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Re: [Discuss-gnuradio] beginning psk31

From: Eric Blossom
Subject: Re: [Discuss-gnuradio] beginning psk31
Date: Sat, 2 Apr 2005 12:43:09 -0800
User-agent: Mutt/1.5.6i

On Fri, Apr 01, 2005 at 08:00:10PM -0500, Chuck Swiger wrote:
> Gang - Todays effort works, a simple script that will repeatedly send the
> letter 'A' :
> http://webpages.charter.net/cswiger/psk_experiment.html


> I'm kind of at a lost at how to leverage 'bytes_to_syms' from a
> single sample to 256 or 1024 samples/symbol.  31.25baud is 8000/256
> or 32000/1024 (that's why it's 31.25 - to match the 8000sps
> typically used).

For a quick solution you might want to try something like what Joshua
Lackey did in the GMSK Tx code 

  # Make samples per symbol copies
  interp_taps = (1,) * sps
  self.interp = gr.interp_fir_filter_fff(sps, interp_taps)

> Some other challenges are buffering keyboard input and sending idle
> when no keys have been hit.

Is typical psk31 usage to buffer up a line using readline or its
equivalent, and then send it?  If so, you might want to create a
source that did a non-blocking read on the tty, or readline, or gui,
or whatever, and return the data it got or an indication that there's
no data to send.  For full 8-bit transparency, you might want to have
the source return a stream of shorts, where values between 0 and 255
are valid chars and 0xFFFF indicate there's no input available.  On
the other hand, does psk31 support full 8-bit transport?  If not, just
use one of the unused codes.


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