Re: how to stop the top_block and restart signal transmission

Really appreciate your reply, Jason! I tried the approach recommended by
using grc_usrp.simple_sink_s to take the place of usrp.sink_s. Then, I
called the set_enable() function on simple_sink_s at the scheduler part
to disable the transmitter after the top_block starts to run. An
attributeError is given, which said ‘gr_hier_block2’ object has no
attribute ‘set_enable’. What’s the problem would be?

I really appreciate all of your help!

Thanks,
Yan

The code that I setup USRP sink is:

#!usr/bin/env python

from gnuradio import gr, usrp, eng_notation
from grc_gnuradio import usrp as grc_usrp;
n2s = eng_notation.num_to_str

_dac_rate = 128e6

class simple_sink_s(gr.hier_block2):

def __init__(self, which=0, subdev_spec='A', if_rate=25e3, freq=0.0, 

verbose=False):
gr.hier_block2.init(self,
“usrp_sink_c”,
gr.io_signature(1,1,gr.sizeof_short),
gr.io_signature(0,0,0)
)
self._verbose = verbose
self._u = grc_usrp.simple_usrp.simple_sink_s (which,side = ‘A’)
#if self._verbose:
# print ‘DAC sample rate is’, n2s(self._u.dac_rate()),
“sps”
self._u.set_auto_tr(True)
self.set_if_rate(if_rate)
self.tune(freq)
self.connect(self,self._u)

def set_if_rate(self, if_rate):
    if if_rate is None:
       self._interp = 512
    else:
       self._interp = int(_dac_rate/( if_rate)+0.5)
       self.if_rate = _dac_rate/self._interp
       self._u.set_interp_rate(self._interp)

    if self._verbose:
    print "dac_rate is ", _dac_rate
    print "USRP interpolation rate is ", self._interp
    print "USRP IF rate is ", n2s(self.if_rate),"sps"

def tune(self, freq):
    self._tune_result = self._u.set_frequency(freq)
    if self._tune_result:
    if self._verbose:
       print "Baseband frequence is ", 

n2s(self._tune_result.baseband_freq), “Hz”
print "Center frequence is ", n2s(freq), “Hz”
print "Residual frequence is ",
n2s(self._tune_result.residual_freq), “Hz”
return True

    return False

if name == “main”:
sink = usrp_sink_c (verbose = True)

The scheduler part related to the enable/disable transmitter:

try:
start_flag = 1
payload_13barker =
‘\x01\x01\x01\x01\x01\x00\x00\x01\x01\x00\x01\x00\x01’
while(start_flag == 1):
msg_13bit = gr.message_from_string(payload_13barker)
top_block._ls.msgq.insert_tail(msg_13bit)
eof_msg = gr.message(1)
top_block._ls.msgq.insert_tail(eof_msg)
top_block._u.set_enable(False)
time.sleep(0.005)
top_block._u.set_enable(True)
top_block.wait()
except KeyboardInterrupt:
pass

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