Microcomputer Systems 1
Introduction to Visual DSP++ Tools
Goals
 Introduction to Visual DSP++ and
Tools
 Specific to Blackfin
 Information on how to analyze
applications and fine tune them.
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Outline
 The VisualDSP++ Tools
 Creating a Project
 Plotting
 Performance improvement using
chip features
 Cache
 L1 Memory
 Voltage Regulator
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Blackfin CROSSCORE Product Line
VisualDSP++
development suite
Performance-tuned C/C++
compiler
Source language debugger
RTOS kernel (VDK)
Device drivers and system
services
Ethernet and USB 2.0 libraries
Tuned DSP libraries
Visual linker
Code wizards
Flash programmer
Multicore code generation and
debugging
Plotting and other advanced
code
generation and debugging tools
Automation API
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EZ-KIT Lite and
Daughter cards
JTAG Emulators
ADSP-BF533
ADSP-BF535
ADSP-BF537
ADSP-BF561
USB 2.0
USB 1.1
PCI
Background Telemetry
A-V EZ-Extender
Audio EZ-Extender
USB-LAN EZ-Extender
FPGA EZ-Extender
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Additional Information
 ADSP-BF533 EZ-KIT Lite Manual
 Tools manuals provided in the On-line help
 Analog Devices web site: www.analog.com
 Email Support:
 For tools questions:
Processor.tools.support@analog.com
 For processor questions:
Processor.support@analog.com
 Licensing and Registration questions:
Processor.tools.registration@analog.com
 Or click the “Ask A Question” button
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DSP Project Development Stages
 Simulation
 Evaluation
 Emulation
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Simulation
 Development Cycle begins in
simulation environment
 VisualDSP++ with simulation target
enables:
 Building
 Debugging
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Evaluation
 EZ-KIT Lite evaluation system in the lab can be used
to:
 Determine Processor Capabilities that best fit target
application
 EZ-KIT Lite Board connected to the PC Development
System via
 USB Port or
 JTAG interface
 This connection can be used for Evaluation as well as
Emulation purposes (see next slide).
 Code download via USB Port is significantly slower
than JTAG interface used for emulation.
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Emulation
 Actual hardware (can be EZ-KIT Lite board)
is connected via JTAG (Joint Test Action
Group) emulator
 We have only 1 JTAG obtained from our entry to
UML-ADI competition
 Emulator enables application software to be
downloaded and debugged from within
VisualDSP++
 Emulation Software performs the
communications that enables measurement of
DSP performance and how current
implementation affects it.
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Development Tools
 VisualDSP++ version 4.5 (from
Analog Devices) – version 5.0 will be
installed soon.
 Vendors other than Analog Dev.:
 MULTI from Green Hills Software
 Open Source GCC tool chain and Clinux
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VisualDSP++
 Project Development and Debugging
is integrated (IDDE).





C/C++ Native Compiler
Graphical Plotting Tools
Statistical Profiling
Cache Visualization
Pipeline Viewer
 VisualDSP++ Kernel (VDK)
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ADSP-BF533 EZ-KIT Lite Evaluation
System Board
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Evaluation Board EZ-KIT LITE
 Analog Devices ADSP-BF533 processor


Performance up to 600 MHz
160-pin mini-BGA package

27 MHz CLKIN oscillator
 The Ball Grid Array (BGA) is descended from the pin grid
array (PGA), which is a package with one face covered (or
partly covered) with pins in a grid pattern.
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Evaluation Board EZ-KIT LITE
 Synchronous dynamic random access
memory (SDRAM)
 MT48LC32M16 - 64 MB (32M x 16 bits)
 Flash memories
 2 MB (512K x 16 x 2chips)
 Analog audio interface
 AD1836 – Analog Devices 96 kHz 24-bit audio
codec
 4 input RCA phono jacks (2 channels)
 6 output RCA phono jacks (3 channels)
 2 MB (512K x 16 bits x 2chips) FLASH memory
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Evaluation Board EZ-KIT LITE

Analog video interface



Universal asynchronous receiver/transmitter (UART)



ADV7183 video decoder w/ 3 input RCA phono jacks
ADV7171 video encoder w/ 3 output RCA phono jacks
ADM3202 RS-232 line driver/receiver
DB9 male connector
LEDs

10 LEDs:






1 power (green),
1 board reset (red),
1 USB (red),
6 general purpose (amber), and
1 USB monitor (amber)
Push buttons


5 push buttons with debounce logic: 1 reset,
4 programmable flags
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Interfaces
 Expansion interface
 PPI, SPI, EBIU, Timers2-0, UART,
programmable flags, SPORT0, SPORT1
 Other features




