic applications using the LabVIEW Real Time Module Programming for Determinism The first thing to consider when implementing a real time system with LabVIEW is whether you need determinism Determinism is the characteristic of a system that describes how consistently it responds to external events or performs operations within a given time limit If you intend to build deterministic applications use the programming techniques in this chapter to achieve high levels of determinism in VIs Overview of Multithreaded Applications Most computers have only one processor so tasks execute one at a time Multitasking is achieved by running one application for a short amount of time and then having other applications run As long as the amount of processor time allocated for each application is small enough computers appear to have multiple applications running simultaneously Multithreading is when you apply the concept of multitasking to a single application by breaking it into smaller tasks that execute for short amounts of time in different execution system threads A thread is a completely independent flow of execution for an application within the execution system Multithreaded application
36. bout the data acquisition daughterboard of plug in devices Refer to the appropriate plug in device documentation for information about the data acquisition daughterboard for plug in devices Real Time Module User Manual 1 2 ni com Chapter 1 Introduction Networked RT Series Devices A networked RT Series device is a networked hardware platform with an embedded processor that runs LabVIEW VIs You can use a separate host computer to communicate with and control VIs on the networked RT Series device through an Ethernet connection but the device is independent of the host computer Some examples of networked RT Series devices include the following e RT Series PXI Controllers A networked device that installs in an NI PXI chassis and communicates with NI PXI modules installed in the chassis You can write VIs that use all the input output I O capabilities of the PXI modules SCXI and other signal conditioning devices installed in a PXI chassis The RT Engine also supports features of the RT Series PXI controller For example you can use the GPIB and serial ports onboard the NI PXI 8176 controller for instrument control Refer to the National Instruments Web site at ni com info and enter the info code RT0001 for information about the features supported by the RT Engine on specific networked devices e RT Series FieldPoint Modules A networked device ideal for distributed real time I O applications e 7041 RT Series Plug In Devices A
37. cess on the Visible VIs list Also disable the Web Server or remove all VIs on the Visible VIs list to avoid losing memory when the Web Server is not in use Real Time Module User Manual 4 16 ni com Creating Deterministic Control Applications This chapter explains how to create control applications using the LabVIEW Real Time Module This chapter also explains how to use the NI Watchdog VIs to monitor a control system for critical failures or events Overview of Control Applications In a typical control application the process variable is a system variable that you want to control Sensors measure the process variable in the dynamic system and provide the data to the control application The set point is the value or command value you want for the process variable A comparator determines if a difference exists between the process variable and the set point If a difference exists and it is deemed large enough the compensator processes the data and determines the desired actuator output to drive the system appropriately Figure 5 1 illustrates a typical control system Comparator Actuator Output System Plant Set Point Compensator Process Variable Measurement Figure 5 1 Typical Control System For example in a temperature measurement system if the actual temperature is 100 C and the temperature set point is 120 C the compensator needs to take some act
38. cessary way If you use software watchdogs inactivity can reset the device set an occurrence in software and activate a PXI backplane trigger Network Watchdog Some RT Series hardware such as the FP 20 xx have a built in network monitor If you enable the network watchdog and the FieldPoint network module loses communication with all hosts or clients over the network the module sets output channels to predefined values corresponding to the watchdog state You can configure these watchdogs to output a certain value when a network failure is detected If no built in network watchdog is available you can create one programmatically For example if TCP is the communication protocol between the host machine and embedded real time applications you can monitor for network disconnect errors and timeouts In these situations you might want to change the behavior of the system For example you might want to log to a file until the network connection is reestablished National Instruments Corporation 5 15 Real Time Module User Manual Chapter 5 Creating Deterministic Control Applications Many real time applications separate time critical tasks into a separate VI and communicate between VIs using protocols such as the Real Time FIFO VIs You can use the API of the Real Time FIFO VIs to detect a failure in the communication path or in one of the participants For example you can check if the RT FIFO is unexpectedly empty or if you are overw
39. communication A graphical user interface for configuring National Instruments hardware and software A device capable of storing data When a computer runs applications for a short amount of time to give the impression of multiple applications running simultaneously Running tasks of an application for a short amount of time to give the impression of multiple tasks running simultaneously An operating system lock around a resource to protect the resource from access by other VIs A protocol for communication between a host VI and a VI running on the RT target using specific network communication programmatic controls A hardware platform with an embedded processor that you can control using a separate host computer through an Ethernet connection Driver software included with all NI measurement devices NI DAQ is an extensive library of VIs and functions you can call from an application development environment ADE such as LabVIEW to program all the features of an NI measurement device such as configuring acquiring and generating data from and sending data to the device Real Time Module User Manual Glossary 0 operating system PCI plug in device preemptive scheduling priorities Property Node Proportional Integral Derivative PID Control protocol PXI Real Time Module User Manual Base level software that controls a computer runs programs interacts with users and communicates with installed
40. cumentation send email to techpubs ni com 1999 2003 National Instruments Corporation All rights reserved Important Information Warranty The media on which you receive National Instruments software are warranted not to fail to execute programming instructions due to defects in materials and workmanship for a period of 90 days from date of shipment as evidenced by receipts or other documentation National Instruments will at its option repair or replace software media that do not execute programming instructions if National Instruments receives notice of such defects during the warranty period National Instruments does not warrant that the operation of the software shall be uninterrupted or error free A Return Material Authorization RMA number must be obtained from the factory and clearly marked on the outside of the package before any equipment will be accepted for warranty work National Instruments will pay the shipping costs of returning to the owner parts which are covered by warranty National Instruments believes that the information in this document is accurate The document has been carefully reviewed for technical accuracy In the event that technical or typographical errors exist National Instruments reserves the right to make changes to subsequent editions of this document without prior notice to holders of this edition The reader should consult National Instruments if errors are suspected In no event shall National
41. d in manual ix related documentation x downloading E software on networked RT Series devices 2 6 VIs to RT target 3 3 error codes in debugging defining custom error codes 8 3 setting custom error file INI tokens 8 4 Express VIs 1 6 F FieldPoint Modules RT Series acquiring measurement data 5 9 definition 1 3 National Instruments Corporation l 3 Index FieldPoint VIs acquiring measurement data 5 9 outputting compensation data 5 14 Flat Sequence structure 5 5 front panel closing front panel connection without closing VIs 3 4 modification of RT target VI front panels not supported 1 7 Front Panel Communication protocol 1 4 purpose and use 1 4 functional global variables 4 6 G global variables functional 4 6 overview 4 5 reducing use of 6 3 H hardware counter for time critical VIs 5 5 timing control loops with 5 5 AI SingleScan VI 5 5 Counter Control VI 5 6 host computer 1 1 inactivity watchdog 5 15 Initialize Array function 6 2 installation Real Time Module 2 1 RT Series plug in devices 2 2 PCI plug in devices 2 2 PXI plug in devices 2 2 Real Time Module User Manual Index J Jitter 4 11 priority inversion induced 6 1 reducing with preallocation arrays 6 2 L LabVIEW debugging tools 1 4 8 1 LabVIEW Memory Manager 6 1 LabVIEW PID Control Toolset VIs 5 10 LabVIEW Real Time Module See Real Time Module LabVIEW software See also RT Engine
42. d text denotes items that you must select or click in the software such as menu items and dialog box options Bold text also denotes parameter names Italic text denotes variables emphasis a cross reference or an introduction to a key concept This font also denotes text that is a placeholder for a word or value that you must supply Text in this font denotes text or characters that you should enter from the keyboard sections of code programming examples and syntax examples This font is also used for the proper names of disk drives paths directories programs subprograms subroutines device names functions operations variables filenames and extensions and code excerpts Text in this font denotes a specific platform and indicates that the text following it applies only to that platform National Instruments Corporation ix Real Time Module User Manual About This Manual Related Documentation Real Time Module User Manual The following documents contain information that you might find helpful as you read this manual RT Series hardware documentation Getting Started with the LabVIEW Real Time Module LabVIEW Real Time Module Release Notes LabVIEW Help available by selecting Help VI Function amp How To Help Getting Started with LabVIEW LabVIEW User Manual LabVIEW Application Builder User Guide X ni com Introduction Most LabVIEW applications run on a general purpose operating system OS like Win
43. dows Linux Solaris or Mac OS Some applications require deterministic real time performance that general purpose operating systems cannot guarantee The LabVIEW Real Time Module and RT Series hardware extend the capabilities of LabVIEW to address the need for deterministic real time performance The Real Time Module combines LabVIEW graphical programming with the power of RT Series hardware enabling you to build deterministic real time systems You develop VIs in LabVIEW and embed the VIs on RT targets The RT target runs VIs without a user interface and offers a stable platform for real time VIs Real Time System Components Host Computer LabVIEW A real time system consists of software and hardware components The software components include LabVIEW the RT Engine and VIs built using LabVIEW The hardware components of a real time system include a host computer and an RT target The following section describes the different components of a real time system The host computer is the computer where you develop the VIs for the real time system The host computer can be a PC Mac or a PXI controller with a Windows operating system You develop VIs with LabVIEW on the host computer The Real Time Module extends the capabilities of LabVIEW to allow you to select an RT target to run VIs National Instruments Corporation 1 1 Real Time Module User Manual Chapter 1 Introduction RT Engine The RT Engine is a version of LabVIE
44. e creating for RT target VIs 4 8 V VI Server communication method 4 12 VIs See also RT target VIs time critical VIs Changed or Missing VIs dialog box 3 5 closing front panel connection without closing VIs 3 4 connecting to VIs running on RT target 3 4 downloading to RT target 3 3 execution systems for categorizing 4 3 Express VIs 1 6 improving performance avoiding subVI overhead 6 5 mass compiling 6 6 setting VI properties 6 5 Network Communication protocol 1 5 outputting compensation data FieldPoint VIs 5 14 NI DAQ VIs 5 11 Real Time Module User Manual Index passing data between VIs 4 5 functional global variables 4 6 global variables 4 5 Real Time FIFO VIs 4 7 PID Control Toolset VIs 5 10 priorities normal 4 2 setting execution system and priority 4 4 subroutine 4 2 types of 4 2 Real Time FIFO VIs 4 7 Real Time Module User Manual W Wait Until Next ms Multiple function 5 3 watchdogs in deterministic control applications 5 14 inactivity watchdog 5 15 network watchdog 5 15 ni com
45. e VI to set the system time set the IP address for the Time Server entry located on the Servers tab of the System Configuration dialog box for the FieldPoint module to 0 0 0 0 National Instruments Corporation Networked RT Series PXI devices The RT Engine on the device obtains the system date and time from the BIOS once at boot up Use the RT Set Date and Time VI to programmatically set the system date and time Refer to the National Instruments Web site at ni com info and enter the info code RT003 for information about setting local time and time zone considerations for RT targets 2 7 Real Time Module User Manual Real Time Module Environment This chapter describes the basic functionality of the LabVIEW Real Time Module such as targeting and downloading VIs to an RT target This chapter also describes the available options for networked RT Series devices Targeting LabVIEW to an RT Target When you first launch LabVIEW after installing the Real Time Module the default execution target is the host computer operating system as shown in Figure 3 1 B LabVIEW File Edit Tools Help T4 LabVIEW NATIONAL INSTRUMENTS Open ss crome l Configure Help z LabVIEW for Windows X Figure 3 1 LabVIEW Dialog Box National Instruments Corporation 3 1 Real Time Module User Manual Chapter 3 3 Real Time Module Environment You can target LabVIEW to an RT target or the host com
