National Instruments 320571-01 User Manual

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™

NI-DSP

Software Reference Manual

for LabVIEW

Digital Signal Processing Software for the PC

December 1993 Edition

Part Number 320571-01

for Windows

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About This Manual.................................................................................................................... xi

Assumption of Previous Knowledge ........................................................................................................ xi

Organization of This Manual.................................................................................................................... xi

Conventions Used in This Manual............................................................................................................ xii

Related Documentation ............................................................................................................................ xiv

Additional Software.................................................................................................................................. xiv

NI-DAQ for DOS/Windows/LabWindows ................................................................................ xiv

Developer Toolkit ...................................................................................................................... xv

Compatible Hardware............................................................................................................................... xv

Customer Communication ........................................................................................................................ xv

Part 1 Getting Started with NI-DSP

Product Overview ..................................................................................................................................... 1-1

The NI-DSP Software............................................................................................................................... 1-1

What Your Distribution Diskettes Should Contain.................................................................... 1-2

Installing NI-DSP for LabVIEW for Windows ........................................................................................ 1-2

Board Configuration ................................................................................................................................. 1-3

Installation on an ISA (or AT) Bus Computer ........................................................................... 1-3

Installation on an EISA Bus Computer ...................................................................................... 1-3

........................................................................................ 1-1

Part 2 Introduction to the NI-DSP Analysis VIs

Using the NI-DSP VIs in LabVIEW ........................................................................................................ 1-1

AT-DSP2200 Software Overview ............................................................................................................ 1-1

Memory Management and Data Transfer................................................................................................. 1-2

Special Features of the NI-DSP Analysis VIs .......................................................................................... 1-5

Hints for Improving the Execution Speed on the DSP Board.................................................... 1-7

An Example of Using NI-DSP Analysis VIs............................................................................................ 1-8

Part 3 NI-DSP Function Reference

Chapter 1 NI-DSP Analysis VI Reference Overview

The NI-DSP Analysis VI Overview ......................................................................................................... 1-1

Analysis VI Organization ......................................................................................................................... 1-3

Accessing the NI-DSP Analysis VIs ........................................................................................................ 1-3

About the Fast Fourier Transform (FFT).................................................................................................. 1-4

About Filtering.......................................................................................................................................... 1-5

About Windowing .................................................................................................................................... 1-6

............................................................................... 1-1

.................................................... 1-1

Chapter 2 NI-DSP Analysis VI Reference

Copy Mem(DSP to DSP).......................................................................................................................... 2-1

Copy Mem(DSP to LV)............................................................................................................................ 2-2

Copy Mem(LV to DSP)............................................................................................................................ 2-3

........................................................................................................ 2-1

Contents

DSP Absolute............................................................................................................................................ 2-4

DSP Add ................................................................................................................................................... 2-5

DSP Allocate Memory.............................................................................................................................. 2-6

DSP Blackman Window........................................................................................................................... 2-7

DSP Blackman Harris Window ................................................................................................................ 2-8

DSP Butterworth Coefficients .................................................................................................................. 2-9

DSP Chebyshev Coefficients.................................................................................................................... 2-10

DSP Clip ................................................................................................................................................... 2-11

DSP Complex FFT.................................................................................................................................... 2-12

DSP Convolution ...................................................................................................................................... 2-13

DSP Correlation........................................................................................................................................ 2-14

DSP Cross Power...................................................................................................................................... 2-15

DSP Custom.............................................................................................................................................. 2-16

DSP Decimate........................................................................................................................................... 2-17

DSP Deconvolution .................................................................................................................................. 2-18

DSP Derivative ......................................................................................................................................... 2-19

DSP Divide ............................................................................................................................................... 2-20

DSP Elliptic Coefficients.......................................................................................................................... 2-21

DSP Equi-Ripple Bandpass ...................................................................................................................... 2-23

DSP Equi-Ripple Bandstop ...................................................................................................................... 2-25

DSP Equi-Ripple HighPass ...................................................................................................................... 2-27

DSP Equi-Ripple LowPass....................................................................................................................... 2-29

DSP Exact Blackman Window................................................................................................................. 2-30

DSP Exponential Window ........................................................................................................................ 2-31

DSP FHT .................................................................................................................................................. 2-32

DSP Flat Top Window.............................................................................................................................. 2-33

DSP Force Window .................................................................................................................................. 2-34

DSP Free Memory .................................................................................................................................... 2-34

DSP Gaussian White Noise ...................................................................................................................... 2-35

DSP General Cosine Window .................................................................................................................. 2-36

DSP Hamming Window ........................................................................................................................... 2-37

DSP Handle to Address ............................................................................................................................ 2-38

DSP Hanning Window.............................................................................................................................. 2-39

DSP IIR Filter........................................................................................................................................... 2-40

DSP Impulse Pattern................................................................................................................................. 2-42

DSP Impulse Train Pattern ....................................................................................................................... 2-43

DSP Index Memory .................................................................................................................................. 2-44

DSP Init Memory...................................................................................................................................... 2-45

DSP Integral.............................................................................................................................................. 2-46

DSP Inv Chebyshev Coeff........................................................................................................................ 2-47

DSP Inverse FFT ...................................................................................................................................... 2-48

DSP Inverse FHT...................................................................................................................................... 2-49

DSP Kaiser-Bessel Window..................................................................................................................... 2-50

DSP Linear Evaluation ............................................................................................................................. 2-51

DSP Load.................................................................................................................................................. 2-51

DSP Log.................................................................................................................................................... 2-52

DSP Max & Min....................................................................................................................................... 2-53

DSP Median Filter .................................................................................................................................... 2-54

DSP Multiply ............................................................................................................................................ 2-55

DSP Parks-McClellan............................................................................................................................... 2-56

DSP Polar to Rectangular ......................................................................................................................... 2-59

DSP Polynomial Evaluation ..................................................................................................................... 2-60

DSP Power Spectrum................................................................................................................................ 2-61

DSP Product.............................................................................................................................................. 2-61

DSP Pulse Pattern..................................................................................................................................... 2-62

DSP Ramp Pattern .................................................................................................................................... 2-63

DSP Random Pattern ................................................................................................................................ 2-64

DSP Rectangular to Polar ......................................................................................................................... 2-65

NI-DSP SRM for LabVIEW for Windows vi © National Instruments Corporation

Contents

DSP ReFFT............................................................................................................................................... 2-66

DSP Reset ................................................................................................................................................. 2-66

DSP Reverse ............................................................................................................................................. 2-67

DSP Sawtooth Pattern............................................................................................................................... 2-68

DSP Set..................................................................................................................................................... 2-69

DSP Shift .................................................................................................................................................. 2-69

DSP Sinc Pattern....................................................................................................................................... 2-70

DSP Sine Pattern....................................................................................................................................... 2-71

DSP Square Pattern................................................................................................................................... 2-72

DSP Square Root ...................................................................................................................................... 2-73

DSP Sort ................................................................................................................................................... 2-74

DSP Start .................................................................................................................................................. 2-75

DSP Subset ............................................................................................................................................... 2-75

DSP Subtract............................................................................................................................................. 2-76

DSP Sum................................................................................................................................................... 2-76

DSP TimeOut............................................................................................................................................ 2-77

DSP Triangle Pattern ................................................................................................................................ 2-78

DSP Triangular Train................................................................................................................................ 2-80

DSP Triangular Window .......................................................................................................................... 2-81

DSP Uniform White Noise ....................................................................................................................... 2-82

DSP Unwrap Phase................................................................................................................................... 2-83

DSP Zero Padder ...................................................................................................................................... 2-84

Part 4 NI-DSP Interface Utilities

Chapter 1 Introduction to the NI-DSP Interface Utilities

Overview of the NI-DSP Interface Utilities.............................................................................................. 1-1

Installing the NI-DSP Interface Utilities .................................................................................................. 1-2

Using the NI-DSP Interface Utilities ........................................................................................................ 1-2

Chapter 2 Getting Started with the NI-DSP Interface Utilities

Creating Your Custom NI-DSP Library................................................................................................... 2-1

1. Create Your Source Code of C Functions............................................................................. 2-1

GMaxMin.c Example.................................................................................................. 2-1

Guidelines for the Custom Functions .......................................................................... 2-2

DSP Board Memory Management............................................................................... 2-3

2. Compile and/or Assemble Source Code................................................................................ 2-4

3. Add Your Object Filenames to a Linker File (ifile).............................................................. 2-4

4. Add Your New Function Names to a Library Function List File.......................................... 2-4

Customizing the DSP Library by Deleting Functions ................................................. 2-5

5. Run the Build Dispatch Application to Generate an Assembly Dispatch File...................... 2-6

6. Compile, Assemble, and Link Your Custom Library............................................................ 2-7

Creating Your LabVIEW Interface .......................................................................................................... 2-8

1. Bundle All of the Input Parameters to Arrays....................................................................... 2-8

2. Call the Custom VI................................................................................................................ 2-10

3. Index the Output Arrays to Obtain the Results ..................................................................... 2-10

Executing the Custom Function from LabVIEW ..................................................................................... 2-12

.................................................................... 1-1

....................................................... 2-1

Chapter 3 DSP Board Function Overview

Data Acquisition Functions ...................................................................................................................... 3-3

...................................................................................................... 3-1

Contents

Chapter 4 Using the DMA VIs

DSP DMA Copy(DSP to LV)................................................................................................................... 4-3

DSP DMA Copy(LV to DSP)................................................................................................................... 4-4

Appendix A

.................................................................................................................................. 4-1

Error Codes

Error Conditions........................................................................................................................................ A-1

.......................................................................................................................................... A-1

Appendix B Customer Communication

............................................................................................... B-1

Glossary........................................................................................................................................... Glossary-1

Index.......................................................................................................................................................... Index-1

NI-DSP SRM for LabVIEW for Windows viii © National Instruments Corporation

Contents

Figures

Part 1

Figure 1-1. Development Paths with the NI-DSP Software............................................................................. 1-1

Part 2

Figure 1-1. Communication between the PC and the DSP Board .................................................................... 1-1

Figure 1-2. DSP Handle Cluster ....................................................................................................................... 1-3

Figure 1-3. The Hexadecimal Encoding of a Typical DSP Handle.................................................................. 1-3

Figure 1-4. Front Panel–An Example of How to Allocate a DSP Handle Cluster........................................... 1-4

Figure 1-5. Block Diagram–An Example of How to Allocate a DSP Handle Cluster..................................... 1-4

Figure 1-6. DSP Add VI ................................................................................................................................... 1-5

Figure 1-7. The error in/error out Cluster...................................................................................................... 1-5

Figure 1-8. An Example That Does Not Use error in/error out for Sequencing VIs .................................... 1-6

Figure 1-9. An Example of Using the error in/error out Cluster for Sequential VI Execution..................... 1-7

Figure 1-10. Front Panel–An Example of Using NI-DSP Analysis VIs ............................................................ 1-8

Figure 1-11. Block Diagram–An Example of Using NI-DSP Analysis VIs ...................................................... 1-8

Part 3

Figure 1-1. Choosing DSP2200 from the Functions Menu .............................................................................. 1-4

Figure 1-2. Spectral Leakage Demonstrated Using Convolution..................................................................... 1-7

Part 4

Figure 1-1. NI-DSP for DOS Directory Structure ............................................................................................ 1-1

Figure 1-2. Interface Layers to Onboard Functions.......................................................................................... 1-2

Figure 2-1. Linker File NIDSPLNK................................................................................................................. 2-4

Figure 2-2. Library Function List File NIDSP.fnc ........................................................................................... 2-4

Figure 2-3. Typical Section of NIDSP.fnc ....................................................................................................... 2-5

Figure 2-4. Signals Group Section in dspfncs.h ............................................................................................... 2-6

Figure 2-5. Signals Group Section in dispatch.s............................................................................................... 2-6

Figure 2-6. How to Bundle Parameters in LabVIEW to Call gmaxmin.c ........................................................ 2-9

Figure 2-7. How to Connect to Custom VI to Call gmaxmin.c........................................................................ 2-10

Figure 2-8. Block Diagram–How to Index the Output Arrays of the Custom VI ............................................ 2-11

Figure 2-9. Block Diagram–Using the Custom VI to Call gmaxmin.c on theDSP Board from LabVIEW..... 2-11

Figure 2-10. Front Panel–Using the Custom VI to Call gmaxmin.c on theDSP Board from LabVIEW........... 2-12

Contents

Tables

Part 1

Table 1-1. Subdirectories Created by SETUP................................................................................................. 1-2

Part 3

Table 1-1. The NI-DSP Analysis VI Groups .................................................................................................. 1-1

Part 4

Table 2-1. Files Required to Build the Custom DSP Library Example .......................................................... 2-7

Appendix A

Table A-1. NI-DSP Analysis Library Error Codes .......................................................................................... A-1

NI-DSP SRM for LabVIEW for Windows x © National Instruments Corporation

About This Manual

The NI-DSP Software Reference Manual for LabVIEW for Windows explains how to use the NI-DSP software package for the LabVIEW for Windows environment. The NI-DSP software package contains the NI-DSP Analysis VIs, which are high-level digital signal processing (DSP) VIs that call the functions that execute on the AT-DSP2200 plug-in board for IBM AT bus and compatible computers. This manual describes how to use the NI-DSP Analysis VIs to develop applications in LabVIEW using the AT-DSP2200 board.

The NI-DSP software package also contains the NI-DSP Interface Utilities. The NI-DSP Interface Utilities are a set of tools and examples that help you customize your NI-DSP Analysis VIs and the DSP Library, which is resident on the board. This manual contains step-by-step instructions and useful examples to help the LabVIEW developer add custom algorithms to the NI-DSP Analysis VIs using the NI-DSP Interface Utilities.

Assumption of Previous Knowledge

The material in this manual is for users who are familiar with LabVIEW and the IBM family of computers and compatible computers.

Organization of This Manual

This manual is divided into four parts.

• Part 1, Getting Started with NI-DSP, contains a brief product overview, information about the NI-DSP for LabVIEW for Windows package, and the procedure for installing the software.

• Part 2, Introduction to the NI-DSP Analysis VIs, describes how to use the NI-DSP Analysis VIs in your LabVIEW applications. This part also describes how to manage memory on the DSP board from your LabVIEW application, and how to transfer data between your LabVIEW application and the NI-DSP functions on the board. This part contains general guidelines for developing NI-DSP applications within LabVIEW.

• Part 3, NI-DSP Function Reference, is intended as a reference for users familiar with Part 2. Part 3 is organized as follows:

- Chapter 1, NI-DSP Analysis VI Reference Overview, contains an overview of the NI-DSP Analysis VIs and

includes a list of the VIs. This chapter describes how the NI-DSP Analysis VIs are organized, and how to access them.

- Chapter 2, NI-DSP Analysis VI Reference, contains a brief explanation of each NI-DSP Analysis VI. The

VIs are arranged alphabetically.

• Part 4, NI-DSP Interface Utilities, explains how to customize the NI-DSP Analysis Library on the board and to create and run interfaces in LabVIEW to your custom library functions. Part 4 is organized as follows:

- Chapter 1, Introduction to the NI-DSP Interface Utilities, contains an overview of the NI-DSP Interface

Utilities, installation instructions, and explains how to use the NI-DSP Interface Utilities.

- Chapter 2, Getting Started with the NI-DSP Interface Utilities, contains a step-by-step example for building

a custom DSP Library, creating a LabVIEW interface to a custom function, and executing the custom function from the LabVIEW environment. The chapter demonstrates this concept with an example of how to add a custom function.

About This Manual

- Chapter 3, DSP Board Function Overview, contains an overview of the prototypes of the C-callable

NI-DSP Analysis functions on the DSP board that you can use in your custom programs.

- Chapter 4, Using the DMA VIs, describes two special VIs that transfer data between the host computer and

the DSP board without interfering with the DSP board.

• Appendix A, Error Codes, contains a list of the error codes returned by the NI-DSP Analysis VIs and the corresponding error messages.