JTAG ICE 14-pin header
USB-based debugger interface
SPORT0 connector
Evaluation suite of VisualDSP++
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Evaluation Board (cont.)
 10 LED’s:





Power
Board Reset
USB Reset
USB Monitor
6 general-purpose (programmable)


1 reset
4 programmable







Parallel Peripheral Interface (PPI)
Synchronous Serial Port Interface (SPI)
External Bus Interface Unit (EBIU)
Timers 0-2
Universal Asynchronous Receiver-Transmitter (UART)
Programmable Flags,
High Speed Serial Ports (SPORT0 & 1)
 5 Push buttons
 3 90-pin connectors providing:
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Development Process on
DSP
VisualDSP++ Integrated
Development & Debugging
Environment
Development Process
Linker
Description
File (.ldf)
Executable
File
(.dxe)
Compiler &
Assembler
Linker
Source Files
Object Files
(.c & .asm)
(.doj)
C Run-Time
Header
(basiccrt.s)
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Debugger
(In-Circuit
Emulator,
Simulator,
or
EX-KIT Lite)
Linker
Description
File (.ldf)
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Bootable Image
Executable
File
Boot Image
Programmable
Memory
(.ldr)
(.dxe)
Loader/
Loader /
Splitter
Writer
EPROM
Boot Code
(.dxe)
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Integrated Development & Debugging
Environment of VisualDSP++
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Code Development Tools
 C/C++ compiler
 Run-time library with over 100 math, DSP,
and C run-time library routines
 Assembler
 Linker
 Splitter
 Loader
 Simulator
 Emulator (EZ-Kit Lite or custom hardware)
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Connecting to Debugging Session
 Start -> All Programs -> … -> VisualDSP++
 VisalDSP++ when launches for the first time
it does not connect to any session (see next
slide)
 Visual DSP++ can connect to a number of
different debugging sessions:
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Connecting to Debugging Session
 EZ-KIT Lite: Dedicated USB connection between
the PC and EZ-KIT Lite.
 Simulator: Software model of the processor.
 No external hardware is required.
 Customized to the selected DSP processor:
 Pipelines
 Caches
 Several order of magnitude slower than actual
hardware execution.
 Cycle-accurate simulation (detailed view of
processor operations)
 Functional simulator (quick simulation at the
expense of detail).
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Connecting to Debugging Session
 Emulator: JTAG emulator ideal for connecting to
hardware
 Maximal performance
 Maximal flexibility
 Emulator is required to connect to any non-EZ-KIT
Lite hardware.
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VisualDSP++ Startup Screen
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Using VisualDSP++
 VisualDSP++ includes basic Linker Description File
(.ldf) for each processor type.
 For Blackfin Processors the default installation path
is:
Program Files\Analog Devices\VisualDSP 4.5\Blackfin\ldf
 The four Tutorial exercises will be covered in more
detail in the LAB.
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Exercise 1.
Building and Running a C Program
Goals of this Exercise:
 Learn to:




Start up the VisualDSP++ environment
Open and build an existing project
Examine windows and dialog boxes
Run the program
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Additional Information
 The source files for this exercise are
in the dot_product_c folder.
 Default installation path:
Program Files\Analog Devices\VisualDSP
4.5\Blackfin\Examples\Tutorial\dot_prod
uct_c
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Step 1: Start VisualDSP++ and
Open a Project
1.
Click the Windows Start button and select:
 Programs, Analog Devices, VisualDSP++ 4.5,
and VisualDSP++ Environment.
 When you need to connect to a debug session, click
the Connect to Target toolbar button or choose from
the available sessions listed under Select Session in
the Session menu. To create a debug session, select
New Session from the Session menu. This will launch
the Session Wizard, which is covered in more detail
later.
 If you have already run VisualDSP++ and the
Reload last project at startup option is selected
on the Project page under Settings and
Preferences, VisualDSP++ opens the last project
that you worked on. To close this project, choose
Close and then Project from the File menu, and
then click No when prompted to save the project.
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Step 1: Start VisualDSP++ and
Open a Project
2.
From the File menu, choose
 Open and then
 Project.
VisualDSP++ displays the Open Project dialog box.
3.
Copy content of dotprodc folder:
Program Files\Analog Devices\VisualDSP4.5\Blackfin\Examples\
Tutorial\dotprodc
This path is based on the default installation.
To:
u:\ece3551\lab1\
4.
In the Look in box, open the folder u:\ece3551\lab1\
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Step 1: Start VisualDSP++ and
Open a Project
5.
Double-click the dotprodc project (.dpj) file.
 VisualDSP++ loads the project in the Project
window, as shown
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Step 1: Start VisualDSP++ and
Open a Project
6.
From the Settings menu, choose Preferences to
open the Preferences dialog box, as shown
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Step 1: Start VisualDSP++ and
Open a Project
7. On the General page, under
General Preferences, ensure that
the following options are selected.
 Run to main after load
 Load executable after build
8. Click OK to close the Preferences
dialog box.
 The VisualDSP++ main window appears.
You are now ready to build the project.
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dot_prod_c Project
 The dotprodc project comprises two C
language source files:
 dotprod.c and
 dotprod_main.c, which define the arrays
and calculates their dot products.
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Step 2:
Building the dotprodc Project
1. Running the Compiler
Linker
Description Executable
File
File (.ldf)
(.dxe)
Compiler &
Assembler
Linker
Source Files
Object Files
(.c & .asm)
(.doj)
C Run-Time
Header
(basiccrt.s)
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Debugger
(In-Circuit
Emulator,
Simulator,
or
EX-KIT Lite)
Linker
Description
File (.ldf)
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Step 2:
Building the dotprodc Project
2. Linking
Linker
Description Executable
File
File (.ldf)
(.dxe)
Compiler &
Assembler
Linker
Debugger
(In-Circuit
Emulator,
Simulator,
or
EX-KIT Lite)
Object Files
Source Files
(.c & .asm)
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(.doj)
C Run-Time
Header
(basiccrt.s)
Linker
Description
File (.ldf)
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Step 2:
Building the dotprodc Project
1. From the Project menu, choose
Build Project.
 VisualDSP++ first checks and updates
the project dependencies and then
 Builds the project by using the project
source files.
 Output window displays status
messages.
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Step 2:
Building the dotprodc Project
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Step 2:
Building the dotprodc Project
 Upon successful build (compile and
link steps) example program can be
run.
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Step 3:
Configuring the Session to Run the Program
 Before running the program:
 Set up the debug session.
 View debugger windows and dialog boxes.
 Note:
 In Preferences dialog box of the General page:
Load executable after build is checked ⇒
automatic loading of dotprodc.dxe on to the target (EZLIT Lite).
 If not connected to a debug target, VisualDSP++ will
prompt to connect to one using
 an existing debug session or
 creating a new debug session
as shown in the next slide:
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Step 3:
Configuring the Session to Run the Program
 Clicking OK will launch the Session Wizard
as shown in the next slide.
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Step 3:
Configuring the Session to Run the Program
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Step 3:
Configuring the Session to Run the Program
 Setting up debug session:
1. On the Select Processor page, select the ADSPBF533 processor from the Blackfin family. Click Next
to continue.
2. On the Select Connection Type page, select
Simulator, and click Next to continue.
3. On the Select Platform page, select ADSP-BF5xx
Single Processor Simulator. You can either use the
default Session name, or give it a more meaningful
name of your choosing. Click Next to review your
choices, then click Finish.
VisualDSP++ closes the Session Wizard dialog box,
automatically loads your project’s executable file
(dotprodc.dxe), and advances to the main function of
your code.
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Step 3:
Configuring the Session to Run the Program
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Step 3:
Configuring the Session to Run the Program
4.
Look at the information in the open windows. The Output
window’s Console page contains messages about the status
of the debug session. In this case, VisualDSP++ reports that
the dotprodc.dxe load is complete.
The Disassembly window displays the assembly code for the
executable. Use the scroll bars to move around the
Disassembly window.
Note that a solid red circle and a yellow arrow appear at the
●
start of the program labeled “main”. The solid red circle (
)
indicates that a breakpoint is set on that instruction, and the
yellow arrow (➨) indicates that the processor is currently
halted at that instruction. When VisualDSP++ loads your C
program, it automatically sets several breakpoints. Most of
the breakpoints set are used as part of advanced features of
VisualDSP++.
There are two breakpoints of interest for this tutorial, one
at the beginning and one at the end of code execution.
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Step 3:
Configuring the Session to Run the Program

From the Settings
menu, choose
Breakpoints to view
the breakpoints set in
your program.
VisualDSP++ displays
the Breakpoints
dialog box, as shown.
The two breakpoints
of interest are set at
these C program
locations:


at main + 0x04
at __lib_prog_term
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Step 4:
Run dotprodc
 To run dotprodc.dxe:
 Click Run button:
 Select Run from Debug Menu.
 VisualDSP++ computes the dot products and
displays the following results on the Console view
of the Output window.
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Exercise 2:
Modifying a C Program Code to Call
an Assembly Routine
Goals of this Exercise
 Learn to:
 Modify the C program to call an
assembly language routine
 Create a Linker Description File (.ldf) to
link with the assembly routine
 Rebuild the project.
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Additional Information
 Ensure that the previous project and its
files are closed:
 From File menu, choose Close and then Project
dotprodc.
 Click Yes when prompted to close all open
source windows.
 Important Note:
 If you have modified your project during the
first exercise you will be prompted to save the
project. Click
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Step 1:
Creating a New Project
1.
From the File menu, choose New and then
Project to open the Project Wizard:
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Step 1:
Creating a New Project
2.
In the Name field, type dot_product.asm
3.
Click the browse button to the right of the Directory field
to open the Browse For Folder dialog box. Locate the
dot_product_asm tutorial folder and click OK. By default
this directory is in the following location.
Program Files\Analog Devices\VisualDSP 4.5\Blackfin\
Examples\Tutorial\dot_product_asm
4.
Click Next to bring up the Output Type page.
5.
Verify that the
 Processor type is ADSP-BF533,
 the Silicon Revision is Automatic, and
 the Project output file is Executable file.
Click Next to display the Add Startup Code/LDF page.
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Step 1:
Creating a New Project
6. Read the displayed text, and scroll down to the
bottom of the page.
 Select the Add an LDF and startup code option.
When this project is created:
 Startup code that initializes and configures the
processor will be added to the project, as well as
 a Linker Description File that defines the target memory
map and the placement of program sections within
processor memory.
The options available to configure the startup code and
LDF are beyond the scope of this tutorial.
 Make sure the Add an LDF and startup code option
is selected, and click Finish.
 The new project is created and is shown in the
Project window of the IDDE.
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Step 1:
Creating a New Project
7.
From the Project menu click the Project Options
command to display the Project Options dialog box
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Step 1:
Creating a New Project
8.
On the Project page (see previous slide) verify that the
values shown in the following table (or image of the
previous slide) are entered.
Field
Value
Processor
ADSP-BF533
Revision
Automatic
Type
Executable file
Name
dot_product_asm
Settings for Configuration
Debug
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Step 1:
Creating a New Project
9.
Take a moment to view the various pages in the
Project Options dialog box by selecting them
from the tree on the left:








Project,
General,
Compile,
Assemble,
Link,
Load,
Pre-Build, and
Post-Build.
On each page, you specify the tool options used to
build the project.
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Step 1:
Creating a New Project
10. Click the Compile tab to display the General page,
shown:
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Step 1:
Creating a New Project
11. Specify these settings in the Code Generation group box:
a. Select the Enable optimization check box to enable
optimization.
b. Select the Generate debug information check box, if it
is not already selected, to enable debug information for
the C source.
12. Click OK to apply changes to the project options and to close
the Project Options dialog box.

Note: These settings direct the C compiler to optimize code
for the ADSP-BF533 processor. Because the optimization
takes advantage of DSP architecture and assembly language
features, some of the C debug information is not saved.
Therefore, debugging is performed through debug information
at the assembly language level.
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Step 2:
Adding Source Files to dot_product_asm
1. To add the source file to the new project:


Click the Add File button
, or
from the Project menu,
 choose Add to Project, and then
 choose File(s).
The Add Files dialog box appears.
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Step 2:
Adding Source Files to dot_product_asm
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Step 2:
Adding Source Files to dot_product_asm
2.
In the Look in box, locate the project folder,
dot_product_asm.
3.
In the Files of type box, select All Source Files from
the drop-down list.
4.
Hold down the Ctrl key and click dotprod.c and
dotprod_main.c. Then click Add.
To display the files that you added in step 4, open the
Source Files folder in the Project window.
5.
Click the Rebuild All button (
) to build the project.
The C source file opens in an editor window, and
execution halts.
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Step 2:
Modifying the Project Source Files
 In this procedure we will:
1. Modify dotprod_main.c to call
a_dot_asm instead of a_dot_c
2. Save the modified file
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Step 2:
Modifying the Project Source Files