46. e checkbox before starting a profiling session Collecting information about VI memory use adds a significant amount of overhead to VI execution which affects the accuracy of any timing statistics gathered during the profiling session Therefore perform memory profiling separate from time profiling Many of the options in the Profile window become available only after you begin a profiling session During a profiling session you can take a snapshot of the available data and save it to an ASCII spreadsheet file The timing measurements accumulate each time you run a VI Refer to the LabVIEW Performance and Memory Management Application Note for information about using the Profile window Verifying Correct Timing Behavior Timing is crucial in a deterministic application Use one of the following methods to verify the timing behavior of an application Using the Tick Count ms Function The Tick Count ms function can be used to measure the time it takes to perform N iterations of a specified operation and calculate the average time in seconds per operation as well as average operations per second Refer to the Benchmarking Shell VI located in the examples Real Time RT Tutorial 11b for an example using Tick Count ms to benchmark code Refer to the NI Developer Zone at ni com zone for information about using the Tick Count ms function to verify timing behavior Using the Pentium Time Stamp Counter Real Time Module User Manual O
47. eating Deterministic Control Applications ee ee Al Wait AO Al Wait AO Al Wait Figure 5 5 Incorrect Timing of a Control System You can use a Flat Sequence structure to force a specific execution sequence as shown in Figure 5 6 In the block diagram in Figure 5 6 the Wait Until Next ms Multiple function precedes the analog input and the system implementation produces results that match the ideal timing Time Critical pHerenaneto ana o atn na alo ana a aonana ae ou aiota aio alanos aiutu Figure 5 6 Flat Sequence Implementation of a Control System Timing Control Loops Using Hardware With the Wait Until Next ms Multiple function you can achieve loop rates of 1 kHz at best However the AI SingleScan VI allows the analog input hardware scan clock of NI E Series data acquisition devices to control when a thread sleeps and wakes up Because the timing is controlled through hardware applications using the AI SingleScan VI can achieve a sleep resolution much finer than 1 ms and dramatically reduce jitter Al SingleScan VI The AI SingleScan VI can continuously acquire one analog data point from each channel in the scan list using hardware timing When you configure an NIE Series data acquisition device for non buffered input at a certain scan rate the hardware scan clock controls the timing of analog to digital A D conversions Each time the scan clock pulses the data acquisition device performs an A D conversio
48. eeees 1 7 Chapter 2 Installing and Configuring the Real Time Module and RT Targets Installing the Real Time Module sser ae E a e 2 1 Installing and Configuring RT Series Plug In Devices ssseesesesseeesseerrrsrrrrsresrrerseses 2 2 RT Senes PCI Plug In Device Siionin irn E E eh 2 2 RT Series PXI Plug In Devices eee eceeeeseseeceseseeeeseeseeeeeeseensesaeensesseenaes 2 2 Configuring RT Series Plug In Devices 0 0 eeeeseeseceseeseeeeeeseeeeeeseesees 2 3 Configuring Networked RT Series Devices 0 0 0 0 ccc eeeeeeccesseeeeeeeeeeeeseeeseeaeeneeesseseaes 2 4 Booting into the Real Time Operating System eee 2 4 Configuring Network Settings 0 0 cece eeeeseceseeseeneeeseeneeeseeeees 2 5 Downloading Software ss gieren reae i 2 6 Setting the System Time of RT Targets eee ee eeecseceeecseesseeseeeeeeseesseeateneeeaeesaes 2 7 National Instruments Corporation v Real Time Module User Manual Contents Chapter 3 Real Time Module Environment Targeting LabVIEW to an RT Target oe ei ee eceeceseeseeeseesecesecseeesesseensecaseseeeaeeneeeaes 3 1 Downloading VIs to an RT Target cece eeceeesecesceseseeeeseceeeeseeseesseeseeesesnseeaeeneeeaes 3 3 Closing a Front Panel Connection without Closing VIs cccececeseeeeseseeseeseeneeees 3 4 Connecting to VIs Running on an RT Target ee eseeseeseeneceseseeeeseseeeeseeeeenees 3 4 Configuring Options of Networked RT Targets 0 ccccceccsessssssssesessessensessesessseseaes 3 5 Se
49. ees 8 2 Using the Tick Count ms FUnction cece eeeceessceeeeeeeeeceseeeeeeeeneeeseeeeaeeeaes 8 2 Using the Pentium Time Stamp Counter 00 eeeeseeeeeseeeeeeeeeeeeaeeeees 8 2 Using an Oscilloscopes esses veces oes iovves cess inate a nieve ates ees He dS 8 3 Using Software DriverScan yidis tistics o hanes sie Mile eee deed ae 8 3 Using and Defining Error CodeS isise e E 8 3 Defining Custom Error Codes eee eeceseeseessceeeseceeeeseeseeesecsecesecaeenaeesenaes 8 3 Setting Custom Error File INI Tokens 2 0 0 ee eeeeeecseeeeeseeeseeseeeseeeees 8 4 Appendix A Configuring and Testing Device Drivers Appendix B Technical Support and Professional Services Glossary Index Real Time Module User Manual viii ni com About This Manual Conventions This manual contains installation information and configuration instructions for the LabVIEW Real Time Module and RT Series hardware This manual also contains real time programming techniques to help you build a deterministic application using the Real Time Module 3 bold italic monospace Platform The following conventions appear in this manual The symbol leads you through nested menu items and dialog box options to a final action The sequence File Page Setup Options directs you to pull down the File menu select the Page Setup item and select Options from the last dialog box This icon denotes a note which alerts you to important information Bol
50. ent You must read data stored in an RT FIFO before the FIFO is full to ensure the transfer of every element without losing data Check the overwrite output of the RTFIFOWrite VI to ensure that data is not overwritten If the RT FIFO overwrites data the overwrite output returns a TRUE value Refer to the LabVIEW Help available by selecting Help VI Function amp How To Help for VI reference information about the Real Time FIFO VIs Refer to the examples Real Time RT Communication 11b for examples of using the Real Time FIFO VIs to communicate between VIs that run on an RT target National Instruments Corporation 4 7 Real Time Module User Manual Chapter 4 Building Deterministic Applications Creating a User Interface for RT Target Vis Real Time Module User Manual Use the RT Communication Wizard to create a user interface for time critical VIs running on an RT target The RT Communication Wizard creates the following three user interface VIs Host VI Provides a user interface that runs on the host computer Time Critical VI Contains the time critical tasks Normal Priority VI Contains all non deterministic network communication tasks used to update the host VI front panel with data received from the time critical VI The normal priority VI also calls the time critical VI Complete the following steps to create the user interface VIs 1 Select Tools RT Communication Wizard to open the RT Communication Wizard
51. enting counter that executes an expiration action when 5 14 ni com Chapter 5 Creating Deterministic Control Applications it reaches some preconfigured terminal count The network watchdog checks the system for network disturbances and responds to a connection failure Inactivity Watchdog Some RT Series devices have hardware watchdogs that you can configure programmatically to respond to system inactivity The hardware watchdog has a timeout period that you can configure The watchdog uses a built in counter to count up to the defined timeout When the watchdog reaches the timeout value it executes the preconfigured expiration action To prevent the watchdog from timing out the application can reset the watchdog count The monitoring of the application is called whacking the dog which essentially resets the counter of the hardware watchdog The application can reset the count while it runs If the application stops running the watchdog counts up to its timeout value and then carries out the expiration action Available expiration actions include setting a trigger generating an occurrence that another application can respond to and rebooting the RT Series device When hardware capability is unavailable you can configure a counter or timer device to behave like the built in PXI watchdog counter You also can toggle a hardware digital line By monitoring this count value from a separate application you can respond to inactivity in the ne
52. es to open the VI Properties dialog box 2 Select Execution from the Category pull down menu 4 4 ni com Chapter 4 Building Deterministic Applications 3 Select the priority from the Priority pull down menu 4 Select the execution system from the Preferred Execution System pull down menu You then can use the different VIs as subVIs to build the final deterministic application in one VI Cooperatively Yielding Time Critical VI Execution Because of the preemptive nature of time critical VIs they can monopolize processor resources A time critical VI might use all of the processor resources not allowing lower priority VIs in the application to execute You must build time critical VIs that periodically yield or sleep to allow lower priority tasks to execute without affecting the determinism of the time critical code By timing control loops you can yield time critical VIs and cooperatively relinquish processor resources Refer to the Timing Control Loops section of Chapter 5 Creating Deterministic Control Applications for information about the methods available for timing time critical VIs to relinquish processor resources Passing Data between VIs Global Variables After dividing tasks in an application into separate VIs of varying priorities you might need to communicate between the different VIs Use global variables functional global variables and the Real Time FIFO VIs to send and receive data between VIs in an a
53. es you to vary the time between inputs and outputs until you achieve an optimized loop cycle time Input Input as Post Processing bi Post Processing i p gt Time Delay Pre Processing gt a aera gt Output Output Shared Clock staggered in out Real Time Module User Manual Figure 5 12 Divided Process Routine Implementation In some cases you can divide the processing routine into a pre processing and post processing section Dividing the processing routine establishes a smaller response time between inputs and outputs by shifting some of the processing elsewhere as shown in Figure 5 12 The block diagram in Figure 5 13 uses the AO SingleUpdate VI to perform an output only operation that writes the new output value to the output register of the device DAC 0 which is hardware timed and driven by the AI Scan Start signal The AI Scan Start clock must trigger the D A conversion for the value to output Refer to the One Channel PID Control VI in the examples Real Time RT Control 11b for an example of outputting data from a PID loop 5 12 ni com Chapter 5 Creating Deterministic Control Applications Reuse memory from scaled data eej output in order to avoid allocating Re new memory each loop iteration 77 ingle Sing read newest data Y Read newest data to avoid missing initial scan s Switch to reading oldest data to enforce real time Write to DACO but do not upda
54. eterministic Control Applications Real Time Module User Manual ideal timing of a control system The example control system reads an analog input writes an analog output and waits in a synchronized cycle that repeats 3 jo gt gt y P Wait Al AO Wait Al AO Wait Figure 5 3 Ideal Timing of a Control System The block diagram in Figure 5 4 uses a loop with the Wait Until Next ms Multiple function to create a control system Time Critcal AI Sample Channel vi 40 Update Channel vi AO Wait Until Next ms Multiple 100 Figure 5 4 Parallel Implementation of a Control System Because of the dataflow properties of LabVIEW programming the Wait Until Next ms Multiple function can execute before after or between the execution of the analog input and output The behavior of the loop differs depending on when the Wait Until Next ms Multiple function executes If the Wait Until Next ms Multiple function executes first the analog input precedes the analog output The control system timing matches the ideal timing shown in Figure 5 3 However when the Wait Until Next ms Multiple function does not execute first the loop sleeps until the function executes Because a portion of the loop sleeps the entire loop sleeps and the analog output waits until the loop returns from sleep to execute which produces results that do not match the ideal timing Figure 5 5 shows the incorrect results 5 4 ni com Chapter 5 Cr
55. ey run on the RT target You can use LabVIEW debugging tools such as probes execution highlighting breakpoints and single stepping to locate errors on the block diagram code Refer to Chapter 8 Debugging Deterministic Applications for information about debugging applications Front Panel Communication is a good communication method typically used during development because it is a quick method for monitoring and interfacing with VIs running on an RT target Use Network Communication to increase the efficiency of the communication between a host computer and the RT Engine 1 4 ni com Chapter 1 Introduction Network Communication With Network Communication a host VI runs on the host computer and communicates with the VI running on the RT target using specific network communication programmatic controls such as TCP VI Server and in the case of non networked RT Series plug in devices shared memory reads and writes You might use Network Communication for the following reasons e You want to run another VI on the host computer but you cannot use LabVIEW for any other task when you target an RT target e You want to control information sent back and forth You can customize communication code to specify which front panel objects get updated and when You also can control which components are visible on the front panel because some controls and indicators might be more important than others e You want to control timing and