• Appendix B, Customer Communication, contains forms you can use to request help from National Instruments or to comment on our products and manuals.

• The Glossary contains an alphabetical list and description of terms used in this manual, including abbreviations, acronyms, metric prefixes, mnemonics, and symbols.

• The Index alphabetically lists topics covered in this manual, including the page where the topic can be found.

Conventions Used in This Manual

The following conventions are used in this manual: <> Angle brackets enclose the name of a key on the keyboard–for example, <enter>. bold Bold text denotes menus, command names, parameters, function panel items, error

messages, and warnings. DSP board DSP board refers to the AT-DSP2200. DSP Handle DSP Handle refers to a 32-bit long integer code that constitutes an indirect reference to a

buffer of memory in the memory space of an AT-DSP2200 board. The code contains

information about the slot number of the board on which that buffer is allocated. DSP Handle Cluster DSP Handle Cluster refers to a cluster that constitutes two fields–a DSP Handle and a

32-bit size that indicates the number of elements the DSP Handle holds. DSP Library DSP Library refers to a common object file format (COFF) that constitutes NI-DSP

software that resides and runs on the AT-DSP2200 board. The DSP Library consists of

the Kernel, memory management routines, execution control routines, data

communication routines, interrupt handling routines, data acquisition routines and a set of

analysis functions. <enter> Key names are in lowercase letters. Interface Library Interface Library refers to the part of the NI-DSP software that resides on the PC and is

linked with your application in order to communicate data to and from the DSP board.

The Interface Library communicates with the DSP board using the driver. italic Italic text denotes emphasis, a cross reference, or an introduction to a key concept.

italic monospace

Italic text in this font denotes that you must supply the appropriate words or values in the

place of these items.

NI-DSP SRM for LabVIEW for Windows xii © National Instruments Corporation

About This Manual

LabVIEW Data Types Each VI description includes a data type picture for each control and indicator, as

illustrated in the following table:

Control Indicator Data Type

Boolean String Signed 16-bit integer

Array of signed 16-bit integers Signed 32-bit integer Array of signed 32-bit integers 32-bit floating-point number; by default,

floating-point numbers are double precision Array of 32-bit floating-point numbers

Path DSP Handle Cluster

Array of DSP Handle Clusters

Error Cluster

monospace Text in this font denotes text or characters that are to be literally input 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, array names, structures, variables, filenames, and extensions, and for

statements and comments taken from program code. NI-DAQ NI-DAQ is used throughout this manual to refer to the NI-DAQ software for

DOS/Windows/LabWindows unless otherwise noted. NI-DSP NI-DSP is used throughout this manual to refer to the NI-DSP software for LabVIEW for

Windows unless otherwise noted. PC PC refers to the IBM PC AT and compatible computers, and to EISA personal computers. WE DSP32C tools WE DSP32C tools is used throughout this manual to refer to the AT&T WE DSP32C

Developer Toolkit. Abbreviations, acronyms, metric prefixes, mnemonics, symbols, and terms are listed in the Glossary.

About This Manual

Additional Software

Additional DSP board software includes NI-DAQ for DOS/Windows/LabWindows and the Developer Toolkit.

NI-DAQ for DOS/Windows/LabWindows

Your AT-DSP2200 is shipped with the NI-DAQ for DOS/Windows/LabWindows software. NI-DAQ has a library of functions that can be called from your application programming environment. These functions include routines for analog input (A/D conversion), buffered data acquisition (high-speed A/D conversion), analog output (D/A conversion), waveform generation, digital I/O, counter/timer, SCXI, RTSI, and self-calibration. NI-DAQ maintains a consistent software interface among its different versions so you can switch between platforms with minimal modifications to your code. NI-DAQ comes with language interfaces for Professional BASIC, Turbo Pascal, Turbo C, Turbo C++, Borland C++, Microsoft C for DOS; and Visual Basic, Pascal, Microsoft C with SDK, and Borland C++ for Windows. NI-DAQ for DOS/Windows/LabWindows software is on high-density 5.25 in. and

3.5 in. diskettes. You can use the DSP board in conjunction with the National Instruments AT Series data acquisition boards and software to create a complete solution for integrated data acquisition and data analysis applications.

NI-DSP SRM for LabVIEW for Windows xiv © National Instruments Corporation

About This Manual

Developer Toolkit

The Developer Toolkit, an optional software package that you can purchase separately from National Instruments, is required for building custom libraries with the NI-DSP Interface Utilities. The Developer Toolkit contains an AT&T C compiler, assembler, linker, and documentation. With these tools, you can program AT Series DSP boards directly, using theboard flexibility to custom tailor the DSP Library. The C compiler optimizes WE DSP32C code and generates assembly language code that can be assembled and linked into a run-time module. When a run-time module is completed, use the download tools and the debugger to load, debug, and execute the code, set parameters, and report results. The Developer Toolkit also includes the WE DSP32C Support Software Library User Manual and the WE DSP32 and WE DSP32C Language Compiler Library Reference Manual.

Compatible Hardware

You can use DSP boards in conjunction with the National Instruments AT Series data acquisition boards. In particular, the National Instruments AT-DSP2200 is a high-performance, DSP board with high-accuracy audio frequency (DC to 51.2 kHz) analog input/output for the PC. The AT-DSP2200 gives the PC a dedicated high-speed numerical computation engine that can perform scientific calculations faster than the general-purpose 80x86 microprocessor on the PC.

Customer Communication

National Instruments wants to receive your comments on our products and manuals. We are interested in the applications you develop with our products, and we want to help if you have problems with them. To make it easy for you to contact us, this manual contains comment and configuration forms for you to complete. These forms are in Appendix B, Customer Communication, at the end of this manual.

Part 1 Getting Started with NI-DSP

This part contains a brief product overview, information about the NI-DSP for LabVIEW for Windows package, and the procedure for installing the software.

Product Overview

The NI-DSP software package comes with a set of LabVIEW VIs that invoke the digital signal processing (DSP) board-resident high-performance functions that efficiently process large blocks of numerical data and perform numerically intensive computations. The NI-DSP Analysis VIs include numerical analysis, signal generation, DSP, windowing, digital filtering, and memory management that are suitable for simulation, modeling, and sophisticated data processing.

You can use NI-DSP to develop programs in the LabVIEW for Windows environment. This software comes with the NI-DSP Interface Utilities so you can customize the DSP Library by adding functions to or deleting functions from the Analysis Library on the DSP board and/or add interfaces to these custom functions in LabVIEW.

Figure 1-1 shows the development path for NI-DSP in the LabVIEW environment.

NI-DSP for

The LabVIEW

for Windows

Development

Environment

AT&T

Development

Environment

and T ools

(Optional)

Figure 1-1. Development Paths with the NI-DSP Software

LabVIEW

for Windows

Interface

Utilities

The NI-DSP Software

The NI-DSP software consists of the NI-DSP for LabVIEW for Windows diskettes.

User

Application

The NI-DSP software contains a Warranty Registration Form. Please fill out this form and return it to National Instruments. The Warranty Registration Form entitles you to receive product upgrades and technical support.

NI-DSP SRM for LabVIEW for Windows 1-1 Part 1: Getting Started with NI-DSP

Getting Started with NI-DSP Part 1

What Your Distribution Diskettes Should Contain

The NI-DSP software package contains the NI-DSP for LabVIEW for Windows Disks (for licensed LabVIEW for Windows users). If your kit is missing any of these components, contact National Instruments.

Installing NI-DSP for LabVIEW for Windows

Note: NI-DSP for LabVIEW for Windows is intended for use with the standard LabVIEW for Windows software.

You must install LabVIEW for Windows before installing NI-DSP. You must install the Data Acquisition Library of LabVIEW to run the NI-DSP software.

Before beginning the software installation, make backup copies of the NI-DSP for LabVIEW for Windows distribution disks. Copy each disk onto a correctly labeled backup disk and store the original distribution disks in a safe place.

You can install NI-DSP for LabVIEW for Windows from the DOS prompt, the Windows File Manager, or with the Run... command from the File menu of the Program Manager.

1. Insert Disk 1 into the disk drive and run the SETUP.EXE program on Disk 1 using one of the following three

methods.

• From the DOS prompt, type X: \SETUP (where X is the proper drive designation).

• From Windows, select Run... from the File menu of the Program Manager. A dialog box appears. Type

X: \SETUP (where X is the proper drive designation).

• From Windows, launch the File Manager. Click on the drive icon that contains Disk 1. Find SETUP.EXE in the list of files on that disk and double-click on it.

2. The installer gives you the option of performing a full installation or a custom installation. Unless you do not have sufficient disk space (approximately 4 megabytes), National Instruments recommends that you perform a full installation. After you choose an installation, follow the instructions that appear on the screen.

After calling SETUP, the appropriate directories are created and the needed files are copied to your hard drive. SETUP can also install the NI-DSP Interface Utilities, discussed in Part 4, NI-DSP Interface Utilities, of this manual. If you choose Full Installation, SETUP does the following things:

1. SETUP creates a subdirectory called DSP2200 of the vi.lib subdirectory of the LabVIEW directory. SETUP decompresses the NI-DSP Analysis VIs (as LabVIEW .LLB files) in the DSP2200 directory.

2. SETUP copies DSP.DLL to your windows directory.

3. SETUP creates the subdirectories shown in Table 1-1 under the directory you specified during setup. These subdirectories make up the NI-DSP Interface Utilities.

4. SETUP creates a subdirectory called DSP2200 of the EXAMPLES subdirectory of the LabVIEW directory. SETUP copies all of the NI-DSP VI examples there.

Table 1-1. Subdirectories Created by SETUP

Subdirectory Name Description

C:\NIDSP\LIB Library files for linking with stand-alone programs C:\NIDSP\DISPATCH The Dispatch utility and related files C:\NIDSP\EXAMPLES Contains source code for the examples

Part 1: Getting Started with NI-DSP 1-2 NI-DSP SRM for LabVIEW for Windows

Part 1 Getting Started with NI-DSP

NIDSP is the name you specify during setup. The SETUP program prompts you for information including the drive letter and directory in which you have

installed the standard LabVIEW package. The program also verifies that your hard disk has enough space to hold the NI-DSP for LabVIEW for Windows files.

If you choose Custom Installation, SETUP installs only the files you specify.

Board Configuration

There are several board configuration parameters that must be established before an NI-DSP application can execute properly. These parameters are the board ID number, the board subtype, the base address, the interrupt level, the DMA channel, and the pathname of the DSP Library files. These parameters are established differently depending on whether you are installing the AT-DSP2200 in an ISA (or AT) bus computer or an EISA bus computer.

Installation on an ISA (or AT) Bus Computer

A configuration utility is supplied with the LabVIEW data acquisition software for establishing all the configuration parameters on ISA bus computers. This utility, called WDAQCONF.EXE, saves the configuration parameters in a file named WDAQCONF.CFG. Use the WDAQCONF utility to assign a board ID number to your AT-DSP2200, to choose the memory subtype (either 64 Kwords or ≥128 Kwords), to set the base address, interrupt level, and DMA channel, and to specify the pathname of the DSP Library file.

Two DSP Library files are supplied with your NI-DSP software–LV2200S.OUT and LV2200.OUT. LV2200S.OUT is intended for use with the 64 Kword version of the AT-DSP2200. LV2200.OUT is intended for use with any other version of the board. With the WDAQCONF utility, you can enter a complete path that will include the DSP Library file name. If you enter complete pathnames, you can configure the NI-DSP software to automatically load custom versions of the DSP Library files.

If you installed the Data Acquisition Library of LabVIEW, you can find WDAQCONF.EXE of your LabVIEW directory. From Windows, you run WDAQCONF.EXE by double-clicking on its icon.

Installation on an EISA Bus Computer

Installing the AT-DSP2200 board on an EISA bus computer involves two different configuration utilities.

• A system configuration utility is supplied with your computer by your computer vendor. This utility, along with the !NIC1100.CFG EISA configuration file installed by the LabVIEW SETUP program, is used to assign a slot number to the AT-DSP2200, to choose the memory subtype (either 64 Kwords or ≥128 Kwords), and to set the base address, interrupt level, and DMA channel.

There are typically two methods for running your EISA system configuration utility.

1. Boot from the diskette containing the utility and place a copy of the !NIC1100.CFG file on this diskette.

2. Run the utility from a directory on your hard disk and place a copy of the !NIC1100.CFG file in this

directory. The EISA system configuration utility is typically named CF.EXE.

• You must use the WDAQCONF utility to enter the DSP Library file pathname. You can only do this after completing the EISA system configuration. Refer to the information concerning the establishment of this pathname in the previous section titled, Installation on an ISA (or AT) Bus Computer.

Before using NI-DSP, you must run WDAQCONF.EXE to configure your DSP board. For more information about board configuration, refer to Chapter 1, Introduction and Configuration, of the

LabVIEW Data Acquisition VI Reference Manual.

NI-DSP SRM for LabVIEW for Windows 1-3 Part 1: Getting Started with NI-DSP

Part 2 Introduction to the NI-DSP Analysis VIs

This part describes how to use the NI-DSP Analysis VIs in your LabVIEW applications. This part also describes how to manage memory on the DSP board from your LabVIEW application, and how to transfer data between your LabVIEW application and the NI-DSP functions on the board. This part contains general guidelines for developing NI-DSP applications within LabVIEW.

Using the NI-DSP VIs in LabVIEW

LabVIEW users use the NI-DSP Analysis VIs as if they were any other standard VIs, as described in the LabVIEW User Manual. Notice, however, that the NI-DSP Analysis VIs run analysis code on the DSP board rather than on the

host CPU. One of the major features includes the memory management and data transfer VIs, which are discussed in detail in the section titled Memory Management and Data Transfer later in this chapter.

AT-DSP2200 Software Overview

The AT-DSP2200 board, working in conjunction with your personal computer, is a powerful numeric processor for high-speed analysis of data arrays. The NI-DSP for LabVIEW for Windows software includes a number of utilities and low-level memory management and data transfer VIs that facilitate communication between the DSP board and the host computer. Figure 1-1 is a block diagram of the software utilities and libraries that control the AT-DSP2200. The DSP Library and the low-level memory management and data transfer functions reside and execute on the board. You can customize the DSP Library to optimize performance, as described in Part 4, Chapter 2, Getting Started with the NI-DSP Interface Utilities, of this manual. Your application programs and the Interface Library, however, reside on the host PC.

User

Application

in LabVIEW

Interface

(CIN)

PC AT-DSP2200

Interface

Library

(DSP.DLL)

Figure 1-1. Communication between the PC and the DSP Board

AT or EISA Bus

DSP Software

Onboard Kernel,

DSP Board

Memory Management, Data Transfer

Functions

DSP Library

DSP Hardware

CPU

Onboard Memory

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Introduction to the NI-DSP Analysis VIs Part 2

The AT-DSP2200 can process large amounts of data, separately and distinctly from the host PC processor. The board consists not only of a signal processing chip, but also memory where data that the board processes must reside. The AT-DSP2200 does not have access to memory locations on the host PC. Therefore, you must download all data from your application programs to DSP board memory before processing it.

The Interface Library, DSP.DLL, and the Code Interface Node (CIN) interface, which reside on the PC, serve as a bridge between your application programs in LabVIEW and the DSP software running on the board. When you call an NI-DSP Analysis VI, the VI passes the parameters to the CIN first, which then passes the parameters to the Interface Library, DSP.DLL. The Interface Library determines what type of parameters are being passed, decides how to set up the data in DSP board memory, and then calls the actual functions that will run on the board.

When a function on the DSP board processes data, it assumes the data is resident in DSP board memory. Because transferring data between the PC and the DSP board slows down processing, none of the NI-DSP Analysis VIs transfer data back and forth internally except the data transferring VIs. The NI-DSP Analysis VIs process the data buffers that are already on the board and leave the results on the board.

