Hi, everyone,
Is there any way in GRC to
stop sending a signal? For example, I attach a snapshot of a
simple GRC flowgraph with a 250 Hz cosine signal source
outputting floats into an audio sink, and also into a file
sink called "test.dat". Everything works fine and I see the
output, and I can graph the file with a simple python script.
But the problem is that after
some time I have to stop the transmission by manually forcing
the flow graph to abruptly end.
Is there any way in GRC to
automatically stop the signal after some time, say a finite
pulse? I don't want to send a continuous signal, but I want it
to stop, say, after ten periods.
Now some of you (e.g.,
Josh) have pointed me to a way of using Python or C++ to
maybe tag the last sample with an EOB metadata, and I will
try this when I need to do something in Python or C++, but I
don't understand how it would change anything in this
particular flow graph. I mean, just coloring the last sample
with an EOB tag won't stop the datafile from being populated
by a continuous data stream.
I guess I don't understand
why it should be so hard just using GRC to stop sending a
signal after some time., or maybe it's easy, and I just
don't get it. I know there is a burst tagger object in GRC
that someone once mentioned in this group, but it was used
to feed into the USRP, and I assume that the USRP knew
somehow to stop reception? I guess I am confused, and need
some kind of help in understanding this. :-(.
Thanks for any insights....
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You can use the "head" block to allow your flow-graph to run for a
certain amount of time and stop.
One of the problems with GRC is that it isn't, really, an
imperative, procedurally-oriented programming environment. It's a
flow-based
environment, and you have to kind of stand on your head to do
"procedural" things with it.
Probes, for example, can be used to call arbitrary python code at
regular intervals. This can sometimes help you "fake up" a
procedural
environment using state machines and the return values from your
python code.
--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org
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