56. f you need to transfer several megabytes of data you must divide the data into smaller portions and then transfer them In doing so you must make sure that data in the shared memory is not overwritten before it is read Refer to the LabVIEW Help available by selecting Help VI Function amp How To Help for information about the Real Time Shared Memory VIs TCP is an industry standard protocol for communicating over networks Host LabVIEW VIs can communicate with RT target VIs using the LabVIEW TCP functions Refer to the LabVIEW Help available by selecting Help VI Function amp How To Help for information about the TCP functions 4 10 ni com UDP DataSocket Chapter 4 Building Deterministic Applications The Real Time Module extends the capabilities of the existing TCP functions to enable communication with networked RT Series devices and to allow communication across shared memory with RT Series plug in devices However TCP is non deterministic and using TCP communication inside a time critical VI adds jitter to the application Jitter is the amount of time that a loop cycle time varies from the desired time UDP is a network transmission protocol for transferring data between two locations on a network UDP is not a connection based protocol so the transmitting and receiving computers do not establish a network connection Because there is no network connection there is little overhead when transmitting data However U
57. for configuration instructions Real Time Module User Manual 3 2 ni com Chapter 3 Real Time Module Environment If the IP address of the host computer appears in the RT Target Access list of the RT target you do not need to enter the password Refer to the Setting Access Permissions for an RT Target section for information about the RT Target Access network options 6 Click the OK button Downloading Vis to an RT Target When you select an RT target in the Select Execution Target dialog box LabVIEW establishes a front panel communication connection with the RT target You can download a VI and its associated subVIs to an RT target by clicking the Run button The RT Engine on the RT target then runs the downloaded VI When a downloaded VI runs on the RT target LabVIEW switches from edit to run mode In run mode you cannot edit VIs You must switch back to edit mode to make changes to the VI Select Operate Change to Edit Mode to switch to edit mode Switching an RT target VI to edit mode removes the VI from memory on the target 3 Note When you edit a VI or convert a VI from a different version of LabVIEW you must save the VI on the host computer before you can download and run it on the RT target You also can download LabVIEW VIs without running them by selecting Operate Download Application while targeted to an RT target To see which VIs have been downloaded to the RT target select Browse Show VI Hierarchy while
58. g RT Engine RT target run time engine S shared memory shift register soft reboot subVI synchronous National Instruments Corporation G 5 Glossary A property of an event or system in which data is processed as it is acquired instead of being accumulated and processed at a later time Uses a combination of round robin and preemptive scheduling to execute threads in the execution system Allows you to operate a front panel on a machine that is separate from where the VI resides and executes using a LabVIEW client or Web browser Scheduling that attempts to share the processor in equal amounts of time among all ready tasks of the same priority A version of LabVIEW that runs on the RT target RT Series hardware that runs VIs downloaded from and built in LabVIEW Runs LabVIEW executables built using the LabVIEW Application Builder on computers without LabVIEW Memory that can be sequentially accessed by more than one controller or processor but not simultaneously accessed Also known as dual mode memory Optional mechanism in loop structures to pass the value of a variable from one iteration of a loop to a subsequent iteration Shift registers are similar to static variables in text based programming languages Restarting a computer without cycling the power usually through the operating system VI used on the block diagram of another VI Comparable to a subroutine 1 Hardware A property of an event
59. gh LabVIEW code The only feature not supported by the Real Time Module is the Call Chain ring which appears in the toolbar of a subVI block diagram window while single stepping The debugging tools are useful for determining the source of errors in an application Refer to the LabVIEW User Manual for information about the LabVIEW debugging tools 3 Note Do not use the LabVIEW debugging tools to debug execution timing because all of the tools affect the timing of an application Using the Profile Window The Profile window is a powerful tool for statistically analyzing how an application uses execution time and memory The Profile window displays information that can identify the specific VIs or parts of VIs you need to optimize For example if you notice that a particular subVI takes a long time to execute you can improve the performance of that VI The Profile window displays the performance information for all VIs in memory in an National Instruments Corporation 8 1 Real Time Module User Manual Chapter 8 Debugging Deterministic Applications interactive tabular format From the Profile window you can select the type of information to gather and sort the information by category You also can monitor subVI performance within different VIs Select Tools Advanced Profile VIs to display the Profile window My Note You must target LabVIEW to an RT target while running the profiler You must place a checkmark in the Profile Memory Usag
60. hybrid between a traditional plug in device and a networked device that communicates through shared memory or communicates through a network connection This manual does not contain hardware related information about specific networked devices Refer to the appropriate device documentation for information about the device Communicating with RT Target Vis The RT Engine on the RT target does not provide a user interface for applications You can use one of two communication protocols Front Panel Communication or Network Communication to provide a user interface for RT target VIs National Instruments Corporation 1 3 Real Time Module User Manual Chapter 1 Introduction Front Panel Communication Real Time Module User Manual With Front Panel Communication LabVIEW and the RT Engine execute different parts of the same VI as shown in Figure 1 1 LabVIEW on the host computer displays the front panel of the VI while the RT Engine executes the block diagram LabVIEW Host Computer Network Communication RT Engine RT Target Figure 1 1 Front Panel Communication Protocol Use Front Panel Communication between LabVIEW on the host computer and the RT Engine to control and test VIs running on an RT target After downloading and running the VIs keep LabVIEW on the host computer open to display and interact with the front panel of the VI You also can use Front Panel Communication to debug VIs while th
61. id or minimize jitter in a time critical VI to ensure determinism Do not use shared resources in time critical VIs The amount of jitter induced by a shared resource depends on the type of shared resource involved For instance when accessing a global variable a VI can finish a read or write operation on a global within a consistent length of time or with very little variance in time Because reading and writing to a global variable is bound in time you can account for the jitter induced by sharing global variables Memory Allocations and Preallocating Arrays When a VI allocates memory the VI accesses the LabVIEW Memory Manager The LabVIEW Memory Manager allocates memory for data storage The LabVIEW Memory Manager is a shared resource and might be locked by a mutex up to several milliseconds Avoid allocating memory within time critical VI control loops If you are using arrays in time critical VI control loops you can reduce jitter by preallocating arrays before entering the loop National Instruments Corporation 6 1 Real Time Module User Manual Chapter 6 Optimizing Applications The block diagram in Figure 6 1 builds an array within the control loop Jitter affects the loop because the Build Array function inside the loop uses the LabVIEW Memory Manager Build Arra The Build Array Function accesses the LabVIEW Memory Manager which might cause jitter Figure 6 1 Memory Allocation in Control Loop The block diagram in
62. ide a loop to determine whether the loop is deterministic Using and Defining Error Codes Use error handling to debug and manage errors in VIs The LabVIEW error handler VIs return error codes when an error occurs in a VI Error codes reveal the specific problem the VI encountered When you configure an RT target LabVIEW automatically copies the error code files used by the error handler VIs to the target Defining Custom Error Codes Use custom error codes with networked RT targets that have media storage devices Create error files using the Error Code File Editor by selecting Tools Advanced Edit Error Codes If you use custom errors with LabVIEW you must place the error files in the c ni rt system user lib errors directory on the networked RT target Use the FTP client in Measurement amp Automation Explorer MAX to transfer the error file to the networked device National Instruments Corporation 8 3 Real Time Module User Manual Chapter 8 Debugging Deterministic Applications Setting Custom Error File INI Tokens You can set two error handling configuration tokens in the ni rt ini file that specify the way LabVIEW searches for custom error files Add RTDownloadErrors TRUE to the ni rt ini file to search for error files on the RT target If the RT Engine does not find any local error files the RT Engine requests available error files from the host computer if a front panel connection exists The host computer searches f
63. ight laws this publication may not be reproduced or transmitted in any form electronic or mechanical including photocopying recording storing in an information retrieval system or translating in whole or in part without the prior written consent of National Instruments Corporation Trademarks DAQ STC DataSocket FieldPoint IVI LabVIEW National Instruments NI NI Developer Zone NI CAN ni com NI DAQ NI IMAQ NI Motion NI VISA RTSI SCXI and TestStand are trademarks of National Instruments Corporation Product and company names mentioned herein are trademarks or trade names of their respective companies Patents For patents covering National Instruments products refer to the appropriate location Help Patents in your software the patents txt file on your CD or ni com patents WARNING REGARDING USE OF NATIONAL INSTRUMENTS PRODUCTS 1 NATIONAL INSTRUMENTS PRODUCTS ARE NOT DESIGNED WITH COMPONENTS AND TESTING FOR A LEVEL OF RELIABILITY SUITABLE FOR USE IN OR IN CONNECTION WITH SURGICAL IMPLANTS OR AS CRITICAL COMPONENTS IN ANY LIFE SUPPORT SYSTEMS WHOSE FAILURE TO PERFORM CAN REASONABLY BE EXPECTED TO CAUSE SIGNIFICANT INJURY TO A HUMAN 2 IN ANY APPLICATION INCLUDING THE ABOVE RELIABILITY OF OPERATION OF THE SOFTWARE PRODUCTS CAN BE IMPAIRED BY ADVERSE FACTORS INCLUDING BUT NOT LIMITED TO FLUCTUATIONS IN ELECTRICAL POWER SUPPLY COMPUTER HARDWARE MALFUNCTIONS COMPUTER
64. ime PXI Boot Disk Insert the boot disk into the disk drive of the PXI controller and power on or reset the controller to boot into the RTOS Configuring Network Settings Complete the following steps to configure the network settings of networked RT Series devices 1 National Instruments Corporation In MAX click the Remote Systems category to expand the Remote Systems list This displays all detected networked RT Series devices on the local subnet Select a device to configure Unconfigured devices appear with a 0 0 0 0 device name The right pane of the MAX window displays the network and software settings of the device Enter a device name in the Name text box located in the Device Identification section The default device name is the IP address of the device Enter the network parameters you want to assign to the device You can choose to assign a static IP address or have the device retrieve an IP address automatically from a Dynamic Host Configuration Protocol DHCP server A DHCP server allocates an IP address to the device when the device starts up Select Obtain IP address from DHCP server in the IP Settings section to obtain an IP address automatically from the DHCP server Use DHCP if a static IP address is not available Consult the network administrator for more information about using a DHCP server 2 5 Real Time Module User Manual Chapter 2 Installing and Configuring the Real Time Module and RT Targets
65. inks all the subVIs and functions on the block diagram with the top level VI Real Time Module User Manual 6 6 ni com Deploying Applications This chapter explains how to use the LabVIEW Application Builder to create stand alone executables of LabVIEW Real Time Module VIs Building Stand Alone Applications Use the Application Builder included with the Real Time Module Professional Development System to create stand alone Real Time Module applications Stand alone applications do not require you to run them from within a LabVIEW environment In LabVIEW select Tools Build Application or Shared Library DLL to launch the LabVIEW Application Builder Refer to the LabVIEW Application Builder User Guide for information about using the Application Builder to build a stand alone application Creating an Application Installer In addition to building applications the Application Builder can create an installer for a stand alone application Select the Installer Settings tab in the Build Application or Shared Library DLL dialog box to access the installer options Click the Advanced button to open the Advanced Installer Settings dialog box Place a checkmark in the LabVIEW Run Time Engine and the LabVIEW RT Support checkboxes to add the LabVIEW Run Time Engine and support for RT Series hardware to the application installer You can use the LabVIEW Run Time Engine to target the application to an RT target from a computer that does not