If the data buffer you want to process using the DSP board is in PC memory, you must copy the data to the DSP board before you call a function on the DSP board to process the data. To see the results, you must then copy the data back to the PC. Several special NI-DSP Analysis VIs perform these transfers. For scalars, the NI-DSP Analysis VIs automatically perform the transfer for you.

The representation of data buffers in the NI-DSP Analysis VIs is not the normal LabVIEW data array representation because the data buffers indicate the data location on the DSP board instead of the PC address. A special structure, called a DSP Handle Cluster, represents the data buffer on the DSP board from LabVIEW. The DSP Handle Cluster is a coded DSP board memory address that indicates where the data buffer is on the DSP board. You must call the DSP Allocate Memory VI to obtain a valid DSP Handle Cluster. Several VIs can manage the memory on the DSP board. You can allocate and deallocate memory on the DSP board using these VIs. The next section, Memory Management and Data Transfer, discusses the VIs used to allocate memory and transfer data buffers to and from the DSP board.

Memory Management and Data Transfer

This section describes how to manage memory on the DSP board from your LabVIEW application and how to transfer data between your LabVIEW application and the DSP board.

The NI-DSP for LabVIEW package contains a set of VIs that manage memory space on the DSP board and help improve data transfers between the DSP board and your application. There are VIs for allocating memory buffers on the DSP board, for indexing into previously allocated buffers, for deallocating buffers and for copying data between DSP and LabVIEW. The following VIs, described in greater detail in Part 3 of Chapter 2, NI-DSP Analysis VI Reference, handle memory management on the DSP board and data transfers between the DSP board and your LabVIEW application:

• Copy Mem[DSP to DSP]

• Copy Mem[DSP to LV]

• Copy Mem[LV to DSP]

• DSP Allocate Memory

• DSP Free Memory

• DSP Index Memory

• DSP Init Memory

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Part 2 Introduction to the NI-DSP Analysis VIs

The DSP Allocate Memory VI allocates memory buffers on the DSP board and returns a DSP Handle Cluster, which has two fields that uniquely describe this buffer–a DSP Handle and a size.

Figure 1-2. DSP Handle Cluster

DSP Handle is a 32-bit integer containing information that indicates the board on which the allocated buffer resides, and an index into an onboard Memory Look Up Table (MLUT) that holds the actual DSP address of the buffer that this handle represents. Figure 1-3 shows how a DSP Handle is encoded. The size field holds the number of elements in this buffer. An element can be 4 bytes (for 32-bit floating-point data or long integer data) or 2 bytes (for 16-bit integer data) depending on the bytes per element selector used in the DSP Allocate Memory VI.

X XXX 3 0 04

Figure 1-3. The Hexadecimal Encoding of a Typical DSP Handle

The first four hexadecimal numbers (upper 16 bits) of the DSP Handle, shown in Figure 1-3, are a special value. The interface code for a particular function that your application calls decodes these four hexadecimal numbers to determine if the argument is a valid DSP Handle.

Notes: Do not change the value of a DSP Handle Cluster. Keep in mind that a DSP Handle Cluster is just an entry

of a table that indicates where the data buffer is on the DSP board. If you want to operate on part of the data in that buffer, use the DSP Index Memory VI or the DSP Subset VI to obtain a new DSP Handle Cluster to hold the part of the data. Then operate on the new DSP Handle Cluster.

}

Board Number of

Special Code

Owner DSP Board

}

Index into the

MLUT of the

Owner DSP Board

The Memory Look-Up Table (MLUT) has only 128 entries. You can allocate only a total of 128 different DSP Handle Clusters. Although you might have physical memory on the DSP board, you will get an error message for not having enough memory if you already have 128 DSP Handle Clusters in use. Free the DSP Handle Clusters that are not in use. The DSP Init Memory VI will free all DSP Handle Clusters on the specified DSP board.

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Introduction to the NI-DSP Analysis VIs Part 2

Figures 1-4 and 1-5 show how to allocate a DSP Handle Cluster of 2,048 4-byte-long elements on board 3. The board number on which the buffer is allocated is important for determining the ownership of the buffer. When making a VI call, the same DSP board on which the function is to execute must own all of the DSP Handle Clusters or an error code is returned. Only the DSP Allocate Memory VI and few other VIs that do not have DSP Handle Clusters as input parameters have a board slot parameter. VIs that have DSP Handle Clusters as input parameters obtain the board slot information from their own DSP Handle Clusters. All of the DSP Handle Clusters should have the same slot information, because the DSP VIs assume that all are executing on the same DSP board.

Figure 1-4. Front Panel–An Example of How to Allocate a DSP Handle Cluster

Figure 1-5. Block Diagram–An Example of How to Allocate a DSP Handle Cluster

For all of the NI-DSP Analysis VIs, the array data type is DSP Handle Cluster. Before you call any of these VIs, call the DSP Allocate Memory VI to obtain a valid DSP Handle Cluster, which you then use as a reference to your data buffer. The Analysis VIs assume that the data is already on the board and stores the results on the board. If you want to copy data between the PC and the DSP board, use either the Copy Mem(LV to DSP) VI or the Copy Mem(DSP to LV) VI to copy data back and forth.

If you use the DSP Allocate Memory VI in your program, use the DSP Free Memory VI to free buffers allocated when you do not need them any more. The board holds these allocations in memory even after your application has completed or you exit LabVIEW unless you execute the DSP Init Memory VI or reload the DSP Library. Thus, it is important to free all buffers your application allocated before you exit the application or you may run out of memory on the board.

Part 2: Introduction to the NI-DSP Analysis VIs 1-4 NI-DSP SRM for LabVIEW for Windows

Part 2 Introduction to the NI-DSP Analysis VIs

Special Features of the NI-DSP Analysis VIs

This section describes the special features of the NI-DSP Analysis VIs that make them different from other LabVIEW VIs.

• DSP Handle Cluster in/out. The way you specify the output data buffers for NI-DSP Analysis VIs is different

from the way you would specify output data buffers for other LabVIEW VIs. DSP Handle Clusters also represent all the output data buffers in the NI-DSP Analysis VIs. To use valid DSP Handle Clusters for the NI-DSP VI output data buffers, you must use the DSP Allocate Memory VI to obtain the DSP Handle Clusters before you use them. Supply all of the output DSP Handle Clusters as inputs to tell the DSP board where the output buffers are. Every output DSP Handle Cluster is identical to the corresponding input DSP Handle Cluster. The two DSP Handle Clusters are internally connected. The output is an indicator. The input is a control. For example, in the DSP Add VI, shown in Figure 1-6, Z is the DSP Handle Cluster that indicates where to store the results. You use Z in to connect to a valid DSP Handle Cluster that you previously allocated. Z in tells the DSP board where the results will be stored. Z out is the location where the results have already been stored. Because Z in and Z out are the same DSP Handle Cluster, you need to free only one of them when you want to deallocate their DSP board buffer.

Figure 1-6. DSP Add VI

All of the controls and indicators in the NI-DSP Analysis VIs follow the Z in, Z out naming convention and work in the same way as previously described in the example, except for the error in/error out cluster.

• Error Handling. All of the NI-DSP Analysis VIs have an error input and an error output for managing and reporting errors. The error in/error out cluster used by the NI-DSP VIs and many other high-level I/O operations is a cluster containing a Boolean indicating whether the data should be treated as an error, a 32-bit error code, and a descriptive string that usually contains the name of the source of the error. The error in/error out cluster is shown in Figure 1-7.

Figure 1-7. The error in/error out Cluster

NI-DSP SRM for LabVIEW for Windows 1-5 Part 2: Introduction to the NI-DSP Analysis VIs

Introduction to the NI-DSP Analysis VIs Part 2

The error in/error out cluster contains the following elements:

The boolean value is true if an error occurred, false if no error occurred.

code is the error code. source is the source of the error. If an error occurs during execution, the VI sets source to the name

of the VI that produced the error.

Every VI checks error in first. If there is an error, the VI does not execute any DSP code but simply passes the contents of error in to the error out cluster. If there is no error, the VI executes. One advantage of this error in/error out design is that you can connect several I/O operations together so that, if an error occurs, subsequent VIs do not perform undesired actions. DSP Free Memory will execute even if an error occurs. This ensures that allocated buffers are freed even if an error occurred.

Another advantage of this error in/error out design is that you can establish the order of a set of operations, even if there is no other data flow between the operations. Connecting the error out of the first VI to the error in of the second VI establishes data flow and therefore execution order. You could do the same thing with a Sequence structure, but with the error in/error out design, you can establish the order with all of the operations at the top level of the block diagram. For example, in Figure 1-8, you allocate DSP Handle Clusters X and Y as inputs, and you want to free X and Y after the DSP Add VI has been executed. If you simply connect X to the DSP Free Memory VI as shown in Figure 1-8, there is no sequential order between the DSP Add VI and the DSP Free Memory VI. If the DSP Free Memory VI executes first, the DSP Add VI will receive an invalid handle because that DSP Handle Cluster was deallocated.

Figure 1-8. An Example That Does Not Use error in/error out

for Sequencing VIs

If you connect the VIs as shown Figure 1-9 instead, you ensure that the DSP Add VI executes before the DSP Free Memory VI.

Part 2: Introduction to the NI-DSP Analysis VIs 1-6 NI-DSP SRM for LabVIEW for Windows

Part 2 Introduction to the NI-DSP Analysis VIs

error out of the Copy Mem(LV to DSP) VI is connected to the error in of the DSP Free Memory VI

error out of the DSP Add VI is connected to the error in of the Copy Mem(LV to DSP) VI

Figure 1-9. An Example of Using the error in/error out Cluster for Sequential VI Execution

For more information about the error in/error out cluster, refer to Chapter 2, Error Handler VIs, in the LabVIEW

Utility VI Reference Manual.

Hints for Improving the Execution Speed on the DSP Board

Check each of the following things to maximize your DSP board performance:

• Allocate as many of the DSP Handle Clusters as you can before you operate on the data. Keep all data on the DSP board until you finish all of the processing. Reduce the number of data transfers between the DSP board and the PC as much as possible. The functions that run on the DSP board are very fast, but transferring data between the DSP board and the PC and memory allocation slows the total processing performance.

• Use the error in/error out cluster for sequencing VI execution. Be sure all of your VIs run in the correct sequence. Use the error in/error out cluster to propagate the errors. If an error occurs, you can tell where the error happens. You can use the LabVIEW error handler VIs in the Utility option of the Functions menu to obtain pop-up error messages. Refer to the LabVIEW Utility VI Reference Manual for more information about these VIs.

• Many analysis routines on the DSP board can be performed in place; that is, the input and output array can be the same array. This is very important to remember when you are processing large amounts of data. Large 32-bit floating-point arrays consume a lot of memory. If the results you want do not require that you keep the original array or an intermediate array of data, perform analysis operations in place whenever possible. For example, use the same DSP Handle Cluster for the input and output data buffers in your diagram in LabVIEW. This will save your DSP board memory.

• Several intermediate-level data acquisition VIs work with DSP Handle Clusters. These VIs can acquire data and leave it on the board. You can use the NI-DSP Analysis VIs to operate on this data and then copy the processed results back to the PC. In this way, you dramatically reduce the data transfer overhead between the PC and the DSP board, and improve the overall performance. For more information about these data acquisition VIs, refer to the LabVIEW Data Acquisition VI Reference Manual. An example that shows you how to use a DSP Handle Cluster to acquire data and process this data on the DSP board can be found in the DSP2200 subdirectory of the EXAMPLES subdirectory of your LabVIEW directory.

NI-DSP SRM for LabVIEW for Windows 1-7 Part 2: Introduction to the NI-DSP Analysis VIs

Introduction to the NI-DSP Analysis VIs Part 2

An Example of Using NI-DSP Analysis VIs

Figures 1-10 and 1-11 show the front panel and block diagram, respectively, of an example using NI-DSP Analysis VIs.

Figure 1-10. Front Panel–An Example of Using NI-DSP Analysis VIs

Figure 1-11. Block Diagram–An Example of Using NI-DSP Analysis VIs

Part 2: Introduction to the NI-DSP Analysis VIs 1-8 NI-DSP SRM for LabVIEW for Windows

Part 2 Introduction to the NI-DSP Analysis VIs

This example shows you how to obtain the power spectrum of a sine wave signal. First, generate a sine wave that you want to analyze using the LabVIEW Analysis VIs, then use the Copy Mem(LV to DSP) VI to copy the data of this sine signal to the DSP board. Before you copy the data, you must call the DSP Allocate Memory VI to allocate a DSP Handle Cluster that reserves a data buffer on the DSP board. Connect this DSP Handle Cluster to the destination in terminal of the Copy Mem(LV to DSP) VI to indicate where the data will be stored on the DSP board. After the data is copied to the DSP board, call the DSP Power Spectrum VI to perform a power spectrum on the data. After you finish the analysis, the results are stored in the data buffer indicated by the DSP Handle Cluster you previously allocated. If you want to see the results, call the Copy Mem(DSP to LV) VI to copy data back to LabVIEW. Figure 1-10 shows the power spectrum of a sine wave. The last step is to call the DSP Free Memory VI to free the DSP Handle Cluster that you allocated. This example connects all of the error out clusters of the previous VIs to the error in clusters of the subsequent VIs to establish the proper sequence and to pass through an error, should it occur, without executing the rest of the VIs.

NI-DSP SRM for LabVIEW for Windows 1-9 Part 2: Introduction to the NI-DSP Analysis VIs

Chapter 1 NI-DSP Analysis VI Reference Overview

This chapter contains an overview of the NI-DSP Analysis VIs and includes a list of the VIs. This chapter describes how the NI-DSP Analysis VIs are organized and how to access them.

The NI-DSP Analysis VI Overview

The NI-DSP Analysis VIs are a set of high-performance VIs that efficiently process large blocks of numerical data and perform numerically intensive computations. The NI-DSP Analysis VIs include numerical analysis, signal generation, digital signal processing, digital filtering, and windowing operations that are suitable for simulation, modeling, and sophisticated data processing.

The NI-DSP Analysis VIs are presented in alphabetical order in Chapter 2, NI-DSP Analysis VI Reference. Table 1-1 lists these VIs by group.

Table 1-1. The NI-DSP Analysis VI Groups

Signal Generation

DSP Sine Pattern DSP Pulse Pattern DSP Impulse Pattern DSP Impulse Train Pattern DSP Ramp Pattern DSP Sinc Pattern DSP Square Pattern DSP Triangle Pattern DSP Triangular Train DSP Sawtooth Pattern DSP Uniform White Noise DSP Random Pattern DSP Gaussian White Noise

Frequency Domain

DSP ReFFT DSP Complex FFT DSP Inverse FFT DSP Power Spectrum DSP Cross Power DSP FHT DSP Inverse FHT DSP Zero Padder

Time Domain

DSP Convolution DSP Deconvolution DSP Correlation DSP Decimate DSP Derivative DSP Integral

(continues)

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NI-DSP Analysis VI Reference Overview Chapter 1

Table 1-1. The NI-DSP Analysis VI Groups (Continued)

Filters

DSP Butterworth Coefficients DSP Chebyshev Coefficients DSP Inverse Chebyshev Coeff DSP Elliptic Coefficients DSP IIR Filter DSP Equi-Ripple LowPass DSP Equi-Ripple HighPass DSP Equi-Ripple BandPass DSP Equi-Ripple BandStop DSP Parks-McClellan DSP Median Filter

Windows

DSP Blackman Window DSP Exact Blackman Window DSP Blackman Harris Window DSP Hanning Window DSP Hamming Window DSP Flat Top Window DSP General Cosine Window DSP Exponential Window DSP Force Window DSP Kaiser-Bessel Window DSP Triangular Window

Array Functions

DSP Add DSP Subtract DSP Multiply DSP Divide DSP Absolute DSP Square Root DSP Product DSP Sum DSP Log DSP Clip DSP Reverse DSP Shift DSP Sort DSP Linear Evaluation DSP Max & Min DSP Polynomial Evaluation DSP Subset DSP Set DSP Unwrap DSP Polar to Rectangular DSP Rectangular to Polar

Memory Management

DSP Allocate Memory Copy Mem(LV to DSP) Copy Mem(DSP to LV) Copy Mem(DSP to DSP) DSP Free Memory DSP Index Memory DSP Init Memory

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Chapter 1 NI-DSP Analysis VI Reference Overview

Table 1-1. The NI-DSP Analysis VI Groups (Continued)

Utility Functions

DSP Reset DSP Load DSP Start DSP Timeout DSP Custom DSP DMA Copy(DSP to LV) DSP DMA Copy(LV to DSP) DSP Handle to Address

Analysis VI Organization

After installation, the NI-DSP Analysis VIs reside in the following VI library files (LabVIEW .LLB files) within the DSP2200 option:

• Signal Generation contains VIs that generate digital patterns.

