# 5.2 Lab 4: lab  (Page 6/7)

 Page 6 / 7

## Compiling and linking

A working program can be produced by compiling the C code and linking assembly modules and the core module. The compilertranslates C code to a relocatable assembly form. The linker assigns physical addresses on the DSP to the relocatable dataand code segments, resolves .global references and links runtime libraries.

The procedure for compiling C code and linking assembly modules has been automated for you in the batch file v:\ece420\54x\dsptools\c_asm.bat . The name of the first file becomes the name of the executable. Once you havecompleted lab4main.c and c_fft_given.asm , type c_asm lab4main.c c_fft_given.asm to produce a lab4main.out file to be loaded onto the DSP. For the C FFT type c_asm lab4main.c lab4fft.c to produce lab4main.out . Load the output file onto the DSP as usual and confirm that validFFTs are calculated. Once valid output is obtained, measure how many clock cycles it takes to compute both the assembly and C FFT.

## Quiz information

From your prelab experiments, you should be able to describe the effect of windowing and zero-padding on FFT spectralanalysis. In your DSP system, experiment with differentinputs, changing $N$ and the type of window. Can you explain what happens as the input frequency is increased beyond the Nyquist rate? Does the $\left|X(k)\right|^{2}$ coincide with what you expect from Matlab? What is the relationship between the observed spectrum and the DTFT?What would happen if the FFT calculation takes longer than it takes to fill inputs with $N$ samples? How long does it take to compute each FFT? What are the tradeoffs between writing code in C versus assembly?

## Appendix a:

1 /* v:/ece420/54x/dspclib/lab4main.c */ 2 /* dgs - 9/14/2001 */ 3 /* mdk - 2/10/2004 C FFT update */ 4 5 #include "v:/ece420/54x/dspclib/core.h" 6 7 /* comment the next line to use assembly fft */ 8 #define C_FFT 9 10 #ifdef C_FFT /* Use C FFT */ 11 12 #include "window.h" 13 #include "lab4.h" /* Number of C FFT points defined here */ 14 15 /* function defined in lab4fft.c */ 16 void fft(void); 17 18 /* FFT data buffers */ 19 int real[N]; /* Real part of data */ 20 int imag[N]; /* Imaginary part of data */ 21 22 #else /* Use assembly FFT */ 23 24 #define N 1024 /* Number of assembly FFT points */ 25 26 /* Function defined by c_fft_given.asm */ 27 void bit_rev_fft(void); 28 29 /* FFT data buffers (declared in c_fft_given.asm) */ 30 extern int bit_rev_data[N*2]; /* Data input for bit-reverse function */ 31 extern int fft_data[N*2]; /* In-place FFT & Output array */ 32 extern int window[N]; /* The Hamming window */ 33 34 #endif /* C_FFT */ 35 36 37 /* Our input/output buffers */ 38 int inputs[N]; 39 int outputs[N]; 40 41 volatile int input_full = 0; /* volatile means interrupt changes it */ 42 int count = 0; 43 44 45 interrupt void irq(void) 46 { 47 int *Xmitptr,*Rcvptr; /* pointers to Xmit & Rcv Bufs */ 48 int i; 49 50 static int in_irq = 0; /* Flag to prevent reentrance */ 51 52 /* Make sure we're not in the interrupt (should never happen) */ 53 if( in_irq ) 54 return; 55 56 /* Mark we're processing, and enable interrupts */ 57 in_irq = 1; 58 enable_irq(); 59 60 /* The following waitaudio call is guaranteed not to 61 actually wait; it will simply return the pointers. */ 62 WaitAudio(&Rcvptr,&Xmitptr); 63 64 /* input_full should never be true... */ 65 if( !input_full ) 66 { 67 for (i=0; i<BlockLen; i++) 68 { 69 /* Save input, and echo to channel 1 */ 70 inputs[count] = Xmitptr[6*i] = Rcvptr[4*i]; 71 72 /* Send FFT output to channel 2 */ 73 Xmitptr[6*i+1] = outputs[count]; 74 75 count++; 76 } 77 } 78 79 /* Have we collected enough data yet? */ 80 if( count >= N ) 81 input_full = 1; 82 83 /* We're not in the interrupt anymore... */ 84 disable_irq(); 85 in_irq = 0; 86 } 87 88 89 main() 90 { 91 /* Initialize IRQ stuff */ 92 count = 0; 93 input_full = 0; 94 SetAudioInterrupt(irq); /* Set up interrupts */ 95 96 while (1) 97 { 98 while( !input_full ); /* Wait for a data buffer to collect */ 99 100 /* From here until we clear input_full can only take * 101 * BlockLen sample times, so don't do too much here. */ 102 103 /* First, transfer inputs and outputs */ 104 105 #ifdef C_FFT /* Use C FFT */ 106 /* I n s e r t c o d e t o f i l l */ 107 /* C F F T b u f f e r s */ 108 109 #else /* Use assembly FFT */ 110 /* I n s e r t c o d e t o f i l l */ 111 /* a s s e m b l y F F T b u f f e r s */ 112 113 #endif /* C_FFT */ 114 115 /* Done with that... ready for new data collection */ 116 count = 0; /* Need to reset the count */ 117 input_full = 0; /* Mark we're ready to collect more data */ 118 119 /**********************************************************/ 120 /* Now that we've gotten the data moved, we can do the */ 121 /* more lengthy processing. */ 122 123 #ifdef C_FFT /* Use C FFT */ 124 125 /* Multiply the input signal by the Hamming window. */ 126 /* . . . i n s e r t C / a s m code . . . */ 127 128 /* Bit-reverse and compute FFT in C */ 129 fft(); 130 131 /* Now, take absolute value squared of FFT */ 132 /* . . . i n s e r t C / a s m code . . . */ 133 134 /* Last, set the DC coefficient to -1 for a trigger pulse */ 135 /* . . . i n s e r t C / a s m code . . . */ 136 137 /* done, wait for next time around! */ 138 139 140 #else /* Use assembly FFT */ 141 142 /* Multiply the input signal by the Hamming window. */ 143 /* . . . i n s e r t C / a s m code . . . */ 144 145 /* Bit-reverse and compute FFT in assembly */ 146 bit_rev_fft(); 147 148 /* Now, take absolute value squared of FFT */ 149 /* . . . i n s e r t C / a s m code . . . */ 150 151 /* Last, set the DC coefficient to -1 for a trigger pulse */ 152 /* . . . i n s e r t C / a s m code . . . */ 153 154 /* done, wait for next time around! */ 155 156 157 #endif /* C_FFT */ 158 159 } 160 }

#### Questions & Answers

anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Ece 320 spring 2004. OpenStax CNX. Aug 24, 2004 Download for free at http://cnx.org/content/col10225/1.12
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