66. ion to raise the temperature National Instruments Corporation 5 1 Real Time Module User Manual Chapter 5 Creating Deterministic Control Applications One actuator output might be to drive a heater at 62 percent of its maximum output capacity The increased heater actuator output causes the system to become warmer which results in an increased temperature This kind of system is called a closed loop control system because the process of reading sensors and calculating the actuator output you want repeats continuously at a fixed loop rate Implementing a Deterministic Control Application Real Time Module User Manual You can use the Real Time Module RT Series hardware and National Instruments I O hardware to create deterministic control applications to monitor a system RT Series hardware can handle the process variable measurement and actuator compensation sections of a control system A LabVIEW application can retrieve sensor measurement data from the hardware compare set point and process variable data values use control algorithms to processes the data and output compensation data to the system compensation hardware Figure 5 2 shows the LabVIEW implementation of a control system Timing the control loop is not represented in Figure 5 2 However the timing of the control loop is important to the success of the control system y Sensor Software Actuator Input Processing Output Data Acquisition RT Target
67. l 11 Instruments Bg Scales FR Historical Data Software al a Figure 2 1 Measurement amp Automation Explorer National Instruments Corporation 2 3 Real Time Module User Manual Chapter 2 Installing and Configuring the Real Time Module and RT Targets 2 Note the device number or name Also note the device number of the data acquisition daughterboard MAX always assigns a device number of 1 to the daughterboard of the NI PCI 7041 Series device You need the device number or name of the RT Series plug in device to download and run LabVIEW VIs You can use MAX to change device numbers or names and other configuration settings for the devices You must reset the device for changes to take effect Refer to the MAX Remote Systems Help available by selecting Help Help Topics Remote Systems from MAX for information about testing the resources of RT Series plug in devices 3 Select Tools Traditional NI DAQ Configuration Save Configuration As and specify a filename to save the configuration information 4 Close MAX The NI PCI 7041 Series plug in device requires you to install software on the device Refer to the Downloading Software section for information about installing software on the device Configuring Networked RT Series Devices You must configure the network settings and install software for networked RT Series devices Use MAX to configure the network settings of networked RT Series device
68. lication Path text box also determines the path and application name that appear when you target Real Time Module User Manual 3 8 ni com Chapter 3 Real Time Module Environment LabVIEW to the RT target and create an embedded stand alone application You first must create a stand alone application before you select this option Refer to the Building Stand Alone Applications section of Chapter 7 Deploying Applications for information about using the LabVIEW Application Builder to create start up applications By changing the entry in the Application Path text box to another filename you can create multiple stand alone applications on the RT target using the LabVIEW Application Builder After building an application using the Application Builder and embedding it on the RT target you can change the entry in the Application Path text box and build another application However if you select Launch Application at Boot up only the application you specify in the Application Path launches at start up Use Downloaded VI Path to specify the default path on the RT target for VIs The RT Engine uses the path specified in Downloaded VI Path for operations that require the VI path For example the Current VI s Path function returns the path of the current VI When you run a VI that contains the Current VI s Path function on the RT target the function returns the path specified in the Downloaded VI Path text box appended with the name of the VI
69. lications e Proportional proportional integral proportional derivative and proportional integral derivative algorithms e Gain scheduled PID e PID autotuning e Error squared PID e Lead lag compensation 5 10 ni com Chapter 5 Creating Deterministic Control Applications e Set point profile generation e Multiloop cascade control e Feed forward control e Override minimum maximum selector control e Ratio bias control Refer to the LabVIEW PID Control Toolset User Manual for information about using the LabVIEW PID Control Toolset Refer to the National Instruments Web site at ni com info and enter the info code recontrol for information about the control toolsets the Real Time Module supports Outputting Compensation Data Using NI DAQ Vis to Output Control Data You can use the AO Update Channel VI to write a specified value to an output channel if you do not need to carefully control the timing of the update event and if you do not have high speed requirements for the control loop You also can time analog output events and synchronize the events to the analog input clock Using Real Time System Integration RTSD you can share a common clock for A D and D A conversions to ensure that both occur simultaneously When you use E Series plug in devices a shared clock can be the output of a counter routed over RTSI to the update clock and scan clock Also the shared clock can be the output of a the scan clock routed
70. n Express VI oriented palette view by default Complete the following steps to switch to the Advanced LabVIEW palette view 1 Select Tools Options from LabVIEW 2 Select Controls Functions Palettes from the Options dialog box pull down menu Real Time Module User Manual 1 6 ni com Chapter 1 Introduction 3 Select Advanced from the Palette View pull down menu 4 Click the OK button Unsupported LabVIEW Features Some LabVIEW features are unavailable when you target a specific RT target For example there is no media storage device on some RT Series plug in devices Therefore when you target LabVIEW to a plug in device the RT Engine might not support disk file I O 3 Note If you attempt to download and run on an RT target a VI that has unsupported functionality the VI still executes However the unsupported functions do not work and return standard LabVIEW error codes Modifying Front Panel Objects of RT Target VIs When a VI or stand alone application runs on an RT target and there is no front panel connection with host LabVIEW you cannot execute VIs that modify a front panel For example you cannot change or read the properties of front panel objects with property nodes because there is no front panel You must establish a front panel connection with the RT target or open a remote front panel connection to read any front panel properties or for any front panel property node changes to reflect on the front panel object
71. n Pentium processor based RT targets you can obtain a time stamp using the Read Time Stamp Counter RDTSC assembly instruction You can make an RDTSC assembly call to read the Time Stamp Counter register from the Pentium processor for every loop iteration Refer to the NI Developer Zone at ni com zone for information about using Pentium Time Stamp Counter to verify timing behavior 8 2 ni com Chapter 8 Debugging Deterministic Applications Using an Oscilloscope The Tick Count ms function and the Pentium Time Stamp Counter allow you to examine the relative timing of sections of LabVIEW VIs and to measure the software jitter in the VIs Sometimes you might need to measure the jitter of the whole system at the hardware level especially when you use hardware timing and the software jitter is masked out at the system level Use external tools such as an oscilloscope to study the relationship between input and output signals and to measure loop rates and jitter levels Using Software Drivers Sometimes you can use software drivers to make sure that the application is capable of keeping up with the desired loop rate For example you can use NI DAQ functions to time loops and determine whether the loop rate is keeping real time The AI SingleScan VI has an output data remaining that returns a 1 or greater when there is data present in the data FIFO The data remaining output is 0 when there is no data in the data FIFO Monitor the value ins
72. n for every channel in the scan list and generates an interrupt that the AI SingleScan VI handles The data National Instruments Corporation 5 5 Real Time Module User Manual Chapter 5 Creating Deterministic Control Applications Real Time Module User Manual acquisition device stores the scan data in the device hardware FIFO buffer When the AI SingleScan VI detects the interrupt the VI that calls the AI SingleScan VI wakes up and acquires the data from the hardware FIFO buffer The remaining code executes and the cycle repeats Using the AI SingleScan VI is the preferred timing mechanism for controlling single point acquisition loop rates The AI SingleScan VI allows for the maximum amount of sleep time and produces the least amount of jitter Even if you do not use the acquired analog data the AI SingleScan VI provides an effective method for timing control loops Counter Control VI Use the Counter Control VI to provide hardware timing for a control loop if you do not have analog hardware for data acquisition if you need to perform a buffered data acquisition or if you use the AI scan clock for other timing tasks You can use an external source or an internal source to configure a counter for pulse train generation You then can use the pulse train to time the control loop Refer to the Data Acquisition VIs for Traditional NI DAQ Help for information about configuring the pulse specifications for counter control You can use
73. n name destination directory or support file directory settings in the Application Builder after you target a networked device If you select Small target file with external file for subVIs in the Build Options section you cannot change the LLB for other files path because this path is determined from the Application Path setting in the Network Options dialog box Refer to the LabVIEW Help available by selecting Help VI Function amp How To Help from LabVIEW for more information about build options Saving Stand Alone Applications Real Time Module User Manual The Application Builder stores the stand alone application on the host computer or on the media storage device of an RT target You can target LabVIEW to an RT target with a media storage device before opening the Application Builder to store the application on the RT target Because some RT targets have no media storage device you cannot permanently store stand alone applications on the target You must launch the applications on the host computer and target them to an RT target When power to the target is lost the application on the RT target also is lost Refer to the Launching Stand Alone Applications section for information about launching stand alone applications using command line arguments 7 2 ni com Chapter 7 Deploying Applications Selecting a Target after Launch When you run a stand alone application built with the Application Builder the Select Execution
74. nalog data point from each channel in the scan list of a data acquisition device Read newest data to avoid missing read oldest data 7 initial scans Switch to reading i aa oldest data to enforce real time Reuse memory From scaled data output in order to avoid allocating new memory each loop iteration Figure 5 9 Al SingleScan VI Data Acquisition Real Time Module User Manual 5 8 ni com Chapter 5 Creating Deterministic Control Applications During each call to the AI SingleScan VI the loop sleeps while waiting for the hardware clock of the E Series data acquisition device to complete the A D conversions of scan data from all required channels The data acquisition device places the scanned data in the hardware FIFO buffer of the device When the acquisition and data conversion completes the AI SingleScan VI wakes up and retrieves the data Because the AI SingleScan VI uses hardware timing to control the acquisition the application loop rates can increase dramatically over software timing with less jitter The AI SingleScan VI dictates how fast the acquisition loop can execute The data remaining output of the AI SingleScan VI returns a numeric value to provide information about data in the hardware FIFO buffer If data remaining is 0 the loop executes fast enough to retrieve every scan from the FIFO buffer If data remaining is 1 or greater the loop does not execute fast enough to retrieve eve
75. nested Case structure for read and write access as shown in Figure 4 1 The While Loop contains uninitialized shift registers that store data A functional global variable receives an action input that specifies which task the VI performs as shown in Figure 4 1 by the Mode input parameter Any subsequent calls to the functional global variable can access the most recent data Functional global variables resemble queues because you can add more shift registers to store a longer history of values You also can add more than one set of shift registers to pass more than one set of data Figure 4 1 Functional Global Variable Unlike global variables you can implement functional global variables such that they are not a shared resource If you right click on a subVI set to subroutine priority and select Skip Subroutine Call If Busy from the shortcut menu the execution system skips the call if the subroutine is currently running in another thread This helps in time critical VIs where the execution system safely skips the subroutine subVI without waiting If you skip the execution of a subVI all outputs of the subVI become the 4 6 ni com Chapter 4 Building Deterministic Applications default value for that data type not the default value for the indicator on the subVI front panel For example numeric outputs are zero string and array outputs are empty and Boolean parameters are FALSE If you want to detect if a subroutine executes make an