• Frequency Domain contains VIs that perform frequency domain transformations, frequency domain analysis, and other transforms such as the Hartley transform.

• Time Domain contains VIs that perform direct time series analysis of signals.

• Filters contains VIs that perform IIR and FIR filtering functions.

• Windows contains VIs that perform smoothing windowing.

• Array contains VIs that perform arithmetic operations on arrays.

• Memory Management contains VIs to perform allocating, indexing, copying, and freeing memory on the AT-DSP2200 board.

• Utility contains VIs for controlling the operation of the AT-DSP2200 board.

After installation, the eight analysis VI libraries appear in the Functions menu in the order shown in the preceding list under the DSP2200 option. You can reorganize the folders and the VIs to suit your needs and applications.

Accessing the NI-DSP Analysis VIs

To access the analysis VIs from the block diagram window, choose DSP2200 from the Functions menu as shown in Figure 1-1, proceed through the hierarchical menus, and select the VI you want. The icon corresponding to that VI appears in the block diagram and is ready to be wired.

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Figure 1-1. Choosing DSP2200 from the Functions Menu

About the Fast Fourier Transform (FFT)

The VIs in the Frequency Domain group are based upon the discrete implementation and optimization of the Fourier Transform integral. The Discrete Fourier Transform (DFT) of a complex sequence X containing n elements is obtained using the following formula:

n-1

Y[i] = ∑ X[k] * exp (-j2π ik / n), for i = 0, 1, …, n-1

k=0

where Y[i] is the ith element of the DFT of X and j = √-1. The DFT of X also results in a complex sequence Y of n elements. Similarly, the Inverse Discrete Fourier

Transform (IDFT) of a complex sequence Y containing n elements is obtained using the following formula:

X[i] = (1/n) ∑ Y[k] * exp (j2π ik / n), for i = 0, 1, …, n-1

where X[i] is the ith element of the IDFT of Y and j = √-1.

n-1

k=0

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Chapter 1 NI-DSP Analysis VI Reference Overview

The discrete implementation of the DFT is a numerically intense process. However, it is possible to implement a fast algorithm when the size of the sequence is a power of two. These algorithms are known as FFTs, and can be found in many introductory digital signal processing (DSP) texts.

The resulting complex FFT sequence has the conventional DSP format as described in this section. If there are n number of elements in the complex sequence and k = n/2, then the output of the FFT is organized as

follows:

Y[0] DC component Y[1] Positive first harmonic Y[2] Positive second harmonic : : Y[k-1] Positive k-1 harmonic Y[k] Nyquist frequency Y[k+1] Negative k-1 harmonic : : Y[n-2] Negative second harmonic Y[n-1] Negative first harmonic

The following conventions and restrictions apply to the VIs in the Frequency Domain folder:

• All arrays must be a power of two: n = 2m, m = 1, 2, 3, …, 24 (limited by onboard memory).

• Complex sequences are manipulated using two arrays. One array represents the real elements. The other array represents the imaginary elements.

The following notation is used to describe the FFT operations performed in the Frequency Domain class:

• Y = FFT {X}, the sequence Y is the FFT of the sequence X.

• Y = FFT-1 {X}, the sequence Y is the inverse FFT of the sequence X.

X is usually a complex array but can be treated as a real array.

About Filtering

All of the VIs in the Filters group are digital filters that can be represented by the computational algorithm that best describes the relationship between the input and output discrete time sequences. This computational algorithm is referred to as the Linear Constant Coefficient Difference Equation. This equation relates the input and output by the basic operations of addition, delay and multiplication. The following equation relates the input and output sequences x and y, respectively at the discrete time instant n:

i = N-1 i = M-1

a(0)*y(n) = ∑ (x[n-i]*b(i)) - ∑ (y[n-i]*a(i)) (a)

where :

x is the discrete time input signal to the system represented by the filter y is the discrete time output signal of the system represented by the filter a is the set of coefficients applied to the input in the linear difference equation and represent the

multiplication factors for delays. The equation suggests that there are N such coefficients.

b is the set of coefficients applied to the output in the linear difference equation and represent the

multiplication factors for delays. The equation suggests that there are M such coefficients.

i = 0 i = 1

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The set of coefficients a and b are often referred to as the numerator and denominator coefficients, respectively. Another common way to refer to them is as the feedforward and feedback coefficients. This is due to the mathematical derivation that led to equation a. Refer to Discrete-Time Signal Processing by Oppenheim and Schafer for more information. Another frequent assumption is that a(0)=1.0. For example, let us assume M = 4, N = 4 and n = 2. Using the filtering equation produces:

a(0)*y(2) = b(0)*x(2) + b(1)*x(1) + b(2)* x(0) + b(3)* x(-1) - a(1)*y(1) - a(2)*y(0) - a(3)*y(-1) (b)

The filtering equation suggests that in order to compute the value of the output at n = 2, you not only need the coefficients that represent the filter that is producing this output sequence, but also the value of the current input and output, the values of the input and output one time unit ago, the values of the input and output two time units ago, and the values of the input and output three time units ago. You need some “history” about the previous outputs of the filter as well as the previous inputs to the filter. The amount of history (number of previous output and input samples) depends on the lengths of the arrays a and b (filter coefficients arrays).

At time n = 0, it is important to note that the filtering equation becomes:

a(0)*y(0) = b(0)*x(0) + b(1)*x(-1) + b(2)* x(-2) + b(3)* x(-3) - a(1)*y(-1) - a(2)*y(-2) - a(3)*y(-3) (c)

Thus, for the function filter to properly operate as of time n = 0, you need to supply some history about previous behavior. The filter function then updates the history as time goes on, keeping track of previous input values and corresponding outputs. This history, at time n = 0, is referred to as the initial conditions on the input and output of the filter.

Digital filters fall into two classes–Infinite Impulse Response filters (IIR filters) and Finite Impulse Response filters (FIR filters). Notice that IIR filters are represented by equation (a) while the FIR filters can be represented by the same equation provided all a's are zero except for a(0) as shown in the following equation:

i = N

a(0)*y(n) = ∑ (x[n-i]*b(i)) (d)

The NI-DSP Analysis VIs have a set of VIs that implement IIR and FIR filters. Because all digital filters are approximations of their analog design counterparts, there are several techniques for designing a digital filter.

For the IIR filter design, the NI-DSP Analysis VIs have four approaches representing four different techniques of obtaining digital filter specifications (coefficients to equation (a))–Butterworth, Chebyshev, inverse Chebyshev, and elliptic techniques. With each design technique, you can obtain the coefficients for lowpass, highpass, bandpass, and bandstop filters from the respective NI-DSP Analysis VIs.

For the FIR filters, the NI-DSP Analysis VIs allow the design of a multiband FIR linear phase filter using the ParksMcClellan algorithm. The frequency response in each band has equal ripples that can be adjusted by a weighting factor. For more information, please refer to Digital Filter Design by Parks and Burrus, or "A Computer Program for Designing Optimum FIR Linear Phase Digital Filters," by McClellan, Parks, and Rabiner.

The IIR VIs generate filter coefficients that represent the a's and b's in the equations a and b. No filtering is actually performed. The IIR filter design coefficients all have a(0) = 1.0. You can use the general-purpose VI that accepts filter coefficients, initial conditions on the input and output sequences, and an input sequence to filter any of the filter specifications. This VI filters the input sequence and provides the final conditions on the output and input of the filter.

i = 0

About Windowing

Almost every application requires you to use finite length signals. This requires that continuous signals be truncated, using a process called windowing.

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Chapter 1 NI-DSP Analysis VI Reference Overview

The simplest window is a rectangular window. Because this window requires no special effort it is commonly referred to as the no window option. Remember, however, that a discrete signal and its spectrum is always affected by a window. Let x[n] be a digitized time-domain waveform that has a finite length of n. w[n] is a window sequence of n points. The windowed output is calculated as follows:

y[i] = x[i] * w[i] (1)

If X, Y, and W are the spectra of x, y, and w, respectively, the time-domain multiplication in formula 1 is equivalent to the convolution shown as follows:

Y[k] = X[k] Θ W[k]. (2)

Convolving with the window spectrum always distorts the original signal spectrum in some way. A window spectrum consists of a big mainlobe and several sidelobes.

The mainlobe is the primary cause of lost frequency resolution. When two signal spectrum lines are too close to each other, they may fall in the width of the mainlobe, causing the output of the windowed signal spectrum to have only one spectrum line. Use a window with a narrower mainlobe to reduce the loss of frequency resolution. It has been shown that a rectangular window has the narrowest mainlobe, so that it provides the best frequency resolution.

The sidelobes of a window function affect frequency leakage. A signal spectrum line will leak into the adjacent spectrum if the sidelobes are large. Once again, the leakage results from the convolution process. Select a window with relatively smaller sidelobes to reduce spectral leakage. Unfortunately, a narrower mainlobe and smaller sidelobes are mutually exclusive. For this reason, selecting a window function is application dependent. An example of a windowed spectrum in the continuous case is shown in Figure 1-2.

Signal Spectru

Windowed Si

Figure 1-2. Spectral Leakage Demonstrated Using Convolution

The original signal spectrum is convolved with the window spectrum and the output is a smeared version of the original signal spectrum. In this example, you can still see four distinctive peaks from the original signal, but each peak is smeared and the frequency leakage effect is clear.

nal Spectrum

Window Spectrum

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Window definitions used in National Instruments analysis libraries are designed in such a way that the window operations in the time domain are exactly equivalent to the operations of the same window in the frequency domain. To meet this requirement, the windows are not symmetrical in the time domain, that is:

w[0] ≠ w[N-1] (3)

where N is the window length. They are usually symmetrical in the frequency domain, however. For example, the Hamming window definition uses the formula:

w[i] = 0.54 - 0.46 cos(2πi/N) (4)

Other manufacturers may use a slightly different definition, such as:

w[i] = 0.54 - 0.46 cos(2πi/N-1) (5)

The difference is small if N is large. Formula 4 is not symmetrical in the time domain, but it ensures that the time domain windowing is equivalent to the

frequency domain windowing. If you want to have a perfectly symmetrical sequence in the time domain, you must write your own windowing function using formula 5.

The choice of a window depends on the application. For most applications, the Hamming or Hanning windows deliver good performance.

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Chapter 2 NI-DSP Analysis VI Reference

This chapter contains a brief explanation of each NI-DSP Analysis VI . The VIs are arranged alphabetically.

Copy Mem(DSP to DSP)

Copies a buffer of data from the Source buffer on the DSP board that is referred to by a DSP Handle Cluster to the destination buffer on the DSP board, which is referred to by another DSP Handle Cluster. Source and destination buffers should be on the same DSP board.

To copy data correctly from one DSP buffer to another DSP buffer, you must set the data type to the appropriate type to indicate what kind of data is on the DSP board. The VI has three data types–32-bit floating-point data, 16-bit short integer data, and 32-bit long integer data.

Source is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the data that you want to copy to the destination.

data type indicates the type of data that Source contains. The VI has three data types:

0: 32-bit floating-point data. 1: 16-bit short integer data. 2: 32-bit long integer data.

data type defaults to 32-bit floating-point data.

Destination in is a DSP Handle Cluster that indicates the destination memory buffer on the DSP board

that will contain the data copied from source buffer.

Destination out is a DSP Handle Cluster that is identical to the Destination in, but with the source buffer data already copied to the memory buffer on the DSP board.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

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Copy Mem(DSP to LV)

Copies an entire or partial buffer of data according to the entire/partial copy selector from the Source buffer on the DSP board that is referred to by a DSP Handle Cluster to the destination buffer in LabVIEW.

To copy data correctly from the DSP board to LabVIEW, you must indicate what type of data is stored in the Source buffer on the DSP board. You must set the destination type to the appropriate type and wire to the corresponding destination terminal. The VI has three destination types–float (32-bit), short (16-bit), and long (32-bit). To copy different types of data, you must wire to the appropriate destination terminal that corresponds to the destination type you choose. Remember, you must wire only one kind of destination terminal.

If you set the entire/partial copy selector to entire copy, all the data in the Source buffer will be copied back to the

destination without considering the values of offset and size. Otherwise, only the number of size the data in the Source buffer, starting from the offset, will be copied back to the destination.

entire/partial copy selector has two types: entire copy and partial copy. It defaults to entire copy.

0: entire copy. 1: partial copy.

Source is a DSP Handle Cluster that indicates the memory buffer on the DSP board which contains the data that you want copy to the destination in LabVIEW.

destination type indicates the type of the destination data on the DSP board. It has three options:

0: 32-bit floating-point. 1: 16-bit short integer. 2: 32-bit long integer.

destination type defaults to 32-bit floating point.

offset indicates where to start to copy data from the Source buffer on the DSP board to the destination buffer in the LabVIEW. offset defaults to 0. This parameter is ignored when entire/partial copy selector is set to entire copy.

size indicates how much data to copy from the Source buffer on the DSP board to the destination buffer

in LabVIEW. size defaults to 0. If offset plus size is greater than the number of elements in the Source buffer, the VI returns an error. This parameter is ignored when entire/partial copy selector is set to entire copy.

destination(float) is the terminal to which you should wire the destination buffer if the data you want to copy is 32-bit floating-point data array.

destination(long) is the terminal to which you should wire the destination buffer if the data you want to copy is 32-bit long data array.

destination(short) is the terminal to which you should wire the destination buffer if the data you want to copy is 16-bit short data array.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

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Copy Mem(LV to DSP)

Copies a buffer of data from the source buffer in LabVIEW to the destination buffer on the DSP board, which is referred to by a DSP Handle Cluster.

The source buffer can contain one of three kinds of data–float (32-bit), short (16-bit), and long (32-bit). To copy different types of data, you must wire to the appropriate source terminal. You must

wire only one kind of source terminal. The destination buffer must be large enough to contain all of the data from the source buffer.

source(float) is the terminal to which you should wire the source buffer if the data you want to copy is 32-bit floating point data array.

source(long) is the terminal to which you should wire the source buffer if the data you want to copy is 32-bit long data array.

source(short) is the terminal to which you should wire the source buffer if the data you want to copy is 16-bit short data array.

Destination in is a DSP Handle Cluster that indicates the destination memory buffer on the DSP board that will contain the data copied from the LabVIEW source buffer.

Destination out is a DSP Handle Cluster that is identical to Destination in, but with the source buffer data already copied to the memory buffer on the DSP board.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

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DSP Absolute

Find the absolute value of input array X. The i element of the output array Y is obtained using the following formula:

Y(i) = |X(i) |. for i = 0, 1, 2, … , n-1

where n is the number of elements in X.

X is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input signal array X.

Y in is a DSP Handle Cluster that indicates the memory buffer on the DSP board that will contain the absolute results of X(i).

Y out is a DSP Handle Cluster that is identical to Y in, but with the absolute results already stored in the memory buffer on the DSP board.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

The operation can be performed in place; that is, the input and output arrays can be the same DSP Handle Cluster.

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DSP Add

Add array X to array Y. The ith element of the output array Z is obtained using the following formula:

Z(i) = X(i) + Y(i). for i = 0, 1, 2, … , n-1

where n is the smaller number of elements in X and Y.

X is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input signal array X.

Y is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input signal array Y.