To modify dotprod_main.c to call assembly function
a_dot_asm do the following:
1.
2.
Resize or maximize the editor window for better viewing
From the Edit menu, choose Find to open the Find dialog
box as shown in the figure.
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Step 2:
Modifying the Project Source Files
3.
In the Find What box,
1.
2.
type “/*”, and then
click Mark All.
The editor bookmarks all lines containing “/*” and positions the
cursor at the first instance of “/*” in the extern int a_dot_c_asm
declaration.
4.
Select the comment characters “/*” and
1.
2.
Use the Ctrl+X key combination to cut the comment characters
from the beginning of the a_dot_c_asm declaration.
Then move the cursor up one line and use the Ctrl+V key
combination to paste the comment characters at the beginning of
the a_dot_c declaration.
Because syntax coloring is turned on, the code changes color as
you cut and paste the comment characters. Repeat this step for
the end-of-comment characters “*/” at the end of the
a_dot_c_asm declaration. The a_dot_c declaration is now fully
commented out, and the a_dot_c_asm declaration is no longer
commented.
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Step 2:
Modifying the Project Source Files
5. Press F2 to move to the next bookmark.
The editor positions the cursor on the “/*” in the function
call to a_dot_c_asm, which is currently commented out.
Note that the previous line is the function call to the
a_dot_c routine.
6. Press Ctrl+X to cut the comment characters from the
beginning of the function call to a_dot_c_asm. Then move
the cursor up one line and press Ctrl+V to paste the
comment characters at the beginning of the call to a_dot_c.
Repeat this step for the end-of-comment characters “*/”.
The main() function is now calling the a_dot_c_asm routine
instead of the a_dot_c function (previously called in
Exercise One).
 Note: The next image displays the changes made in the
step 6.
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Step 2:
Modifying the Project Source Files
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Step 2:
Modifying the Project Source Files
7.
From the File menu, choose Save and then File
dotprod_main.c to save the changes to the file.
8.
Place the cursor in the editor window. Then, from
the File menu, choose Close and then File
dotprod_main.c to close the dotprod_main.c file.
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Step 3:
Use the Expert Linker to Modify dot_prod_asm.ldf
 In this procedure we will:
 View the Expert Linker representation of the .ldf
file that is created.
 Modify .ldf file to map in the section for the
a_dor_c_asm assembly routine.
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Step 3:
Use the Expert Linker to Modify dot_prod_asm.ldf

To examine and then modify dot_prod_asm.ldf to
link eith the assembly function do the following:
1. Click the Ad File button
.
2. Select dotprod_func.asm and click Add.
3. Build the project by performing one of these actions:
 Click the Build Project button
.
 From the Project menu, choose Build Project.
4. Notice the error in the Output window.
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Step 3:
Use the Expert Linker to Modify dot_prod_asm.ldf
 Output Window: Linker Error
 To correct this error the do the following:
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Step 3:
Use the Expert Linker to Modify dot_prod_asm.ldf

In the Project window, double-click in the dot_prod_asm.ldf file.
The Expert Linker window (see Figure in the next slide) opens
with a graphical representation of your file.
Resize the window to expand the view and change the view mode.
To display the tree view shown in next slide, right-click in the right
pane, choose View Mode, and then choose Memory Map Tree.
The left pane (Input Sections) contains a list of the input
sections that are in your project or are mapped in the .LDF file. A
red X is over the icon in front of the section named
“my_asm_section” because Expert Linker has determined that the
section is not mapped by the .LDF file.
The right pane (Memory Map) contains a representation of the
memory segments that Expert Linker defined when it created the
.LDF file.
Expert Linker Window depicts the procedure followed in this step.
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Step 3:
Use the Expert Linker to Modify dot_prod_asm.ldf
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Step 3:
Use the Expert Linker to Modify dot_prod_asm.ldf
6.
Map my_asm_section into the memory segment named
MEM_PROGRAM as follows.
In the Input Sections pane, open my_asm_section by clicking on
the plus sign in front of it. The input section expands to show that
the linker macros:



$COMMAND_LINE_OBJECTS and
$OBJECTS and
the object file dotprod_func.doj have a section that has not been
mapped.

In the Memory Map pane,


expand MEM_L1_CODE and
drag the icon in front of $OBJECTS onto the program_ram output
section under MEM_L1_CODE.
As shown in Figure in the next slide, the red X should no longer
appear because the section my_asm_section has been mapped.
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Step 3:
Use the Expert Linker to Modify dot_prod_asm.ldf
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Step 3:
Use the Expert Linker to Modify dot_prod_asm.ldf
7.
From the Tools menu, choose Expert Linker and
Save to save the modified file. Then close the
Expert Linker window.
If you forget to save the file and then rebuild the
project, VisualDSP++ will see that you modified
the file and will automatically save it.
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Step 4:
Rebuild and Run dot_prod_asm

Build the project by:
1. Click the Build Project button
, or
2. From the Project menu, choose Build Project.