76. ning Configuring Options of Networked RT Targets You can set access and start up options for networked RT targets With LabVIEW targeted to the RT target select Tools RT Target x x x x Options to access the RT target Options dialog box where x x x x is the IP address of the RT target Setting Access Permissions for an RT Target Use the RT Target Access page available by selecting RT Target Access from the RT target Options dialog box pull down menu to limit which computers can establish a front panel connection with the RT Engine on networked RT targets National Instruments Corporation 3 5 Real Time Module User Manual Chapter 3 Real Time Module Environment To access the RT target the IP address of the host computer must match an entry that allows access in the RT Target Access List and you must provide the correct password for the RT target You can allow or deny access to computers by adding entries in the RT Target Access List Complete the following steps to add entries to the RT Target Access List 1 From the RT Target Access page enter the computer IP address or domain name entry of the computer 3 Note Ifthe RT target does not have access to a Domain Name Server DNS do not use domain name entries in the RT Target Access List Requests to resolve the domain name fail and affect the performance of VIs running on the RT target Real Time Module User Manual 2 Select the Allow Access or Deny Access radi
77. o button and click the Add button When you try to target LabVIEW to an RT target the RT Engine on the RT target compares the host computer IP address to the entries in the RT Target Access List to determine accessibility You define the RT Target Access List entries to indicate whether a host computer is permitted or denied access Permissions are granted to list entries in descending order meaning that any entry in the list supersedes a previous list entry For example in Figure 3 4 a test site com and b test site comcan access the RT target even though a previous list entry indicates by the wildcard that all addresses ending in test site com are denied access A checkmark next to a list entry denotes that access is permitted while an X denotes that access is denied If no entry matches the host computer address access is denied unless you supply a password Place frequently matched entries toward the bottom of the RT Target Access List to improve system performance 3 6 ni com Options Chapter 3 Real Time Module Environment RT Target Access site com X test site com atest site com x b test site com X public site com 130 164 3 130 164 133 133 g Figure 3 4 RT Target Access Page Table 3 1 shows examples of RT Target Access List entries and provides an explanation of matching entries Table 3 1 Example RT Target Access List Entries Access String Matches All hosts
78. o prevent the loss of data from overflow ay Note Remove the checkmark from the control or indicator Select checkbox to leave the control or indicator in place without converting it to an RT FIFO If the time critical VI contains a control or indicator of type 1D array you must set the array length for each RT FIFO element If you have no controls or indicators of type 1D array skip step 8 8 Enter the length of the array that will be contained in each element of the RT FIFO in the Array Length text box and click the Next button The RT Communication Wizard creates three VIs and provides a different name for each VI 9 Verify the VI names and directory in which to save the VIs and click the Finish button The original VI is not changed The RT Communication Wizard generates the three VIs and creates front panel code for the time critical VI using the specified communication method in the normal priority VI However if you want more than one communication method to handle the front panel communication code or you want to vary the order in which the network communication VI sends and receives data use network communication methods to create a network communication VI Refer to the Exploring Communication Methods section for information about the network communication methods you can use in LabVIEW Exploring Communication Methods You can use high level software protocols to communicate between host LabVIEW VIs and RT target VIs
79. o the end of the queue and the next thread runs When a thread completes the execution system removes it from the queue The execution systems are not responsible for managing the user interface If a thread in one of the queues needs to update the user interface the execution system passes responsibility to the user interface execution system which updates the user interface National Instruments Corporation 4 3 Real Time Module User Manual Chapter 4 Building Deterministic Applications Dividing Tasks to Create Deterministic Multithreaded Applications Real Time Module User Manual Deterministic control applications depend on time critical tasks to complete on time every time Therefore time critical tasks need enough processor resources to ensure their completion Separate time critical tasks from all other tasks in the application and place them in a separate VI so you can ensure they receive enough processor resources For example if a control application processes measurement data at regular intervals and stores the data on disk you must handle the timing and control of the data acquisition in a time critical VI However storing the data on disk is inherently a non deterministic task because file I O operations have unpredictable response times that depend on the hardware and the availability of the hardware resource Place file I O operations in the normal priority VI The time critical priority VI receives the processor res
80. of that period must wait to complete during the next allocation of time Conversely preemptive scheduling means that any higher priority thread that needs to execute immediately pauses execution of all lower priority threads and begins to execute A time critical priority thread is the highest priority and preempts all priorities Assigning Priorities You can select from the following VI priorities listed in order from lowest to highest to assign VIs to an execution system thread e background priority lowest e normal priority e above normal priority e high priority e time critical priority highest Threads of higher priority preempt threads of lower priority Normal priority is the default thread priority for all VIs created in LabVIEW The time critical priority preempts all thread priorities A time critical priority thread does not relinquish processor resources until it has completed or until it cooperatively relinquishes the processor resources You must ensure that the time critical thread does not monopolize the processor resources Because time critical priority threads cannot preempt each other create only one time critical thread in an application to guarantee deterministic behavior 4 2 ni com Chapter 4 Building Deterministic Applications In addition to the five priority levels listed above you can set VIs to subroutine priority VIs set for subroutine priority do not share execution time with other VIs When a
81. oot up checkbox Launching Applications Automatically Using Command Line Arguments Use command line arguments to disable the Select Execution Target dialog box and explicitly specify a target for the application Use command line arguments in a batch file or shortcut from the operating system startup folder to automatically launch stand alone applications when the host computer starts up To disable the Select Execution Target dialog box specify the RT target in a command line argument using target For example c mybuiltapp_rtengine exe target DAQ 3 You also can target the host computer and automatically launch a host computer application on start up For example c mybuiltapp_host exe target host To disconnect the host computer from the RT target after downloading the application leaving the embedded application running use quithost For example the following command automatically downloads and runs mybuiltapp_rtengine exe on data acquisition device and closes LabVIEW on the host computer c mybuiltapp_rtengine exe target DAQ 1 quithost 3 Note Ifthe host computer requires a login before entering the operating system the application starts only after the login completes Real Time Module User Manual 7 4 ni com Chapter 7 Deploying Applications You also can reset a specified plug in device using reset For example c mybuiltapp_rtengine exe target DAQ 3 reset This command automatically resets the pl
82. or available error files and transfers the parsed error data back to the RT target Add RTDownloadErrorList to the ni rt ini file equal to a list of available files on the host computer such as RTDownloadErrorList LabVIEW error txt Anlys error txt Adding this token to the ni rt ini file causes the RT target to search for the LabVIEW error txt and Anlys error txt files on the host computer parse them and transfer the error data back to the RT target Real Time Module User Manual 8 4 ni com Configuring and Testing Device Drivers This appendix explains the configuration and testing of device drivers for National Instruments I O hardware Configuring and Testing NI Device Drivers Refer to the National Instruments Web site at ni com info and enter the info code RT0001 for information about the device drivers supported by the RT Engine on a specific RT target Refer to the following documents for information about the configuration and testing of device drivers for National Instruments I O hardware NI DAQ NI Motion NI IMAQ NI Serial National Instruments Corporation A 1 Refer to the National Instruments Web site at ni com info and enter the info code RTDRVS for information about configuring and testing the NI DAQ driver Refer to the National Instruments Web site at ni com info and enter the info code RTDRVS for information about configuring and testing the NI Motion driver
83. ources necessary to complete the task and does not relinquish control of the processor until it cooperatively yields to the normal priority VI or until it completes the task The normal priority VI then runs until preempted by the time critical VI The process repeats until all tasks complete If the application contains two normal priority VIs in addition to the time critical VI the timing of the application changes For example if the application also requires updates to a LabVIEW front panel you must create a separate normal priority VI for network communication The network communication VI can receive data from other VIs in the application using different communication methods The communication VI then can execute the non deterministic network communication code to update the front panel When the application runs the time critical VI uses the processor resources until the task completes or until it cooperatively relinquishes control The two normal priority VIs then round robin the control of the processor resources in equal amounts of time until the tasks complete or until preempted by the time critical VI again for control of the processor resources After separating all deterministic tasks from non deterministic tasks in the application into different VIs assign the VIs to an execution system and prioritize them accordingly Complete the following steps to set the execution system and priority of a VI 1 Select File VI Properti
84. output Boolean return TRUE if it executes successfully and FALSE if it did not Skip functional global variables in time critical VIs but not in lower priority VIs In lower priority VIs you can wait to receive non default values Functional global variables can be a lossy form of communication that lose data if a VI overwrites the shift register data before you read the data Refer to the examples Real Time RT Communication 11b for examples of using Functional Global Variables to communicate between VIs that run on an RT Target Real Time FIFO Vis Use the Real Time FIFO VIs to transfer data between VIs in an application An RT FIFO acts like a fixed queue where the first value in is the first value out Use the RTFIFOWrite VI to add data to an RT FIFO Next reference the RT FIFO in another VI Use the RTFIFORead VI to read the data from the referenced RT FIFO RT FIFOs and LabVIEW queues both transfer data from one VI to another However unlike a LabVIEW queue an RT FIFO ensures deterministic behavior by imposing a size restriction You must define the number and size of the RT FIFO elements before the data enters the time critical VI Both a reader and writer can access the data in an RT FIFO at the same time allowing RT FIFOs to work safely from within a time critical VI Because of the fixed size restriction an RT FIFO can be a lossy communication method Writing data to an RT FIFO when the FIFO is full overwrites the oldest elem
85. pass parameter values to and from the RT target VIs creating a distributed application A host VI can invoke only VIs in memory on the RT target The host VI cannot dynamically download LabVIEW VIs to the RT target for use with the VI Server Refer to the Downloading VIs to an RT Target section of Chapter 3 Real Time Module Environment for information about downloading VIs without running them One advantage to using the VI Server for communication is that it allows you to access the functionality of TCP while working within the framework of LabVIEW However VI Server is non deterministic and using VI Server communication inside a time critical VI adds jitter to the application Refer to the LabVIEW User Manual for information about using the VI Server 4 12 ni com Chapter 4 Building Deterministic Applications Table 4 1 lists the characteristics of the different network communication methods Table 4 1 Characteristics of Network Communication Protocols Protocol Speed Loss TCP Fast Lossless UDP Very Fast Lossy DataSocket Fast Lossy VI Server Slow Lossless Data can be overwritten if items are not read from the DataSocket Server before the next write Not for large data transfers Mostly used for monitoring or controlling one shot runs of remote VIs VI Server is primarily suited for remote control of VIs SMTP Use the SMTP VIs to send data from a VI running on the RT target to VIs
