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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