Hello, Johnathan,
Thank you for your reply.
What I want to do is collect the samples from the usrp2 and use
gr.probe_avg_mag_sqrd_cf to check that if the one channel is free or not. If
it is free, wait 3 second and repeat checking the samples again. I think it
just the simple example of spectrum sensing.
self.u = usrp2.source_32fc(options.interface, options.mac_addr)
nsamples = 10
self.head = gr.head(gr.sizeof_float, int(nsamples))
self.c2mag = gr.probe_avg_mag_sqrd_cf(1, 0.001)
self.sink = gr.null_sink(gr.sizeof_float)
self.connect (self.u, self.c2mag, self.head,self.sink)
def main():
t = my_top_block()
while not t.c2mag.unmuted():
t.run()
print t.c2mag.unmuted(): #show exceed threshold or not
print t.c2mag.level() #show power
time.sleep(3)
if __name__ == '__main__':
try:
main()
except KeyboardInterrupt:
pass
But if the flow graph lifetime ended with return of "head" module, how can I
get the print output more than twice? After that, the error message arised.
It confused me a lot since I can not find many information about error in
maillist
usrp2: channel 0 not receiving
usrp2::rx_samples() failed
Thank you.
regards,
Andy
Johnathan Corgan-2 wrote:
>
> On Wed, Apr 14, 2010 at 12:27, Andy_Long <luckshiw...@yahoo.com.cn> wrote:
>
>> I have faced the same problem. I try to received the limited samples from
>> USRP2 by using "head"block. It should return a -1 and the flow graph will
>> stop, am I right?
>
> The flowgraph will not only stop, but will end its lifetime. Once
> run() has returned, the flowgraph is no longer usable, or as we like
> to say, further operations on it are "undefined."
>
> In general, starting and stopping an individual flowgraph should occur
> at the same level of processing as application startup and shutdown.
> Anything else is usually a sign of incorrect design (though not
> always.) The run() method on a top block is really just a convenient
> way of telling GNU Radio your application has nothing else to do until
> the flowgraph exits.
>
> Can you describe what you are trying to do?
>
> Johnathan
>
>
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>
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