Z in is a DSP Handle Cluster that indicates the memory buffer on the DSP board that will contain the results of X(i) + Y(i).

Z out is a DSP Handle Cluster that is identical to Z in, but with the added results already stored in the memory buffer on the DSP board.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

The operation can be performed in place; that is, the input and output arrays can be the same DSP Handle Cluster.

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DSP Allocate Memory

Allocates a block of memory buffer on the DSP board specified by slot and returns a DSP Handle Cluster that contains the coded DSP board memory and the number of elements in this buffer.

The number of bytes allocated for this buffer depends on size and

bytes/element selector. If bytes/element selector selects 4 bytes, then the number of bytes = size*4. If bytes/element selector selects 2 bytes, then the number of bytes = size*2.

The allocation routines on the board assure alignment to the nearest 4-byte boundary ≥ number of bytes to guarantee memory alignment on 4-byte addresses. For example, if you request to allocate a buffer of size 1,022 or 1,024 bytes, the allocation routines allocate 1,024 bytes in both cases.

slot is the board ID number. slot defaults to 3.

size is the number of elements to allocate for this buffer. size defaults to 0.

bytes/element selector specifies the number of bytes per element. It has two options:

0: 4 bytes. 1: 2 bytes.

bytes/element selector defaults to 4 bytes.

DSP Handle Cluster indicates the allocated memory buffer on the DSP board.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

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DSP Blackman Window

Applies a Blackman window to the input sequence X. If Y represents the output sequence Blackman{X}, the elements of Y are obtained from the following formula:

yi = xi [0.42 - 0.50 cos(w) + 0.08 cos(2w)] for i = 0, 1, 2, … , n-1 ,

2πi

w =

where n is the number of elements in X.

X is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input signal array.

Note: The operation is performed in place and the input array X is overwritten by the output

Blackman {X}.

Blackman {X} is a DSP Handle Cluster that is identical to X, but with the results of Blackman {X}

already stored in the memory buffer on the DSP board.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

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DSP Blackman Harris Window

Applies a Blackman Harris window to the input sequence X. If Y represents the output sequence Blackman Harris{X}, the elements of Y are obtained using the following formula:

yi = xi [0.42323 - 0.49755 cos(w) +0.07922 cos(2w)] for i = 0, 1, 2, … , n-1

2πi

w =

where n is the number of elements in X.

X is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input signal array.

Note: The operation is performed in place and the input array X is overwritten by the output

Blackman Harris {X}.

Blackman Harris {X} is a DSP Handle Cluster that is identical to X, but with the results of Blackman Harris {X} already stored in the memory buffer on the DSP board.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

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DSP Butterworth Coefficients

Generates the set of filter coefficients to implement an IIR filter as specified by the Butterworth filter model. You can then pass these coefficients to the DSP IIR Filter VI to filter a sequence of data.

filter type specifies the passband of the filter. It has four options:

0: lowpass. 1: highpass. 2: bandpass. 3: bandstop.

filter type defaults to lowpass.

sampling freq : fs is the sampling frequency and must be greater than 0. If it is less than or equal to zero, the VI returns an error. sampling freq : fs defaults to 1.0.

high cutoff freq: fh is the high cutoff frequency. The VI ignores this parameter when filter type is lowpass. high cutoff freq: fh defaults to 0.45.

low cutoff freq: fl is the low cutoff frequency. The VI ignores this parameter when filter type is highpass. low cutoff freq: fl defaults to 0.125.

Note:fh and fl must observe the Nyquist criterion: 0 ≤ fl ≤ fh ≤ fs /2.

Forward Coefficients in is a DSP Handle Cluster that indicates the memory buffer on the DSP board

that will contain the forward coefficients.

Feedback Coefficients in is a DSP Handle Cluster that indicates the memory buffer on the DSP board that will contain the feedback coefficients.

Forward Coefficients out is a DSP Handle Cluster that is identical to the Forward Coefficients in, but with the forward coefficients already stored in the memory buffer on the DSP board.

Feedback coefficients out is aDSP Handle Cluster that is identical to the Feedback Coefficients in, but with the feedback coefficients already stored in the memory buffer on the DSP board.

order must be greater than zero. If order is less than or equal to zero, the VI returns an error. order defaults to 2.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

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Parameter Discussion

The arrays Forward Coefficients in/out and Feedback Coefficients in/out must have a size of at least (order + 1) for lowpass and highpass filters. The arrays Forward Coefficients in/out and Feedback Coefficients in/out must have a size of at least (2*order + 1) for bandpass and bandstop filters.

DSP Chebyshev Coefficients

Generates the set of filter coefficients to implement an IIR filter as specified by the Chebyshev filter model. You can then pass coefficients to the DSP IIR Filter VI to filter a sequence of data.

filter type specifies the passband of the filter. It has four options:

0: lowpass. 1: highpass. 2: bandpass. 3: bandstop.

filter type defaults to lowpass.

sampling freq : fs is the sampling frequency and must be greater than 0. If it is less than or equal to zero, the VI returns an error. sampling Freq : fs defaults to 1.0.

high cutoff freq: fh is the high cutoff frequency. The VI ignores this parameter when filter type is lowpass. high cutoff freq: fh defaults to 0.45.

low cutoff freq: fl is the low cutoff frequency. The VI ignores this parameter when filter type is highpass. low cutoff freq: fl defaults to 0.125.

Note: fh and fl must observe the Nyquist criterion: 0 ≤ fl ≤ fh ≤ fs /2.

ripple must be greater than 0. If ripple is less than or equal to zero, the VI returns an error. ripple

defaults to 0.1.

order must be greater than zero. If order is less than or equal to zero, the VI returns an error. order defaults to 2.

Forward Coefficients in is a DSP Handle Cluster that indicates the memory buffer on the DSP board that will contain the forward coefficients.

Feedback Coefficients in is a DSP Handle Cluster that indicates the memory buffer on the DSP board that will contain the feedback coefficients.

Forward Coefficients out is a DSP Handle Cluster that is identical to the Forward Coefficients in, but with the forward coefficients already stored in the memory buffer on the DSP board.

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Feedback Coefficients out is a DSP Handle Cluster that is identical to the Feedback Coefficients in, but with the feedback coefficients already stored in the memory buffer on the DSP board.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

Parameter Discussion

The arrays Forward Coefficients in/out and Feedback Coefficients in/out have to have a size of at least (order +

1) for lowpass and highpass filters.The arrays Forward Coefficients in/out and Feedback Coefficients in/out have

to have a size of at least (2*order + 1) for bandpass and bandstop filters.

DSP Clip

Clips the input array values. The range of the resulting output array is [lower:upper]. Let Y represent the output array. The i element of the resulting array is obtained by using the following formulas:

upper if X(i) > upper





lower if X(i) < lower



Y(i) =

for i = 0, 1, 2, …, size-1 ,

where n is the number of elements in X. The operation can be performed in place; that is, the input and output arrays can be the same DSP Handle Cluster.



X(i) otherwise



X is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input signal array X.

upper limit. upper limit ≥ lower limit. upper limit defaults to 1.0.

lower limit. lower limit defaults to 0.0.

Clipped{X} in is a DSP Handle Cluster that indicates the memory buffer on the DSP board that will contain the output array of Clipped{X}.

Clipped{X} out is a DSP Handle Cluster that is identical to Clipped {X} in, but with the Clipped{X}

already stored in the memory buffer on the DSP board.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

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DSP Complex FFT

Computes the Fast Fourier transform of the complex input sequence X. If Y represents the complex output sequence, then:

Y = F{X}.

Re{X} is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the real part of the input signal array X.

Im{X} is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the imaginary part of input signal array X.

Notes: The number of elements for the input array must be a power of 2.

If the size of Re{X} is different from the size of Im{X}, the VI uses the smaller number as the size of the Complex FFT.

The operation is performed in place and the input array Re{X} and Im{X} is overwritten by the Re FFT{X} and Im FFT{X}.

The largest complex FFT that can be computed depends upon the amount of memory on your board.

Re FFT{X} is a DSP Handle Cluster that is identical to Re{X}, but with the real part of FFT{X}already stored in the memory buffer on the DSP board.

Im FFT{X} is a DSP Handle Cluster that is identical to Im{X}, but with the imaginary part of FFT{X}already stored in the memory buffer on the DSP board.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

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DSP Convolution

Computes the convolution of the input sequences X and Y. The convolution Cxy(t), of the signals x(t) and y(t), is defined as follows:

∞

Cxy(t) = x(t)

where the symbol * denotes convolution.

For the discrete implementation of the convolution, let Cxy represent the output sequence X * Y, n be the number of elements in the input sequence X, and m be the number of elements in the input sequence Y. Assuming that indexed elements of X and Y that lie outside their range are zero,

xi = 0, i < 0 or i ≥ n

and

= 0, j < 0 or j ≥ m,

then you obtain the elements of Cxy using:

n-1

Cxyi =

k = 0

∑

xk y

y(t) = ∫

i-k

x(τ) y(t-τ) dτ ,

-∞

for i = 0, 1, 2, …, size-1 ,

size = n + m - 1,

where size is the total number of elements in the output sequence X * Y.

X is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input signal array X.

Y is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input signal array Y.

Cxy in is a DSP Handle Cluster that indicates the memory buffer on the DSP board that will contain the convolution of X with Y.

Note: The size of Cxy in must be (n+m-1) elements long. n is the size of X, m is the size of Y. You

cannot perform the operation in place.

Cxy out is a DSP Handle Cluster that is identical to the Cxy in but with the convolution of X and Y already stored in the memory buffer on the DSP board.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

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DSP Correlation

Computes the cross correlation of the input sequences X and Y. The cross correlation Rxy(t) of the signals x(t) and y(t) is defined as follows:

∞

Rxy(t) = x(t) ⊗ y(t) =

where the symbol ⊗ denotes correlation.

x(t) y(t+t) dt ,

∫

-∞

For the discrete implementation of the correlation, let R elements in the input sequence X, and m be the number of elements in the input sequence Y. You then obtain the elements of R

xy i

using the following formula:

n-1

x[k] y[k+m-1] for i = 0, 1, 2, …, m+n-1 ,

∑

k=0

X is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input signal array X.

Y is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input signal array Y.

Rxy in is a DSP Handle Cluster that indicates the memory buffer on the DSP board that will contain the correlation results.

Note: The size of Rxy in must be at least (n+m-1) elements long. n is the size of X, m is the size

of Y.

Rxy out is a DSP Handle Cluster that is identical to the Rxy in, but with the correlation of X and Y already stored in the memory buffer on the DSP board.

Note: If X and Y are the same array, an auto correlation is performed, otherwise, a cross correlation is

performed. You cannot perform the operation in place.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

represent the output sequence X ⊗ Y, n be the number of

error out contains the error information for this call.

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DSP Cross Power

Computes the cross power spectrum of the input sequences X and Y. The cross power, Sxy(f), of the signals x(t) and y(t) is defined as follows:

Sxy(f) = X*(f)Y(f)

where X*(f) is the complex conjugate of X(f),

X(f) = F{x(t)}, and Y(f) = F{y(t)}.

This VI uses the FFT routine to compute the cross power spectrum, that is given by the following formula:

n = 2

where Sxy represents the complex output sequence Sxy, and

F*{X} F{Y} ,

n is the number of samples that can accommodate both input sequences X and Y.

X is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input signal array X.

Y is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input signal array Y.

Notes: If the size of X is different than Y, the VI uses the smaller number as the size of input arrays X

Re{Sxy} is a DSP Handle Cluster that is identical to X, but with the real part of Sxy already stored in the

memory buffer on the DSP board.

for k = 1, 2, 3, …, 23,

and Y. The number of elements for the input arrays must be a power of two. The operation is performed in place and the input arrays X and Y are overwritten by the

outputs Re{Sxy} and Im{Sxy}. The largest Cross Power Spectrum that can be computed depends upon the amount of memory

in your DSP board. This VI allocates a temporary workspace on the DSP board equal to the size of the input signal

array.

Im{Sxy} is a DSP Handle Cluster that is identical to Y, but with the imaginary part of Sxy already stored in the memory buffer on the DSP board.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

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DSP Custom

Use this VI as the interface to call your own custom functions written on the DSP board from LabVIEW. For more details about how to use this VI, refer to Part 4, NI-DSP Interface Utilities, of this manual.

slot is the board ID number. slot defaults to 3.

function code indicates which function on the DSP board LabVIEW is calling. function code defaults

to 0.

Array of Handles in is an array of DSP Handle Clusters that hold all of the references to the input and output data buffers used in your custom functions on the DSP board.

Array of SGL Scalars in is an array of 32-bit floating-point scalars that hold all of the input 32-bit floating-point scalars used in your custom functions on the DSP board.

Array of I32 Scalars in is an array of 32-bit long integer scalars that hold all of the input 32-bit long integer scalars used in your custom functions on the DSP board.

Array of Handles out is an array of DSP Handle Clusters that is identical to Array of Handles in, but with the output results already stored in the memory buffers on the DSP board.

Array of SGL Scalars out is an array of 32-bit floating-point scalars that is identical to Array of SGL Scalars in, but with the output results already stored in the array.

Array of I32 Scalars out is an array of 32-bit long integer scalars that is identical to Array of I32 Scalars in, but with the output results already stored in the array.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

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DSP Decimate

Decimates the input sequence X by the decimating factor and the averaging control. If Y represents the output sequence Decimated Array, the elements of the sequence Y are

obtained using:





m−1

 



for i = 0, 1, 2, …, size -1

∑

k=0

i(m+ k)

if ave = no averaging if ave = averaging

size = trunc

where n is the number of elements in X,

m is the decimating factor, ave is the averaging option, and size is the number of elements in the output sequence Y.

()

X is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input signal array.

Y in is a DSP Handle Cluster that indicates the memory buffer on the DSP board that will contain the decimated output array.

Y out is a DSP Handle Cluster that is identical to Y in, but with the results of the decimated array already stored in the memory buffer on the DSP board.

decimating factor must be greater than zero:

0 < decimating factor ≤ n.

If decimating factor is greater than the number of samples in X or less than or equal to zero, the VI returns an error. decimating factor defaults to 1.

averaging has two options:

0: averaging. 1: no averaging.

averaging defaults to no averaging.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

The operation can be performed in place; that is, the input X and the output Y can be the same DSP Handle Cluster.

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DSP Deconvolution

Computes the deconvolution of the input sequences X and Y. The convolution operation can be realized using Fourier identities because

x(t)

y(t) ⇔ X(f) Y(f)

is a Fourier transform pair, where the symbol denotes convolution, and the deconvolution is

the inverse of the convolution operation. If h(t) is the signal resulting from the deconvolution of the signals x(t) and y(t), the VI obtains h(t) using the equation

X(f)

h(t) = F

where X(f) is the Fourier transform of x(t), and

The VI performs the discrete implementation of the deconvolution using the following steps.

1. Compute the Fourier transform of the input sequence X * Y.

2. Compute the Fourier transform of the input sequence Y.

3. Divide the Fourier transform of X * Y by the Fourier transform of Y. Call the new sequence H.

4. Compute the inverse Fourier transform of H to obtain the deconvoluted sequence X.

-1

{}

Y(f) is the Fourier transform of y(t).

Cxy is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input signal array Cxy. The number of elements in Cxy must be greater than or equal to the number of elements in Y.

Y is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input signal array Y.

Y(f)

X in is a DSP Handle Cluster that indicates the memory buffer on the DSP board that will contain the deconvolution results.

Note: The size of X in must be n elements long, although only (n-m+1) elements are valid. n is the

size of Cxy, m is the size of Y.

X out is a DSP Handle Cluster that is identical to X in, but with the deconvolution results already stored in the memory buffer on the DSP board.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

Note: The deconvolution operation is a numerically unstable operation, and it is not always possible to solve the

system numerically. Computing the deconvolution via FFTs is perhaps the most stable generic algorithm that does not require sophisticated DSP techniques. However, it is not free of errors (for example, when there are zeros in the Fourier transform of the input sequence Y).

