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Testing with the vsa

The VSA is an instrument capable of demodulating digital signals. You may use the VSA to demodulate your FSK signaland display the symbols received.

Configuring the vsa

The VSA is the big HP unit on a cart in the front of the classroom. Plug the output from the DSP board into the"Channel 1" jack on the front of the vector signal analyzer, and then turn on the analyzer and follow theseinstructions to display your output:

After powering the signal analyzer up, the display will not be in the correct mode. Use the following sequence ofkeypresses to set it up properly:

If this doesn't work, hit "Save/Recall," F7 (Catalog), point at ECE320.STA with the wheel, and hit F5 (Recall State) and F1 (Enter).
  • "Freq" button, followed by F1 (center), 11.025 (on the keypad), and F3 (KHz)
  • F2 (span), 22, and F3 (KHz)
  • "Range," then F5 (ch1 autorange up/down)
  • "Instrument Mode," then F3 (demodulation)

Viewing the signal spectrum on the vsa

The VSA is also capable of displaying the spectrum of a signal. Hook up the output of your PN generator to theVSA and set it up properly to view the spectrum of the random sequence. Hit "Instrument Mode" and then F1(Scalar) to see the spectrum. Note that you can also use your Lab 4 code for this purpose.

Does what you see match the Matlab simulations?

Optimization

One purpose of this lab is to teach optimization and efficient code techniques. For this reason, for your labgrade you will be judged primarily on the total execution time of your system. You are not required to optimize memory use. Note that by executiontime we mean cycle count, not the number of instructions in your program. Remember that several of the TMS320C54xxinstructions take more than one cycle. The multicycle instructions are primarily the multi-word instructions,including instructions that take immediates, like stm , and instructions using direct addressing of memory (such as ld *(temp),A ). Branch and repeat statements also require several cycles to execute.Most C instructions take more than one cycle. The debugger can be used to determine the exact number of cycles used byyour code; ask your TA to demonstrate. However, since the number of execution cycles used by an instruction is usuallydetermined by the number of words in its encoding, the easiest way to estimate the number of cycles used by yourcode is to count the number of instruction words in the .lst file or the disassembly window in the debugger.

We will grade you based on the number of cycles used between the return from the WAITDATA call and the arrival at the next WAITDATA call in assembly, or the return from one WaitAudio call and the arrival at thenext WaitAudio call in C. If the number of cycles between the two points is variable, the maximum possible number ofcycles will be counted. You must use the core.asm file in v:\ece320\54x\dsplib\core.asm or the C core file in v:\ece320\54x\dspclib\core.asm as provided by the TAs; these files may not be modified . You explicitly may not change the number of samples read and written by each WAITDATA or WaitAudio call! We reserve the right to test your code by substituting the test vector corefile.

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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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