|From:||Anderson, Douglas J.|
|Subject:||[Discuss-gnuradio] Confusion about delay block|
|Date:||Thu, 16 Oct 2014 20:24:31 +0000|
A little while back I submitted an issue (http://gnuradio.org/redmine/issues/693) regarding the inability to instantiate the delay block with a negative int (to consume samples) despite the code comments and documentation.
Tom submitted a commit and clarified that you have to instantiate with a int >=0, but that you can set a negative delay after the block is instantiated via set_dly().
I am still unable to set a negative delay and I'm wondering if maybe I'm misunderstanding something.
In a topblock, I do...
self.delay = blocks.delay(gr.sizeof_gr_complex, 0)
...and connect it to a USRP source.
Then in a main loop which I use to run the flowgraph, I do...
... I'd like to skip 1 fft_frame worth of samples for each run of the flowgraph (after a frequency retune).
I get the following error, with both Ettus Research's stable binary of gnuradio/uhd and with pybombs gnuradio and uhd, built today:
terminate called after throwing an instance of 'std::invalid_argument'
what(): buffer_add_reader: nzero_preload must be >= 0
Aborted (core dumped)
It seems that the delay block still can't accept a negative delay (to consume samples) even after instantiating at 0, or am I missing something simple?
Thanks in advance!
Douglas Anderson | Intern
DOC/NTIA/ITS-T | 325 Broadway St., Boulder, CO 80305 | P: 303 497 3582
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