Absolute time reception through python interface

Hello,

I am able to use UHD C++ code to have an ettus device record data at a
specified absolute time. I am trying to implement this functionality in
python. I have read in a discussion topic that the recv command used in
C++
to start receiving at a specified absolute time is not implemented
through
SWIG in gnuradio and that gnuradio scheduler should be used instead. I
have
looked through the code files including ‘scheduler’ in gnuradio as well
as
gr_flat_flowgraph and can’t see how to implement an absolute timed start
through these codes. I also looked at gr_timer but read that this is not
currently fully implemented. Could someone point me in the right
direction
in terms of starting reception at a specified absolute time through
gnuradio/grc please?

Thanks in advance

Nicholas Lan

Nicholas Lan
Systems Engineer

Ursa Minor Space & Navigation B.V.
Rotterdamseweg 183c, 2629 HD Delft, The Netherlands
Tel (Delft): +31 (0)15 2682559
Fax: +31 (0)8 42233565
Mobile: +31 (0)6 28569546
mailto:[email protected] [email protected]
www.ursaminor.nl


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On 11/11/2011 04:23 AM, Nicholas Lan wrote:

gr_flat_flowgraph and can’t see how to implement an absolute timed start
through these codes. I also looked at gr_timer but read that this is not
currently fully implemented. Could someone point me in the right direction
in terms of starting reception at a specified absolute time through
gnuradio/grc please?

If you use my next branch you can write blocks in python. All facilities
of tags and message passing are available in python:
http://gnuradio.org/redmine/projects/gnuradio/wiki/WriteBlocksInPython

Also, look at gr-uhd/examples/tags_demo.cc for an example of how to
intercept and use the tags.

-josh

Dear Josh,

Thanks for your reply. Does this mean that there is no method to
implement
the C++ recv and stream commands using an absolute start time in the
currently implemented gnuradio python api?

Regards
Nicholas Lan


This e-mail communication contains confidential information that may
also be
privileged. It is intended for the exclusive use of the addressees. If
you
are not the person or organization to whom it is addressed, you must not
copy, distribute or take any action based on the information contained
within. If you have received this communication in error, please notify
Ursa
Minor B.V. immediately [telephone +31 (0) 15 2682559]. Ursa Minor B.V.
will
not accept liability for contractual commitments made by individuals
employed by this company outside the scope of our business.

On 11/14/2011 06:38 AM, Nicholas Lan wrote:

Dear Josh,

Thanks for your reply. Does this mean that there is no method to implement
the C++ recv and stream commands using an absolute start time in the
currently implemented gnuradio python api?

You may set absolute time on the device, and receive downstream tags
with absolute timestamps. However, you cannot yet tell the block to
stream at a specific time. I believe this to be a trivial change. One
may imagine a call that sets the time into the source block, and when
the source block’s start() routine is called, it uses the time
programmed by the user.

-josh

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