[Discuss-gnuradio] Reading from TVRX board

[Jonathon Pendlum]

Hello,

I'm a student trying to use the USRP with the TVRX board to do a simple FM stereo receiver. I previously wrote a MATLAB model of a FM transmitter and receiver, and I wanted to use real data in my model. I've been modifying the wideband fm example to record data from the TVRX board by basically inserting some of the l1_record.py code like this:

self.dst = gr.file_sink(gr.sizeof_gr_complex, 'data.txt')
self.head = gr.head(gr.sizeof_gr_complex, 800000)
self.connect(self.u, self.head, self.dst)

Then, I use a script written to convert the binary data file into a MATLAB vector. However, the recorded data is not meaningful to me. When plotting the data, instead of seeing some kind of waveform, I see what looks similar to a NRZI waveform. If you wish to see what I am seeing, here is a screenshot of the data: http://web.ics.purdue.edu/~jpendlum/usrpdata.bmp

It is also important to note that the example wideband FM code runs flawlessly. I can tune to local radio stations and listen to them.

These are the questions that I've tried very hard to answer, but I can't seem to figure out:
2. Is the recorded data in some kind of encoded format, and if so, what is this format?
3. If not, then what am I doing incorrectly in my record script?


If anyone could help, I would greatly appreciate it. Thanks.


Jon Pendlum