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DSP Derivative

Performs a discrete differentiation of the sampled signal X. The differentiation f(t) of a function F(t) is defined as follows:

f(t) =

Let Y represent the sampled output sequence d/dt X. The discrete implementation is given by the following formula:

yi =

where n is the number of samples in x(t)

initial condition and final condition minimize the error at the boundaries.

F(t).

- x

) for i = 0, 1, 2, …, n-1.

i+1

2dt

i-1

x-1 is specified by initial condition when i = 0, and xn is specified by final condition when i = n-1.

X is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input signal array.

initial condition defaults to 0.0.

final condition defaults to 0.0.

dt is the sampling interval and must be greater than zero. If dt is less than or equal to zero, the VI returns an error. dt defaults to 1.0.

Y in is a DSP Handle Cluster that indicates the memory buffer on the DSP board that will contain the

results of the differentiation of X. Y out is a DSP Handle Cluster that is identical to Y in, but with the results of differentiation already

stored in the memory buffer on the DSP board.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

The operation can be performed in place; that is, the input X and the output Y can be the same DSP Handle Cluster.

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DSP Divide

Divide array X by array Y. The ith element of the output array Z is obtained using the following formula:

Z(i) = X(i) / Y(i). for i = 0, 1, 2, …, n-1.

where n is the smaller number of elements in

X and Y.

X is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input

signal array X.

Y is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input signal array Y.

Z in is a DSP Handle Cluster that indicates the memory buffer on the DSP board that will contain the results of X(i) / Y(i).

Z out is a DSP Handle Cluster that is identical to Z in, but with the divided results already stored in the memory buffer on the DSP board.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

The operation can be performed in place; that is, the input and the output arrays can be the same DSP Handle Cluster.

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DSP Elliptic Coefficients

Generates the set of filter coefficients to implement a digital elliptic IIR filter. You can then pass these coefficients to the DSP IIR Filter VI.

filter type specifies the passband of the filter. filter type has four options:

0: lowpass. 1: highpass. 2: bandpass. 3: bandstop.

filter type defaults to lowpass.

sampling freq : fs is the sampling frequency and must be greater than 0. If it is less than or equal to zero, the VI returns an error. sampling freq : fs defaults to 1.0.

high cutoff freq: fh is the high cutoff frequency. The VI ignores this parameter when filter type is lowpass. high cutoff freq: fh defaults to 0.45.

low cutoff freq: fl is the low cutoff frequency. The VI ignores this parameter when filter type is highpass. high cutoff freq: fh defaults to 0.125.

Note: fh and fl must observe the Nyquist criterion: 0 ≤ fl ≤ fh ≤ fs /2.

passband ripple must be greater than 0, and you must express it in decibels. If passband ripple is less than or equal to zero, the VI returns an error. passband ripple defaults to 1.0.

order must be greater than zero. If order is less than or equal to zero, the VI returns an error. order

defaults to 2.

stopband attenuation must be greater than 0, and you must express it in decibels. If stopband attenuation is less than or equal to zero, the VI returns an error. stopband attenuation defaults to 60.0.

Forward Coefficients in is a DSP Handle Cluster that indicates the memory buffer on the DSP board

that will contain the forward coefficients.

Feedback Coefficients in is a DSP Handle Cluster that indicates the memory buffer on the DSP board that will contain the feedback coefficients.

Forward Coefficients out is a DSP Handle Cluster that is identical to Forward Coefficients in, but with the forward coefficients already stored in the memory buffer on the DSP board.

Feedback Coefficients out is a DSP Handle Cluster that is identical to Feedback Coefficients in, but with the feedback coefficients already stored in the memory buffer on the DSP board.

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error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

Parameter Discussion

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DSP Equi-Ripple BandPass

Generates a bandpass FIR filter with equi-ripple characteristics using the Parks-McClellan algorithm and the number of taps, lower stop frequency, higher stop frequency, lower pass frequency, higher pass frequency, and sampling frequency. The VI then filters the input sequence X to obtain the bandpass filtered linearphase sequence Filtered Data.

The first stopband of the filter region goes from zero (DC) to the lower stop frequency. The passband region goes from the lower pass frequency to the higher pass frequency, and the second stopband region goes from the higher stop frequency to the Nyquist frequency.

higher pass freq must be greater than lower pass freq frequency. If higher pass freq is less than or equal to lower pass freq, the VI returns an error. higher pass freq defaults to 0.3.

lower pass freq must be greater than the lower stop freq. If lower pass freq is less than or equal to lower stop freq, the VI returns an error. lower pass freq defaults to 0.2.

X is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input

data array.

# of taps must be greater than 0. If the number of taps is less than or equal to zero, the VI returns an error. # of taps defaults to 32.

lower stop freq must be greater than zero. If lower stop freq is less than or equal to zero, the VI returns an error. lower stop freq defaults to 0.1.

higher stop freq must be greater than higher pass freq and must observe the Nyquist criterion:

0 < f0 < f1 < f2 < f3 ≤ 0.5fs ,

where f0 is lower stop freq, f1 is lower pass freq, f2 is higher pass freq, f3 is the higher stop freq, and fs is the sampling frequency. If any of these conditions is violated, the VI returns an error. higher stop

freq defaults to 0.4.

sampling freq: fs defaults to 1.0.

Filtered Data in is a DSP Handle Cluster that indicates the memory buffer on the DSP board that will

contain the filtered data output.

Filtered Data out is a DSP Handle Cluster that is identical to Filtered Data in, but with the filtered data already stored in the memory buffer on the DSP board. Because the VI filters via convolution, the number of elements, k, in Filtered Data is as follows:

k = n + m - 1,

where n is the number of elements in X, and m is the number of taps.

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A delay is also associated with the output sequence

delay =

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

The operation cannot be performed in place; that is, the input X and the output Filtered Data cannot be the same DSP Handle Cluster.

m-1

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DSP Equi-Ripple BandStop

Generates a bandstop FIR digital filter with equi-ripple characteristics using the Parks-McClellan algorithm and number of taps, lower pass frequency, higher pass frequency, lower stop frequency, higher stop frequency, and sampling frequency. The VI then filters the input sequence X to obtain the bandstop filtered linear-phase sequence Filtered Data.

The first passband region of the filter goes from zero (DC) to the lower pass frequency. The stopband region goes from the lower stop frequency to the higher stop frequency, and the second passband region goes from the higher pass frequency to the Nyquist frequency.

higher pass freq must be greater than higher stop freq and observe the Nyquist criterion:

0 < f0 < f1 < f2 < f3 ≤ 0.5fs,

where f0 is the lower pass freq, f1 is the lower stop freq, f2 is the higher stop freq, f3 is the higher pass

freq, and fs is the sampling freq. If any of these conditions is violated, the VI returns an error. higher pass freq defaults to 0.4.

lower pass freq must be greater than zero. If lower pass freq is less than or equal to 0, the VI returns an error. lower pass freq defaults to 0.1.

X is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input

data array.

# of taps must be odd and must be greater than 0. If the number of taps is an even number or is less than or equal to zero, the VI returns an error. # of taps defaults to 31.

lower stop freq must be greater than lower pass freq. If lower stop freq is less than or equal to lower pass freq, the VI returns an error. lower stop freq defaults to 0.2.

higher stop freq must be greater than lower stop freq. If higher stop freq is less than or equal to lower stop freq, the VI returns an error. higher stop freq defaults to 0.3.

sampling freq: fs defaults to 1.0.

Filtered Data in is a DSP Handle Cluster that indicates the memory buffer on the DSP board that will

contain the filtered data output.

k = n + m - 1,

where n is the number of elements in X, and m is the number of taps.

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A delay is also associated with the output sequence:

delay =

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

The operation cannot be performed in place; that is, the input X and the output Filtered Data cannot be the same DSP Handle Cluster.

m-1

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DSP Equi-Ripple HighPass

Generates a highpass FIR filter with equi-ripple characteristics using the Parks-McClellan algorithm and the number of taps, high frequency, stop frequency, and sampling frequency. The VI then filters the input sequence X to obtain the highpass filtered linear-phase sequence Filtered Data.

The stopband of the filter goes from zero (DC) to the stop frequency. The transition band goes from the stop frequency to the high frequency, and the passband goes from the high frequency to the Nyquist frequency.

X is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input data array.

# of taps must be greater than 0 and must be an odd number. If the number of taps is an even number or is less than or equal to zero, the VI returns an error. # of taps defaults to 31.

stop freq must be greater than zero. If stop freq is less than or equal to 0, the VI returns an error. stop freq defaults to 0.2.

high freq must be greater than stop freq and observe the Nyquist criterion:

0 < f0 < f1 ≤ 0.5fs,

where f0 is the stop freq, f1 is the high freq, and fs is the sampling frequency. If any of these conditions is violated, the VI returns an error. high freq defaults to 0.3.

sampling freq: fs defaults to 1.0.

Filtered Data in is a DSP Handle Cluster that indicates the memory buffer on the DSP board that will

contain the filtered data output.

k = n + m - 1,

where n is the number of elements in X, and m is the number of taps. A delay is also associated with the output sequence:

delay =

m-1

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error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

The operation cannot be performed in place; that is, the input X and the output Filtered Data out cannot be the same DSP Handle Cluster.

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DSP Equi-Ripple LowPass

Generates a lowpass FIR filter with equiripple characteristics using the ParksMcClellan algorithm and the number of taps, pass frequency, stop frequency, and sampling frequency. The VI then filters the input sequence X to obtain the lowpass filtered linear-phase sequence Filtered Data.

The passband of the filter goes from zero (DC) to pass freq. The transition band goes from pass freq to stop freq, and

the stopband goes from stop freq to the Nyquist frequency.

X is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input data array.

# of Taps must be greater than 0. If the number of taps is less than or equal to zero, the VI returns an error. # of Taps defaults to 31.

pass freq must be greater than 0. If pass freq is less than or equal to zero, the VI returns an error. pass freq defaults to 0.2.

stop freq must be greater than the pass freq and observe the Nyquist criterion:

0 < f0 < f1 ≤ 0.5fs,

where f0 is the pass freq, f1 is the stop freq, and fs is the sampling frequency. If any of these conditions is violated, the VI returns an error. stop freq defaults to 0.3.

sampling freq: fs defaults to 1.0.

Filtered Data in is a DSP Handle Cluster that indicates the memory buffer on the DSP board that will

contain the filtered data output.

k = n + m - 1,

where n is the number of elements in X, and

m is the number of taps.

A delay equal to

m-1

is also associated with the output sequence.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

The operation cannot be performed in place; that is, the input X and the output Filtered Data cannot be the same DSP Handle Cluster.

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DSP Exact Blackman Window

Applies an Exact Blackman window to the input sequence X. If Y represents the output sequence Exact Blackman{X}, the elements of Y are obtained using the formula:

yi = xi [0.42659071

- 0.49656062 cos(w) + 0.07684867 cos(2w)] for i = 0, 1, 2, … , n-1

2πi

w =

where n is the number of elements in X.

X is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input signal array.

Note: The operation is performed in place and the input array X is overwritten by the output Exact

Blackman {X}.

Exact Blackman {X} is a DSP Handle Cluster that is identical to X, but with the results of Exact Blackman {X} already stored in the memory buffer on the DSP board.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

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DSP Exponential Window

Applies an exponential window to the input sequence X. If Y represents the output sequence Exponential{X}, the elements of Y are obtained using the formula:

yi = xi exp(a * i)

for i = 0, 1, 2, … , n-1,

ln |f|

a =

where f is the final value, and

You can use the Exponential Window VI to analyze transients.

n - 1

n is the number of elements in X.

X is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input signal array.

Note: The operation is performed in place and the input array X is overwritten by the output

Exponential {X}.

final value defaults to 0.10.

Exponential {X} is a DSP Handle Cluster that is identical to X, but with the results of Exponential {X}

already stored in the memory buffer on the DSP board.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

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DSP FHT

Computes the fast Hartley transform (FHT) of the input sequence X. The Hartley transform of a function x(t) is defined as follows:

∞

X(f) = ∫

where cas(x) = cos(x) + sin(x). If Y represents the output sequence FHT {X} obtained via the FHT, then Y is obtained through the discrete

implementation of the Hartley integral:

Yk =

where n is the number of elements in X.

x(t) cas(2πft) dt

-∞

n-1

Xi cas

∑

i=0

X is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input signal array.

2π ik

, for k = 0, 1, 2, … , n-1 .

()

Notes: The number of elements for the input array must be a power of two.

The operation is performed in place and the input array X is overwritten by the output FHT{X}.

The largest FHT that can be computed depends upon the amount of memory on your DSP board.

FHT{X} is a DSP Handle Cluster that is identical to X, but with the results of FHT{X} already stored in the memory buffer on the DSP board.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

The Hartley transform maps real-valued sequences into real-valued frequency domain sequences. You can use it instead of the Fourier transform to convolve signals, deconvolve signals, correlate signals, and find the power spectrum. Furthermore, you can derive the Fourier transform from the Hartley transform.

When the sequences to be processed are real-valued sequences, the Fourier transform produces complex-valued sequences in which half of the information is redundant. The advantage of using the Hartley transform instead of the Fourier transform is that the Hartley transform uses half the memory to produce the same information the FFT produces. Further, the FHT is calculated in place and is as efficient as the Fourier transform.

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DSP Flat Top Window

Applies a flat top window to the input sequence

X. If Y represents the output sequence Flattop{X}, the elements of Y are obtained

using the formula:

yi = xi [0.2810639 - 0.5208972 cos(w)

+ 0.1980399 cos(2w)]

for i = 0, 1, 2, … , n-1

2πi

w =

where n is the number of elements in X.

X is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input signal array.

Note: The operation is performed in place and the input array X is overwritten by the output

Flattop {X}.

Flattop {X} is a DSP Handle Cluster that is identical to X, but with the results of Flattop {X} already

stored in the memory buffer on the DSP board.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

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DSP Force Window

Applies a force window to the input sequence X If Y represents the output sequence Force{X}, the elements of Y are obtained using the formula:

if 0 ≤ i ≤ d





yi =





0 elsewhere



for i = 0, 1, 2, …, n-1 , d = (0.01)(n)(duty)

where n is the number of elements in X. You can use the Force Window VI to analyze transients.

X is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input signal array.

Note: The operation is performed in place and the input array X is overwritten by the output

Force {X}.

duty. 0.0 ≤ duty ≤ 100.0. duty defaults to 50.0.

Force {X} is a DSP Handle Cluster that is identical to X, but with the results of Force {X} already

stored in the memory buffer on the DSP board.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

DSP Free Memory

Frees the memory space referred by DSP Handle Cluster on the specified DSP board.

DSP Handle Cluster is a DSP Handle Cluster that indicates the memory buffer to free.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and the VI also frees the DSP Handle Cluster.

error out contains the error information for this call.

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DSP Gaussian White Noise

Generates a Gaussian distributed pseudorandom pattern whose statistical profile is as follows:

(µ, σ) = (0, s) ,

where s is the absolute value of the specified standard deviation.

standard deviation defaults to 1.0.

seed < 65536.0. If seed > 0.0, the generated noise will be the same in repeated invocations if the seed

value does not change. If seed ≤ 0.0, the VI generates a random value to use as the seed, and the noise will differ in repeated invocations although the value in seed does not change. seed defaults to 0.0.

Gaussian Pattern in is a DSP Handle Cluster that indicates the memory buffer on the DSP board that will contain the output Gaussian pattern.

Gaussian Pattern out is a DSP Handle Cluster that is identical to Gaussian Pattern in, but with the generated pattern already stored in the memory buffer on the DSP board. The largest Gaussian pattern that can be generated depends upon the amount of memory on your DSP board.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

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DSP General Cosine Window

Applies a general cosine window to the input sequence X. If A represents the Cosine Coefficients input sequence and Y represents the output sequence GenCos{X}, the elements of Y are obtained using the formula:

yi = xi

for i = 0, 1, 2, … , n-1

w =

where n is the number of elements in X, and

m-1

(-1)k ak cos (kw)

∑

k=0

2πi

m is the number of elements in Cosine Coefficients.

