[amsat-bb] Help Needed: GNU Radio + FoxTelem
zleffke at vt.edu
Thu Oct 8 17:20:38 UTC 2015
I am frantically rushing to get GNU Radio to 'play nice' with
foxtelem. I'm running all linux here. I'm hoping someone can maybe
throw me a few pointers on getting the fox telem software to work with
external SDR applications. I'm attempting to pipe signals from GNU
Radio in three ways, all met with failure:
First is by running an FM receiver flowgraph and then trying to pipe the
audio out via a Linux FIFO using the 'Wav File Sink' block in GR. I
point the SDR flowgraph to my pipe, and then I point the FoxTelem
software to the same pipe and fire the programs up. I've successfully
used this method in the past to feed a sound streaming application that
"thinks" is reading from a standard wav file, but is actually the GR
flowgraph audio output. GNU Radio seems to run for a second or two
(probably the amount of time it takes to fill the buffer) then the Fox
Telem Software crashes with exceptions:
'javax.sound.sampled.UnsupportedAudioFileException: could not get the
audio input stream from input file.'
In gnu radio I'm using the wav file sink with a single port and sample
rate of 48k and 16bits. This "appears" to match what FoxTelem is
expecting, but I'm getting the crashes.
An alternative method I'm attempting is to use a standard audio sink in
gnuradio (I can hear the audio on my laptop speakers) and then try to
pipe that into the fox sw with a virtual audio cable. I'm attempting to
use JACK and qjackctl, but I have little experience with this and so far
have failed to get it to do anything other than listen to the soundcard
mic and line in ports. If someone knows of a simple to use Virtual
Audio Cable for Linux so that I can pipe the audio via the sound card
that would be great and I can give that a go.
The third method I'm trying to get working is by placing the fox sw in
IQ mode and again attempting to use a 'wave file source' in foxtelem
pointed at a FIFO to pipe the IQ data from GNU radio into foxtelem.
again I get the exception mentioned above. This would be the preferred
method in my case over the audio piping. If someone has any experience
with this that would be great. For those familiar with GNU Radio I'm
taking the complex stream (250ksps), reesampling to 192ksps, converting
to float, then taking the real and complex streams and feeding them into
a 'Wav file sink' with TWO ports pointed at the fifo, again with 16 bit
depth and set to 192ksps. Foxtelem is looking for a wav file at
192ksps. I'm hoping the two port file sink allows I data on the right
channel (in0) and Q data on the left channel (in1).
Any and all pointers would be welcome.
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