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Re: [Discuss-gnuradio] attribute/control stream question

From: Eric A. Cottrell
Subject: Re: [Discuss-gnuradio] attribute/control stream question
Date: Wed, 13 Jun 2007 21:53:11 -0400
User-agent: Thunderbird (X11/20060911)

Tom Rondeau wrote:
> Matt Ettus wrote:
>> Eric A. Cottrell wrote:
>>> Hello,
>>> The processing of pulses into data requires me to keep track of valid
>>> pulses (following samples are above threshold) and leading edges (sample
>>> is 6 dB or more than previous sample and following sample is 6 dB or
>>> less than current sample).  I also want to indicate preamble start and
>>> pass timestamps along.  I have thought of three methods to do this but
>>> do not know which would be the best one.
>> You can do this, or you may be able to break things up into chunks of
>> samples and process them as vectors.  See the ofdm_sync code for an
>> example of how we do that.
> Also, off the top of my head, you might find the peak_detector and
> sample_and_hold blocks useful for what you're doing. If these won't do
> what you need, that at least the S/H block illustrates the use of
> different streams where input stream 0 is some data type (float,
> gr_complex, bytes, ints) and input stream 1 is a byte stream
> (sizeof_char) as the control line.
> Tom

Thanks for the suggestions and observations.  I will look at the OFDM
code and other blocks.

This is getting to be a big project.  PPM is so simple but there are
some interesting enhanced receiving techniques to squeeze the last drop
of performance.  I took a text description and turned it into code so no
doubt there are other functions I can use to optimize the current code.
 I want to add capability to time stamp the frames and get signal levels
so I am modifying the code again.  I also want to comment it so others
can figure out what is going on.  Sorry it is taking some time to get
the code ready but I want the code structure to be set before check-in.

I am still figuring out GNURadio and Python so I looked at the cfile
example and used it to improve my log program.  I noticed that I may be
able to use a higher sample rate if I go with the 4rx0tx USRP file.  A
future enhancement may be to put the AM detector in the USRP and just
send shorts over the USB bus.  I want to try 10 or 16 MSPS rate to see
if performance improves.

I want to try the OFDM code anyway and see if I get any data off the
BPSK carriers of IBOC AM stations used for station information.

73 Eric

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