X is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input signal array.

Note: The operation is performed in place and the input array X is overwritten by the output

GenCos {X}.

Cosine Coefficients is a DSP Handle Cluster that indicates the memory buffer on the DSP board that

contains the cosine coefficients.

GenCos {X} is a DSP Handle Cluster that is identical to X, but with the results of GenCos {X} already stored in the memory buffer on the DSP board.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

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DSP Hamming Window

Applies a Hamming window to the input sequence X. If Y represents the output sequence Hamming {X}, the elements of Y are obtained from the formula:

yi = xi [0.54 - 0.46 cos(w)]

for i = 0, 1, 2, …, n-1 ,

2πi

w =

where n is the number of elements in the input sequence X.

X is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input data array.

Note: The operation is performed in place and the input array X is overwritten by the output

Hamming {X}.

Hamming {X} is a DSP Handle Cluster that is identical to X, but with the results of Hamming {X}

already stored in the memory buffer on the DSP board.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

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DSP Handle To Address

Finds the actual DSP address value of DSP Handle Cluster that indicates a

memory buffer on the DSP board. You can use the output DSP Address as

the input of the DSP Address terminal in the DSP DMA Copy(DSP to LV) VI or the DSP DMA Copy(LV to DSP) VI.

DSP Handle Cluster indicates a memory buffer on the DSP board.

DSP Address is the actual DSP address of the memory buffer on the DSP board referred to by DSP Handle Cluster.

error in(no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

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DSP Hanning Window

Applies a Hanning window to the input sequence X. If Y represents the output sequence Hanning {X}, the elements of Y are obtained using the formula:

yi = 0.5 xi [1 - cos(w)]

for i = 0, 1, 2, …, n-1 ,

2πi

w =

where n is the number of elements in the input sequence X.

X is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input data array.

Note: The operation is performed in place and the input array X is overwritten by the output

Hanning {X}.

Hanning {X} is a DSP Handle Cluster that is identical to X, but with the results of Hanning {X} already

stored in the memory buffer on the DSP board.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

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DSP IIR Filter

Performs IIR filtering on the X input array and reports the result in Y. It uses the arrays a and b of sizes sza and szb respectively in implementing the linear difference equation that describes IIR filtering:

k = sza - 1 k = szb-1

y[i] = ∑ a(k) * x(i-k) - ∑ b(k) * y(i-k) i = 0,1 ..... ,n-1

k = 0 k = 1

where:

a is the array of forward coefficients describing an IIR filter (obtained from DSP Butterworth Coefficients VI for example)

b is the array of feedback coefficients describing an IIR filter (obtained from the same filter design VI)

Notes: b(0) = 1.0 in the above equation.

This VI may be called in a loop to perform filtering on data frames that are part of the same data stream. At time i = 0, the initial conditions on X (for example, X(1-sza) through X(-1)) are obtained from the array

Initial Conditions on input. At exit (the end of the VI execution), this array holds the final conditions on X that could be used as the initial conditions for the next DSP IIR Filter VI call if you were to call it in a

loop. At time i = 0, the initial conditions on Y (for example, Y(1-szb) through Y(-1)) are obtained from the array

Initial Conditions on output. At exit (the end of the VI execution), this array holds the final conditions on Y that could be used as the initial conditions for the next DSP IIR Filter VI call if you were to call it in a

loop.

X is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input signal array.

Y in is a DSP Handle Cluster that indicates the memory buffer on the DSP board that will contain the output array of filtered data.

Initial Conditions on input is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the initial conditions on input at time zero.

Initial Conditions on output is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the initial conditions on output at time zero.

Forward Coefficients is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the forward coefficients of the IIR filter.

Feedback Coefficients is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the feedback coefficients of the IIR filter.

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Y out is a DSP Handle Cluster that is identical to Y in, but with the filtered data already stored in the memory buffer on the DSP board.

Final Conditions on input is a DSP Handle Cluster that is identical to Initial Conditions on input, but contains the final conditions on input.

Final Conditions on output is a DSP Handle Cluster that is identical to Initial Conditions on output, but contains the final conditions on output.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

The operation can be performed in place; that is, the input X and the output Y can be the same DSP Handle Cluster.

Parameter Discussion The arrays X and Y should be the same size. The arrays Forward Coefficients and Initial/Final Conditions on

input should be the same size. The arrays Feedback Coefficients and Initial/Final Conditions on output should

be the same size. In successive calls to this VI, while performing filtering on large data streams, one buffer at a time, the final conditions of the filter are stored in Final Condition on input and in Final Condition on output, and are used as the initial conditions of the filter in the subsequent call. For example, if you designed a filter with all of the initial conditions set to zero, and you then wanted to filter a stream of 8,192 data points, 1,024 points at a time, after the first call, the final conditions of the filter are stored in Final Condition on input and in Final Condition on output. These can be used as the initial conditions to the filter in the filtering of the next 1,024 points, and so on.

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DSP Impulse Pattern

Generates an array containing an impulse pattern. If the Impulse Pattern is represented by the sequence X, the VI generates the pattern according to the following formula:

a if i = d





xi =





0 elsewhere



for i = 0, 1, 2, … , n-1 ,

where a is the amplitude,

d is the delay, and n is the number of elements in Impulse Pattern.

amplitude defaults to 1.0.

delay must be greater than or equal to 0. If delay is less than zero or greater than or equal to the size of Impulse Pattern, the VI returns an error. delay defaults to 0.

Impulse Pattern in is a DSP Handle Cluster that indicates the memory buffer on the DSP board that

will contain the output impulse pattern. Impulse Pattern out is a DSP Handle Cluster that is identical to Impulse Pattern in, but with the

generated pattern already stored in the memory buffer on the DSP board. The largest impulse pattern that can be generated depends upon the amount of memory on your DSP board.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

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DSP Impulse Train Pattern

Generates a train of impulses of value amplitude at sample delay.

If the impulse train pattern is represented by the sequence X, the VI generates the pattern according to the following formula:

amplitude if i modulo P = d





xi =





0.0 elsewhere



for i = 0, 1, 2, … , n-1 ,

where P is the period,

d is the delay, and n is the number of elements in the impulse train.

amplitude defaults to 1.0.

delay defaults to 0.

period defaults to 1.

Impulse Train in is a DSP Handle Cluster that indicates the memory buffer on the DSP board that will

contain the output impulse train. Impulse Train out is a DSP Handle Cluster that is identical to Impulse Train in, but with the generated

pattern already stored in the memory buffer on the DSP board. The largest impulse train that can be generated depends upon the amount of memory on your DSP board.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

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DSP Index Memory

Indexes into a DSP buffer allocated in the memory space of the specified DSP board. The return value is another DSP Handle Cluster. This VI does not allocate memory.

In order to index into a buffer correctly, you need to indicate

what type of data is in the DSP buffer. You must set data type to the appropriate type. data type has two options–4 bytes (for 32-bit long and floating-point data) and 2 bytes (for 16-bit short data).

DSP Handle Cluster is a DSP Handle Cluster into which you want to index.

data type indicates the type of data in the buffer on the DSP board that is referred to by DSP Handle Cluster. data type has two options:

0: 4 bytes (for 32-bit long and floating-point data). 1: 2 bytes (for 16-bit short data).

data type defaults to 4 bytes.

offset is the index where to start to index into the array referenced by DSP Handle Cluster. offset

defaults to 0.

Indexed DSP Handle Cluster is a DSP Handle Cluster that contains the number of size data in DSP Handle Cluster starting from offset.

Notes: If you free a DSP Handle Cluster using the DSP Free Memory VI, then all other DSP Handle

Clusters obtained by using DSP Index Memory VI will no longer be valid. This VI returns a new DSP Handle Cluster. If you no longer need this DSP Handle Cluster,

remember to free it.

size indicates how many elements you want to index starting from the offset. size defaults to 0.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

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DSP Init Memory

Initializes the memory heaps and frees all allocations of memory on the specified DSP board.

slot is the board ID number. slot defaults to 3.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

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DSP Integral

Performs the discrete integration of the sampled signal X. The integral F(t) of a function f(t) is defined as follows:

F(t) = ∫

Let Y represent the sampled output sequence Integral X. The VI obtains the elements of Y using the following formula:

yi =

where n is the number of elements in X,

f(t) dt .

+ 4xj + x

∑

j=0

j-1

) dt for i = 0, 1, 2, …, n-1 ,

j+1

x-1 is specified by initial condition when i = 0, and xn is specified by final condition when i = n-1.

The initial condition and final condition minimize the overall error by increasing the accuracy at the boundaries, especially when the number of samples is small. Determining boundary conditions before the fact enhances accuracy.

X is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input signal array.

initial condition defaults to 0.0.

final condition defaults to 0.0.

dt is the sampling interval and must be greater than zero. If dt is less than or equal to zero, the VI returns an error. dt defaults to 1.0.

Y in is a DSP Handle Cluster that indicates the memory buffer on the DSP board that will contain the

results of the integration of X. Y out is a DSP Handle Cluster that is identical to Y in, but with the results of integration already stored

in the memory buffer on the DSP board.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

The operation can be performed in place; that is, the input X and the output Y can be the same DSP Handle Cluster. Note: You can also use the DSP Integral x(t) VI to numerically evaluate the finite integral:

∫

f(t) dt = F(b) - F(a) ≈ y

n-1

by extracting the last element of the output sequence Y.

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DSP Inv Chebyshev Coeff

Generates the set of filter coefficients to implement an inverse IIR filter as specified by the Chebyshev II Filter mode. You can then pass these coefficients to the DSP IIR Filter VI to filter a sequence of data.

filter type specifies the passband of the filter. filter type has four options:

0: lowpass. 1: highpass. 2: bandpass. 3: bandstop.

filter type defaults to lowpass.

sampling Freq : fs is the sampling frequency and must be greater than 0. If it is less than or equal to zero, the VI returns an error. sampling Freq : fs defaults to 1.0.

high cutoff freq: fh is the high cutoff frequency. The VI ignores this parameter when filter type is lowpass. high cutoff freq: fh defaults to 0.45.

low cutoff freq: fl is the low cutoff frequency. The VI ignores this parameter when filter type is highpass. low cutoff freq: fl defaults to 0.125.

Note: fh and fl must observe the Nyquist criterion: 0 ≤ fl ≤ fh ≤ fs /2.

attenuation must be greater than 0.0. If attenuation is less than or equal to zero, the VI returns an error. attenuation defaults to 60.0.

order must be greater than zero. If the filter order is less than or equal to zero, the VI returns an error. order defaults to 2.

Forward Coefficients in is a DSP Handle Cluster that indicates the memory buffer on the DSP board

that will contain the forward coefficients.

Feedback Coefficients in is a DSP Handle Cluster that indicates the memory buffer on the DSP board that will contain the feedback coefficients.

Forward Coefficients out is a DSP Handle Cluster that is identical to Forward Coefficients in, but with the forward coefficients already stored in the memory buffer on the DSP board.

Feedback Coefficients out is a DSP Handle Cluster that is identical to Feedback Coefficients in, but with the feedback coefficients already stored in the memory buffer on the DSP board.

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error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

Parameter Discussion

DSP Inverse FFT

Computes the inverse Fourier transform of the complex input sequence FFT {X}. If Y represents the output sequence, then:

Y = F-1{X}.

Re FFT{X} is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the real part of input signal array FFT {X}.

Im FFT{X} is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the imaginary part of input signal array FFT {X}.

Notes: The number of elements for the input array must be the power of two. If the size of Re

FFT{X} is different from the size of Im FFT{X}, the VI uses the smaller number as the size of

the inverse FFT. The operation is performed in place and the input array Re FFT{X } and Im FFT{X} is

overwritten by Re {X} and Im {X}. The largest inverse FFT that can be computed depends upon the amount of memory on your

DSP board.

Re {X} is a DSP Handle Cluster that is identical to Re FFT{X }, but with the real part of X already stored in the memory buffer on the DSP board.

Im {X} is a DSP Handle Cluster that is identical to the Im FFT{X} but with the imaginary part of X already stored in the memory buffer on the DSP board.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

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DSP Inverse FHT

Computes the inverse fast Hartley transform of the input sequence FHT {X}. The inverse Hartley transform of a function X(f) is defined as

∞

x(t) = ∫

where cas(x) = cos(x) + sin(x). If Y represents the output sequence X, the VI calculates Y through the discrete implementation of the inverse

Hartley integral:

Yk =

where n is the number of elements in X. The inverse Hartley transform maps real-valued frequency sequences into real-valued sequences. You can use it

instead of the inverse Fourier transform to convolve, deconvolve, and correlate signals. Furthermore, you can derive the Fourier transform from the Hartley transform.

X(f) cas(2πft) df

-∞

n-1

Xi cas

∑

i=0

2π ik

for k = 0, 1, 2, … , n-1

()

See the description of the DSP FHT VI for a comparison of the Fourier and Hartley transforms.

FHT {X} is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input signal array.

Notes: The number of elements for the input array must be a power of 2.

The operation is performed in place and the input array FHT {X} is overwritten by the output array X.

The largest inverse FHT that can be computed depends upon the amount of memory in your DSP board.

X is a DSP Handle Cluster that is identical to FHT {X}, but with the results of inverse FHT {X } already stored in the memory buffer on the DSP board.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

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DSP Kaiser-Bessel Window

Applies a Kaiser-Bessel window to the input sequence X. If Y represents the output sequence Kaiser-Bessel{X}, the elements of Y are obtained using the formula:

1.0 - a

()

 

yi = xi





for i = 0, 1, 2, … n - 1

i - k

a =

n-1

k =

where n is the number of elements in X, and

Io(•) is the zeroth-order modified Bessel function.

X is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input signal array.

Note: The operation is performed in place and the input array X is overwritten by the output

Kaiser-Bessel {X}.

beta is proportional to the sidelobe attenuation–that is, the larger beta is, the greater the sidelobe attenuation is. beta defaults to 0.0.

Kaiser-Bessel {X} is a DSP Handle Cluster that is identical to X, but with the results of Kaiser-Bessel {X} already stored in the memory buffer on the DSP board.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

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DSP Linear Evaluation

Performs a linear evaluation of the input array X. The i obtained using the following formula:

where n is the number of elements in X.

element of the output array Y is

Y(i) = a* X(i) + b for i = 0, 1, 2, …, n-1,

X is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input signal array X.

a is the multiplicative constant. a defaults to 1.0.

b is the additive constant. b defaults to 0.0.

Y in is a DSP Handle Cluster that indicates the memory buffer on the DSP board that will contain the

results of output array.

Y out is a DSP Handle Cluster that is identical to Y in, but with the results already stored in the memory buffer on the DSP board.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

The operation can be performed in place; that is, the input and output arrays can be the same DSP Handle Cluster.

DSP Load

Downloads a library specified by path name to the DSP board in slot. path name must contain the full path name of a valid COFF file (.out file).

slot is the board ID number. slot defaults to 3.

path name is the path name of the .out file.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

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DSP Log

Computes the logarithm base 10 of the X input array. The ith element of resulting array is obtained by using the following formula:

y(i) = log10 (X(i)) * mult for i = 0, 1, 2, …, n-1,

where n is the number of elements in X. This VI is useful for converting values that represent power to decibels. This VI returns the most negative number

for any input less than or equal to zero.

X is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input signal array.

mult defaults to 1.0.

Y in is a DSP Handle Cluster that indicates the memory buffer on the DSP board that will contain the

results of logarithm X.

Y out is a DSP Handle Cluster that is identical to Y in, but with the results of logarithm X already stored in the memory buffer on the DSP board.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

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DSP Max & Min

Finds the maximum and minimum values in the input array, as well as the respective indices of the occurrence of the maximum and minimum values.

