Real Time Programming with LabVIEW

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Real Time Programming with LabVIEW RT
John Limroth Software Engineer Thurs Aug
17 1015-115 p.m., 145-445 p.m. Exhibit (3G)
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Agenda

• LabVIEW RT basics
• Current RT hardware targets
• Using LabVIEW RT
• Advanced programming techniques
• Software/hardware watchdogs
• Application builder

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What is Real-time?

• Real-time does NOT mean real fast!
• Requires deterministic response
• Windows does NOT guarantee determinism

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RT Hardware Architecture
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LabVIEW RT Software

• LabVIEW RT adds two extra components to regular
  LabVIEW

• The RT Development System
• Part of it runs on host PC
• Programming and debugging LabVIEW code

• The RT Engine
• Runs on target
• Executes embedded code
• Independent of host PC

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Software Architecture

• Three separate instances of LabVIEW

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Software Architecture
(Instance B)
(Instance C)
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Agenda

• LabVIEW RT basics
• Current RT hardware targets
• Using LabVIEW RT
• Advanced programming techniques
• Software/hardware watchdogs
• Application Builder

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RT Series DAQ Devices

• Hardware
• Processor
• 486 133 MHz AMD chip
• Memory
• 8 MB of DRAM for LabVIEW executable and
  NI-DAQ.dll
• 1 kB of SRAM for shared memory
• Two user-defined LEDs

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RT Series DAQ Devices

• Form Factors
• Single product based on DAQ devices
• 7030/6040E 16 channel, 12-bit resolution, 250
  kS/s
• 7030/6030E 16 channel, 16-bit resolution, 100
  kS/s
• 7030/6533 32 high-speed digital lines
• Single PCI slot
• Double PXI slot
• All SCXI and accessories supported

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Installing the RT Series DAQ Card

• Installed and seen in MAX
• RT intelligent card has one device number
• Daughter card has separate device number
• No test panels

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RT PXI Controller

• General description
• Connected through Ethernet
• Pre-loaded RTOS and software
• Available with LV RT 5.1.2 and NI-DAQ 6.7
• PXI-8156B (233 or 333 MHz) must be configured
• Communication
• Default user interface thread
• VI Server
• TCP/IP

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RT PXI Hardware

• Supported hardware
• All PXI chassis without monitors
• All of regular NI-DAQ
• MXI-3
• Configure your own system

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Remote System Explorer

• Configures system
• Installs or upgrades software
• Creates utility disks
• Lists installed software or hardware

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Installation Procedure

• Ensure the system is ready to be configured
• Must reside on same subnet
• Run the uninstall disk if questionable

• Create boot floppy (RT system specific)

• Reboot system with floppy installed
• IP 0.0.0.0
• Serial number is from Ethernet chip set

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Installation Procedure (cont.)

• Assign IP address, name, password, etc
• Password is optional

• Reboot system

• Upgrade/download software
• Choose install script
• Verify software versions

• Reboot system

• RT system is ready

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Exercise 1 Configuring a PXI Controller
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File Structure

• Viewable through Windows OS
• Ph_exec.exe and ni-rt.ini in root directory
• Embedded PXI File Structure (c\ni-rt\)
• \system\ includes emblview.exe, ni-daq.dll, etc
• \startup\ includes boot up executables

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Useful Tools in MAX

• Remote DAQ Configuration
• Sets the properties of the remote DAQ boards
• Also available through Remote System Explorer
• Remote Device Access
• RDA Server enabled on RT Series PXI controller
• Allows user to test the board with test panels

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Exercise 2 Troubleshooting RT Series PXI
controller
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Agenda

• LabVIEW RT Basics
• Current RT hardware targets
• Using LabVIEW RT
• Advanced programming techniques
• Software/hardware watchdogs
• Application Builder

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Embedding a VI Step 1

• Select target platform

• Host

• RT intelligent card

• PXI controller on network

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Embedding a VI Step 2

• Download code on target

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Embedding a VI Step 3

• Exit without closing RT Engine

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Exercise 3 Download a VI
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Shared Memory

• Incremental read/write high-level continuous
  transfer of array of singles
• Read/write VIs incorporates a flag (8-bit word)
  to make reading and writing more efficient
• Low-level peeks and pokes basic building blocks
  for other levels

