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TMS320C5510 DSK USER MANUAL
Cranes Software International Limited (TI-Solutions)
3. TO DESIGN FIR(LOW PASS/HIGH PASS)USING WINDOWING
TECHNIQUE. a) USING RECTANGULAR WINDOW
b) USING TRIANGULAR WINDOW
c) USING KAISER WINDOW
4. TO DESIGN IIR FILTER (LP/HP).
5. TO FIND THE FFT OF GIVEN 1-D SIGNAL AND PLOT
6. TO COMPUTE POWER DENSITY SPECTRUM OF A SEQUENCE
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Package Contents
Overview The 5510 DSP Starter Kit (DSK) is a low-cost platform, which lets enables customers to evaluate and develop applications for the TI C55X DSP family. The primary features of the DSK are:
• 200 MHz TMS320C5510 DSP
• TLV320AIC23 Stereo Codec
• Four Position User DIP Switch and Four User LEDs
• On-board Flash
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DSK Board Features
Feature Details
TMS320VC5510 DSP 200MHz, fixed point, 160Kwords internal RAM
CPLD Programmable "glue" logic
External SDRAM 8Mbytes, 32-bit interface
External Flash 256Kwords, 16-bit interface
AIC23 Codec Stereo, 8KHz –96KHz sample rate, 16 to 32 bit samples, mic, line-in, line-out and speaker jacks
4 User LEDs Writable through CPLD
4 User DIP Switches Readable through CPLD
5 Jumpers Select power-on configuration and boot modes
Daughtercard Expansion Interface
Allows user to enhance functionality with add-on daughtercards
HPI Expansion Interface Allows high speed communication with another DSP
Embedded JTAG Emulator Provides high speed JTAG debug through widely accepted USB host interface
BOARD DESCRIPTION OF TMS320C5510 DSK
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Key Features of the C5510 DSK The DSK supports a TMS320VC5510 DSP which can operate at a clock frequency of up to 200 MHz. The DSP core is optimized for efficient, low power operation with the ability to perform most operations in a single cycle. Beyond the DSP core, the ‘5510 integrates a number of on-chip resources that improve functionality and minimize hardware development complexity. 160Kwords memory – high speed internal memory for maximum performance. On-chip PLL – generates processor clock rate from slower external clock reference. 2 Timers – generates periodic timer events as a function of the processor clock. Used by DSP/BIOS to create time slices for multitasking. DMA Controller – 6 channel direct memory access controller for high speed data transfers without intervention from the DSP. 3 McBSPs – Multichannel buffered serial ports. Each McBSP can be used for high speed serial data transmission with external devices or reprogrammed as general purpose I/Os. McBSP2 is used to transmit and receive audio data from the AIC23 stereo codec. McBSP1 is used to control the codec through its serial control port. McBSP0 is always brought out to the peripheral expansion connector. The the MISC register in the CPLD is used to select whether McBSP1 and McBSP2 are routed to the the AIC23 or the expansion connectors. EMIF – External memory interface. The EMIF provides a 32-bit bus on which external memories and other devices can be connected. It included features like internal wait state generation and SDRAM control. The EMIF can interface to both synchronous and asynchronous memories. The native data size on the ‘5510 is a single 16-bit word. Data addresses and data structure sizes are generally given in terms of 16-bit words rather than traditional 8-bit bytes on other processors to match the underlying architecture. A 40-bit accumulator allows higher precision calculations using a sequence of 16-bit operations.
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INSTALLATION DSK HARDWARE INSTALLATION
• Shut down and power off the PC
• Connect the supplied USB port cable to the board
• Connect the other end of the cable to the USB port of PC
Note: If you plan to install a Microphone, speaker, or Signal generator/CRO these must be plugged in properly before you connect power to the DSK
• Plug the power cable into the board
• Plug the other end of the power cable into a power outlet
• The user LEDs should flash several times to indicate board is operational
• When you connect your DSK through USB for the first time on a Windows loaded PC the new hardware found wizard will come up. So, Install the drivers (The CCS CD contains the require drivers for C5510 DSK).
• Install the CCS software for C5510 DSK. Troubleshooting DSK Connectivity If Code Composer Studio IDE fails to configure your port correctly, perform the following steps:
• Test the USB port by running DSK Port test from the start menu Use Start�Programs�Texas Instruments�Code Composer Studio�Code Composer Studio C5510DSK Tools�C5510 DSK Diagnostic Utilities
• The below Screen will appear
• Select� Start�Select 5510 DSK Diagnostic Utility Icon from Desktop
• The Screen Look like as below
• Select Start Option
• Utility Program will test the board
• After testing Diagnostic Status you will get PASS
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If the board still fails to detect Go to CMOS setup� Enable the USB Port Option (The required Device drivers will load along with CCS Installation)
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SOFTWARE INSTALLATION You must install the hardware before you install the software on your system. The System requirements for the Host Machine are;
Minimum
Recommended
• 233MHz or Higher Pentium-Compatible CPU with USB Ports
• 600MB of free hard disk space
• 64MB of RAM
• SVGA (800 x 600 ) display
• Internet Explorer (4.0 or later) or
• Netscape Navigator (4.7 or later)
• Local CD-ROM drive
• 500MHz or Higher Pentium – Compatible CPU with USB Ports
• 128MB RAM
• 16bit Color
Supported Operating Systems
• Windows® 98
• Windows NT® 4.0 Service Pack 4 or higher
• Windows® 2000 Service Pack 1
• Windows® Me
• Windows® XP
The Installation program automatically configures CC Studio IDE for operation with your DSK and creates a CCStudio IDE DSK icon on your desktop. To install, follow these instructions:
• Insert the installation CD into the CD-ROM drive
An install screen appears; if not, goes to the windows Explorer and run setup.exe
• Choose the option to install Code Composer Sutido
If you already have C5000 CC Studio IDE installed on your PC, do not install DSK software. CC Studio IDE full tools supports the DSK platform
• Respond to the dialog boxes as the installation program runs.
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INTRODUCTION TO CODE COMPOSER STUDIO Code Composer is the DSP industry's first fully integrated development environment (IDE) with DSP-specific functionality. With a familiar environment liked MS-based C++TM, Code Composer lets you edit, build, debug, profile and manage projects from a single unified environment. Other unique features include graphical signal analysis, injection/extraction of data signals via file I/O, multi-processor debugging, automated testing and customization via a C-interpretive scripting language and much more. CODE COMPOSER FEATURES INCLUDE:
• IDE
• Debug IDE
• Advanced watch windows
• Integrated editor
• File I/O, Probe Points, and graphical algorithm scope probes
• Advanced graphical signal analysis
• Interactive profiling
• Automated testing and customization via scripting
• Visual project management system
• Compile in the background while editing and debugging
• Multi-processor debugging
• Help on the target DSP
Note : Documents for Reference:
spru509 ���� Code Composer Studio getting started guide.
Soft Copy of Documents are available at : c:\ti\docs\pdf.
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Procedure to work on Code Composer Studio
To create the New Project Project � New (File Name. pjt , Eg: Vectors.pjt)
To Create a Source file File � New � Type the code (Save & give file name, Eg: sum.c). To Add Source files to Project Project � Add files to Project � sum.c To Add rts.lib file & hello.cmd: Project � Add files to Project �rts55.lib Library files: rts55.lib(Path: c:\ ti\c5500\cgtools\lib\rts55.lib) Note: Select Object & Library in (*.o,*.l) in Type of files
Project � Add files to Project �hello.cmd CMD file – Which is common for all non real time programs. (Path: c:\ti\tutorial\dsk5510\hello1\hello.cmd) Note: Select Linker Command file (*.cmd) in Type of files Compile: Project � Compile file To Rebuild: Project � Rebuild, Which will create the final .out executable file.(Eg. Vectors.out). Procedure to Load and Run program:
Load the program to DSK: File � Load program �Debug� Vectors. out
To Execute project: Debug � Run.
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sum.c # include<stdio.h> main() { int i=0; i++; printf("%d",i); } To Perform Single Step Debugging:
1. Keep the cursor on the on to the line from where u want to start single step debugging.(eg: set a break point on to first line int i=0; of your project.)
To set break point select icon from tool bar menu.
2. Load the Vectors. out file onto the target.
3. Go to view and select Watch window.
4. Debug � Run.
5. Execution should halt at break point.
6. Now press F10. See the changes happening in the watch window.
7. Similarly go to view & select CPU registers to view the changes happening in CPU registers.
8. Repeat steps 2 to 6.
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‘C’ PROGRAM TO IMPLEMENT LINEAR CONVOLUTION #include<stdio.h> int y[10]; main() { int m=4; /*Lenght of i/p samples sequence*/ int n=4; /*Lenght of impulse response Co-efficients */ int i=0,j; int x[10]={1,2,3,4,0,0,0,0}; /*Input Signal Samples*/ int h[10]={1,2,3,4,0,0,0,0}; /*Impulse Response Co-efficients*/
/*At the end of input sequences pad ‘M’ and ‘N’ no. of zero’s*/ for(i=0;i<m+n-1;i++) { y[i]=0; for(j=0;j<=i;j++) y[i]+=x[j]*h[i-j]; } for(i=0;i<m+n-1;i++) printf("%d\n",y[i]); }
Program to Implement Circular Convolution #include<stdio.h> int m,n,x[30],h[30],y[30],i,j,temp[30],k,x2[30],a[30]; void main() { printf(" enter the length of the first sequence\n"); scanf("%d",&m); printf(" enter the length of the second sequence\n"); scanf("%d",&n); printf(" enter the first sequence\n"); for(i=0;i<m;i++) scanf("%d",&x[i]); printf(" enter the second sequence\n"); for(j=0;j<n;j++) scanf("%d",&h[j]); if(m-n!=0) /*If length of both sequences are not equal*/ { if(m>n) /* Pad the smaller sequence with zero*/ { for(i=n;i<m;i++) h[i]=0; n=m; } for(i=m;i<n;i++) x[i]=0; m=n; } y[0]=0; a[0]=h[0]; for(j=1;j<n;j++) /*folding h(n) to h(-n)*/ a[j]=h[n-j]; /*Circular convolution*/ for(i=0;i<n;i++) y[0]+=x[i]*a[i]; for(k=1;k<n;k++) { y[k]=0; /*circular shift*/ for(j=1;j<n;j++) x2[j]=a[j-1]; x2[0]=a[n-1]; for(i=0;i<n;i++) { a[i]=x2[i]; y[k]+=x[i]*x2[i]; } } /*displaying the result*/ printf(" the circular convolution is\n"); for(i=0;i<n;i++) printf("%d \t",y[i]); }
IN PUT: Eg: x[4]={3, 2, 1, 0} h[4]={1, 1, 0, 0} OUT PUT y[4]={3, 5, 3, 1}
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IIR filter Designing Experiments MATLAB PROGRAM TO GENRATE FILTER CO-EFFICIENTS % IIR Low pass Butterworth and Chebyshev filters % sampling rate - 24000 % cutoff frequency – 2500 order = 2; cf = 2 * 2500/24000; [num_bw1,den_bw1]=butter(order,cf(1)); [num_cb1,den_cb1]=cheby1(order,3,cf(1));
Note: We have Multiplied Floating Point Values with 32767(2
15) to get Fixed Point Values.
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‘C’ PROGRAM TO IMPLEMENT IIR FILTER #include "xyzcfg.h" #include "dsk5510.h" #include "dsk5510_aic23.h" Int16 l_input; Int16 l_output; Int16 r_input; Int16 r_output; const signed int filter_Coeff[] = { //48,48,48, 32767, -30949, 29322 //96,96,96,32767,-30918,29614 /*fc=600*/ //188,259,188,32767,-29498,27695/*fc=1000*/ 11617,11617,11617,32767,8683,15505/*fc=8000*/ //1455,1455,1455,32767,-23140,21735/*fc=2500*/ //5058,-5058,5058,32767,9995,15803/*fc=7000 -HP */ //22586,-22586,22586,32767,-20964,15649 //20539,-20539,20539,32767,-18173,13046 //15241,-15241,15241,32767,-10161,7877 }; /*Select particular set of co-efficients different Cut-off frequencies from given Tables */ DSK5510_AIC23_Config config = { \ 0x001c, /* 0 DSK5510_AIC23_LEFTINVOL Left line input channel volume */ \ 0x001c, /* 1 DSK5510_AIC23_RIGHTINVOL Right line input channel volume */\ 0x01f9, /* 2 DSK5510_AIC23_LEFTHPVOL Left channel headphone volume */ \ 0x01f9, /* 3 DSK5510_AIC23_RIGHTHPVOL Right channel headphone volume */ \ 0x0011, /* 4 DSK5510_AIC23_ANAPATH Analog audio path control */ \ 0x0000, /* 5 DSK5510_AIC23_DIGPATH Digital audio path control */ \ 0x0000, /* 6 DSK5510_AIC23_POWERDOWN Power down control */ \ 0x0043, /* 7 DSK5510_AIC23_DIGIF Digital audio interface format */ \ 0x0081, /* 8 DSK5510_AIC23_SAMPLERATE Sample rate control */ \ 0x0001 /* 9 DSK5510_AIC23_DIGACT Digital interface activation */ \ }; void main () { DSK5510_AIC23_CodecHandle hCodec; // Initialize the board support library DSK5510_init(); // Start the codec hCodec = DSK5510_AIC23_openCodec(0, &config); // Set codec frequency DSK5510_AIC23_setFreq(hCodec,3); // Endless loop IO audio codec while(1) { /* Receive a sample from the left channel */ while (!DSK5510_AIC23_read16(hCodec, &l_input));
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/* Receive a sample from the right channel */ while (!DSK5510_AIC23_read16(hCodec, &r_input)); l_output=IIR_FILTER(&filter_Coeff,l_input); /* Send a sample to the left channel */ while (!DSK5510_AIC23_write16(hCodec,l_output)); /* Send a sample to the right channel */ while (!DSK5510_AIC23_write16(hCodec,l_output)); } /* Close the codec */ DSK5510_AIC23_closeCodec(hCodec); } signed int IIR_FILTER(const signed int * h, signed int x1) { static signed int x[6] = { 0, 0, 0, 0, 0, 0 }; /* x(n), x(n-1), x(n-2). Must be static */ static signed int y[6] = { 0, 0, 0, 0, 0, 0 }; /* y(n), y(n-1), y(n-2). Must be static */ long temp=0; temp = x1; /* Copy input to temp */ x[0] = (signed int) temp; /* Copy input to x[stages][0] */ temp = ( (long)h[0] * x[0]) ; /* B0 * x(n) */ temp += ( (long)h[1] * x[1]); /* B1/2 * x(n-1) */ temp += ( (long)h[1] * x[1]); /* B1/2 * x(n-1) */ temp += ( (long)h[2] * x[2]); /* B2 * x(n-2) */ temp -= ( (long)h[4] * y[1]); /* A1/2 * y(n-1) */ temp -= ( (long)h[4] * y[1]); /* A1/2 * y(n-1) */ temp -= ( (long)h[5] * y[2]); /* A2 * y(n-2) */ /* Divide temp by coefficients[A0] */ temp >>= 15; if ( temp > 32767 ) { temp = 32767; } else if ( temp < -32767) { temp = -32767; } y[0] = (short int) ( temp ); /* Shuffle values along one place for next time */ y[2] = y[1]; /* y(n-2) = y(n-1) */ y[1] = y[0]; /* y(n-1) = y(n) */
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x[2] = x[1]; /* x(n-2) = x(n-1) */ x[1] = x[0]; /* x(n-1) = x(n) */ /* temp is used as input next time through */ return ((short int)temp*1); }
Procedure: Procedure for Real time Programs : 1. Connect CRO to the Socket Provided for LINE OUT. 2. Connect a Signal Generator to the LINE IN Socket. 3. Switch on the Signal Generator with a sine wave of frequency 500 Hz. And
Vp-p=1.5v 4. Now Switch on the DSK and Bring Up Code Composer Studio on the PC. 5. Create a new project with name codec.pjt. 6. Open “tone.cdb” file and save it as “xyz.cdb” in current project folder. 7. Add “xyz.cdb” to the current project. 8. Add the given “IIR.c” file to the current project which has the main function and calls
all the other necessary routines. 9. Add the library file “dsk5510bslx.lib” to the current project
Path � “C:\ti\C5500\dsk5510\lib\dsk5510bslx.lib” 10. Build, Load and Run the program. 11. You can notice the input signal of 500 Hz. appearing on the CRO verifying the codec
configuration. 12. You can also pass an audio input and hear the output signal through the speakers. 13. You can also vary the sampling frequency using the DSK5510_AIC23_setFreq
Function in the “IIR.c” file and repeat the above steps.
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FIR filter Designing Experiments
Matlab Program to generate ‘FIR Filter-Low Pass’ Coefficients using FIR1
% FIR Low pass filters using rectangular, triangular and kaiser windows % sampling rate - 8000 % cutoff frequency - 1000 order = 30; cf=2 * 1000/8000; b_rect1=fir1(order,cf(1),boxcar(31)); Rectangular b_tri1=fir1(order,cf(1),bartlett(31)); Triangular b_kai1=fir1(order,cf(1),kaiser(31,8)); Kaisar [Where 8-->Beta Co-efficient]
T.1 : Matlab generated Coefficients for FIR Low Pass Kaiser filter:
MATLAB Program to generate ‘FIR Filter-High Pass’ Coefficients using FIR1
% FIR High pass filters using rectangular, triangular and kaiser windows % sampling rate – 8000 % cutoff frequency - 1000 order = 30; cf= 2 * 1000/8000; ;cf--> contains set of cut-off frequencies[Wc] b_rect1=fir1(order,cf(1),'high',boxcar(31)); b_tri1=fir1(order,cf(1),'high',bartlett(31)); b_kai1=fir1(order,cf(1),'high',kaiser(31,8)); Where Kaiser(31,8)--> '8'defines the value of 'beta'.
T.1 : MATLAB generated Coefficients for FIR High Pass Kaiser
‘C’ Program to implement FIR filter: #include "tonecfg.h" #include "dsk5510.h" #include "dsk5510_aic23.h" static int in_buffer[100]; const signed int h[] = { -5,-3,2, 6,5,0,-7,-9,-4,8,16,12,-8,-38,-65,176, -65,-38,-8,12,16,8,-4,-9,-7,0,5,6,2,-3,-5}; /* LPF,fc=1000Hz, rectangular, order=12*/ /* Codec configuration settings */ DSK5510_AIC23_Config config = { \ 0x001c, /* 0 DSK5510_AIC23_LEFTINVOL Left line input channel volume */ \ 0x001c, /* 1 DSK5510_AIC23_RIGHTINVOL Right line input channel volume */\ 0x01f9, /* 2 DSK5510_AIC23_LEFTHPVOL Left channel headphone volume */ \ 0x01f9, /* 3 DSK5510_AIC23_RIGHTHPVOL Right channel headphone volume */ \ 0x0011, /* 4 DSK5510_AIC23_ANAPATH Analog audio path control */ \ 0x0000, /* 5 DSK5510_AIC23_DIGPATH Digital audio path control */ \ 0x0000, /* 6 DSK5510_AIC23_POWERDOWN Power down control */ \ 0x0043, /* 7 DSK5510_AIC23_DIGIF Digital audio interface format */ \ 0x0081, /* 8 DSK5510_AIC23_SAMPLERATE Sample rate control */ \ 0x0001 /* 9 DSK5510_AIC23_DIGACT Digital interface activation */ \ }; void main() { DSK5510_AIC23_CodecHandle hCodec; Int16 l_input,r_input,l_output; /* Initialize the board support library, must be called first */ DSK5510_init(); /* Start the codec */ hCodec = DSK5510_AIC23_openCodec(0, &config); /*set sampling frequency*/ DSK5510_AIC23_setFreq(hCodec, 1); while(1) { /* Receive a sample from the left channel */ while (!DSK5510_AIC23_read16(hCodec, &l_input)); /* Receive a sample from the right channel */ while (!DSK5510_AIC23_read16(hCodec, &r_input)); l_output=FIR_filter (&h,(l_input>>8)); /* Send a sample to the left channel */ while (!DSK5510_AIC23_write16(hCodec,l_output)); /* Send a sample to the right channel */ while (!DSK5510_AIC23_write16(hCodec,l_output)); } /* Close the codec */ DSK5510_AIC23_closeCodec(hCodec); }
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signed int FIR_filter(const signed int * h1, signed int x) { int i=0; signed long output=0; in_buffer[0] = x; /* new input at buffer[0] */ for(i=30;i>0;i--) in_buffer[i] = in_buffer[i-1]; /* shuffle the buffer */ for(i=0;i<31;i++) output = output + h1[i] * in_buffer[i]; return(output); }
Procedure: � Connect CRO to the Socket Provided for LINE OUT.
� Connect a Signal Generator to the LINE IN Socket.
� Switch on the Signal Generator with a sine wave of frequency 500 Hz. And
Vp-p=1.5v
� Now Switch on the DSK and Bring Up Code Composer Studio on the PC.
� Create a new project with name codec.pjt.
� Open “tone.cdb” file and save it as “xyz.cdb” in current project folder
� Add “xyz.cdb” to the current project.
� Add the given “FIR.c” file to the current project which has the main function and calls all the other necessary routines.
� Add the library file “dsk5510bslx.lib” to the current project
Path � “C:\ti\C5500\dsk5510\lib\dsk5510bslx.lib”
� Build, Load and Run the program.
� You can notice the input signal of 500 Hz. appearing on the CRO verifying the
codec configuration.
� You can also pass an audio input and hear the output signal through the speakers.
� You can also vary the sampling frequency using the DSK5510_AIC23_setFreq
Function in the “FIR.c” file and repeat the above steps.
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MATLAB GENERATED FREQUENCY RESPONSE
High Pass FIR filter(Fc= 800Hz).
Low Pass FIR filter (Fc=1000Hz)
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Fast Fourier Transforms(FFT) The DFT Equation
Twiddle Factor
In the Definition of the DFT, there is a factor called the Twiddle Factor
where N = number of samples. If we take an 8 bit sample sequence we can represent the twiddle factor as a vector in the unit circle. e.g.
Note that
1. It is periodic. (i.e. it goes round and round the circle !!) 2. That the vectors are symmetric 3. The vectors are equally spaced around the circle.
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Why the FFT?
If you look at the equation for the Discrete Fourier Transform you will see that it is quite complicated to work out as it involves many additions and multiplications involving complex numbers. Even a simple eight sample signal would require 49 complex multiplications and 56 complex additions to work out the DFT. At this level it is still manageable, however a realistic signal could have 1024 samples which requires over 20,000,000 complex multiplications and additions. As you can see the number of calculations required soon mounts up to unmanageable proportions.
The Fast Fourier Transform is a simply a method of laying out the computation, which is much faster for large values of N, where N is the number of samples in the sequence. It is an ingenious way of achieving rather than the DFT's clumsy P^2 timing.
The idea behind the FFT is the divide and conquer approach, to break up the original N point sample into two (N / 2) sequences. This is because a series of smaller problems is easier to solve than one large one. The DFT requires (N-1)^2 complex multiplications and N(N-1) complex additions as opposed to the FFT's approach of breaking it down into a series of 2 point samples which only require 1 multiplication and 2 additions and the recombination of the points which is minimal.
For example Seismic Data contains hundreds of thousands of samples and would take months to evaluate the DFT. Therefore we use the FFT.
FFT Algorithm
The FFT has a fairly easy algorithm to implement, and it is shown step by step in the list below. Thjis version of the FFT is the Decimation in Time Method
1. Pad input sequence, of N samples, with ZERO's until the number of samples is the nearest power of two.
e.g. 500 samples are padded to 512 (2^9)
2. Bit reverse the input sequence.
e.g. 3 = 011 goes to 110 = 6
3. Compute (N / 2) two sample DFT's from the shuffled inputs.
See "Shuffled Inputs"
4. Compute (N / 4) four sample DFT's from the two sample DFT's.
See "Shuffled Inputs"
5. Compute (N / 2) eight sample DFT's from the four sample DFT's.
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See "Shuffled Inputs"
6. Until all the samples combine into one N-sample DFT
Shuffled Inputs
The process of decimating the signal in the time domain has caused the INPUT samples to be re-ordered. For an 8 point signal the original order of the samples is
0, 1, 2, 3, 4, 5, 6, 7
But after decimation the order is
0, 4, 2, 6, 1, 5, 3, 7
At first it may look as if there is no order to this new sequence, BUT if the numbers are
represented as binary a patter soon becomes apparent.
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What has happened is that the bit patterns representing the sample number has been reversed. This new sequence is the order that the samples enter the FFT.
ALGORITHM TO IMPLEMENT FFT:
• Step 1 - Select no. of points for FFT(Eg: 64)
• Step 2 – Generate a sine wave of frequency ‘f ‘ (eg: 10 Hz with a sampling rate = No. of Points of FFT(eg. 64)) using math library function.
• Step 3 - Take sampled data and apply FFT algorithm .
• Step 4 – Use Graph option to view the Input & Output.
• Step 5 - Repeat Step-1 to 4 for different no. of points & frequencies.
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C PROGRAM TO IMPLEMENT FFT :
Main.c (fft 256.c): #include <math.h> #define PTS 64 //# of points for FFT #define PI 3.14159265358979 typedef struct {float real,imag;} COMPLEX; void FFT(COMPLEX *Y, int n); //FFT prototype float iobuffer[PTS]; //as input and output buffer float x1[PTS]; //intermediate buffer short i; //general purpose index variable short buffercount = 0; //number of new samples in iobuffer short flag = 0; //set to 1 by ISR when iobuffer full COMPLEX w[PTS]; //twiddle constants stored in w COMPLEX samples[PTS]; //primary working buffer main() { for (i = 0 ; i<PTS ; i++) // set up twiddle constants in w { w[i].real = cos(2*PI*i/(PTS*2.0)); //Re component of twiddle constants w[i].imag =-sin(2*PI*i/(PTS*2.0)); //Im component of twiddle constants } for (i = 0 ; i < PTS ; i++) //swap buffers {
for (i = 0 ; i < PTS ; i++) //swap buffers { samples[i].real=iobuffer[i]; //buffer with new data } for (i = 0 ; i < PTS ; i++) samples[i].imag = 0.0; //imag components = 0
FFT(samples,PTS); //call function FFT.c for (i = 0 ; i < PTS ; i++) //compute magnitude { x1[i] = sqrt(samples[i].real*samples[i].real + samples[i].imag*samples[i].imag); } } //end of main
fft.c: #define PTS 64 //# of points for FFT typedef struct {float real,imag;} COMPLEX; extern COMPLEX w[PTS]; //twiddle constants stored in w void FFT(COMPLEX *Y, int N) //input sample array, # of points { COMPLEX temp1,temp2; //temporary storage variables int i,j,k; //loop counter variables int upper_leg, lower_leg; //index of upper/lower butterfly leg int leg_diff; //difference between upper/lower leg int num_stages = 0; //number of FFT stages (iterations) int index, step; //index/step through twiddle constant i = 1; //log(base2) of N points= # of stages
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do { num_stages +=1; i = i*2; }while (i!=N); leg_diff = N/2; //difference between upper&lower legs step = (PTS*2)/N; //step between values in twiddle.h for (i = 0;i < num_stages; i++) //for N-point FFT { index = 0; for (j = 0; j < leg_diff; j++) { for (upper_leg = j; upper_leg < N; upper_leg += (2*leg_diff)) { lower_leg = upper_leg+leg_diff; temp1.real = (Y[upper_leg]).real + (Y[lower_leg]).real; temp1.imag = (Y[upper_leg]).imag + (Y[lower_leg]).imag; temp2.real = (Y[upper_leg]).real - (Y[lower_leg]).real; temp2.imag = (Y[upper_leg]).imag - (Y[lower_leg]).imag; (Y[lower_leg]).real = temp2.real*(w[index]).real -temp2.imag*(w[index]).imag; (Y[lower_leg]).imag = temp2.real*(w[index]).imag +temp2.imag*(w[index]).real; (Y[upper_leg]).real = temp1.real; (Y[upper_leg]).imag = temp1.imag; } index += step; } leg_diff = leg_diff/2; step *= 2; } j = 0; for (i = 1; i < (N-1); i++) //bit reversal for resequencing data { k = N/2; while (k <= j) { j = j - k; k = k/2; } j = j + k; if (i<j) { temp1.real = (Y[j]).real; temp1.imag = (Y[j]).imag; (Y[j]).real = (Y[i]).real; (Y[j]).imag = (Y[i]).imag;
� Open Code Composer Studio, make sure the DSP kit is turned on. � Start a new project using ‘Project-new ‘ pull down menu, save it in a
separate directory(c:\ti\myprojects) with name “FFT.pjt”.
� Add the source files “FFT256.c“ and “FFT.C” in the project using ‘Project�add files to project’ pull down menu.
� Add the linker command file “hello.cmd” . � Add the rts file “rts_ext.lib”
� Set ‘-mf ‘option
� Compile the program using the ‘Project-compile’ pull down menu or by
clicking the shortcut icon on the left side of program window.
� Load the program in program memory of DSP chip using the ‘File-load program’ pull down menu.
� Run the program and observe output using graph utility.
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POWER SPECTRUM The total or the average power in a signal is often not of as great an interest. We are most often interested in the PSD or the Power Spectrum. We often want to see is how the input power has been redistributed by the channel and in this frequency-based redistribution of power is where most of the interesting information lies. The total area under the Power Spectrum or PSD is equal to the total avg. power of the signal. The PSD is an even function of frequency or in other words To compute PSD: The value of the auto-correlation function at zero-time equals the total power in the signal. To compute PSD We compute the auto-correlation of the signal and then take its FFT. The auto-correlation function and PSD are a Fourier transform pair. (Another estimation method called “period gram” uses sampled FFT to compute the PSD.) E.g.: For a process x(n) correlation is defined as: Power Spectral Density is a Fourier transform of the auto correlation.
( ) { ( ) ( ) }R E x n x nτ τ= +
1
1l i m ( ) ( )
N
Nn
x n x nN
τ→ ∞
=
= +∑
1
1
1
ˆ( ) ( ( )) lim ( )
1( ) ( ( )) ( )
2
Nj
NN
j
S F T R R e
R FT S S e d
ω τ
τ
ω τ
ω τ τ
τ ω ω ωπ
−−
→ ∞= − +
−
= =
= =
∑
∫
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ALGORITHM TO IMPLEMENT PSD:
• Step 1 - Select no. of points for FFT(Eg: 64)
• Step 2 – Generate a sine wave of frequency ‘f ‘ (eg: 10 Hz with a sampling rate = No. of Points of FFT(eg. 64)) using math library function.
• Step 3 - Compute the Auto Correlation of Sine wave
• Step4 - Take output of auto correlation, apply FFT algorithm .
• Step 4 - Use Graph option to view the PSD.
• Step 5 - Repeat Step-1 to 4 for different no. of points & frequencies.
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‘C’ Program to Implement PSD:
PSD.c: /************************************************************* * FILENAME * Non_real_time_PSD.c * DESCRIPTION * Program to Compute Non real time PSD * using the TMS320C6711 DSK. *************************************************************** * DESCRIPTION * Number of points for FFT (PTS) * x --> Sine Wave Co-Efficients * iobuffer --> Out put of Auto Correlation. * x1 --> use in graph window to view PSD /*===========================================================*/ #include <math.h> #define PTS 128 //# of points for FFT #define PI 3.14159265358979 typedef struct {float real,imag;} COMPLEX; void FFT(COMPLEX *Y, int n); //FFT prototype float iobuffer[PTS]; //as input and output buffer float x1[PTS],x[PTS]; //intermediate buffer short i; //general purpose index variable short buffercount = 0; //number of new samples in iobuffer short flag = 0; //set to 1 by ISR when iobuffer full float y[128]; COMPLEX w[PTS]; //twiddle constants stored in w COMPLEX samples[PTS]; //primary working buffer main() { float j,sum=0.0 ; int n,k,i,a; for (i = 0 ; i<PTS ; i++) // set up twiddle constants in w { w[i].real = cos(2*PI*i/(PTS*2.0));
/*Re component of twiddle constants*/ w[i].imag =-sin(2*PI*i/(PTS*2.0)); /*Im component of twiddle constants*/ } /****************Input Signal X(n) *************************/ for(i=0,j=0;i<PTS;i++) { x[i] = sin(2*PI*5*i/PTS); // Signal x(Fs)=sin(2*pi*f*i/Fs);
/********************** FFT of R(t) ***********************/ for (i = 0 ; i < PTS ; i++) //swap buffers { samples[i].real=iobuffer[i]; //buffer with new data } for (i = 0 ; i < PTS ; i++) samples[i].imag = 0.0; //imag components = 0 FFT(samples,PTS); //call function FFT.c /******************** PSD ********************/ for (i = 0 ; i < PTS ; i++) //compute magnitude { x1[i] = sqrt(samples[i].real*samples[i].real + samples[i].imag*samples[i].imag); } } //end of main FFT.c: #define PTS 128 //# of points for FFT typedef struct {float real,imag;} COMPLEX; extern COMPLEX w[PTS]; //twiddle constants stored in w void FFT(COMPLEX *Y, int N) //input sample array, # of points { COMPLEX temp1,temp2; //temporary storage variables int i,j,k; //loop counter variables int upper_leg, lower_leg; //indexof upper/lower butterfly leg int leg_diff; //difference between upper/lower leg int num_stages = 0; //number of FFT stages (iterations) int index, step; //index/step through twiddle constant
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i = 1; //log(base2) of N points= # of stages do { num_stages +=1; i = i*2; }while (i!=N); leg_diff = N/2; //difference between upper&lower legs step = (PTS*2)/N; //step between values in twiddle.h// 512 for (i = 0;i < num_stages; i++) //for N-point FFT { index = 0; for (j = 0; j < leg_diff; j++) { for (upper_leg = j; upper_leg < N; upper_leg += (2*leg_diff)) { lower_leg = upper_leg+leg_diff; temp1.real = (Y[upper_leg]).real + (Y[lower_leg]).real; temp1.imag = (Y[upper_leg]).imag + (Y[lower_leg]).imag; temp2.real = (Y[upper_leg]).real - (Y[lower_leg]).real; temp2.imag = (Y[upper_leg]).imag - (Y[lower_leg]).imag; (Y[lower_leg]).real = temp2.real*(w[index]).real -temp2.imag*(w[index]).imag; (Y[lower_leg]).imag = temp2.real*(w[index]).imag +temp2.imag*(w[index]).real; (Y[upper_leg]).real = temp1.real; (Y[upper_leg]).imag = temp1.imag; } index += step; } leg_diff = leg_diff/2; step *= 2; } j = 0; for (i = 1; i < (N-1); i++)
//bit reversal for resequencing data { k = N/2; while (k <= j) { j = j - k; k = k/2; } j = j + k; if (i<j) { temp1.real = (Y[j]).real; temp1.imag = (Y[j]).imag; (Y[j]).real = (Y[i]).real; (Y[j]).imag = (Y[i]).imag; (Y[i]).real = temp1.real; (Y[i]).imag = temp1.imag; } } return; }
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HOW TO PROCEED
� Open Code Composer Studio, make sure the DSP kit is turned on.
� Start a new project using ‘Project-new ‘ pull down menu, save it in a separate directory(c:\ti\myprojects) with name “PSD.pjt”.
� Add the source files “PSD.c“ and “FFT.c” in the project using ‘Project�add files to project’ pull down menu.
� Add the linker command file “hello.cmd” . � Add the rts file “rts_ext.lib”
� Compile the program using the ‘Project-compile’ pull down menu or by
clicking the shortcut icon on the left side of program window.
� Load the program in program memory of DSP chip using the ‘File-load program’ pull down menu.
� Run the program and observe output using graph utility.