[Discuss-gnuradio] After calling stop(), USRP still seems active.

[Jonas]

Hello,

I have run into a problem using flow_graph stop(). To test the problem, 
I wrote a quick test script that simply sinks a tone to the USRP 
(test_tone.py).

Basically this is:

-------------------------------------------------
class test_tone(gr.flow_graph):

   def __init__(self):
       gr.flow_graph.__init__(self)

   etc, etc

       |
       |
       |
      \ /
       '

   # Connects the signal source (src = gr.sig_source_f) to the FM 
modulation, provides software gain
   # and finally sinks to the USRP.
   self.connect(src, fmtx, gain, self.u)
-------------------------------------------------

This works fine as I am able to receive the tone. However, the code 
below produces strange results:

-------------------------------------------------
#!/usr/bin/env python
from test_tone import *
import time

def hold(seconds):
   print "holding for %d seconds" % seconds
   time.sleep(seconds)

# First run I get a tone.
hold(2)
t.start()
print "play back started"
hold(5)
print "play back ended"
t.stop()

# On this second run I don't get a tone.
hold(2)
t.start()
print "play back started again"
hold(5)
print "play back ended"
t.stop()
-------------------------------------------------

The first time through I receive the tone, the second time through 
(stop, then restart the flowgraph) I don't get a tone (rather what 
sounds like garbage). Additionally, according to my RSSI reading the 
USRP continues to transmit a residual signal, even though the flow graph 
should be stopped. The only way I can get the USRP to actually stop 
transmitting something is to delete and then re-instantiate my test_tone 
object.

When stop() tells the scheduler to stop evaluating the graph, this 
should stop everything, right?

Has anyone else encountered similar problems when using flowgraph stop() 
in conjunction with the USRP?

(I am running the latest stable release, 3.0.3**, on Ubuntu).

Thanks,

Jonas


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