86. per frame at a rate of up to 1 Mbit per second You can network multiple RT systems using NI CAN interface cards and NI CAN driver software You cannot use CAN communication with the RT Series plug in devices You must install NI CAN RT on the RT target from MAX Mac 0S Install using the Remote System Explorer Refer to the NI CAN Hardware and Software Manual for information about using NI CAN hardware and software with LabVIEW Using Remote Panels with RT Target Vis Use remote panels to view or remotely control an RT target VI from a remote LabVIEW client or Web browser Only one user may control a VI at any specific time but several users at different locations can view the VI front panel simultaneously Enabling Remote Panel Connections to RT Target VIs The RT target Web Server must be enabled to allow remote panel control of an RT target VI or to view the front panel of an RT target VI remotely using a Web browser Complete the following steps to enable the RT target Web Server and add VIs to the Web server Visible VIs list 1 Target LabVIEW to the RT target 2 Select Tools RT Target x x x x Options and select Web Server Configuration from the pull down menu 3 Place a checkmark in the Enable Web Server checkbox to enable the Web Server 4 Enter the Web Server root directory in the Root Directory text box The Web Server root directory is the top directory in a Web Server file system 5 Select Web Server Visible
87. pplication Use global variables to access and pass small amounts of data between VIs such as from a time critical VI to a lower priority VI Global variables are a lossy form of communication meaning the data in a global variable can be overwritten before actually being read Tasks in a lower priority thread might not have enough processor time to read the data before other tasks in a different thread overwrite the data A global variable is a shared resource that you must use carefully in a time critical VI If you use a global variable to pass data out of a time critical VI you must ensure that a lower priority VI reads the data and unlocks the global before the time critical VI attempts to write to the global again Refer to Chapter 6 Optimizing Applications for information about shared resources National Instruments Corporation 4 5 Real Time Module User Manual Chapter 4 Building Deterministic Applications Using a global variable is a good way to pass small amounts of data such as scalar data between VIs For larger amounts of data use functional global variables or the Real Time FIFO VIs Refer to the LabVIEW User Manual for information about creating and using global variables Functional Global Variables Real Time Module User Manual Use functional global variables like global variables to pass data between VIs A functional global variable is a subVI set to subroutine priority The subVI contains a While Loop with a
88. put and the input have the same data type representation Arrays must have the same structure and number of elements for function outputs to reuse the input buffer Reducing the Use of Global Variables LabVIEW creates an extra copy in memory of every global variable you use in a VI Reduce the number of global variables to improve the efficiency and performance of VIs Creating copies of the global variable takes up memory resources on an RT target Avoiding Contiguous Memory Conflicts LabVIEW handles many of the memory details that you normally deal with in a conventional text based language For example functions that generate data must allocate storage for the data When that data is no longer needed LabVIEW deallocates the associated memory When you add new information to an array or a string LabVIEW allocates new memory to accommodate the new array or string However running out of memory in LabVIEW is usually not a concern You must design memory conscious VIs for RT targets Always preallocate space for arrays equal to the largest array size that you might encounter When you reboot or reset an RT target the Real Time Operating System RTOS and the RT Engine load into memory as shown in diagram 1 of Figure 6 3 National Instruments Corporation 6 3 Real Time Module User Manual Chapter 6 Optimizing Applications Liss Real Time Operating System RTOS RT Engine Real Time Real Time Re
89. puter to open a front panel communication connection When you select an execution target other than the host computer LabVIEW downloads any LabVIEW VIs you subsequently run to the selected execution target Complete the following steps to target LabVIEW to an execution target 1 Start LabVIEW Previously targeted execution targets appear in the Execution Target pull down menu in the LabVIEW dialog box If you are using a previously targeted device select the execution target from the Execution Target pull down menu and skip the remaining steps If you are connecting to a networked device and have not targeted the device previously select Select Target with Options from the Execution Target pull down menu to open the Select Execution Target dialog box Select RT Engine on Network from the target list to enter a new networked device as shown in Figure 3 2 lf Select Execution Target Jt Engine on Network Ba Machine Name IP 4 Password Configure OK Cancel Help Figure 3 2 Select Execution Target Dialog Box Enter the IP address and password set for the networked device in Measurement amp Automation Explorer MAX Leave the password field blank if the networked device does not have a password specified in MAX Note If you have not configured the hardware in MAX click the Configure button to open MAX Refer to Chapter 2 Installing and Configuring the Real Time Module and RT Targets
90. quiring measurement data See measurement data AI Sample Channel VI acquiring measurement data 5 7 AI SingleScan VI acquiring measurement data 5 8 timing control loops 5 5 AO Single Update VI outputting measurement data 5 12 AO Update Channel VI outputting measurement data 5 11 Application Builder 7 1 See also stand alone applications applications See deterministic applications deterministic control applications stand alone applications arrays preallocating 6 1 bios options setting 6 6 C CAN Controller Area Network 4 14 casting data to proper data types 6 3 command line arguments for launching stand alone applications 7 4 communicating with RT target VIs 1 3 Front Panel Communication 1 4 Network Communication 1 5 National Instruments Corporation communication methods 4 9 CAN 4 14 DataSocket 4 11 serial 4 13 shared memory 4 10 SMTP 4 13 TCP 4 10 UDP 4 11 VI Server 4 12 compensation data outputting 5 11 FieldPoint VIs 5 14 NI DAQ VIs 5 11 configuration counter for pulse train generation 5 6 networked RT Series devices 2 4 booting into Real Time Operating System 2 4 downloading software 2 6 network settings 2 5 networked RT target options 3 5 RT target start up applications 3 8 setting access permissions 3 5 plug in devices 2 3 contiguous memory conflicts avoiding 6 3 control applications See also deterministic control applications overview 5 1 typical control system
91. quitting after launching stand alone applications 7 3 real time system component 1 1 targeting LabVIEW to RT target 3 1 unsupported features with RT target VIs 1 7 modifying front panel objects 1 7 using OS specific technologies 1 7 launching stand alone applications 7 3 automatically on start up 7 4 automatically using command line arguments 7 4 manual See documentation mass compiling of VIs 6 6 Measurement amp Automation Explorer MAX 2 3 measurement data acquiring 5 7 AI Sample Channel VI 5 7 DAQ devices 5 8 FieldPoint devices 5 9 Wait Until Next ms Multiple function 5 7 processing 5 10 Real Time Module User Manual l 4 memory allocation and preallocating arrays 6 1 avoiding contiguous memory conflicts 6 3 minimizing usage by RT target Web Server 4 16 multithreaded applications 4 1 cooperative yielding of time critical VIs 4 5 definition 4 1 dividing tasks for deterministic applications 4 4 execution systems for categorizing VIs 4 3 overview 4 1 round robin scheduling 4 2 VI priorities 4 2 mutex definition of 6 1 Network Communication 1 5 network watchdog 5 15 networked RT Series devices configuring 2 4 booting into Real Time Operating System 2 4 downloading software 2 6 network settings 2 5 examples 1 3 overview 1 3 0 operating system mutex 6 1 oscilloscope timing behavior verification 8 3 outputting compensation data 5 11 FieldPoint VIs 5 14 NI DAQ VIs 5 1
92. r 2 Insert the LabVIEW Real Time Module CD into the CD ROM drive The Real Time Module installation program runs automatically 3 Follow the instructions that appear on the screen Complete the following steps to install device drivers for NI hardware that you want to use with the Real Time Module 1 Insert the National Instruments Device Driver CD into the CD ROM drive The device driver installation program runs automatically 2 Follow the instructions that appear on the screen to install the hardware device drivers that you need National Instruments Corporation 2 1 Real Time Module User Manual Chapter 2 Installing and Configuring the Real Time Module and RT Targets Installing and Configuring RT Series Plug In Devices You can install an RT Series plug in device in any available PCI or PXI expansion slot in the computer or PXI chassis This section contains general installation instructions Refer to the computer user manual or technical reference manual for specific instructions and warnings about installing hardware Ss Note You must install the Real Time Module software Traditional NI DAQ 7 0 from the National Instruments Device Driver CD and PCI 7041 and PCI PXI 7030 support from the National Instruments Device Driver CD before you install an RT Series plug in device RT Series PCI Plug In Devices Complete the following steps to install an RT Series PCI plug in device 1 2 Power off and unplug the compu
93. riable G global variable H host computer Hz T O INI Real Time Module User Manual A stand alone application built using the LabVIEW Application Builder and embedded as the start up application on an RT target The target on which to run a LabVIEW VI Can be either an RT target or the host computer First in first out memory buffer The first data stored is the first data sent to the acceptor A protocol for communication between LabVIEW on the host computer and the RT Engine on an RT target typically used during development Is a subVI set to subroutine priority used to pass data between several VIs on a block diagram Accesses and passes data between several VIs on a block diagram The computer on which you develop VIs using LabVIEW and download them to an RT target Hertz The number of scans read or updates written per second Input Output The transfer of data to from a computer system involving communications channels operator interface devices and or data acquisition and control interfaces A file used to set application configuration options G 2 ni com jitter Logos Measurement amp Automation Explorer MAX media storage device multitasking multithreading mutex Network Communication networked device NI DAQ National Instruments Corporation G 3 Glossary The amount of time that the loop cycle time varies from the desired time A mechanism for interprocess
94. riting data Appropriate expiration actions for this kind of failure include shutting down entirely until you can reestablish communication returning to a known state and continuing as usual Refer to the examples Real Time RT Watchdog PXI 11b for examples of using the NI Watchdog VIs to configure watchdogs for RT Series devices Refer to the LabVIEW Help for information about the NI Watchdog VIs Real Time Module User Manual 5 16 ni com Optimizing Applications This chapter explains techniques that can improve the determinism of applications Avoiding Shared Resources In LabVIEW there are resources that two or more VIs might need to share These shared resources include global variables non reentrant subVIs the LabVIEW Memory Manager queues semaphores single threaded DLLs and so on If a VI uses a shared resource the VI acquires an operating system mutex around the resource to protect the resource from access by other VIs A mutex locks the resource so that other VIs may not access the resource If a time critical priority VI preempts a lower priority VI and attempts to use a locked resource the time critical VI must wait because the shared resource is not available The lower priority VI becomes more important than the time critical VI because it must finish its work and release the shared resource before the time critical VI can proceed This scenario is a priority inversion Priority inversions induce jitter Avo
95. ry data point and the loop rate is not deterministic Always check the value of data remaining to ensure that the application executes in real time The value of data remaining might become skewed during the first loop iterations with fast hardware loop rates because the processor might initially execute the loop at rates slower than the data acquisition due to caching effects After multiple calls to the AI SingleScan VI the processor cache saves the VI and the loop executes at a maximum speed Use the AI SingleScan VI opcode input to retrieve the oldest scan data or the newest scan data from the hardware FIFO buffer Retrieving the newest scan data erases all older scan data from the buffer Therefore by obtaining the newest data during the first few iterations of the acquisition loop you can ensure that the data remaining output always equals 0 After the loop executes at a consistent speed you can read the oldest scan data from the buffer and use the data remaining output to detect if the loop runs in real time Using FieldPoint Devices to Acquire Measurement Data The block diagram in Figure 5 10 shows an example of a FieldPoint implementation of a data acquisition loop The example uses the FieldPoint Read VI to acquire measurement data Refer to examples FieldPoint Getting Started for examples of using FieldPoint VIs to acquire measurement data in a control loop You can modify the example VIs to acquire data by changing the tag config
