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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. 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

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

Fft routine

As the list of operations indicates, bit-reversal and FFT computation are to be done in assembly. We are providingyou with a shell assembly file, available at v:\ece320\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.

Now, we explain how to use the FFT routine provided by TI for the C54x. The FFT routine fft.asm located in v:\ece320\54x\dsplib\ computes an in-place, complex FFT. The length of the FFT is defined as a label K_FFT_SIZE and the algorithm assumes that the input starts at data memory location _fft_data . To have your code assemble for an N -point FFT, you will have to include the following label definitions in your assembly code.

N .set 1024 K_FFT_SIZE .set N ; size of FFT K_LOGN .set 10 ; number of stages (log_2(N))

In addition to defining these constants, you will have to include twiddle-factor tables for the FFT. These tables twiddle1 and twiddle2 ) are available in the shared directory v:\ece320\54x\dsplib\ . Note that the tables are each N points long representing values from 0 to just shy of 180 degrees and must be accessed using a circular pointer . To include these tables at the proper location in memory with the appropriatelabels referenced by the FFT, use the following

Questions & Answers

what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
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
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
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 2003. OpenStax CNX. Jan 22, 2004 Download for free at http://cnx.org/content/col10096/1.2
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