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VI Server

• Similar to normal VI Server
• Different machine name that corresponds to RT
  Series Intelligent Card device number (DAQ1)
• Requirements
• VI must be loaded in memory
• LabVIEW RT must be running on target

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Download Application

• Loads VI into dynamic memory without running it
• VI is now ready to run (Download bar will not
  appear)

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LabVIEW RT Running on Target

• Important aspect of VI Server
• Exit without closing RT Engine VIs
• Keeps LabVIEW RT open
• Closes user interface

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Exercise 4 Using VI Server
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TCP/IP with LabVIEW RT

• Similar to regular LabVIEW
• Requires different machine names to correspond to
  Intelligent DAQ Cards (DAQ1)
• Used to communicate large chunks of data
• Not deterministic

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Exercise 5 Using TCP/IP
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Agenda

• LabVIEW RT basics
• Current RT hardware targets
• Using LabVIEW RT
• Advanced programming techniques
• Software/hardware watchdogs
• Application Builder

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Programming Tips Timing

• Keep unnecessary computations outside of the
  time-critical loop
• Keep configuration VIs outside of the loop
• Sleep mode helps maintain loop rates while
  allowing other loops to share time

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Programming Tips Memory

• Determinism
• Pre-allocate arrays
• Avoid shared resources
• Performance
• Cast data to the proper type
• Inplaceness
• Global Variables

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Exercise 6 Reducing the Jitter in a LabVIEW RT
Program
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Single-Threaded LabVIEW
Computer
Thread
Co-routines
User Interface Loop
Exec( )
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Multithreaded LabVIEW
Computer
Messages
Thread
UI Loop Exec()
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LabVIEW RT Target System
RT Computer
Messages
Thread
Communication Loop Exec()
TCP/IP
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LabVIEW RT Deployed System
-Shared memory -TCP/IP -VI server
RT Series hardware target
Host PC
Thread
Thread
Communication Exec()
UI Loop Exec()
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Understanding Priorities

• Normal priority
• Allows the CPU to be shared
• Time-critical priority
• 100 of CPU time
• Sleep mode is very important
• Subroutine priority
• Highest priority level
• Releases thread only when done

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Exercise 7 Understanding Priorities
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Agenda

• LabVIEW RT basics
• Current RT hardware targets
• Using LabVIEW RT
• Advanced programming techniques
• Software/hardware watchdogs
• Application Builder

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Watchdogs

• Hardware or software mechanism that checks the
  status of the embedded system
• Increases the systems robustness
• Generally requires a low overhead

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Software Watchdog
Host PC

• Software watchdog can use the shared memory
• One side writes a value that is constantly
  changing
• Both host PC and embedded PC can implement
  watchdogs

(?)

1K
(?)
Embedded PC
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Hardware Watchdog

• Digital/counter lines can be used to trigger
  other systems

External System 1
(?)

External System 2
(?)
Embedded PC
CTR/DIO
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Built-in Hardware Watchdog API

• Extra hardware counter/timer
• Continuously counts down
• Software continually resets the counter
• Can be configured to take action
• Reset PXI System
• Set Occurrence
• Trigger

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Exercise 8 Implementing a Hardware Watchdog
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Agenda

• LabVIEW RT basics
• Current RT hardware targets
• Using LabVIEW RT
• Advanced programming techniques
• Software/hardware watchdogs
• Application Builder

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Application Builder

• Usually targeted to host PC
• Extra RT options
• Show RT target selection dialog
• Quit RT boot application after downloading

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Targeting to the PXI Controller

• Able to save executable to disk
• Remove serpdrv
• App Settings Tab is disabled

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Networked Preferences

• Application Builder (when connected to TARGET)
• Default name Startup.exe (C\ni-rt\startup)
• NETWORKED PREFERENCES-gtRT Target Miscellaneous
• Install path
• Name must be 8.3

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Command Line Arguments

• Used to alter execution
• Ex c\mybuiltapp.exe target DAQ1 reset
  quithost

RT Series DAQ device RT Series PXI system
-target DAQ1 130.164.48.51
-reset Resets device not available
-quithost Exits without closing RT Engines Exits without closing RT Engines
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Exercise 9 Using Application Builder
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End of LabVIEW RT Hands-onQuestions?