96. s The following features do not work on an RT target with no front panel connection e Front panel property nodes and control references e Dialog VIs e VI Server front panel functions Using OS Specific Technologies in RT Target Vis VIs on the RT target cannot use VIs that leverage Windows only technology The following features do not work on an RT target e ActiveX VIs e NET VIS e VIs that use NI IVI drivers National Instruments Corporation 1 7 Real Time Module User Manual Chapter 1 Introduction e Windows Registry Access VIs e TestStand VIs ActiveX based e Report Generation Toolkit VIs e Call Library Nodes that access an operating system API other than Pharlap e Graphics and Sound VIs e Database Connectivity Toolset e XML DOM Parser and G Web Server for CGI Support Real Time Module User Manual 1 8 ni com Installing and Configuring the Real Time Module and RT Targets This chapter explains installation and configuration of the LabVIEW Real Time Module and RT Series hardware Installing the Real Time Module Complete the following steps to install the Real Time Module on the host computer Mac OS Refer to the LabVIEW Real Time Module for Mac OS X User Manual Addendum for installation and configuration instructions Windows 2000 NT XP You must log in to the host computer as an administrator or as a user with administrator privileges 1 Verify that LabVIEW has been installed on the host compute
97. s and then to install software on the device RT Series controllers must boot into the Real Time Operating System RTOS before you attempt to configure the network settings Some RT Series PXI controllers require a boot disk to boot into the RTOS Skip to the Configuring Network Settings section if you do not require a PXI boot disk to boot into the RTOS nye Note This section contains general instructions to configure the network settings and software of networked RT Series devices Refer to the device documentation for specific hardware installation instructions Real Time Module User Manual Booting into the Real Time Operating System You must boot RT Series controllers into the RTOS before you can configure the network settings of the controller Some RT Series PXI controllers do not have the RTOS pre installed However you can use a floppy disk to boot into the RTOS on a PXI controller that does not have the RTOS installed 2 4 ni com Chapter 2 Installing and Configuring the Real Time Module and RT Targets Complete the following steps to create a boot disk from the host computer 1 2 3 Place a floppy disk in the host computer disk drive Launch MAX on the host computer Select Tools RT PXI Disk Utilities Create PXI Boot Disk to open the PXI Boot Disk dialog box Click the Yes button to make the boot disk and follow the instructions that appear on the screen Remove the floppy disk and label the disk LabVIEW Real T
98. s maximize the efficiency of the processor because the processor does not sit idle if there are other threads ready to run Any application that reads and writes from a file performs I O or polls the user interface for activity can benefit from multithreading simply because you can use the processor to run other tasks during these activities National Instruments Corporation 4 1 Real Time Module User Manual Chapter 4 Building Deterministic Applications Creating Multithreaded Applications in LabVIEW Real Time Module User Manual To create a multithreaded application in LabVIEW you must separate time critical tasks from non time critical tasks You then can build VIs to complete each task You prioritize the VIs and then categorize them into one of the available execution systems to control the amount of processor resources each VI receives LabVIEW assigns each VI to an execution system thread according to the VI priority The threads execute on the processor accordingly Scheduling Threads The Real Time Operating System RTOS on RT targets uses a combination of round robin and preemptive scheduling to execute threads in the execution system Round robin scheduling applies to threads of equal priority Equal shares of processor time are allocated between equal priority threads For example each normal priority thread is allotted 10 ms to run The processor executes all the tasks it can in 10 ms and whatever is incomplete at the end
99. sequencing of the data transfer e You want to perform additional data processing or logging In Figure 1 2 the RT target VI is similar to the VI in Figure 1 1 that runs on the RT target using Front Panel Communication to update the front panel controls and indicators However the RT target VI in Figure 1 2 uses Real Time FIFO VIs to pass data to a communication VI The communication VI then communicates with a host computer VI using network communication methods to update controls and indicators Refer to Chapter 4 Building Deterministic Applications for information about methods of communication available in LabVIEW National Instruments Corporation 1 5 Real Time Module User Manual Chapter 1 Introduction _ gt LabVIEW ee oe mai Host Computer Network Communication VI Communication RT Engine Do a nE RT Target Figure 1 2 Network Communication Protocol Real Time Module and Express VI Considerations LabVIEW Express VIs increase LabVIEW ease of use and improve productivity with interactive dialog boxes that minimize programming for measurement applications Express VIs do require additional performance overhead during execution therefore do not use Express VIs in time critical or processor intensive applications Instead develop real time applications with standard LabVIEW VIs Refer to the Getting Started with LabVIEW manual for information about LabVIEW Express VIs LabVIEW shows a
100. solutions visit our extensive library of technical support resources available in English Japanese and Spanish at ni com support These resources are available for most products at no cost to registered users and include software drivers and updates a KnowledgeBase product manuals step by step troubleshooting wizards conformity documentation example code tutorials and application notes instrument drivers discussion forums a measurement glossary and so on Assisted Support Options Contact NI engineers and other measurement and automation professionals by visiting ni com support Our online system helps you define your question and connects you to the experts by phone discussion forum or email e Training Visit ni com custed for self paced tutorials videos and interactive CDs You also can register for instructor led hands on courses at locations around the world e System Integration lIf you have time constraints limited in house technical resources or other project challenges NI Alliance Program members can help To learn more call your local NI office or visit ni com alliance If you searched ni com and could not find the answers you need contact your local office or NI corporate headquarters Phone numbers for our worldwide offices are listed at the front of this manual You also can visit the Worldwide Offices section of ni com niglobal to access the branch office Web sites which provide up to date contac
101. t ms function 8 2 dividing tasks 4 4 multithreaded applications 4 1 dividing tasks for deterministic applications 4 4 execution systems for categorizing VIs 4 3 overview 4 1 VI priorities 4 2 optimizing 6 1 avoiding contiguous memory conflicts 6 3 avoiding shared resources 6 1 avoiding subVI overhead 6 5 casting data to proper data types 6 3 disabling disk cache 6 5 mass compiling VIs 6 6 memory allocations and preallocating arrays 6 1 reducing global variable use 6 3 setting bios options 6 6 setting VI properties 6 5 passing data between VIs 4 5 functional global variables 4 6 global variables 4 5 Real Time FIFO VIs 4 7 user interface for RT target VIs 4 8 yielding time critical VI execution 4 5 deterministic control applications 5 1 acquiring measurement data 5 7 AI Sample Channel VI 5 7 DAQ devices 5 8 FieldPoint devices 5 9 Wait Until Next ms Multiple function 5 7 ni com implementing 5 2 outputting compensation data 5 11 FieldPoint VIs 5 14 NI DAQ VIs 5 11 overview 5 1 processing measurement data 5 10 timing control loops 5 3 hardware methods 5 5 overview 5 3 software method 5 3 typical LabVIEW control application figure 5 2 typical steps for building 5 2 watchdogs 5 14 inactivity watchdog 5 15 network watchdog 5 15 device drivers configuring and testing A 1 creating for third party PXI devices A 2 disk cache disabling 6 5 documentation conventions use
102. t information support phone numbers email addresses and current events National Instruments Corporation B 1 Real Time Module User Manual Glossary Symbol Prefix Value m milli 10 3 k kilo 103 M mega 106 G giga 10 A address Character code that identifies a specific location or series of locations in memory application A collection of VIs that together accomplish the real time system task D DAQ See data acquisition DAQ data acquisition DAQ DataSocket determinism device driver 1 Acquiring and measuring analog or digital electrical signals from sensors transducers and test probes or fixtures 2 Generating analog or digital electrical signals An Internet programming technology to share live data between VIs and other computers Characteristic of a system that describes how consistently it can respond to external events or perform operations within a given time limit An instrument or controller you can access as a single entity that controls or monitors real world I O points A device often is connected to a host computer through some type of communication network Software unique to the device or type of device and includes the set of commands the device accepts National Instruments Corporation G 1 Real Time Module User Manual Glossary E embedded application execution target F FIFO Front Panel Communication functional global va
103. targeted to an RT target The VI hierarchy appears with a pin in the upper left corner of each VI When the pin is in the vertical position as shown to the left the VI has been downloaded When the pin is in the horizontal position as shown to the left the VI has not been downloaded National Instruments Corporation 3 3 Real Time Module User Manual Chapter 3 Real Time Module Environment Closing a Front Panel Connection without Closing VIs You can select Operate Switch Execution Target and then select another execution target to close the networking connection to the RT target without closing VIs You also can exit LabVIEW on the host computer without closing the VIs on the RT target Select File Exit without closing RT Engine VIs to close LabVIEW on the host computer The VIs running on the RT target continue running VIs downloaded but not running remain loaded in memory on the RT target If you select File Exit Lab VIEW opens a dialog box that asks if you want to exit LabVIEW without closing RT Engine VIs If you click the Yes button LabVIEW exits without closing the VIs on the RT target If you click the Close all RT Engine VIs button LabVIEW closes all the VIs running on the RT target unloads the VIs from memory and closes LabVIEW Connecting to Vis Running on an RT Target When you target LabVIEW to an RT target to open a front panel communication connection LabVIEW detects VIs currently running on the
104. te Let the AI Scan Start signal do the updates a Figure 5 13 One Channel PID Output National Instruments Corporation 5 13 Real Time Module User Manual Chapter 5 Creating Deterministic Control Applications Using FieldPoint Vis to Output Control Data The block diagram in Figure 5 14 uses FieldPoint VIs to perform a synchronous write to a specified channel Figure 5 14 One Channel PID Output Using FieldPoint Using Watchdogs in Applications Real Time Module User Manual In control applications it might be necessary to respond to a failure or system event quickly If a critical component of a motion control system fails keeping the system motor running might risk the safety of both the equipment and operators While shutting down the equipment quickly might be the best solution not every failure must be handled in the same manner When a network connection between an RT target data logging VI and a host computer VI fails the application should continue running and logging data to disk until you reestablish the network connection Watchdog utilities monitor for specific system events and failures These utilities can be either software or hardware where available The watchdog waits until a specific event occurs and executes a preconfigured action There are two implementations of the watchdog the inactivity watchdog and the network watchdog The inactivity watchdog uses a continuously increm
105. ter Remove the cover to the computer and make sure there are no lighted LEDs on the motherboard If any are lit wait until they turn off before continuing the installation Remove the expansion slot cover on the back panel of the computer Insert the plug in device into a 5 V PCI slot Gently rock the board to ease it into place Do not force the board into place Screw the mounting bracket of the plug in device to the back panel rail of the computer Visually verify the installation Make sure the board is not touching other boards or components and is fully inserted in the slot Replace the cover plug in and power on the computer Refer to the Configuring RT Series Plug In Devices section for information about configuring the PCI device RT Series PXI Plug In Devices Complete the following steps to install the RT Series PXI plug in device Real Time Module User Manual 1 2 3 4 Power off and unplug the PXI chassis Choose two adjacent unused PXI slots in the system Remove the filler panels for the slots you have chosen Insert the RT Series plug in device into the 5 V PXI slots Use the injector ejector handle to fully insert the board into the chassis 2 2 ni com Chapter 2 Installing and Configuring the Real Time Module and RT Targets 5 Screw the front panel of the RT Series plug in device to the front panel mounting rail of the system Plug in and power on the PXI chassis Refer to the Configuring