At the end of the build, the Output window should
display this message in the Build view:


“Build completed successfully”
VisualDSP++



loads the program
Runs to main, and
Displays the Output, Disassembly, and editor
windows (as seen in the next slide)
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Step 4:
Rebuild and Run dot_prod_asm
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Step 4:
Rebuild and Run dot_prod_asm
 Click the Run button
to run dot_product_asm.
The program calculates the three dot products and displays
the results in the Console view of the Output window.
When the program stops running, the message “Halted”
appears in the status bar at the bottom of the VisualDSP++
main window. The results, shown below, are identical to the
results obtained in Exercise One.
Dot product [0] = 13273595
Dot product [1] = –49956078
Dot product [2] = 35872518
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Exercise 3
Plotting Data
Goals of this Exercise
 Learn to:
 Load and debug a prebuilt program that applies a
simple Finite Impulse Response (FIR) filter to a buffer
of data
 Use VisualDSP++’s plotting engine to view the
different data arrays graphically, both before and
after running the program.
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Digression: What is an FIR Filter
 Digital Filtering, in general, is one of the most
powerful tools of Digital Signal Processing.
 In general any Digital Signal Processing of a Linear
Time Invariant (LTI) system can be expressed
with a difference equation (more on this latter)
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Linear Constant-Coefficient
Difference Equations
 Nth-order linear constant-coefficient difference
equation is of the form:
N
M
 a yn  k    b xn  k 
k 0
k
m 0
k
 Accumulator Example
y[n] 
n
 x[k ]
k  
y[n  1] 
n 1
 x[k ]
k  
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Linear Constant-Coefficient
Difference Equations (cont.)
y[n]  x[n] 
n 1
 x[k ]
k  
y[n]  x[n]  y[n  1]
y[n]  y[n  1]  x[n]
x[n]
y[n]
One-sample
delay
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General Formulation of Difference
Equation
 Equation: N
M
yn    k yn  k     k xn  k 
k 1
k 0
 Along with initial conditions:
y[-1], y[-2], …, y[-N]
Uniquely specifies the LTI system.
 General equation must be computed using
recursive procedure.
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Example
 Recursive Computation of Difference Equations:
y[n] = ay[n-1]+x[n]
Initial condition is given by y[-1] = c;
Input x[n] = K[n]
 Solution n≥0:
y[0] = ac+K
y[1] = y[0]+0 = a(ac+K) = a2c+aK
…
y[n] = an+1c+anK, n≥0
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Example (cont.)
 Solution n<0:
y[n] = ay[n-1]+x[n] ➲ y[n-1] = a-1(y[n]-x[n])
y[-1] = c
y[-2] = a-1(y[-1]-x[-1]) = a-1 (c+0) = a-1c
…
y[n] = an+1c, n<0
 Overall solution
y[n] = an+1c+Kanu[n], n
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Z-Transform
 Interesting specific class of rational functions of
the form:
P( z )
X ( z) 
Q( z )
 Roots of the polynomial P(z) define the zeros, and
 Roots of the polynomial Q(z) define the poles of
the z-transform.
 Partial fraction expansion method can be used for
rational functions.
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Difference Equation & Z-Transform
 By definition variable Z is equal to unit delay.
 There is direct relationship between difference
equation and Z-Transform:
N
M
k 1
k 0
yn    k yn  k     k xn  k 
Y ( z)
H ( z) 
X ( z)
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Property of Z-Transform
xn  X ( z )
xn  k   z X ( z )
k
N
M
k 1
k 0
N
M
yn    k yn  k     k xn  k 
Y  z     k Y  z z
k
k 1
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   k X  z z
k
k 0
91
Difference Equation & Z-Transform
Y z  
N
M
k 1
k 0
k
k





Y
z
z


X
z
z
 k
 k
or
M
Y z 
H z  

X z 
k

z
 k
k 0
N
1    k z k
k 1
 Last expression is a rational function with numerator and
denominator that are polynomials of z-1.
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Filters
 Any Linear Time Invariant digital filter is
expressed by its difference equation.
 There are two classes of digital filters:
 Finite Impulse Response (FIR), and
 Infinite Impulse Response (IIR).
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FIR Filters
 The impulse response of an FIR filter has finite
duration and corresponds to having no
denominator in the rational function H(z): ➨
 There is no feedback in the difference Equation. This
results in the reduced form difference equation:
M
yn     r xn  r 
r 0
 Impulse sample response (input x[0]=1; x[n]=0
elsewhere for n≠0) of FIR filter is:
hn   n ,0  n  M
hn  0, otherwise
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Step 1:
Loading the FIR Program
1.
Keep the Disassembly window and Console page (of the
Output window) open, but close all other windows.
2.
From the File menu, choose Load Program or click
The Open a Processor Program dialog box appears.
3.
Select the FIR program to load as follows.
a.
Open the Analog Devices folder and double-click:
VisualDSP 4.5\Blackfin\Examples\Tutorial\fir
b.
c.
Double-click the Debug subfolder.
Double-click FIR.DXE to load the program.
If VisualDSP++ does not open an editor window (shown in
Figure in the next slide), right-click in the Disassembly
window and select View Source.
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Step 1:
Loading the FIR Program
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Step 1:
Loading the FIR Program
4.
Look at the source code of the FIR program.
You can see two global data arrays:


IN
OUT
You can also see one function, _fir, that operates on
these arrays.
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Step 2:
Opening a Plot Window
1.
From the View menu, choose Debug Windows and
Plot. Then choose New to open the Plot
Configuration dialog box, shown in the next slide
Figure.
Here you add the data sets that you want to view in a
plot window.
2.
3.
In the Plot group box, specify the following values.
 In the Type box, select Line Plot from the dropdown list.
 In the Title box, type fir.
Enter two data sets to plot by using the values in Table
in the slide after next.
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Step 2:
Opening a Plot Window
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Step 2:
Table Specifying 2 Data sets: Input & Output
Box
Input Data Set
Output Data
Set
Description
Name
Input
Output
Data set
Memory
BLACKFIN Memory
BLACKFIN Memory
Data memory
Address
IN
OUT
The address of this data set is that of the
Input or Output array. Click Browse to select
the value from the list of loaded symbols
Count
128
128
The array is 260 elements long, but you are
plotting the first 128 elements
Stride
1
1
The data is contiguous in memory
Data
short
short
Input & Output are arrays of int values
 After entering each data set, click Add to add the data
set to the Data sets list on the left of the dialog box.
 The Plot Configuration dialog box should now look like
the one in the Figure presented in the next slide.
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Step 2:
Opening a Plot Window
 Plot Configuration Dialog Box with Input/Output Data
Sets
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Step 2:
Opening a Plot Window
4.
Click OK to apply the changes and to open a plot window with
these data sets.
The plot window now displays the two arrays. By default, the
simulator initializes memory to zero, so the Output data set
appears as one horizontal line, shown in Figure below.
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Step 2:
Opening a Plot Window
5.
Right-click in the plot window and choose Modify Settings.
On the General page, in the Options group box, select
Legend and click OK to display the legend box.
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Step 3:
Run the FIR Program and View the Data

Press F5 or click the Run button
program.
to run to the end of the
When the program halts, you see the results of the FIR filter in
the Output array. The two data sets are visible in the plot
window, as shown in Figure below:
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Step 3:
Run the FIR Program and View the Data
2.
Additional Features of the Plotting interface allows
you to select the region and to zoom in.
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Step 3:
Run the FIR Program and View the Data
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Step 3:
Run the FIR Program and View the Data
 To return to the view before magnification, right-click in the
plot window and choose Reset Zoom from the pop-up
menu.
 Individual data points can be viewed as described in the
following procedure:
3. Right-click inside the plot window and choose Data Cursor
from the pop-up menu.

Move to each data point in the current data set by pressing
and holding the Left (←) or Right (→) arrow key on the
keyboard.

To switch data sets, press the Up (↑) or Down (↓) arrow key.

The value of the current data point appears in the lower-left
corner of the plot window, as shown in Figure in the next slide.
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Step 3:
Run the FIR Program and View the Data
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Step 3:
Run the FIR Program and View the Data
4.
Right-click in the plot window and choose Data Cursor from the popup menu.
Next you will look at data sets in the frequency domain.
5.
6.
Right-click in the plot window and choose Modify Settings to open
the Plot Settings dialog box.
Complete these steps:
a. Click the Data Processing tab to display the Data Processing
page, shown in next Figure.
b. In the Data Sets box, ensure that Input (the default) is selected.
In the Data Process box, choose FFT Magnitude.
c.
In the Sample rate (Hz) box, type 10000.
d. In the Data Sets box, select Output. In the Data Process box,
choose FFT Magnitude
e. Click OK to exit the Plot Settings dialog box.
VisualDSP++ performs a Fast Fourier Transform (FFT) on the
selected data set before it is plotted. The FFT enables you to view
the signal in the frequency domain, as shown in Figure after next.
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Step 3:
Run the FIR Program and View the Data
 Data Processing Page
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Step 3:
Run the FIR Program and View the Data
 FFT Performed on a Selected Data Set
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Step 4:
Analysis of the Data
 FIR filter’s response in the frequency domain
1. From the View menu, choose Debug
Windows and Plot. Then choose New to
open the Plot Configuration dialog box.
2. Set up the Filter Frequency Response plot by
completing the Plot and Data Setting group
boxes as shown in Figure in the next slide.
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Step 4:
Analysis of the Data
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Step 4:
Analysis of the Data
3.
Click Add to add the data set to the Data sets box.
4.
Click OK to apply the changes and to open the plot window
with this data set.
5.
Right-click in the plot window and choose Modify Settings to
open the Plot Settings dialog box.
6.
Click the Data Processing tab to display the Data
Processing page. Complete this page as follows.
a. In the Data Sets box, select h.
b. In the Data Process box, choose FFT Magnitude.
c. In the Sample rate (Hz) box, type 10000.
d. Click OK to exit the Data Processing page.
VisualDSP++ performs a Fast Fourier Transform (FFT) on the
selected data set, and enables you to view the filters
frequency response plot in the frequency domain, as shown in
Figure in the next slide.
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Step 4:
Analysis of the Data
 Filter’s Frequency Response Plot
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Step 4:
Analysis of the Data
 This plot shows that the low-pass FIR filter cuts off
all frequency components above 4,000 Hz.
 When you apply this low-pass filter to the input
signal, the resulting signal has no output above
4,000 Hz.
 On the importance of filtering more later:
 Telephony toll-quality signal requires that signal has
no frequency components above 4000 Hz to avoid
aliasing.
 The effect of aliasing is depicted as a low frequency
noise “reflected” from the components above 4000
Hz.
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Exercise 4
Linear Profiling
Goals of this Exercise
 Learn to:
 Load and debug the FIR program from the
previous exercise 3
 Use linear profiling to evaluate the
program’s efficiency and to determine where
the application is spending the majority of
its execution time in the code
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VisualDSP++ Profiling
 VisualDSP++ supports two types of profiling: linear
and statistical.
 Linear Profiling:
 You use linear profiling with a simulator. The count in
the Linear Profiling Results window is incremented
every time an assembly instruction is executed.
 Statistical Profiling:
 You use statistical profiling with a JTAG emulator
connected to a processor target. The count in the
Statistical Profiling Results window is based on
random sampling of the program counter.
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Step 1:
Loading the FIR Program
1.
Close all open windows except the Disassembly window and the
Output window.
2.
Keep the Disassembly window and Console page (of the
Output window) open, but close all other windows.
3.
From the File menu, choose Load Program or click
The Open a Processor Program dialog box appears.
4.
Select the FIR program to load as follows.
a.
Open the Analog Devices folder and double-click:
VisualDSP 4.5\Blackfin\Examples\Tutorial\fir
b.
Double-click the Debug subfolder.
c.
Double-click FIR.DXE to load and run the FIR program.
If VisualDSP++ does not open an editor window, right-click in the
Disassembly window and select View Source.
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Step 2:
Opening the Profiling Window
1.
From the Tools menu, choose Linear Profiling and then
choose New Profile.
The Linear Profiling Results window opens without any data.
2.
Click in the profiling window’s title bar and then drag and drop
the window to the top of the VisualDSP++ main window, as
shown in Figure in the next slide. You will have a better view
of the profile data.
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Step 2:
Opening the Profiling Window
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Step 2:
Opening the Profiling Window
 The Linear Profiling Results window is initially
empty.
 Linear profiling is performed when you run the FIR
program.
 After you run the program and collect data, this
window displays the results of the profiling session.
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Step 3:
Collecting & Examining the Linear Profiling Data
1.
Press F5 or click
to run to the end of the program.
When the program halts, the results of the linear profile
appear in the Linear Profiling Results window.
2.
Examine the results of your linear profiling session.
The Linear Profiling Results window is divided into two
three-column panes.
The left pane shows the results of the profile data. You can
see the percentages of total execution time consumed, by
function and by address.
Double-clicking a line with a function enables you to display
the source file that contains that function. For example,
double-click the fir function to display the assembly source file
(fir.asm) in the right pane, as shown in Figure in the next
slide.
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Step 3:
Collecting & Examining the Linear Profiling Data
 Linear Profiling Results, FIR Program Performance
Analysis.
Note: your results may be slightly different.
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Interpreting Collected Data
Histogram
A graphical representation of the percentage of time spent in a
particular execution unit. This percentage is based on the total time
that the program spent running, so longer bars denote more time
spent in a particular execution unit. The Linear Profiling Results
window always sorts the data with the most time-consuming
(expensive) execution units at the top.
%
The numerical percent of the same data found in the Histogram
column. You can view this value as an absolute number of samples by
right-clicking in the Linear Profiling Results window and by
selecting View Sample Count from the pop-up menu.
Execution
Unit
The program location to which the samples belong. If the instructions
are inside a C function or a C++ method, the execution unit is the
name of the function or method. For instructions that have no
corresponding symbolic names, such as hand-coded assembly or
source files compiled without debugging information, this value is an
address in the form of PC[xxx], where xxx is the address of the
instruction. If the instructions are part of an assembly file, the
execution unit is either an assembly function or the assembly file
followed by the line number in parentheses.
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Interpreting Collected Data
 In previous Figure, the left pane shows that the fir
function consumes over 96% of total execution time.
 The right (source) pane, shown in next Figure, displays
the percentage that each line in the fir function
consumes.
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Linear Profile Data for fir.asm
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End of Tutorial