I accidentally posted this in usrp-users instead of discuss-gnuradio, so
I’m reposting here.
Sean
From: [email protected]
[[email protected]] on behalf of Nowlan, Sean
[[email protected]]
Sent: Friday, December 02, 2011 11:32 PM
To: [email protected]
Subject: Re: [USRP-users] set_start_time problem
Josh,
I think I’ve got it working. I haven’t checked with a spectrum analyzer
or an oscilloscope; I just watched for the transmit LED to come on. I’ve
included the fix below; I’m not sure if you need to make a similar
change on the RX side of things, i.e., in gr_uhd_usrp_source.cc.
— jblum/gr-uhd/lib/gr_uhd_usrp_sink.cc 2011-12-02
10:29:50.801978304 -0500
+++ gnuradio/gr-uhd/lib/gr_uhd_usrp_sink.cc 2011-12-02
23:24:54.203518213 -0500
@@ -389,7 +389,7 @@
_metadata.start_of_burst = true;
_metadata.end_of_burst = false;
-
_metadata.has_time_spec = _stream_now;
-
_metadata.has_time_spec = !(_stream_now); if (_start_time_set){ _start_time_set = false; //cleared for next run _metadata.time_spec = _start_time;
Sean
From: [email protected]
[[email protected]] on behalf of Nowlan, Sean
[[email protected]]
Sent: Friday, December 02, 2011 7:54 PM
To: [email protected]
Subject: [USRP-users] set_start_time problem
Hi everyone, especially Josh 
I’m having a problem using the set_start_time function in gr-uhd. My
flowgraph begins transmitting immediately even though I’ve specified a
time in the future. Any ideas? Example flowgraph:
class test(gr.top_block):
def init(self):
gr.top_block.init(self, “test”)
…
self.usrp = uhd.usrp_sink(
device_addr=“addr=192.168.10.2”,
io_type=uhd.io_type.COMPLEX_FLOAT32,
num_channels=1)
…
self.usrp.set_time_source(“external”,0)
self.usrp.set_clock_source(“external”,0)
…
t = self.usrp.get_time_now(0).get_real_secs() + 20.0
self.usrp.set_start_time(uhd.time_spec_t(t))
…
if name = ‘main’:
…
tb = test()
…
tb.start()
raw_input('press enter to quit: ')
tb.stop()