Re: [Discuss-gnuradio] How to create uhd's time_spec_t from Python

[Marcus Müller]

Hi Piotr,

uhd.time_spec.from_ticks(full_ticks_as_int, ticks_per_second_as_float)
does the trick for me, usually. You can make one time_spec with
from_ticks(12, 1.0f) that is exactly 12 full seconds, and then add a
second one that has 0 full_secs, and a double fractional seconds.

Personally, I'm not overly happy about the fractional part of the
time_spec being double – that means that we waste a lot of the bits of a
double on exponents that never occur, and also that we're getting
different resolutions around 1.0000001 and 1.9000001. But it's like it
is, and it, in practice, works pretty well :)

Best regards,

Marcus


On 09/13/2017 07:08 PM, Piotr Krysik wrote:
> Hi All,
>
> time_spec_t is a class representing time in UHD. It uses time_t (long
> int) for representing full seconds and double for parts of a second.
> This format of time is usable to tell USRPs when to do certain tasks. It
> is also very usable for operations on time without loosing precision.
>
> In c++ time_spec_t can be constructed from time represented by a double
> (not precise if number of full seconds is large) or from time_t and
> double. Both constructors are exposed by SWIG in Python.
>
> When I construct time_spec from double everything is fine:
>
>>>> from gnuradio import uhd
>>>> uhd.time_spec(10)
> But when I construct from int and float I get an error:
>
>>>> uhd.time_spec(10,0.1)
> Traceback (most recent call last):
>   File "<stdin>", line 1, in <module>
>   File "/usr/lib/python2.7/dist-packages/gnuradio/uhd/uhd_swig.py", line
> 1576, in __init__
>     this = _uhd_swig.new_time_spec_t(*args)
> NotImplementedError: Wrong number or type of arguments for overloaded
> function 'new_time_spec_t'.
>   Possible C/C++ prototypes are:
>     uhd::time_spec_t::time_spec_t(double)
>     uhd::time_spec_t::time_spec_t(time_t,double)
>     uhd::time_spec_t::time_spec_t(time_t,long,double)
>
> Somehow Python's integer is not recognized as compatible with time_t
> parameter in the second constructor
> (uhd::time_spec_t::time_spec_t(time_t,double) ).
>
> My question:
> Is there a way to use time_spec_t's constructor
> uhd::time_spec_t::time_spec_t(time_t,double) from Python interface
> exposed by GNU Radio? In my opinion there should be, otherwise why to
> expose it through SWIG.
>
> --
> Best Regards,
> Piotr Krysik
>
>
> _______________________________________________
> Discuss-gnuradio mailing list
> address@hidden
> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio