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We now provide an explanation of the shell C program lab4main.c listed in Appendix A . The lab4main.c file contains the function interrupt void irq and a main program. The main program is an infinite loop over blocks of N 1024 samples. Note that while the DSP is executing instructions in this loop, interrupts occur every BlockLen samples. Inside the infinite loop, you will insert code to do the operations whichfollow. Although each of these operations may be performed in C or assembly, we suggest you follow the guidelinessuggested.

  • Transfer inputs and outputs (C)
  • Apply a Hamming Window (C/assembly)
  • Bit-reverse the input (C and assembly)
  • Apply an N -point FFT (C and assembly)
  • Compute the magnitude-squared spectrum (C/assembly)
  • Include a trigger pulse (C/assembly)

The function WaitAudio is an assembly function in the core code which handles the CODEC interrupts. An interrupt from the CODEC occurs every BlockLen samples. The SetAudioInterrupt(irq) call in the main program tells the core code to jump to the irq function when an interrupt occurs. In the irq function, BlockLen samples of the A/D input in Rcvptr (channel 1) are written to a length N inputs buffer, and BlockLen of the output samples in the outputs buffer are written to the D/A output via Xmitptr on channel 2. In C, pointers may be used as array names so that Xmitptr[0] is the first word pointed to by Xmitptr . As in the assembly core, the input samples are not inconsecutive order. The right and left inputs are offset from Rcvptr respectively by 4 i and 4 i 2 , i 0 ,, BlockLen 1 . The six output channels are accessed consecutively as offsetsfrom Xmitptr . On channel 1 of the output, the input is echoed out. You are to fill the buffer outputs with the windowed magnitude-squared FFT values by performing the operationslisted above.

In the main code, the while(!input_full); loop waits for N samples to collect in the inputs buffer. Next, the N inputs and outputs must be transferred. You are to write this portion of code. This portion of code is tobe done first, within BlockLen sample times; otherwise the first BlockLen of samples of output would not be available on time. Once this loop isfinished, the lengthy processing of the FFT can continue. During this processing, the DSP is interrupted every BlockLen samples to transfer samples. Once this processing is over, the infinite loop returns to while(!input_full); to wait for N samples to finish collecting.

The flow diagram in summarizes the operation of the interrupt handling routine

interrupt handler
Overall program flow of the main function and the interrupt handling function.

Assembly fft routine

As the list of operations indicates, bit-reversal and FFT computation are to be done in both C and assembly. For theassembly version, make sure that the line defining C_FFT is commented in lab4main.c . We are providing you with a shell assembly file, available at v:\ece420\54x\dspclib\c_fft_given.asm and shown in Appendix B , containing many useful declarations and some code. The code for performingbit-reversal and other declarations needed for the FFT routine are also provided in this section. However, we would like you to enter this code manually, as you will be expected to understand itsoperation.

Questions & Answers

How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
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.
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
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
characteristics of micro business
for teaching engĺish at school how nano technology help us
How can I make nanorobot?
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
how can I make nanorobot?
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
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.
what is the actual application of fullerenes nowadays?
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.
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.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
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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