106. that is synchronized to a reference clock 2 Software A property of a function that begins an operation and returns only when the operation is complete Real Time Module User Manual Glossary T target TCP thread Traditional NI DAQ UDP VI VI Server Virtual Instrument Software Architecture VISA Real Time Module User Manual See RT target Transmission Control Protocol A standard format for transmitting data in packets from one computer to another A completely independent flow of control in an application An upgrade to the earlier version of NI DAQ Traditional NI DAQ has the same VIs and functions and works the same way as NI DAQ 6 9 x You can use both Traditional NI DAQ and NI DAQmx on the same computer which is not possible with NI DAQ 6 9 x User Datagram Protocol Virtual Instrument 1 A combination of hardware and or software elements typically used with a PC that has the functionality of a classic stand alone instrument 2 A LabVIEW software module VI which consists of a front panel user interface and a block diagram program Mechanism for controlling VIs and LabVIEW applications programmatically locally and remotely Single interface library for controlling GPIB VXI RS 232 and other types of instruments G 6 ni com Index A access permissions for RT target setting 3 5 example RT target access list entries table 3 7 RT Target Access page figure 3 7 ac
107. the Counter Control VI and set the control code input to wait available only for data acquisition devices with DAQ STC counters to asynchronously wait for a hardware event and time a control loop To use the Counter Control VI with the control code input set to wait you must provide a timeout value in case expected source pulses do not occur Place the Counter Control VI in the control loop to wait for a pulse train wake up edge A wake up edge is a source pulse edge that causes the Counter Control VI to wake up Wake up edges occur every n PS1 PS2 PS1 1 active source edges where n 0 1 2 and so on When the Counter Control VI runs it waits until one active source edge or wake up edge before the active source edge where the output pulse occurs For example if PS1 5 and PS2 5 the Counter Control VI wakes up at the fourth active source edge which is one source edge before the output pulse occurs as shown in Figure 5 7 Regardless of the output polarity the Counter Control VI wakes up one active source edge before the output pulse 5 6 ni com Chapter 5 Creating Deterministic Control Applications Program i Source Counter control with wait control code wakes up y 2 3 4 5 6 7 8 9 10 Output Figure 5 7 Example Time Sequence If one or multiple wake up edges occur before the next time the Counter Control VI runs the VI does not w
108. the Disk Cache The Real Time Module provides a disk cache when writing data to the hard disk of RT targets with a media storage device The disk cache is efficient for writing small amounts of data much less than 512 bytes When writing amounts of data much greater than 512 bytes disable the disk caching feature for better performance To disable the disk caching feature you must change the RTTarget DiskCache Enable token in the RT target ni rt ini file from the default value of TRUE to FALSE When you disable the disk cache feature for RT Series PXI controllers you must perform writes to the disk in multiples of 512 bytes because the hard drives of the controllers have 512 byte sectors National Instruments Corporation 6 5 Real Time Module User Manual Chapter 6 Optimizing Applications Setting BIOS Options Another way to improve performance of VIs running on RT Series PXI controllers is to disable USB hardware in the BIOS of the controller Make the following BIOS settings changes Integrated Peripherals USB Keyboard DISABLED Additionally for NI PXI 8170 controllers make the following BIOS settings changes PnP PCI Configuration Assign IRQ for USB DISABLED These changes can reduce or even eliminate jitter caused by USB device interrupts Mass Compiling Vis Mass compiling a VI is another way to improve performance Mass compiling a VI compiles the top level VI and also recompiles and re l
109. to VIs running on RT target 3 4 disabling disk cache 6 5 downloading VIs to RT target 3 3 Express VIs 1 6 installing 2 1 targeting LabVIEW to RT target 3 1 Real Time Operating System RTOS booting into 2 4 memory usage 6 3 Remote Panels and RT target VIs 4 14 enabling connections to RT target VIs 4 14 minimizing memory usage by RT target Web Server 4 16 regaining control of RT Engine VIs 4 15 Replace Array Subset function 6 2 round robin scheduling 4 2 RT Communication Wizard 4 8 RT Engine See also Real Time Module description 1 2 launching stand alone applications automatically on start up 7 4 memory usage 6 4 regaining control of RT target VIs 4 15 RT Series FieldPoint Modules 1 3 5 9 Real Time Module User Manual Index RT Series networked devices See networked RT series devices RT Series plug in devices See plug in devices RT series RT Series PXI controllers See PXI controllers RT Series RT target s See also RT target VIs configuring networked RT target options 3 5 RT target start up applications 3 8 setting access permissions 3 5 connecting to target using crossover cable B 5 connecting to VIs running on RT target 3 4 definition 1 2 downloading VIs to RT target 3 3 memory diagrams figure 6 4 networked RT Series devices configuring 2 4 booting into Real Time Operating System 2 4 downloading software 2 6 network settings 2 5 examples 1 3 overview 1 3 RT series plug in de
110. to see a list of software available on the host computer and the software currently on the device Click the Install Software button to open the Select software to download dialog box Place checkmarks in the checkboxes of the software that you want to install on the device Click the OK button to install the software Refer to Appendix A Configuring and Testing Device Drivers for information about configuring National Instruments hardware I O device drivers Refer to the MAX Remote Systems Help available by selecting Help Help Topics Remote Systems from MAX for information about using MAX to configure remote systems 2 6 ni com Chapter 2 Installing and Configuring the Real Time Module and RT Targets Setting the System Time of RT Targets Each type of RT target obtains the system time differently on start up RT Series plug in devices The RT Engine on the plug in device obtains the system time from the host computer when you reset the device FieldPoint 20xx Series network modules The RT Engine on the device obtains the time from a time server at each power up to set the internal clock If a time server is not available use the RT Set Date and Time VI to programmatically set the system date and time Refer to the National Instruments Web site at ni com info and enter the info code RT003 for information about setting local time and time zone considerations for RT targets ik Note If you use the RT Set Date and Tim
111. tomatically launch stand alone applications each time you reboot the RT target Refer to the Launching Stand Alone Applications section for information about launching applications from the media storage device of the host computer or RT target automatically Launching Stand Alone Applications You can configure RT targets to launch stand alone applications on start up differently depending on the RT target If the RT target has a media storage device you can embed the application directly on the target and then launch it automatically on start up If the RT target does not have a media storage device you can still launch the application from the host computer on startup using command line arguments National Instruments Corporation 7 3 Real Time Module User Manual Chapter 7 Deploying Applications Launching Applications Automatically on Start up The RT Engine can launch embedded stand alone applications each time you boot the RT target Complete the following steps to launch an embedded stand alone application when the RT target starts up 1 Target LabVIEW to the networked RT target Refer to the Targeting LabVIEW to an RT Target section of Chapter 3 Real Time Module Environment for information about targeting LabVIEW 2 Select Tools RT Target x x x x Options where x x x x is the IP address of the device 3 Select RT Target Miscellaneous from the pull down menu 4 Place a checkmark in the Launch Application at B
112. tting Access Permissions for an RT Target eceeseeeseeseneeeeeeee 3 5 Setting Options for RT Target Start up Applications 0 eee eee 3 8 Chapter 4 Building Deterministic Applications Programming for Determinism eecceeseeesecesceceeeeseeesceceseecceceaeeeseeceaeceaeessneeeaeerses 4 1 Overview of Multithreaded Applications 00 0 eeeceeceseeeeeteteeeeseeeeees 4 1 Creating Multithreaded Applications in LabVIEW seseeeeeseeseeeeeerseerreereerses 4 2 Scheduling ThreddSviicneen aner R Gene E ART 4 2 ASSISMING Priorities sor a perterir e E E AEE ER aias 4 2 Assigning VIs to Execution SystemSs essesseresesrerrerrerererrsresreee 4 3 Dividing Tasks to Create Deterministic Multithreaded Applications cceecceesceesneeeseeeneeeeeeeneeeeaes 4 4 Cooperatively Yielding Time Critical VI Execution eects 4 5 Passing D ta between VIS ivi dente tata E E E at 4 5 Global Variables oa ied ape e EEE ace alee ieee Heavens terested 4 5 Functional Global Variables 0 0 eee ees ceeeceeseeeseseeeeseeseeeseeseeeseeseeeaeeaeenees 4 6 Real Time FIFO VAs is cecacccetdste teed enne t ode e a e A E 4 7 Creating a User Interface for RT Target VIS eee ceeeseceeceeteeeeseteeeeaeeseeeseeneees 4 8 Exploring Communication Methods 0 e cee eeeeeseseeceseeseeeseceessesseeesecaeeneeeseseaeeaeenaes 4 9 Shared Memorya pen a hia ia ein dette 4 10 CP aloes aces A Nebate tte vost user E E EE cuctavensesesteed OE 4 10 UDP A E iat
113. ug in device specified by target before downloading the application Refer to the LabVIEW Help for information about LabVIEW command line arguments Connecting to Applications Running on RT Targets You cannot open a Front Panel Communication connection to a stand alone application running on an RT target Use a remote panel connection to connect to the application or use the RT Communication Wizard to create VIs to provide a user interface on a host computer Refer to Chapter 4 Building Deterministic Applications for information about using remote panels and the RT Communication Wizard National Instruments Corporation 7 5 Real Time Module User Manual Debugging Deterministic Applications Building deterministic LabVIEW applications requires programming techniques different from typical LabVIEW programming With deterministic applications there are two levels of debugging to verify application behavior and timing behavior Verifying Correct Application Behavior You first must ensure that the application behaves as expected Use the LabVIEW debugging tools to detect errors and step through the flow of execution to locate the error source Finally use the Profile window to test the execution timing and memory usage of an application Using the LabVIEW Debugging Tools Use the LabVIEW debugging tools such as execution highlighting and single stepping while the host computer is targeted to an RT target to step throu
114. uration which allows you to switch from one FieldPoint module to another without changing the code National Instruments Corporation 5 9 Real Time Module User Manual Chapter 5 Creating Deterministic Control Applications Control execution Flow with sequence structure to ensure consistent wait behavior Read amp chart data until the stop button pressed ieldPoint 10 Point In ms Multiple Figure 5 10 Acquiring Data Using FieldPoint Processing Measurement Data Real Time Module User Manual There are many data processing algorithms to consider when creating a control application You can create custom control algorithms using LabVIEW You also can use VIs such as the LabVIEW PID Control Toolset VIs to process control application data The LabVIEW PID Control Toolset which is included with the Real Time Module offers several libraries that you can use to develop a control application The most commonly used control algorithm is the Proportional Integral Derivative PID but the toolset also includes tools for fuzzy logic and advanced control algorithms Fuzzy logic is a method of rule based decision making used for expert systems and process control to emulate the process of human decision making The LabVIEW PID Control Toolset Advanced Control VIs include VIs for complex control applications and for hardware in the loop HIL applications Using the PID VIs you can develop the following control app
115. vices configuring 2 3 creating PXI device drivers A 2 installing 2 2 overview 1 2 problems with connecting B 3 setting system time 2 7 stand alone applications configuring settings for 7 2 connecting to applications running on targets 7 5 launching stand alone applications 7 3 selecting target after launching 7 3 Real Time Module User Manual l 6 targeting LabVIEW to RT target 3 1 RT target VIs communicating with 1 3 Front Panel Communication 1 4 Network Communication 1 5 creating using interface for 4 8 enabling Remote Panel connections 4 14 Network Communication protocol 1 5 regaining control from Remote Panel connections 4 15 unsupported LabVIEW features 1 7 modifying front panel objects 1 7 using OS specific technologies 1 7 RT target Web Server minimizing memory usage by 4 16 RTFIFO Read VI 4 7 RTOS See Real Time Operating System RTOS S saving stand alone applications 7 2 serial communication method 4 12 shared memory communication method 4 10 shared resources avoiding 6 1 casting data to proper data types 6 3 memory allocations and preallocating arrays 6 1 reducing global variable use 6 3 Skip Subroutine Call If Busy 4 6 SMTP communication method 4 12 software See also LabVIEW software timing control loops 5 3 software drivers downloading for networked RT Series devices 2 6 for timing behavior verification 8 3 stand alone applications 7 1 configuring target settings 7 2

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