X is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input signal array X.

max value is the maximum value of the input array.

max index is the index into the input array where maximum occurred.

min value is the minimum value of the input array.

min index is the index into the input array where minimum occurred.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

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DSP Median Filter

Applies a median filter of rank to the input sequence X. The median filter is a nonlinear filter that combines lowpass filters characteristics (to remove highfrequency noise) and high-frequency characteristics (to detect edges).

If Y represents the output sequence Filtered Data, if Ji represents a subset of the input sequence X centered about the i

element of x:

Ji = {x

, x

, …, x

i-r

i-r+1

, xi, x

i-1

, …, x

i+1

i+r-1

, x

i+r

and if the indexed elements outside the range of X equal zero, the VI obtains the elements of Y using:

yi = Median(Ji) for i = 0, 1, 2, …, n-1,

where n is the number of elements in the input sequence X, and

r is the filter rank.

X is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input data array. The number of elements in X must be greater than the rank:

n>r≥0.

If the number of elements in X is less than or equal to rank, the VI returns an error.

rank must be greater than or equal to zero. If rank is less than zero, the VI returns an error. rank defaults to 2.

Filtered Data in is a DSP Handle Cluster that indicates the memory buffer on the DSP board that will contain the filtered data output.

Filtered Data out is a DSP Handle Cluster that is identical to Filtered Data in, but with the filtered data already stored in the memory buffer on the DSP board.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

The operation cannot be performed in place; that is, the input X and the output Filtered Data cannot be the same DSP Handle Cluster.

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DSP Multiply

Multiply array X by array Y. The ith element of the output array Z is obtained using the following formula:

Z(i) = X(i) * Y(i) for i = 0, 1, 2, …, n-1,

where n is the smaller number of elements in X and Y.

X is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input signal array X.

Y is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input signal array Y.

Z in is a DSP Handle Cluster that indicates the memory buffer on the DSP board that will contain the results of X(i) * Y(i).

Z out is a DSP Handle Cluster that is identical to Z in, but with the multiplied results already stored in the memory buffer on the DSP board.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

The operation can be performed in place; that is, the input and output arrays can be the same DSP Handle Cluster.

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DSP Parks-McClellan

Generates a set of linear-phase finite impulse response multiband digital filter coefficients using the number of taps, sampling frequency, filter type, and Band Parameters.

# of taps is the total number of coefficients in H. A tap corresponds to a multiplication and an addition. If there are n taps, every filtered sample requires n multiplications and n additions. # of taps must be greater than 0. If # of taps is less than or equal to zero, the VI returns an error. # of taps defaults to 32.

sampling freq : fs defaults to 1.0.

Band Parameters is a cluster. Each cluster element contains the necessary information associated with

each band for the FIR design. Each cluster contains four elements, as shown in the following figure:

The Band Parameters cluster must contain at least one element, that is, one band.

amplitude is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the desired amplitude for each band.

lower freq is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the lower frequency bands.

higher freq is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the upper frequency bands.

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weighted ripple is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the weighting factor for each band. For each band, higher freq must be greater than lower freq, and for adjacent bands, lower freq in the higher band must be greater than higher freq in the lower band,

> f

, for i = 0, 1, 2, …, m-1,

> f

where f

i+1

, for i = 0, 1, 2, …, m-2,

represents the lower freq in the i

band, and f

represents the higher freq in the i

band. The higher freq in the last band must observe the Nyquist criterion:

≤ 0.5fs ,

m-1

where fs is the sampling frequency. If Band Parameters does not contain any elements, or if any of the preceding frequency

conditions is violated, the VI returns an error.

filter type has three options:

0: multiband. 1: differentiator. 2: Hilbert.

filter type defaults to multiband.

ripple is the optimal ripple the VI computes and is a measure of deviation from the ideal filter

specifications.

H in is a DSP Handle Cluster that indicates the memory buffer on the DSP board that will contain the FIR coefficients.

H out is a DSP Handle Cluster that is identical to H in, but with the coefficients already stored in the memory buffer on the DSP board.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

Note: The DSP Parks-McClellan VI finds the coefficients using iterative techniques based upon an error criterion.

Although you specify valid filter parameters, the algorithm may fail to converge. The DSP Parks-McClellan VI generates only the filter coefficients. It does not perform the filtering

function. To filter a sequence X using the set of FIR filter coefficients H, use the DSP Convolution VI with X and H as the input sequences.

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The equi-ripple filters use a similar technique to filter the data.

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Parameter Discussion

The weights are usually the same for every band and inversely proportional to frequency f for a differentiate. The amplitudes of the bands are usually the same for every band and form a slope for a differentiation. The designed filter is unconstrained, that is the frequency response in transitional period specifications is not guaranteed. Adjust the parameters if there are discrepancies between specifications and results.

Generally, when type = multiband and bands ≥ 2, the DSP Parks-McClellan VI designs a multiband filter. When

filter type = differentiator and bands = 1, the DSP Parks-McClellan VI designs a differentiation. When filter type = Hilbert and bands = 1, the DSP Parks-McClellan VI designs a Hilbert transform. The following tables

contain the brief requirements you must meet when you design different types of filters. For more information, please refer to Digital Filter Design by Parks and Burrus, or "A Computer Program for Designing Optimum FIR Linear Phase Digital Filters," by McClellan, Parks, and Rabiner.

When filter type = Multiband:

Filter Band Type LowPass HighPass BandPass BandStop

# of Bands (n) 2 2 ≥3 ≥3 # of taps odd/even odd odd/even odd fl[0] 0.0 0.0 0.0 0.0 fh[n-1] 0.5fs 0.5fs 0.5fs 0.5fs amp[0] >0.0 ≥0.0 ≥0.0 >0.0 amp[n-1] 0.0(for even taps)

≥0.0(for odd taps)

>0.0 0.0(for even taps)

≥0.0(for odd taps)

>0.0

fl[0] represents the first value in the array of Lower Freq. fh[n-1] represents the last value in the array of Higher Freq. amp[0] represents the first value in the array of Amplitude. amp[n-1] represents the last value in the array of Amplitude. fs is the sample frequency.

When filter type = Differentiator or Hilbert:

Filter Type Diff(odd) Diff(even) Hilbert(odd) Hilbert(even)

bands(n) ≥1 ≥1 ≥1 ≥1 fl[0] 0.0 0.0 0.0+∆ 0.0+∆ fh[n-1] 0.5fs-∆ 0.5fs 0.5fs-∆ 0.5fs

odd or even in the table refers to the value of the # of taps. fl[0] represents the first value in the array of Lower Freq. fh[n-1] represents the last value in the array of Higher Freq. fs is the sample frequency. ∆ is a small number that specifies the transitional band.

Although the DSP Parks-McClellan VI is the most flexible way to design a FIR linear phase filter, it has more complex parameters and requires some DSP knowledge. You may find it more convenient to use DSP Equi-Ripple LowPass, DSP Equi-Ripple HighPass, DSP Equi-Ripple BandPass, and DSP Equi-Ripple BandStop. These functions, which provide lowpass, highpass, bandpass and bandstop FIR filters with equal weighting factors in all bands, are special cases of the DSP Parks-McClellan VI with simplified parameters.

NI-DSP SRM for LabVIEW for Windows 2-59 Part 3: NI-DSP Function Reference

NI-DSP Analysis VI Reference Chapter 2

DSP Polar to Rectangular

Converts a set of polar coordinate points (Magnitude, Phase) to a set of rectangular coordinate points (X, Y). The ith elements of the rectangular set is obtained using the following formulas:

X(i) = Magnitude(i) * cos(Phase(i)) Y(i) = Magnitude(i) * sin(Phase(i))

Note: The operation is performed in place and the input arrays Magnitude and Phase are overwritten by X and

Magnitude is the DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input signal array Magnitude.

Phase is the DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input signal array Phase.

X is the DSP Handle Cluster that is identical to Magnitude but with the caculated rectangular

coordinate values already stored in the memory buffer on the DSP board.

Y is the DSP Handle Cluster that is identical to Phase but with the caculated rectangular coordinate values already stored in the memory buffer on the DSP board.

error in(no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

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Chapter 2 NI-DSP Analysis VI Reference

DSP Polynomial Evaluation

Performs a polynomial evaluation on the input array X. The i is obtained using the following formula:

Y(i) = ∑ (Coefficients(j) * X(i)j)

for i = 0, 1, 2, …, n-1,

where n is the number of elements in X and k is the number of elements in Coefficients.

element of the output array Y

k-1

j=0

X is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input signal array X.

Coefficients is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the coefficients array.

Y in is a DSP Handle Cluster that indicates the memory buffer on the DSP board that will contain the results of output array.

Y out is a DSP Handle Cluster that is identical to Y in, but with the results already stored in the memory buffer on the DSP board.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

The operation can be performed in place; that is, the input X and the output Y can be the same DSP Handle Cluster.

NI-DSP SRM for LabVIEW for Windows 2-61 Part 3: NI-DSP Function Reference

Chapter 2 NI-DSP Analysis VI Reference

DSP Power Spectrum

Computes the Power Spectrum of the input sequence X. The Power Spectrum Sxx(f) of a function x(t) is defined as

Sxx(f) = X*(f)X(f) = | X(f) | 2 ,

whereX(f) = F{x(t)}, and X*(f) is the

complex conjugate of X(f).

X is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input signal array.

Notes:The number of elements for the input array must be a power of two.

The operation is performed in place and the input array X is overwritten by the output Power

Spectrum.

The largest power spectrum that can be computed depends upon the amount of memory on your DSP board.

This VI allocates a temporary workspace on the DSP board equal to the size of the input signal array.

Power Spectrum is a DSP Handle Cluster that is identical to X, but with the results of Power Spectrum already stored in the memory buffer on the DSP board.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

DSP Product

Finds the product of the elements of the input array X. The product of the elements is obtained using the following formula:

product = X(i)

where n is the smaller number of elements in X.

n−1

∏

i=0

X is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input signal array X.

product is the product of the elements in X.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

NI-DSP SRM for LabVIEW for Windows 2-62 Part 3: NI-DSP Function Reference

NI-DSP Analysis VI Reference Chapter 2

DSP Pulse Pattern

Generates an array containing a pulse pattern. If Pulse Pattern is represented by the sequence X, then the pattern is generated according to the following formula:

a if d ≤ i < last





xi =





0 elsewhere



for i = 0, 1, 2, … , n-1 , last = d + w ,

wherea is the amplitude,

d is the delay, w is the width, and n is the number of elements in Pulse Pattern.

amplitude defaults to 1.0.

delay must be greater than or equal to 0. delay defaults to 0.

width must be greater than or equal to 0. width defaults to 1.

Pulse Pattern in is a DSP Handle Cluster that indicates the memory buffer on the DSP board that will

contain the output pulse pattern. Pulse Pattern out is a DSP Handle Cluster that is identical to Pulse Pattern in, but with the generated

pattern already stored in the memory buffer on the DSP board. The largest pulse pattern that can be generated depends upon the amount of memory on your DSP board.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

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Chapter 2 NI-DSP Analysis VI Reference

DSP Ramp Pattern

Generates an array containing a ramp pattern. If the Ramp Pattern is represented by the sequence X, then the pattern is generated according to the formula:

xi = x0 + i ∆x

for i = 0, 1, 2, … , n-1 ,

- x

n-1

where∆x =

is the final,

n-1

x0 is the init, and n is the number of elements in Ramp Pattern.

The Ramp Pattern VI does not impose conditions on the relationship between init and final. The VI can therefore generate ramp-up and ramp-down patterns.

final defaults to 0.0.

n - 1

init defaults to 1.0.

Ramp Pattern in is a DSP Handle Cluster that indicates the memory buffer on the DSP board that will

contain the output ramp pattern. Ramp Pattern out is a DSP Handle Cluster that is identical to Ramp Pattern in, but with the generated

pattern already stored in the memory buffer on the DSP board. The largest ramp pattern that can be generated depends upon the amount of memory on your DSP board.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

NI-DSP SRM for LabVIEW for Windows 2-64 Part 3: NI-DSP Function Reference

NI-DSP Analysis VI Reference Chapter 2

DSP Random Pattern

Generates a uniformly distributed pseudorandom pattern whose values are in the range [0:1]. The sequence is generated using the Very-Long-Cycle random number generator algorithm.

seed < 65536.0. If seed > 0.0, the generated noise will be the same in repeated invocations if the seed value does not change. If seed ≤ 0.0, the VI generates a random value to use as the seed, and the noise differs in repeated invocations although the value in seed does not change. seed defaults to 0.0.

Random Pattern in is a DSP Handle Cluster that indicates the memory buffer on the DSP board that will contain the output random pattern.

Random Pattern out is a DSP Handle Cluster that is identical to Random Pattern in, but with the generated pattern already stored in the memory buffer on the DSP board. The largest random pattern that can be generated depends upon the amount of memory on your DSP board.

error in (no error) contains the error information from a previous VI. If an error occurs, it is passed out error out and no other calls are made.

error out contains the error information for this call.

Part 3: NI-DSP Function Reference 2-65 NI-DSP SRM for LabVIEW for Windows

National Instruments 320571-01 User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual

Contents

Figures

Tables

About This Manual

Assumption of Previous Knowledge

Organization of This Manual

Conventions Used in This Manual

Related Documentation

Additional Software

NI-DAQ for DOS/Windows/LabWindows

Developer Toolkit

Compatible Hardware

Customer Communication

Part 1 Getting Started with NI-DSP

Product Overview

Figure 1-1. Development Paths with the NI-DSP Software

The NI-DSP Software

What Your Distribution Diskettes Should Contain

Installing NI-DSP for LabVIEW for Windows

Table 1-1. Subdirectories Created by SETUP

Board Configuration

Installation on an ISA (or AT) Bus Computer

Installation on an EISA Bus Computer

Part 2 Introduction to the NI-DSP Analysis VIs

Using the NI-DSP VIs in LabVIEW

AT-DSP2200 Software Overview

Figure 1-1. Communication between the PC and the DSP Board

Memory Management and Data Transfer

Figure 1-2. DSP Handle Cluster

Figure 1-3. The Hexadecimal Encoding of a Typical DSP Handle

Figure 1-4. Front Panel–An Example of How to Allocate a DSP Handle Cluster

Figure 1-5. Block Diagram–An Example of How to Allocate a DSP Handle Cluster

Special Features of the NI-DSP Analysis VIs

Figure 1-6. DSP Add VI

Figure 1-7. The error in/error out Cluster

Figure 1-8. An Example That Does Not Use error in/error out

Figure 1-9. An Example of Using the error in/error out Cluster for Sequential VI Execution

Hints for Improving the Execution Speed on the DSP Board

An Example of Using NI-DSP Analysis VIs

Figure 1-10. Front Panel–An Example of Using NI-DSP Analysis VIs

Figure 1-11. Block Diagram–An Example of Using NI-DSP Analysis VIs

Chapter 1 NI-DSP Analysis VI Reference Overview

The NI-DSP Analysis VI Overview

Table 1-1. The NI-DSP Analysis VI Groups

Analysis VI Organization

Accessing the NI-DSP Analysis VIs

Figure 1-1. Choosing DSP2200 from the Functions Menu

About the Fast Fourier Transform (FFT)

About Filtering

About Windowing

Figure 1-2. Spectral Leakage Demonstrated Using Convolution

Chapter 2 NI-DSP Analysis VI Reference

Copy Mem(DSP to DSP)

Copy Mem(DSP to LV)

Copy Mem(LV to DSP)

DSP Absolute

DSP Add

DSP Allocate Memory

DSP Blackman Window

DSP Blackman Harris Window

DSP Butterworth Coefficients

DSP Chebyshev Coefficients

DSP Clip

DSP Complex FFT

DSP Convolution

DSP Correlation

DSP Cross Power

DSP Custom

DSP Decimate

DSP Deconvolution

DSP Derivative

DSP Divide

DSP Elliptic Coefficients

DSP Equi-Ripple BandPass

DSP Equi-Ripple BandStop

DSP Equi-Ripple HighPass