Acquiring signals via PIC18F4550 and making FFT

[MetalKaiser]

Thanks for taking the time to read my question.

I'm doing the following system for my university proyect:

An audiofrequency signal (0 - 20 KHz) is sampled by the PIC18F4550 ADC (AN0), and its sent to PC via USB Bulk transfer. At the PC, LabVIEW 2009 receives the data throught a subVI created by José Adrián Pérez Cueto (picusb.vi) in U8 array format. Now, when LV receives the data, the program must reconstruct the signal, and finally, do the spectral measurements in order to show the spectral components in a graph.

Ok, now I explain my problem:

The subVI receives the data correctly, and I successfully converted the data to digital waveform, but I fail when trying to convert to analog waveform. I need analog waveform for doing spectral measurement to that, and the U8 array is, in effect, coming from the PIC ADC.

Now, I've been trying to use that array as the Y array in the Build Waveform, but there is something that I'm doing wrong, or maybe I'm forgetting something, because I haven't successfully build the waveform.

How must I input the rest of the Waveform components into the Build Waveform primitive? Because it has 4 components, and the Y array component would be the U8 array

My questions:

How can I successfully obtain the correct analog waveform for doing the spectral measurement to that?

Is there another way for getting the spectrum graph with the obtained data from the subVI?

Attached in a zip file:

• PIC program compiled in CCS PIC-C
  
• USB Bulk Transfer subVI and its respective drivers
  
• Driver for PIC18F4550 USB device
  
• My VI, where I attempt to do spectral measurements
  
• Acquisition Card Schematic on Proteus
  

Thanks for your help! Any redaction error, excuse me, english is not my mother language...Spectral measurement.zip